Professor Zhili Sun

•Two accuracy measures of Kriging for reliability analysis are proposed.•The joint PDF of performance values at untried points is derived.•The proposed accuracy measures are validated by four benchmark examples. The Kriging model for structural reliability analysis applications has attracted much attention within recent years. Several Kriging-based strategies of design of experiments are constructed for structural reliability analysis procedure. However, the quantitative accuracy measure of Kriging is still undesirable. Two accuracy measures are introduced. The first one is further studied through derivation and proposed to quantify accuracy of the Kriging-based estimate of the limit state. This paper treats the target failure probability as a variable with epistemic randomness. The second measure is innovatively defined as the standard deviation of the target failure probability. Combining with Chebyshev's inequality, the second measure is available to construct a lower upper bound of the error of the failure-probability estimate. The joint distribution of performance values at untried points of a given Kriging model is derived and proved, which is indeed essential for computing the innovative accuracy measure because it takes the correlation between performance values of untried points into account. Monte Carlo simulation is employed to compute them with acceptable computational cost. To validate the accuracy measures, four benchmark examples are studied. Results demonstrate the availability of them.

To achieve the heat generation of an angular contact ball bearing, especially when confronted with a difficult challenge, is a complexity of numerical and analytical models of bearings. A combination method of the Kriging model and particle swarm optimization algorithm is proposed for optimizing structure parameters of the bearing to obtain the minimum heat generation of the bearing. Therefore, the heat generation and stiffness of the angular contact ball bearing, which are acquired based on pseudo statics analysis and raceway control theory of the bearing, are the optimization goal and constraint condition, respectively, that are used in particle swarm optimization. Taking the angular contact ball bearing NSK-7016A5 as an example, the results show that the total heat generation of the bearing is decreased and that the axial stiffness of the bearing is increased by optimizing the structure parameters of the bearing. In the end, the combination method that uses both Kriging and particle swarm optimization to optimize the structure parameters of the bearing could obtain satisfactory design results and increased bearing design efficiency; it also bears the potential for the design parameter optimization of other mechanical structures, which may lead to better design results.

The sorption isotherms of xylenes in CoAlPO 4-5 were measured by the gravimetric technique at 342 K. The isotherms of para- and meta-xylenes followed typical type-I and could be well fitted by the Langmuir model; while the isotherm of ortho-xylene did not show a distinct saturation with the increase of pressure and could be then described by the Freundlich equation. In opposition to the adsorption in AlPO 4-5, the isotherms of para- and meta-xylene in CoAlPO 4-5 lay above that of ortho-xylene. The free energy change (Δ G) of adsorption increased with the loadings, while the diffusivities of xylenes decreased with the loadings. Moreover, the diffusivities of ortho-xylene were slower than those of other two isomers.

Research into the established area of the intelligent transportation system is evolving into the Internet of Vehicles, a fast-moving research area, fuelled in part by rapid changes based on cyber-physical systems. It needs to be recognized that existing vehicular communication systems are susceptible to privacy vulnerabilities which require addressing. A practical challenge is that many vehicular communication applications and services make use of basic safety messages that contain the identity of the vehicle, location, and other personal data. A popular way of dealing with this privacy issue is to utilize a pseudonym change scheme to protect the vehicle's identity and location. However, many such schemes suffer that the cost grows and the certificate management difficulty raises with the number of pseudonyms generated and stored, casting doubt of the economic feasibility of that approach. We propose a decentralized blockchain-based solution for pseudonym management that overcomes these limitations. This scheme consists of pseudonym distribution and a shuffle operation, allowing the reuse of existing pseudonyms to different vehicles. The results reported here, including those from our simulations, demonstrate that the proposed scheme can reuse existing pseudonyms and achieve a better degree of anonymity at a lower cost than existing schemes.

Energy constraint is a crucial factor in wireless sensor networks (WSNs). One of the best solutions for networking in the WSNs is a clustering-based technique to deal with the energy constraint. However, cluster heads (CHs) in such technique tend to consume much more energy than ordinary nodes and, eventually, deplete quickly. In this paper, we propose a clustering technique, included CH selection and rotation, using an event-driven data reporting during continuous data monitoring of ambient. SNs in this technique report only necessary data when data changes exceeding a given threshold. Therefore, clusters are created only upon specific places where such necessary data changes are happening. Furthermore, the clusters are operated as long as the ambient situation is changing. Once the situation becomes stable, the clusters will be reset and every sensor node in these clusters switch to sleep mode in order to conserve energy consumed by CHs and members. Results show that the network lifetime and stability is better than some existing protocols.

Transcritical CO2 refrigeration cycle integrated with mechanical subcooling (MS) cycle operating with zeotropic mixture is proposed in this study, based on the concept of Lorenz cycle. An energetic model is developed and analyses are conducted in detail. A maximum overall coefficient of performance (COP) is achieved at the optimum discharge pressure and optimum subcooling degree. The maximum overall COP, optimum subcooling degree and discharge pressure are closely related to the temperature glide of the mixtures. The energy efficiency of the transcritical CO2 refrigeration cycle can be efficiently improved, and the high pressure can be reduced when mixtures with proper temperature glide are used as MS cycle refrigerant. Compared with pure R32, the overall COP is enhanced by 4.91%, and the discharge pressure decreases by 0.11 MPa at evaporation temperature of −5 °C and ambient temperature of 35 °C when R32/R1234ze(Z) (55/45) is employed as MS refrigerant. The mixtures with proper temperature glide are recommended. The thermal performance of the overall cycle can be enhanced more significantly for hot and warm climate regions, or relative low evaporation temperature applications, though a high subcooling degree is required to meet the optimum operation condition. •Transcritical CO2 refrigeration cycle combined with mechanical subcooling (MS) cycle using zeotropic mixture is proposed.•Maximum overall COP is achieved at optimum discharge pressure and subcooling degree.•The overall COP enhancement is strongly linked to the temperature glide of the mixture.•The mixtures with proper temperature glide are recommended to be used in MS cycle.•The cycle is more efficient to be used in high temperature climates, or for low evaporation temperature applications.

The wear experimental project on contact pressure, sliding speed and surface hardness was instituted by the uniform design method, the wear properties were investigated on a vertical universal friction/wear tester, the worn surfaces of specimens were observed by scanning electron microscope (SEM). The wear rate predication model was established by polynomial regression analysis, and the goodness of fit and the significance of influencing factors was verified. The results showed that the experimental efficiency was evidently increased, and the experimental cycle was shortened by the uniform design. It is found that the wear rate predication model established is reasonable and valid, and the impact of three factors on the wear :ate is coupling effect. The main wear mechanism is abrasive wear and adhesive wear.

•Techno-economic analysis on ASHP frosting/defrosting operations presented.•Economic performance of the modified ASHP unit efficiently improved.•Total running costs in heating seasons decreased by about 9.88%.•Total cost saved 5,177.99 CNY ($ 776.36), or 6.68%, in 15 years’ service life. In recent years, air source heat pump (ASHP) units have found applications worldwide due to their advantages. For an ASHP unit with a multi-circuit outdoor coil, when the refrigerant distribution adjusted with the valves, system defrosting efficiency could be optimized. Meanwhile, adjusting the refrigerant distribution by using valves located at each circuit could improve the frosting evenness value, and system coefficient of performance and the defrosting efficiency are thereby both optimized. However, in open literature, no tech-economic analysis work on frosting/defrosting performances of ASHP units is reported, which limits the development of innovation technologies in this field. Therefore, a techno-economic analysis on frosting/defrosting operations for an ASHP unit used in typical cold regions is given, basing on previous experimental work and series of assumptions. As concluded, the total running costs of the new ASHP unit could decrease as much as 5,327.99 CNY ($ 798.87), or 7.67%, and the total cost about 5,177.99 CNY ($ 776.36), or 6.68%, in 15 years’ service life, compared with a traditional one. The payback period of additional first cost of valves is less than 1 year. Conclusions of this study might provide a new analytical tool for scholars, researchers, product developers, and policy designers, and shed new light on the designing and performance optimization of ASHP units.

Because of easy for the bomb-stirring system of feed mechanism to reverse at it's non-working position, which can affect the stability of the whole system. Virtual Prototyping Technology can help people to complete the design of overall structure of feed mechanism and anti-reversion mechanism of automaton. ADAMS, one kind of dynamics simulation software, can help to complete the motion characteristics analysis of anti-reversion mechanism, achieving the motion law of mechanism parts and movement dynamic characteristics, as well as verifying the rationality of the design of mechanism.

Metal- matrix composites layers were prepared by laser cladding with Ni-based Super-alloy onto CrMo cast iron. Applying uniform experiment design, under conditions of different velocity and load, the wear tests of alloy layers were carried out and the stepwise regression method are used to establish the wear rate model for prediction of wear rate. It is proved that the modal is significant and represents the character of the wear trend. According to the wear rate model,the wear characteristics are analysed and the wear mechanisms are identified. The main wear mechanism of laser cladding layer are delamination, adhesive wear and abrasive wear.

• An efficient MEMS structural reliability simulation method is presented.• We propose an efficient CAE software integration method for reliability simulation.• We evaluate the reliability of the latching mechanism in a MEMS Safety and Arming device.• We perform the sensitivity analysis to identify the significant random variables.• Some improvement measures are proposed for the latching mechanism of interest. Based on the deterministic performance analysis of latching mechanism in MEMS (micro-electro-mechanical system)-based Safety and Arming device (S&A device), probabilistic algorithms and Kriging approximation method coupling with finite element simulation are used to quantify the effect of input uncertainties on the response metrics of the mechanism. It firstly uses performance function to represent the failure of the latching mechanism mathematically, and then constructs the corresponding reliability model according to structural reliability theory. In order to relieve the burden of further reliability and sensitivity calculations, Kriging interpolation technique is adopted to approximate the performance function and hence simplify the reliability model. Samples of input variables and the corresponding response, which all together serve as the inputs of Kriging approximation, are gotten through finite element simulations based on the design of experiments. An efficient CAE software integration method is proposed to facilitate the repetitive FE-based calculations of those samples. Finally, FORM (First Order Second Moment Method) is utilized to get the reliability index and its sensitivities with respect to the input random variables and their parameters, which can not only be employed for reliability assessment of the latching mechanism, but also can help to identify key factors for additional structural improvements.

MFI-type(ZSM-5) and FAU-type(NaY) zeolites nanocrystals have been synthesized through crystallization of gel in mesoporous system of carbon nanotubes(CNTS) with an internal diameter of 20∼30 nm. Investigation by using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscope (TEM) and scanning electron microscope (SEM) shows that the nanocrystals possess the typical nanosized zeolites' structural characteristic which is different from those of microsized zeolites.

Adsorption and kinetic behaviors of thiophene, benzene, n-octane, and 1-octene in NaY, Ce(IV)Y, Ag(I)Y and Cu(I)Y have been investigated using a microgravimetric technique over a range of temperatures. The differences in isotherms, saturation adsorption capacities, isosteric heats of adsorption, entropies of sorbed phases and kinetics were discussed according to the different interaction mechanisms between the sorbates and the FAU zeolites. The dynamics and competitive adsorption of the above adsorbate mixtures have also been investigated. Ce(IV)Y has a very high selectivity to thiophene according to the kinetics of binary competitive adsorption of thiophene and benzene.

Generally, the redundancy allocation problem is characterized as a kind of NP-hard combinatorial optimization problem, which is difficult to solve with the classical method because it has exponentially increasing complexity with the augmented size. In this paper, we propose the efficient approach with two phases that is comprised of particle swarm optimization (PSO), which can efficiently represent the region search, and a local search, to solve the adjacent domains of best particle, which is great useful to improve optimization efficiency, and the parameter of local search is also studied.

In satellite networks, voice over IP performance is degraded by long delays and low bandwidth. Both call setup time and quality of service (QoS) for voice calls are affected. Separate studies have been undertaken for these performance metrics. In this paper, we have carried out experiments using different voice codecs to evaluate SIP call setup time and QoS parameters together. The experiments are performed on the satellite network testbed at Centre for Communication Systems Research (CCSR) at University of Surrey. The results present a comparison of different codecs, highlighting their performance.

Intelligent Automation and Computer Engineering offers the state of the art of tremendous advances in intelligent automation and computer engineering and also ...

Satellites are expected to play an essential role in bridging the ldquodigital dividerdquo; satellite networks are likely to be the only way to provide broadband services to regions that cannot be economically reached by terrestrial networks, in particular the more remote regions of Europe and the rest of the world. Security can be a problem for such global services. This paper presents a link layer security solution and how it is implemented for the unidirectional lightweight encapsulation (ULE). A satellite testbed is constructed where the ULE security implementation is validated. The experiments results are presented in this paper.

This paper introduces a novel design method of highly loaded compressor blades with air injection. CFD methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade. A compressor blade is designed with a curvature induced pressure-recovery concept. A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure, which is referred to as a curvature induced 'Shock'. An injection slot downstream from the 'Shock' is used to prevent 'Shock' induced separation, thus reducing the loss. As a result, the compressor blade achieves high loading with acceptable loss. First, the design concept based on a 2D compressor blade profile is introduced. Then, a 3D cascade model is investigated with uniform air injection along the span. The effects of the incidence are also investigated on emphasis in the current study. The mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow field. For the highly loaded cascade without injection, the flow separates immediately downstream from the 'Shock'; the initial location of separation shows little change in a large incidence range. Thus air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced 'Shock' and reduces the size of the separation zone at different incidences. Near the endwall, the flow within the incoming passage vortex mixes with the injected flow. As a result, the size of the passage vortex reduces significantly downstream from the injection slot. After air injection, the loss coefficient along spanwise reduces significantly and the flow turning angle increases. (C) 2017 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.

As a common physical phenomenon, frost deposition is inevitable and always has significant negative effects in many industry fields, such as aerospace, aviation, and HVAC&R, etc. To accurately predict and control a frosting-defrosting cycle, the frost layer thickness should be firstly obtained, which is the most fundamental and important parameter. During the last several decades, frost layer thickness measurement methods and different correlations were widely reported, basing on experimental, semi-empirical, theoretical, and numerical approaches. To provide an overview of the analytical tools for scholars, researchers, product developers, and policy designers, a review and comparative analysis of frost layer thickness studies were conducted. The existing gaps in the frost research are identified and recommendations are made as authors’ outlooks in final conclusions.

This study presents a comparative analysis of thermodynamic performance of cascade refrigeration systems (CRSs) for refrigerant couples R41/R404A and R23/R404A to discover whether R41 is a suitable substitute for R23. The discharge temperature, input power of the compressor, coefficient of performance (COP), exergy loss (X) and exergy efficiency (eta) are chosen as the objective functions. The operating parameters considered in this paper include condensing temperature, evaporating temperature, superheating temperature and subcooling temperature in both high-temperature cycle (HTC) and low-temperature cycle (LTC). The results indicate that an optimum condenser temperature exists for LTC (T-4opt) at which COP acquires maximum value. Under the same operation condition, the input power of R41/R404A CRS is lower than that of R23/R404A CRS, and COPopt is higher than that of R23/R404A CRS. The maximum exergy efficiency of R41/12404A and R23/R404A CRSs are 44.38% and 42.98% respectively. The theoretical analysis indicates that R41 /R404A is a more potential refrigerant couple than R23/R404A in CRS. (C) 2016 Elsevier Ltd. All rights reserved.

Hepatitis C virus (HCV) infects an estimated 170 million individuals worldwide, and the current standard of care, a combination of pegylated interferon alpha and ribavirin, is efficacious in achieving sustained viral response in ~50% of treated patients. Novel therapies under investigation include the use of nucleoside analog inhibitors of the viral RNA-dependent RNA polymerase. NM283, a 3'-valyl ester prodrug of 2'-C-methylcytidine, has demonstrated antiviral efficacy in HCV-infected patients (N. Afdhal et al., J. Hepatol. 46[Suppl. 1]:S5, 2007; N. Afdhal et al., J. Hepatol. 44[Suppl. 2]:S19, 2006). One approach to increase the antiviral efficacy of 2'-C-methylcytidine is to increase the concentration of the active inhibitory species, the 5'-triphosphate, in infected hepatocytes. HepDirect prodrug technology can increase intracellular concentrations of a nucleoside triphosphate in hepatocytes by introducing the nucleoside monophosphate into the cell, bypassing the initial kinase step that is often rate limiting. Screening for 2'-C-methylcytidine triphosphate levels in rat liver after oral dosing identified 1-[3,5-difluorophenyl]-1,3-propandiol as an efficient prodrug modification. To determine antiviral efficacy in vivo, the prodrug was administered separately via oral and intravenous dosing to two HCV-infected chimpanzees. Circulating viral loads declined by ~1.4 log(10) IU/ml and by >3.6 log(10) IU/ml after oral and intravenous dosing, respectively. The viral loads rebounded after the end of dosing to predose levels. The results indicate that a robust antiviral response can be achieved upon administration of the prodrug.

This paper provides an energy efficiency study of transcritical carbon dioxide systems by comparing six cycles with and without an expressor (expander–compressor), which serves as an assistant compressor or the main compressor. Several different expander–compressor arrangements in the system are investigated. The mass flow rate and compression ratio of the expander–compressor are affected by these arrangements. The COP (coefficient of performance) of STM (series model of two-stage compression transcritical CO2 cycle with an expressor as the main compressor) is found to be the highest. Although the intermediate pressure between the two compressor stages in STS (series model of two-stage compression transcritical CO2 cycle with an expressor as an assistant compressor in the second stage) cannot approach the optimum value, its COP approaches that of STM at a high evaporation temperature. PSE (parallel model of single-stage compression CO2 transcritical cycle with an expressor) and PSS (parallel model of single-stage compression CO2 transcritical cycle with an expressor and gas–liquid separator) may be feasible options for reducing the dimensions of a compressor. And the expander and compressor efficiencies are very important factors for the utilization of an expressor.

The Ni-P composite coatings onto 4043 aluminum alloy were prepared by electroless plating with nickel sulfate and sodium hypoposphite as raw material. The Ni-P composite coatings were heat-treated for 1 hour at 200 degrees C, 300 degrees C, 400 degrees C, 500 degrees C and 600 degrees C, respectively. The tribological behaviour of the coatings was investigated on a vertical universal friction/wear tester under dry friction. The morphology and phase structure of the composite coatings were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), and the microhardness of the composite coatings were measured by Vickers diamond indenter. The results showed that the as-deposited coatings had smooth cellular pattern and amorphous structure, and the microhardness of the coatings reached the maximum at 400 degrees C heat treatment, the reason is the formation of Ni3P alloy phase with increasing of the heat treatment temperature. The friction coefficient of coatings annealed at 400 degrees C is the lowest. The wear loss was found to increase with corresponding increase in load and sliding speed. It was found that the wear mechanism of the as-deposited Ni-P composite coatings was dominated by adhesive wear and scuffing under the experimental conditions, but the wear mechanism of the coatings annealed at 400 degrees C was scuffing.

Energy efficiency has become a major research topic in the Internet community as a result of unprecedented rise in the Information and Communication Technology (ICT) sector. One typical approach towards energy efficiency is to select a subset of IP routers or interfaces that will go to sleep mode during the off-peak period. However, on-the-fly network reconfiguration is generally deemed harmful especially to real time packets due to routing re-convergence. In this paper, we develop an efficient algorithm for achieving energy efficiency which is disruption free. The objective is to incrementally wake up sleeping links upon the detection of increased traffic demand. Unlike normal approaches of manipulating link weights or reverting to full topology in case of even minor network congestion and thereby sacrificing energy savings, our algorithm wakes up the minimum number of sleeping links to the network in order to handle this dynamicity. The performance of our algorithm was evaluated using the GEANT network topology and its traffic traces over a period of one week. According to our simulation results, up to almost 47% energy gains can be achieved without any obstruction to the network performance. Secondly, we show that the activation of a small number of sleeping links is still sufficient to cope with the observed traffic surge.

Super-high speed point grinding is a new high-speed grinding technology with some excellent machining performances. In such a grinding process, there is a high-speed airflow rotating around the edge of grinding wheel which hinders the grinding fluid from injecting into the contact area and makes the fluid atomization and splash during grinding process, so as to decrease the ratio of effective grinding fluid into contact area and affect the surface integrity of workpiece. In this paper, the structure and properties of grinding fluid jet is analyzed, the velocity distribution field of the round turbulent jet is discussed theoretically and simulated. Based on the pressure balance principle, a mathematical model is established for the jet velocity at the fluid nozzle, which enables the grinding fluid to pass through the high speed airflow and enter into the contact area. According to the analysis of the grinding fluid velocity in the jet core, an engineering formula is given to calculate the position limit of nozzle during grinding process, as well as a practical design example for the high speed grinding machine is presented.

SO 3H-functionalized ionic liquids could be an efficient catalyst for the alkylation of phenol with tert-butyl alcohol (TBA) and were found to catalyze this reaction with good conversion and selectivity. ▪ Alkylation reaction of phenol with tert-butyl alcohol (TBA) catalyzed by SO 3H-functionalized ionic liquids has been investigated. The influences of different ionic liquids, reaction time, reaction temperature, reactant ratio (mole ratio of phenol to that of TBA), the amount and the recycle of ionic liquid were studied. The conversion of phenol and the selectivity of 2,4-DTBP were 80.4 and 60.2%, respectively, under optimum reaction condition. At the same time, the reaction mechanism was discussed based on the distribution of products.

Five-axis CNC machine tool is the top product of numerically controlled machine tool. Kinmatic accuracy is an important index to evaluate the quality of mechanism. Kinematic accuracy analysis of the Five-axis machine tool in previous study ignores the randomness of each input error component, so the conclusions are imprecise. Using the homogeneous transformation, inverse kinematics of VMC650 Five-axis machine tool is calculated. Based on Multi-body System Theory, error model of the machine tool is presented. Considering the randomness of every input error components, applying the Monte Carlo method, math model of kinematic reliability of the mechanism is deduced. The calculation method of kinematics reliability are put forward applying point evaluation and track evaluation. Kinematic reliability analysis provides some theoretical reference for improving the machining accuracy and operation life of machine tool.

•Droplet solidification process on different material plate surfaces was explored.•Plate surface roughness affects freezing temperature and critical nucleation energy.•The inhibitor concentration affects subcooling and the critical nucleation energy.•The liquid property and the surface roughness dominate heterogeneous nucleation energy. Ice slurry has been widely used for thermal energy storage system due to its high cold energy storage capacity. To effectively improve the efficiency of ice slurry generator, it is essential to have a deeper understanding about the solidification mechanism on the plate surface of ice generator, which is affected by many factors, such as the roughness of surface and the apparent contact angle. This work studies the impacts of roughness and inhibitor concentration on the freezing temperature, subcooling and the heterogeneous nucleation energy at the surface of aluminum, copper and Teflon plates. Results show that both the roughness and the inhibitor concentration can clearly affect the freezing temperature of water droplet and the heterogeneous nucleation energy. In general, the freezing temperature rises and the subcooling and the heterogeneous nucleation energy drop as the surface roughness increases for all studied materials; and the heterogeneous nucleation energy also increases with the increase of inhibitor concentration. Since the heterogeneous nucleation energy is mainly determined by the substance and the roughness, while not by the surface material, it is important to increase the roughness in order to reduce subcooling and save energy, especially for copper and aluminum.

Residual stress generated in welding process lead to fatigue failure. Therefore, it is important to optimize welding process for improving fatigue life of weld parts. As the traditional optimization and simulation results are liable to fall into local optimum or more iterations about model. In this paper, improving the global optimization of kriging-based is proposed to find the optimum welding parameters for maximum residual stress. Based on the initial sample, Kriging model is implemented to approximate the objective function regarding the design variables. the introduce of calibration points about MAXEI and maximum variance MSE, Kriging model is updated iteratively by adding two new points to the original sample till the global optimum is obtained. The results show that the proposed method has faster convergence, reducer the iterations and it can search for a more global optimal solution. Applying the method to design optimization of residual stress generated in welding process can better guide designer of welding process planning.

As the high speed bearings, hybrid journal bearings are usually used in high and super high speed grinding machine spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of bearing is a key factor to lower the accuracy of the spindle system and limit the bearings working speed, so restrict the bearing applications. In this paper, the model of hybrid journal bearing is established to analyze the heat mechanism. In addition, the temperature field distribution for the certain hybrid journal bearing at high speed is studied by ANSYS considering the heat transfer characters between fluid and solid. The experiment of temperature for hybrid journal bearing system in super high speed grinding machine is also performed. The thermal properties and the measure for controlling temperature rise of such bearings are analyzed.

Quick UDP Internet connection(QUIC) protocol and bottleneck bandwidth and round-trip propagation time (BBR) based congestion control algorithm are two major contributions out of Google's persistent attempts to make the Internet faster. QUIC is an user level reliable protocol running on top of UDP to enable evolution of transport mechanisms, while BBR is designed for better TCP congestion control. Although in two different directions, they also converge with BBR support in QUIC. Many researches have proved the performance of QUIC and BBR in different network scenarios, but the evaluation in satellite Internet with long propagation delays and relatively high error rates is still missing.In this paper, we have a preliminary evaluation of the performance of QUIC with BBR via GEO satellite Internet access on dedicated network emulation testbeds. The results and our analysis confirms that for satellite Internet QUIC with the new BBR congestion control has improvements compared with the classic CUBIC.

The main task of structural reliability analysis is to estimate failure probability of a studied structure taking randomness of input variables into account. To consider structural behavior practically, numerical models become more and more complicated and time-consuming, which increases the difficulty of reliability analysis. Therefore, sequential strategies of design of experiment (DoE) are raised. In this research, a new learning function, named least improvement function (LIF), is proposed to update DoE of Kriging based reliability analysis method. LIF values how much the accuracy of estimated failure probability will be improved if adding a given point into DoE. It takes both statistical information provided by the Kriging model and the joint probability density function of input variables into account, which is the most important difference from the existing learning functions. Maximum point of LIF is approximately determined with Markov Chain Monte Carlo(MCMC) simulation. A new reliability analysis method is developed based on the Kriging model, in which LIF, MCMC and Monte Carlo(MC) simulation are employed. Three examples are analyzed. Results show that LIF and the new method proposed in this research are very efficient when dealing with nonlinear performance function, small probability, complicated limit state and engineering problems with high dimension. •Least improvement function (LIF) is proposed for structural reliability analysis.•LIF takes both Kriging based statistical information and joint PDF into account.•A reliability analysis method is constructed based on Kriging, MCS and LIF.

This paper presents a novel, precision, maneuverable, 3-DOF translational parallel mechanism. The mechanism’s important feature is that all of the kinematic joints are the revolute joints. The paper derives the mechanism’s kinematic forward solution and inverse solution by using of coordinate transformation elimination method and vector method, and establishes proper kinematic modeling. Kinematic simulation is carried out by ADAMS virtual prototyping software. The operating data is obtained, it verifies the correctness of solving the forward and inverse solution, and solve the question of choices for many results during the theoretical solution. This technique can provide a useful tool in the design of kinematic trajectory of the parallel mechanism’s end-effector and the kinematic analysis of other parallel mechanism.

For increasing the experimental efficiency and shortening the experimental time, the uniform design method was used to establish the wear experiment scheme on the tribological properties of the sealing material CrMo cast iron. The experiments were investigated on a vertical universal friction and wear tester, the worn surfaces of specimens were observed by scanning electron microscope (SEM). The results showed that the experiment points chosen by the uniform design is reasonable and effective, and the wear rate distribution rule of the CrMo cast iron was established and was divided three regions, the effect on wear rate in the I region and the III region was more serious than the II region, and the variation of the friction coefficient is bigger under experimental conditions, the main wear mechanism of the CrMo cast iron is desquamation wear and adhesive wear. The load and sliding speed coupling effect on wear of the CrMo cast iron must be thought over.

Research into the established area of ITS is evolving into the Internet of Vehicles (IoV), itself a fast-moving research area, fuelled in part by rapid changes in computing and communication technologies. Using pseudonym certificate is a popular way to address privacy issues in IoV. Therefore, the certificate management scheme is considered as a feasible technique to manage system and maintain the lifecycle of certificate. In this paper, we propose an efficient pseudonym certificate management scheme in IoV. The Blockchain concept is introduced to simplify the network structure and distributed maintenance of the Certificate Revocation List (CRL). The proposed scheme embeds part of the certificate revocation functions within the security and privacy applications, aiming to reduce the communication overhead and shorten the processing time cost. Extensive simulations and analysis show the effectiveness and efficiency of the proposed scheme, in which the Blockchain structure costs fewer network resources and gives a more economic solution to against further cybercrime attacks.

Temperature-programmed desorption (TPD) of cyclopentane, benzene and cyclohexane in silicalite-1 from room temperature to 400 °C at different loading has been investigated by intelligent gravimetry. TPD of cyclopentane and benzene at different heating rates (5, 10, 15 and 20 °C/min) has also been studied. There are two different peaks in cyclopentane and benzene TPD profiles at loading over four molecules per unit cell. Only one peak appears at loading lower than (or equal to) four molecules per unit cell in cyclopentane and benzene TPD profiles and in cyclohexane TPD profiles. The maximum desorption peak temperature increases with the increasing of initial adsorbate loading.

A tandem decarboxylation/Diels–Alder reaction of 5-amino-1-phenyl-4-pyrazolecarboxylic acid with various 1,3,5-triazines was reported. The dienophile, 5-amino-1-phenylpyrazole, was generated in situ via decarboxylation and immediately trapped by 1,3,5-triazines leading to 4,6-disubstituted 1-phenylpyrazolo[3,4- d]pyrimidines in one step. Graphic

In Vehicular Ad hoc Networks (VANETs), broadcasted beacon messages are critical as most safety applications rely on them. However, the design of a secure broadcast authentication faces many security and privacy challenges as vehicles are vulnerable to active attacks and the revealing of location. In this paper, we propose a lightweight authentication scheme using Timed Efficient Stream Loss-Tolerant Authentication (TESLA) scheme and Bloom Filters that not only prevents active attacks but also adds a privacy-preserving feature to make the scheme have better performance. Simulation results indicate the scheme outperforms the existing schemes in terms of verification time and the level of anonymity. (C) 2017 The Korean Institute of Communications and Information Sciences (KICS). Publishing Services by Elsevier B.V.

The some five-axis machining center was investigated, and it divided ten subsystems. Based on analysis of fault data, the distribution of fault time submits to Weibull distribution, the distribution function and reliability function of each subsystem were confirmed. The reliability allocation model with the constraints of cost is established based on reliability prediction to get optimal reliability allocation results of the complicated mechano-electronic system. The most growth potential of the reliability of subsystem and growth situation of reliability of each subsystem could be got by using this method. The reliability allocation is an important part of reliability design, because its result influences system design directly. This provides reference for design improving of this series of new products.

For an air source heat pump (ASHP) unit, reverse cycle defrosting operations are always conducted to solve the undesired frosting problem. Previous studies verified that, uneven refrigerant distribution (URD) and melted frost downwards flowing (MFDF) along the vertically installed multi-circuit outdoor coil would degrade system defrosting performance. However, it is hardly possible to separate the URD and MFDF effects in a practical multi-circuit outdoor coil. In addition, it is a fundamental coupled problem of uneven heat and mass transfer. Consequently, to investigate the coupled effects of MFDF and URD on system defrosting performance, a sequential experimental study is carried out and reported in this paper. Firstly, a special testing facility and tailor-made three-circuit outdoor coil were introduced. This is followed by two experimental cases designed, with frost evenly accumulated on the surface of each circuit by adjusting the stop valves’ opening degrees. After the experimental results compared, basing on refrigerant evenly and unevenly distributed into each circuit, energy analysis was also given. Finally, as concluded, the coupled effects were negative on system energy performance, and defrosting efficiency increased by 7.4%, from 40.5% to 47.9%, when the refrigerant’s distribution changed from uneven to even. This study makes contributions on the optimization of system control strategies.

As everyone knows, reliability growth technology is an essential part in the mechanical reliability theory as well as an insurance of the products capability in usage. It exists throughout the entire lifespan of development, manufacturing and application. Concerning the reliability characters of mechanical products, that product life obeys Weibull distribution, which is mostly resulted from the test on the small sample, three parameters of life distribution are estimated by the grey estimation in this paper. Then according to the data acquired in the test, Duane growth model is surely developed to assess the situation of reliability growth. Furthermore, the following example ascertains that the developed model is in accordance with mechanical characters. From the result, Duane model is reasonable to evaluate the reliability growth level of mechanical products. It is obvious that the improved measure is effective to enhance the reliability and the value of MTBF can be calculated with the model.

Experiment plays the prime method in soldering reflow profile forecasting. While its high cost and low efficiency makes the company hard to develop. According to the nonlinear relationship between the multi input and output, reflow profile input parameters setting method based on BP neural network and genetic algorithm(BPNN-GA) is proposed in the paper. Establish the finite element model of the PCB products with ANSYS software, and simulate the reflow profile. Temperature field in the PCBAs heat process is analyzed to help adjust to provide guidance for parameter settings partially. The result shows that the process of parameters set methods with BPNN-GA and simulating analysis with ANSYS is effective in establish the virtual test system. The obtained characteristic value meets product quality requirements well.

Adefovir dipivoxil, a marketed drug for the treatment of hepatitis B, is dosed at submaximally efficacious doses because of renal toxicity. In an effort to improve the therapeutic index of adefovir, 1-aryl-1,3-propanyl prodrugs were synthesized with the rationale that this selectively liver-activated prodrug class would enhance liver levels of the active metabolite adefovir diphosphate (ADV-DP) and/or decrease kidney exposure. The lead prodrug (14, MB06866, pradefovir), identified from a variety of in vitro and in vivo assays, exhibited good oral bioavailability (F = 42%, mesylate salt, rat) and rate of prodrug conversion to ADV-DP. Tissue distribution studies in the rat using radiolabeled materials showed that cyclic 1-aryl-1,3-propanyl prodrugs enhance the delivery of adefovir and its metabolites to the liver, with pradefovir exhibiting a 12-fold improvement in the liver/kidney ratio over adefovir dipivoxil.

A dielectric barrier structure with hollow electrodes (HEDBS), in which gas flow oriented parallel to the electric field, was proposed. Results showed that with this structure, air can be effectively ignited, forming atmospheric low temperature plasma, and the proposed HEDBS could achieve much higher electron density (5 x 10(15)/cm(3)). It was also found that the flow condition, including outlet diameter and flow rate, played a key role in the evolution of electron density. Optical emission spectroscopy diagnostic results showed that the concentration of reactive species had the same variation trend as the electron density. The simulated distribution of discharge gas flow indicated that the HEDBS had a strong recoil effect on discharge gas, and could efficiently promote generating electron density as well as reactive species. (C) 2015 AIP Publishing LLC.

The spiral bevel gears of attack helicopter transmission systems are taken as an object in this paper. The numerical analysis model for starved elastohydrodynamic lubrication (SEHL) of spiral bevel gears is established on the basis of the analysis of load tooth contacts analysis and SEHL in elliptical contacts. The SEHL characteristics of spiral bevel gears are also analyzed. The results are as follows: during the course of a gear-tooth meshing cycle of the spiral bevel gear, the extremum of minimal film thickness and maximal film pressure occurs near midpoint of the path of contact, and leans to dedendum. The minimal value of the minimal film thickness is 0.39 um, and the maximal value of the maximal film pressure is 0.69 GPa. The value of minimal film thickness gradually increases with the increasing of meshing point velocity. When the velocity of meshing point exceeds 110 m/s, the increase became tardiness. As the load of meshing point increases, the value of minimal film thickness gently diminishes.

Aiming to provide low-cost universal broadband access, this paper describes the strategy that supports the integration of hybrid satellite and WiMAX, based on the network architecture proposed in the IST Satsix project. In this context, WiMAX networks can be used as wireless local loops integrated with a satellite network, lowering the cost of the broadband internet connections and providing a universal access to rural and marine areas. The paper presents the problems concerning the interworking between DVB-RCS and WiMAX technologies and the solutions adopted in the SatSix research project, partially funded by European Commission within the Information Society Technologies (IST) 6th Framework Programme.

The thermal performance of CO2 transcrtical refrigeration cycle can be improved by cooling the CO2 fluid exiting the gas cooler with an assisted vapor compression refrigeration cycle (auxiliary cycle). Thus, a thermodynamic analysis is performed to study the operation characteristics of the subcooling CO2 transcritical refrigeration cycle. The results indicate that a maximum COP is achieved at the corresponding optimum discharge pressure and the optimum subcooling temperature. The improvement in COP is more significant in the case of higher ambient temperature and lower evaporation temperature, and the discharge pressure and temperature can be obviously reduced. The auxiliary cycle refrigerant is screened and R717 performs with the highest COP. The CO2 transcritical assisted with mechanical subcooling is recommended for the cases with higher ambient temperature and lower evaporation temperature.

•System drying performance influenced by air flow ratio changing was investigated.•Drying performances of adjusting air temperature and flow ratio was compared.•Drying time decreased 42 min, or 15.0%, by the strategy of hot air bypassed.•Energy consumption of compressor was shorted from 4.27 kWh to 3.63 kWh.•Contributions of this study can guide low temperature material drying process. As the quick development of industry drying technology, different heat pump drying systems were proposed in recent decades. Enclosed heat pump drying system was considered as the most widely used system. For an existed enclosed fixed frequency heat pump drying system, drying time could be decreased by increasing air temperature at inlet of drying chamber. However, as a fundamental problem, system drying performance influenced by air flow ratio was not tested and reported in open literatures. Therefore, basing on adding an air bypass duct, drying performance of an enclosed system was experimental investigated in this study, with 15 mm thickness fresh carrot chips used. Furthermore, qualitatively and quantitatively comparisons and discussions on experimental results were conducted. A whole drying process were firstly divided into three stages by different water content ratios, preheating stage at 98–100%, fast drying stage at 20–98%, and later drying stage at 0–20%, respectively. For the inlet air temperature of drying chamber is fixed at 40 °C, material drying time for water content ratio reaching 20% could be effectively decreased as much as 42 min, or 15.0%, by the strategy of hot air bypassed. After the drying time shortened, the calculated energy consumption for compressor was also decreased from 4.27 kWh for AFR at 1.0 to 3.63 kWh for AFR at 0.6. Contributions of this study can guide low temperature material drying process. Clearly, system control optimization and energy saving were both expected.

Aiming at the defects that failure samples of five-axis NC machine tools is small, traditional reliability analysis is not accurate, this paper presents reliability analysis mode based on improved Bayesian method for AMSAA model. Firstly, we obtain the failure model of NC machine tools meets the AMSAA model according to goodness-of-fit test, and in order to meet the requirements of simplifying engineering calculations, this paper adpots a method of Coefficient equivalent which converts failure Data into index-life data; then using Bayesian methods to estimate reliability parameters for the Index-life data; for the last we proceed point estimation and interval estimation for the MTBF of the machine. Take High-speed five-axis NC machine tools t of VMC650m for example, the result proved that the method can take advantage of a small sample of the equipment to proceed point estimation and interval estimation for MTBF failure data, and provide a reference for the optimization of maintenance strategies and Diagnostic work of the NC machine tools.

A new strategy is reported for the synthesis of supported metal sulfides with high dispersion by sulfidation in dielectric barrier discharge (DBD) plasma under ambient conditions. According to the characterization data obtained by XRD, BET, UV-vis, TEM, XPS, ICP, and elemental analysis, the DBD plasma method not only reduces the preparation time but also achieves an increased dispersion, small particle size and uniform distribution compared to the traditional thermal method. These results prove that the plasma preparation method is a facile and flexible approach for the synthesis of metal sulfides. The plasma-prepared CdS/Al2O3 and ZnS/Al2O3 catalysts exhibited high performances for hydrogen production from H2S with reduced energy costs. The enhancement might be attributable to the smaller particle size, higher surface area and dispersion, which enhances the semiconductor catalytic efficiency.

To solve the problem of large computation when failure probability with time-consuming numerical model is calculated, we propose an improved active learning reliability method called AK-SSIS based on AK-IS algorithm [1]. First, an improved iterative stopping criterion in active learning is presented so that iterations decrease dramatically. Second, the proposed method introduces Subset simulation importance sampling (SSIS) into the active learning reliability calculation, and then a learning function suitable for SSIS is proposed. Finally, the efficiency of AK-SSIS is proved by two academic examples from the literature. The results show that AK-SSIS requires fewer calls to the performance function than AK-IS, and the failure probability obtained from AK-SSIS is very robust and accurate. Then this method is applied on a spur gear pair for tooth contact fatigue reliability analysis.

In this paper two VSAT satellite network architectures are proposed to offer access to the B-ISDN and accommodate ATM service needs in an integrated manner, while achieving maximum bandwidth utilisation of the satellite. The first architecture uses a traditional ‘bent pipe’ repeater satellite. The need for optimization of the channel capacity allocation scheme is discussed, using a preliminary performance analysis for a Dynamic Reservation TDMA system which takes advantage of the flexibility and the statistical multiplexing capabilities of ATM and supports various VBR and CBR services. Some bottlenecks, introduced by the satellite link, in the performance of protocols such as TCP/IP are highlighted. The second architecture uses an OBP satellite with spot beams and cell-switching capabilities. A novel approach, in which statistical multiplexing is performed on-board the satellite, is suggested and results show that a much better satellite bandwidth utilization can be achieved. In this architecture, smaller earth terminals can be used without complex dynamic reservation protocols, but at the cost of a more complex satellite payload.

The generation of different waveforms by axial impacts involving a non-uniform bar can be applied in percussive drilling to increase wave energy transfer. It is a good method for obtaining the force and velocity histories at the impacted ends by introducing a delta function, based on 1-D theory. However, they could not be directly predicted, considering that the two impacted ends may be separated from one another, and a clearance is therefore generated between them. In addition, the changing-status of the non-linearities given the repeated separations and contacts is discussed in this paper. The conditions of separation and contact are provided to present a procedure for predicting the parameters at the impacted ends throughout the non-linear process, and the boundary conditions are also considered. As illustrated in an example impact model, the self-recontact behavior resulting from the wave motion occurs, and the possibility for repeated contacts and separations phenomenon is revealed. (C) 2016 Elsevier Ltd. All rights reserved.

Aircrafts in commercial routes have been proposed in some previous work as a novel DTN bundle carriers [1]. Satellites can be one of the hops in this application. DTN suffers from intermittent disconnections, long delays and has scarce resources. It is a challenge to control the admission to these resources to provide better QoS and ensure optimum resource utilisation. Furthermore, providing fairness to different users who compete to access limited and scarce resources makes the solution even harder. In this paper, we propose a fair novel admission control model for DTN aircrafts applications based on feedback history logging of past admissions. This model will locally estimate the resources and provide fair admissions for users within a group of users in the same area. We will show an analysis of aircrafts fair admission control design for both aircraft initiated and user initiated approaches, which will provide integrated service per flow basis. The paper also presents the initial simulation model using a modified version of DTN2 emulator and DTNperf_2 performance monitoring tool.

Network virtualization is an efficient way to enhance the resource utilization of physical network. It enables numerous heterogeneous virtual networks (VNs) coexist and share the resources of same physical network. Virtual network provisioning has been a key issue in network virtualization. Since the optimal virtual network provisioning is an NP-hard problem, existing studies devote to propose heuristic approaches for a tradeoff between computational complexity and the quality of VN provision. A traditional physical/substrate network usually sustains numerous infrastructure providers (InPs), and many applications in the substrate network can be characterized by hybrid virtual network which composed by both unicast and multicast virtual network. However, few research has conducted for the problem of hybrid virtual network provisioning (HVNP) among multiple domains. In our research, we model the HVNP problem through integer linear programming (ILP) for minimizing provisioning cost. Furthermore, we propose two effective algorithms to address the researched problem: (i) the decomposition-based algorithm, HVNP_D; and (ii) the spectral clustering based algorithm, HVNP_SC. Extensive simulation experiments have been carried out to assess the proposed algorithms. Simulation results demonstrate that our approaches have better performance than existing approach. •We study the problem of mapping hybrid virtual network across multiple domains in cloud computing.•We model the problem by using mixed integer linear programming to minimize the total mapping cost.•We design two efficient algorithms to solve the researched problem.•We conduct extensive simulations for evaluating the performance of our proposed algorithms.

This paper presents a Priority based Routing Protocol (PRP) in Vehicular Ad hoc Network (VANET), according to message types. We focus mainly on a safety messaging application for safe driving in distributed environment, i.e., ad hoc manner. Broadcast based routing protocol is proposed along with priority and position enhancement to provide i) fully distributed routing protocol, ii) different quality of services (QoS) for different types of messages, iii) maximum message dissemination distance per hop. The proposed protocol, PRP, is evaluated using simulation software called OMNeT++. The performance parameters include average MAC delay, percentage of message reception and collision, as well as average message dissemination distance per hop. The results show the PRP achieves both message prioritization and maximum dissemination distance in fully distributed environment.

The wear experimental project on main influencing factor with load, sliding speed, surface hardness and lubrication was instituted by the uniform design, the wear properties were investigated on a MMW-1 friction and wear tester. The predication formula for wear rate was defined. The wear rate predication model was established by the partial least squares based on the test data, the influencing degree on the main influencing factors was analyzed, the results show the influence on wear rate from big to small is in turn load, lubrication, surface hardness and sliding speed. The lubrication property improved is a handy valid path to decrease the wear rate. The check results show that it is a valid method by partial least squares to establish wear predication model based on test data.

In this paper, a method of analyzing the reliability of tooth surface contact strength was presented and several kinds of errors of tooth shape were taken into consideration. In the method, experimental design method and Finite Element Method (FEM) were used to get the samples of tooth surface contact stress, and then Weibull distribution was used to fit these samples. On the basis of both stress and strength obeying to Weibull distribution, the reliability of tooth surface contact strength was calculated. The result of the calculation example indicates that the method is correct and effective.

Since the first space probe flew to the Moon in 1959, over 200 deep-space exploration missions have already been carried out on the eight planets, various asteroids and comets in the solar system. Amount of deep-space scientific experiments promoted people to understand about the origin and evolution of the universe. With the rapid developments of equipment and spacecraft with high-accuracy detector and long-term energy, more and more ambitious deep-space exploration plans have also been scheduled or under discussion about space resources utilization and space migration, e.g., manned landing on the Mars, guard infrastructures on the Moon and human-flight to the edge of the solar system (>100 AU), etc.

Organic Rankine Cycle(ORC) can effectively recover the low grade heat source due to its distinctive thermodynamic performance. Based on Genetic Algorithm, net power output per unit mass of geothermal water is set as the objective function. Evaporation pressure, superheating of the steam, the minimum temperature in the evaporator are analyzed to obtain the optimal performance of the system. The results indicate that under the assumption condition that the optimal level constitution of system parameters is determined as the working fluid of R227ea, the power output of the system of 596kw and the corresponding power output per unit mass of geothermal water of 11.91kJ/kg. R245ca has the maximal efficiency of 5.75% among the selected 6 working fluids (Butane, R236fa, R227ea, R236ea, R245fa, R245ca). The effect of pinch temperature in evaporator on power output per unit mass is more seriously than that of superheating. It is about 7 times in terms of increasing 1K of R227ea.

As a major step surface mount technology, reflow process is the key factor affecting the quality of the final product. The setting parameters and characteristic value of temperature curve shows a nonlinear relationship. So parameter impacts on characteristic values are analyzed and the parameters adjustment process based on orthogonal experiment is proposed in the paper. First, setting parameters are determined and the orthogonal test is designed according to production conditions. Then each characteristic value for temperature profile is calculated. Further, multi-index orthogonal experiment is analyzed for acquiring the setting parameters which impacts the PCBA product quality greater. Finally, reliability prediction is carried out considering the main influencing parameters for providing a theoretical basis of parameters adjustment and product quality evaluation in engineering process.

A series of transition metal methanesulfonates were prepared and characterized by FTIR and TG. Characteristic peaks for the methyl and sulfonyl groups were observed in the i.r. spectra. The number of crystal waters and the process of dehydration and decomposition were determined by TG. The catalytic behavior of transition metal methanesulfonates in Biginelli one-pot cyclocondensation of aldehydes, 1,3-dicarbonyl compounds and urea in absolute EtOH under refluxing temperatures was investigated. The products, 3,4-dihydropyrimidinones, were characterized by elemental analysis, ^sup 1^H n.m.r. and FTIR. The experimental results showed transition metal methanesulfonates were efficient for the Biginelli reaction.[PUBLICATION ABSTRACT]

The adsorption and diffusion of benzene, p-xylene, cyclohexane, cis- and trans-1,4-dimethylcyclohexane ( c- and t-DMCH) in silicalite-1 zeolite have been investigated using the frequency response (FR) experimental method and the simulation techniques such as the canonical ensemble Monte Carlo simulation, the force field minimisation and dynamics. It has been found by the FR measurements that two independent fluxes of p-xylene exist in the two channels of silicalite-1 respectively at low loadings and low temperatures, while at high temperatures, only one single, pure diffusion process is observed. The diffusivity of benzene is slower than that of p-xylene and the saturated hydrocarbons diffuse much more slowly than their aromatic equivalents. As found with benzene and p-xylene, t-DMCH has been found to diffuse much more rapidly than cyclohexane. The c-DMCH, on the other hand, diffuses extremely slowly. The theoretical calculations give rational interpretations to these interesting experimental results.

The wear volume is obtained by means of experiment and the wear random process model is established according to the result. The Carbon steel material is used and the samples are grouped five after surface treatment, each group tests six times under the same condition. The wear volume under each wear time shows big dispersion. The additional study indicates that the sample has the large wear volume is in the serious wear state from the beginning, and the wear of running-in phase is inflected by the work velocity and the state condition of the surface of the samples. The wear process which the mean value is a constant and the standard deviation is different is a normal process generally, it is a stationary normal process if the standard deviation has no relation to the start of the wear time, or a Wiener process if the standard deviation is liner with the wear time, it is valuable to forecast the wear reliability.

Catalytic Beckmann rearrangement of oximes is investigated in a novel task-specific ionic liquid consisting sulfonyl chloride with easy separation of the products by extraction with water. Under mild conditions and without any additional organic solvents, Beckmann rearrangement of ketoximes was performed in a novel task-specific ionic liquid consisting sulfonyl chloride. Especially for the conversion of cyclohexanone oxime to ε-caprolactam, ε-caprolactam has good solubility in water while the task-specific ionic liquid is immiscible with water, therefore, ε-caprolactam could be easily separated from the reaction system by water extraction.

Aimed at three-translational parallel mechanism, the velocity Jacobian matrix is formulated on the basis of analytical method, so the velocity and acceleration of the moving platform is calculated. Then the velocity and acceleration formulas of all components' centroids are deduced based on the vector method. The above formulas are very simple and easy to solve. Kinematic simulation is carried out by ADAMS virtual prototyping software. The operating data is obtained, it verifies the correctness of the theoretical calculation.

Satellite-based Universal Mobile Telecommunications System (S-UMTS) is used to provide all kinds of Transmission Control Protocol/Internet Protocol (TCP/IP) based Internet services for global end users. However due to the high propagation delay and high bit error rates over satellite links, the TCP performance degrades considerably and affects many qualities of TCP based services. In this work, we focus on studying the TCP performance in S-UMTS using radio link control (RLC) with fragmentation and retransmission mechanisms. Analytical and simulation studies have been carried out to study this cross-layer problem. Two scenarios have been studied, i.e., the satellite operates in either transparent mode or with onboard processor (OBP) mode. The results indicate that the TCP performance can be enhanced substantially by employing the relay function using OBP and appropriate configurations of RIC parameters, thus providing useful information to the design the next generation communication satellite with onboard processing.

Software reliability is an important attribute of software quality. Based on the concept of software reliability and reliability indicator, this paper presents the analysis techniques of software reliability for the vehicle navigation system, obtains the appropriate forecasting model of vehicle navigation software reliability through tests and calculation, and puts forward suggestions for promoting the vehicle navigation software reliability.

AMP-activated protein kinase (AMPK) is a heterotrimeric kinase that regulates cellular. energy metabolism by affecting energy-consuming pathways such as de novo. lipid biosynthesis and glucose production as well as energy-producing pathways such as lipid oxidation and glucose uptake. Accordingly, compounds that activate AMPK represent potential drug candidates for the treatment of hyperlipidemia and type 2 diabetes. Screening of a proprietary library of AMP mimetics identified the phosphonic acid 2 that bears little structural resemblance to AMP but is capable of activating AMPK with high potency (EC(50) = 6 nM vs AMP EC(50) = 6 mu M) and specificity. Phosphonate prodrugs of 2 inhibited de novo lipogenesis In cellular and animal models of hyperlipidemia.

This paper introduces the quantitative research method for the personnel configuration of the software project by studying the effects of the overall competence of the developers in the vehicle navigation software project on the factors like project quality. The study shows the overall competence of the developers is related to the aftersubmission defect density, productivity and the average delay of software Version 0.99. Further, a quantitative formula of competence and competence is drawn on the basis of statistics; meanwhile, according to the research result an integer programming configuration method for the navigation software project personnel based on competence analysis is concluded.

Communication technology for vehicles has become an important topic for research. IEEE standards including IEEE 802.11p and IEEE P1609.1-4 have emerged to provide a framework for intervehicular communication (IVC). However, due to particular characteristics of IVC, such as high mobility, unstable connectivity, and network partitioning, information routing becomes inevitably challenging. This article reviews the recent research progress to highlight research challenges in vehicular routing protocol as a guideline for future development of IVC applications. The article focuses on the IEEE DSRC/WAVE standard. The state of the art in IVC routing protocols is surveyed, and open issues for further research are highlighted in the article.

Real-time interactive multimedia multiparty communication is becoming a vital part of modern Internet services. As one of its applications, online gaming attracts a huge group of fans playing over the Internet. It has new requirements for relative QoS. This article gives a brief introduction to these new QoS requirements, and then presents an algorithm to satisfy these requirements in the differentiated services network for client-server-topology-based online gaming services. Our simulation results show that this algorithm can provide optimized relative QoS support for online gaming as an example of multiparty communications.

Under mild conditions and without any additional organic solvent, esterification of alcohols by carboxylic acids could be carried out in three new halogen-free Brønsted acidic ionic liquids, 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate, 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate and N-(4-sulfonic acid)butyl triethylammonium hydrogen sulfate. Especially for esterification of ethanol by acetic acid, good conversion rate and high selectivity were obtained, and the liquid esters formed a separate phase that was decanted. The ionic liquid could be reused after removal of water under vacuum.

The automatic measuring system of stone milling force is studied in the article. The columned diamond milling cutters are used to mill stone on NC milling machines. Through analyzing the milling force, the mathematic model is established. Combining the measuring force index, the experimental facility of the automatic measuring system is established and solving methods of the key problems on the software data acquisition is detailed. The system is utilized to measure three component force of milling, that is, horizontal force, vertical force and axial force. Reliable data is acquired. Finally the automatic acquisition of data and the drawing of curve are realized. The achievement of automatic measurement of stone milling force provides theory basis for the further research on the wearing characteristics of diamond cutters, cutting quality of stones and the optimizing of processing technological parameter etc.

All IPPM QoS parameter metrics are defined for end-to-end one-way measurement These metrics provide exact indicators of network layer quality in the pair communications. However, further attention should be put on the multiparty communications, which might use multicast routing protocols, e.g., the IP conferencing services, online gaming, online stock market and etc. To qualify the multiparty communications, the future QoS study and metrics are required to be defined. The purpose of this paper is to highlight the new QoS requirements of the multiparty communication services in terms of relative delay, relative jitter and relative packet loss. A set of parameter metrics is derived from the existing one-way metrics in IP performance metrics (IPPM) for the multiparty communications to present these new requirements. These parameter metrics are supposed to provide methods and rules for engineers to measure and judge the QoS of the multiparty communications.

Hybrid journal bearings are used in the high and super high speed cases mainly, such as the super-high speed spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of the bearing is a major reason to lower the accuracy of the main shaft system and limit the bearings working speed higher, as a result, restrict the bearing applications. In this paper, the thermal properties and the heat mechanism of such bearings are analyzed. The mathematical model of hybrid journal bearing is established to analyze the mechanism of generating heat. In addition, the temperature field distribution for the certain hybrid journal bearing at speed of 10000 rpm is studied by means of software ANSYS considering the heat transfer characters between fluid and solid. An improved measure about temperature rise of hybrid journal bearing is presented.

The application of dimensionality reduction method on the reliability and reliability sensitivity analysis of vibration systems was examined. The dimensionality of a vibration reliability problem was reduced to only two independent dimensions by the means of polar transformation. As the safe and failure classes of samples are clearly distinguishable and occupy a standard position in a two-dimensional plot in the case that the important direction exists, the relevant samples are selected visually. The reliability and reliability sensitivity problems were solved using the position of the relevant samples. Before the reliability and reliability sensitivity estimation, an essential visualization analysis is conducted to examine the capacity of the method in terms of the existence of the important direction which is used to reduce the dimensionality of the reliability problem. In order to calculate the design point correctly, the improved Hasofer-Lind-Rackwitz-Fiessler method was extended with a procedure for determining the perturbation in the calculation of the gradient vector by finite differences according to the numerical precision of the limit state function. The dimensionality reduction method saves the numbers of calling limit state function a lot and has the same accuracy as Monte Carlo method. Examples involving single and multiple degree-of-freedom nonlinear vibration systems were used to demonstrate the approach.

New configurations of transcritical CO2 refrigeration cycle combined with a thermoelectric (TE) subcooler and an expander (TES+EXPHM and TES+EXPML) are proposed. The expander can operate between the high-pressure to the vessel pressure, or from vessel pressure to evaporation pressure. A power system is utilized to balance and supply power to thermoelectric subcooler and compressor. Thermodynamic performance optimizations and analyses are presented. Comparisons are carried out with the BASE, EXPHM, EXPML, and TES cycles. The results show that the coefficient of performance (COP) improvement is more notable when the expander is installed between the liquid receiver and the evaporator. Maximum COP is obtained for the new cycles with a simultaneous optimization of discharge pressure and subcooling temperature. The new proposed TES+EXPML cycle shows an excellent and steady performance than other cycles. It operates not only with the highest COP, but also the lowest discharge pressure. Under the working conditions of high gas cooler outlet temperature or low evaporation temperature, the merits of COP improvement and discharge pressure reduction are more prominent. The new cycle is more suitable for the hot regions where the CO2 can not be sufficiently subcooled or the refrigerated space operates at low evaporation temperature. •New configurations of transcritical CO2 refrigeration cycle are proposed.•New cycles are optimized and compared with other cycles.•The position of expander has an evident influence on the performance of CO2 cycle.•TES+EXPML cycle shows the highest COP and lowest discharge pressure.•The range of application for the TES+EXPML cycle is recommended.

Without the assumption of contemporaneous end to end connectivity in challenged wireless networks, Delay Tolerant Networking (DTN) routing is an important research area. The contribution in this paper is to take advantage of the proposed DTN geographic replication to overcome the limitation of topology based utility replication, since message replication is prevented due to the local maximum problem that the utility metric of encountered node is worse than message carrier. In brief, the proposed DTN geographic replication is activated only if the utility replication is unable to route message, this hybrid approach promotes a seamless message replication given limited message lifetime. Borrowing from the concept of gravity, messages are under prioritized transmission for load balancing and achieving less delivery latency. Extensive simulation results show promising improvement of the proposed algorithm in terms of delivery ratio, transmission cost, average latency as well as number of aborted messages.

[Display omitted] The dynamic loading in human body, along with the corrosive body fluid, presents a great challenge for the practical use of biodegradable magnesium implants. In this study, a high purity magnesium (99.99wt.%) and two typical promising biodegradable magnesium alloys (binary Mg–1Ca and ternary Mg–2Zn–0.2Ca) were chosen as the experimental materials. Their dynamic mechanical performances were comparatively evaluated by carrying out fatigue tests in air and in simulated body fluid (SBF). The fatigue strengths of HP-Mg, Mg–1Ca and Mg–2Zn–0.2Ca were all around 90MPa in air, however, they decreased to 52MPa, 70MPa and 68MPa in SBF at 4×106cycles, respectively. The fatigue cracks initiated from the microstructural defects when tested in air, but nucleated from surface corrosion pits when tested in SBF. Cyclic loading significantly increased the corrosion rates of all the experimental materials compared to that in static SBF. Moreover, based on our findings, the fatigue failure processes and interactions between material, corrosion and cyclic loading were systematically discussed. Fatigue strength and life are vital parameters to the design of metallic implant devices. For the corrosion fatigue of biomedical magnesium alloys, we reported the corrosion fatigue behavior of AZ91D and WE43 in SBF (Acta Biomaterialia, 6 (2010) 4605–4613), and till now there is no other reports to our knowledge. We spent 3years to finish the fatigue testing and get S-N curves for three more magnesium biomaterials, and our significant finding is that the fatigue strengths of HP-Mg, Mg–1Ca and Mg–2Zn–0.2Ca are all around 90MPa in air but 52MPa, 70MPa and 68MPa in SBF at 4×106cycles, which will provide the first-hand data for the future magnesium implants design.

This research analyze the gear for body temperature field, according to the body temperature field, it calculates comprehensive deformation of the loaded gear by using the contact method. It extracts the deformation of gear surface along the gear thickness and gear tall direction, calculating the gear non-involute error. It calculates the gear transmission error considering the thermal deformation. The results show that: Considering thermal deformation non-involute error of addendum is maximum, and there are no mutations in gear non-involute error the transmission error caused by mutation of elastic deformation mutate at single and double tooth alternating position. The bigger mutation becomes, the bigger vibration amplitude will be. The results of the study provide a solid basis to improve the motion transmission accuracy of gear.

The Terminal at High Speed for European Stock Exchange USers (THESEUS) is a European research project. THESEUS with its multimedia communications capabilities enables brokers to trade not only with their national stock exchange but also with all the European stock exchanges. This will make secure trading in the stock exchanges more effective through Europe. This paper presents an overview of the THESEUS system design and architecture and the terrestrial, satellite and security field demonstrations.

The Green function method (GFM) is utilized to analyze the in-plane forced vibration of curved pipe conveying fluid, where the randomicity and distribution of the external excitation and the added mass and damping ratio are considered. The Laplace transform is used, and the Green functions with various boundary conditions are obtained subsequently. Numerical calculations are performed to validate the present solutions, and the effects of some key parameters on both tangential and radial displacements are further investigated. The forced vibration problems with linear and nonlinear motion constraints are also discussed briefly. The method can be radiated to study other forms of forced vibration problems related with pipes or more extensive issues.

The adsorption behaviour of benzene in silicalite-1, AlPO4-5 and EU-1 has been investigated using gravimetric techniques and molecular simulation methods. For the one-dimensional, 12-membered ring (MR) channels of AlPO4-5 and the unidirectional, 10-MR channels with 12-MR side pockets of EU-1, the isotherms of benzene show simple type I behaviour. For the three dimensional 10-MR channels of silicalite-1, an anomalous behaviour of the benzene molecules sorbed has been observed. Two steps at loadings of ca. 4 and 6 molecules per unit cell [m.(u.c.)(-1)], respectively, and an hysteresis loop between loadings from 6 to 8 m.(u.c.)(-1) can be found in the isotherms of this system. These stepped isotherms can be classified as showing type VI isotherm behaviour but in this system the reasons behind the steps are of a new and novel nature. These abnormal adsorption properties have been ascribed to the subtle interplay of increased sorbate-sorbate interactions and decreases in the entropy of sorption due to the energetically heterogeneous surfaces which are present in silicalite-1. The composition and structure of the silicalite-1 samples also play an important role on the adsorption properties of this system.

Pure and binary adsorption isotherms of propylene and ethylene on silicalite-1 were determined using the intelligent gravimetric method. The ideal adsorbed solution (IAS) theory and the extended Langmuir (EL) model were used to predict binary adsorption isotherms from the adsorption isotherms of the pure components. At higher molar fraction of propylene in the gas phase, the results predicted by both the IAS theory and the EL model are in good agreement with the experimental data, but at low molar fraction of propylene in the gas phase, the predicted results deviate from the experimental data evidently.

Most current common cause failure models are static models in which failure rate is assumed constant. The assumption is unrealistic in numerous situations, especially for mechanical systems. Based on the idea of shock models, this paper modifies unreasonable assumptions in conventional models and describes common cause failure process with non-homogeneous Poisson process, power-exponential process. A dynamic model is obtained. The parameters are estimated with neural network. The model presented in this paper, which is based on time-related power-exponential failure rate like bathtub curve, has more advantages and wider application than the model based on constant failure rate. Examples are given to illustrate its feasibility and precision of computation.

Kinematic accuracy is an important index to evaluate the quality of mechanisms. Kinematic reliability is a significant standard to examine dynamic kinematic accuracy of mechanisms. Having deduced inverse kinematics and calculated model for position errors of Delta mechanism, kinematic reliability of the mechanism is calculated considering the randomness of every error components. Analytic method sensitivity analysis is adopted to describe contribution of the randomness of each error component to kinematic reliability of the mechanism, and the calculating approach is exactly given that the sensitivity analysis which is for getting the error contributions to reliability of which the position errors during movement is in the range of allowable accuracy at any time. Kinematic reliability and its sensitivity analysis can search key factor influencing kinematic accuracy, which can provide the foundation for error compensate and accuracy assurance technology of the mechanism.

This paper proposes a meshed very small aperture terminal (VSAT) satellite communications network which uses an on-board processing (OBP) satellite with spot beams and cell switching capabilities. A novel approach is used for maximizing the bandwidth utilization of the satellite by performing statistical multiplexing on-board the satellite. MF-TDMA is used as the satellite multiple access protocol since it takes advantage of the flexibility and statistical multiplexing capabilities of ATM. Finally, the cell loss resulting from the limited bandwidth of the satellite link can be prevented by effective traffic control functions. A preventive control scheme has been used for this purpose. The leaky bucket (or generic cell rate algorithm) used as usage parameter control (UPC) controls the source traffic parameters for conformance with the traffic contract. Furthermore a rate-based flow control is used to control ABR services. The results of the performance analysis of the proposed system indicate that a high increase in satellite bandwidth utilization can be achieved, compared to circuit-switched satellite systems.

In this paper, we propose a new quad-decomposition approach for the instantaneous flow field which has the secondary flows. Different from the previously reported quad-decomposition, where the velocity field is decomposed into a mean part, a streamwise part and a cross-flow part of the secondary flow, and the residual three-dimensional fluctuation part, our new quad-decomposition separates the flow field into a mean part, a streamwise streaks-related part, a cross-flow roll-cells-related part and a residual cross-flow fluctuation part. These two decomposition approaches are used to explore the underlying physics of the energy balance and transfer among different shares of the turbulent kinetic energy in spanwise-rotating turbulent plane Couette flows. The new quad-decomposition can provide clear pictures of the energy transfer from the streaks to the residual cross-flow fluctuations due to the system rotation and the correlation between pressure and streamwise velocity fluctuations’ gradient, in addition to the bridge role of the cross-flow roll-cells-related field between the mean field and the residual fluctuation field, which can also be demonstrated by the previous quad-decomposition.

As a non-linear finite element analysis software ANSYS/LS-DYNA is used to carry out virtual reliability test in transmission mechanism of reciprocating compressor and response surface method is used to analyze reliability and sensitivity of sliding bearing according to testing data. This paper uses ANSYS to preprocess testing models of virtual prototype and put out the K file; designs sample points of random variables based on central composite method and modifies the K files to carry out random sampling of prototype and uses LS-DYNA970 to solve the submitted K files repeatedly; plots relationship curves of output responses and time history and gets a group of sample points of structure response with post-processing results of LS-PREPOST. Lastly this paper uses response surface method to build limit state equation and analyze reliability and sensitivity of sliding bearing, and provides theoretical basis for design of bearing.

The formation and lubrication mechanism of boundary lubricating film were discussed. The boundary lubricating film includes adsorption film and chemical reaction film, and has respective temperature operating range. The adsorption film adsorbed in metal surface by Van-der Wads, and the parenchyma is the external friction between adsorption molecule layers. The chemical reaction film is made by the reaction between metal and extreme pressure additive in base oil, and the anti-wear capability is realized by the low-melting point eutectic alloy. The temperature is regarded as a judge criterion for failure of boundary lubrication. The failure model for boundary lubricating film is established. According to the failure model, the failure criterion proposed is effective by analysis of the spiral bevel gear using the finite element method. These results provide a basis for the application of boundary lubrication.

In order to improve design reliability of wind turbine, it is needed that calculating method of aerodynamic load during wind turbine run. In paper from the angle of the project, NACA special airfoil of wind turbine is analyzed. Combined with thin-theory, airfoil angle of attack variation is deduced, meanwhile wind turbine actual force is calculated in each blade location point when blade of wind turbine is running based on wind shear theory and tower shadow effect. According to actual condition calculation method is engineering amplified, aerodynamic load calculation method of wind turbine blade is obtained. By this method aerodynamic load which is calculated match with experiment result, it fits better.

Repairable system is complex, because of its diversity distribution form of units’ lives and its complex structure. In this paper we studied on a complex system. Lives and repairing time of units obey general distributions, we got the unit transient availability by using Markov renewal process, then got the system transient availability by using the character of coherent system. Finally gave example which verified by Monte Carlo method. This paper provided calculation base for more complex system.

In vertical milling process of Ti-6Al-4V titanium alloy thin-walled workpieces, chatter as a thorny problem occurs easily, which can lead to the instability of the machining process, tool wear, and poor surface finish. It has become a focus issue to identify and avoid chatter in machining process. In this paper, the milling force signals in the direction perpendicular to the machined surface were analyzed by fast Fourier transform and wavelet transform for detecting chatter. The combination of the surface topography and the prediction theory of regenerative chatter were put forward to further verify chatter. The results show that fast Fourier transform in some cases, wavelet transform, and the combination of surface topography and the prediction theory of regenerative chatter can obtain better results for the detection and verification of chatter, and the stable cutting zone was obtained using a stability lobe diagram, which can assist in the selection of reasonable cutting parameters to avoid chatter.

The adsorption isotherm, differential thermal gravimetry (DTG), thermal gravimetry (TG), diffusion and thermodynamic parameters of cyclopentane at various adsorption coverages have been investigated using microgravimetric technique over a range of temperature. The differences in equilibrium adsorption capacity and in diffusion coefficient at different temperature are discussed in terms of the characteristics of silicalite-1 and the features of cyclopentane molecule. The heat of sorption Qst varies significantly with sorption coverage indicating that the adsorption and diffusion mechanism is complex. The dependences of thermodynamic properties like free energy change (ΔG) and entropy change (ΔS) on sorption coverage show a sharp decrease and increase suggesting that the adsorption sites of the silicalite-1 are not energetically uniform to cyclopentane. Two desorption peaks in the DTG and TG curves suggest that two heterogenous binding sites surely exist in silicalite-1 to cyclopentane.

With the proliferation of massive explorations on Lunar Far-side Surface (LFS), deployments of scientific infrastructures have drawn substantial attention with the aids of relay satellites for the moon, i.e., China's "Queqiao", which allows real-time reporting for current status information from the landing equipment and space vehicles. Without suitable constellation with well-designed scheduling scheme, it would be very difficult to get timely information if depending only on single Halo relay satellite due to large coverage gap and limited energy budget for the communication links. In this paper, we design a hybrid circular-Halo orbital multi-relay constellation system for the LFS communication by minimizing the average per-device Age of Information (AoI) of users on the earth. In particular, we develop an age-optimal scheduling strategy with constellation design for accessing different relay satellite of constellation by solving a Constrained Markov Decision Process (CMDP) optimization problem to significantly reduce the average coverage gap in LFS area. Simulation results show that the average per-device AoI of the proposed scheduling algorithm with the well-designed constellation could achieve 16.20% less in time than that of single Halo satellite relay system compared with typical algorithms.

The random reliability analysis model for wear was established based on random process theory and wear research. The wear experiment scheme on load, sliding speed, surface hardness and bearing capacity of lubrication was instituted by the uniform design method, and carried out on a vertical universal friction/wear tester. The static wear predication model was established by the partial least squares based on test data. It is found that the wear extent obey to normal distribution by checkout of the probability paper and mathematic expectation function fitting and residuals distribution, the variance function fitting and residuals distribution based on the test data of random process. The reliability of definite working life was gained by calculating with established reliability model, and compared with test data, the analysis method is a valid method for wear reliability.

According to the standard GB/T13799-92 of People's Republic of China, the reliability design for the double circular-arc cylindrical gear transmission is completed by applying limit state theory. Weibull distribution is used to describe random factors in the design. A computer applied program is developed based on VC++ platform to achieve the computer-aided reliability design of circular-arc gear, and get the reliability information of the designed gear quickly and accurately.

Due to inadequate management of Vehicular Ad hoc Networks (VANETs), malicious nodes could participate in communications along with misbehavior, e.g., dropping packets and spreading fake information. Therefore, it is essential to detect misbehavior of internal attackers that will cause network performance degradation (e.g., taking longer time to receive messages or reaching destinations with detours). Apart from the capture of dynamic network topology of VANETs, the social relationship among nodes can also be applied as a relatively stable metric to qualify nodes. This paper proposes a misbehavior detection mechanism based on social relationships, from which nodes determine trust for the receiver or transmitter. Based on the proposed mechanism, road traffic control applications can avoid the interference from malicious nodes. The construction of social relationships depends on the geographic information reflected by the movement of nodes, including contact frequency and trajectory similarity, since the geographic information can accurately indicate the relevance among nodes. In addition to the social relationship, the proposed mechanism also evaluates the data trust from time and spatial factors to reduce the interference of fake data. Finally, the proposed mechanism integrates data trust and social relationships to enable misbehavior detection decisions. Extensive results of simulations show that the proposed mechanism has outstanding malicious nodes detection rates under various proportions of malicious nodes and movement patterns.

A novel decentralized routing algorithm for air-ground integrated networks is proposed in this paper. Different from existing air-ground integrated network schemes focusing on ground or satellite, this scheme proposed an associated mechanism that satellite and ground nodes are treated equally. Self-organizing routing guarantees the autonomy and flexibility of routing operation. Simulation results show that the proposed scheme can provide the global-coverage network service to satisfy quality of service.

The implementation of the Session Initiation Protocol (SIP)-based Voice over Internet Protocol (VoIP) and multimedia over MANET is still a challenging issue. Many routing factors affect the performance of SIP signaling and the voice Quality of Service (QoS). Node mobility in MANET causes dynamic changes to route calculations, topology, hop numbers, and the connectivity status between the correspondent nodes. SIP-based VoIP depends on the caller’s registration, call initiation, and call termination processes. Therefore, the SIP signaling performance has an important role for the overall QoS of SIP-based VoIP applications for both IPv4 and IPv6 MANET. Different methods have been proposed to evaluate and benchmark the performance of the SIP signaling system. However, the efficiency of these methods vary and depend on the identified performance metrics and the implementation platforms. This survey examines the implementation of the SIP signaling system for VoIP applications over MANET and highlights the available performance enhancement methods.

It becomes more and more important to integrate satellites with transparent or on-board switching payload into future Global Broadband Network Infrastructure. This paper presents an overview of the important issues and the recent development of satellite systems for broadband communications. Particularly, it discusses the architecture and performance of broadband network interconnection and terminal access using ATM over satellite. It covers a range of topics including: the major issues on the role of satellites in broadband networks, satellite system structure and architecture with transparent and on-board switching payload, management and control over satellite, performance and Quality of Service (QoS) of ATM and IP over satellites, bandwidth resource management, future satellite systems and convergence of ATM and Internet.

Multicast research has explored the security challenges faced in group communications. Multicast transport and multicast security need to work in close collaboration to realise a multicast service. However, there has been comparatively little work to combine the two technologies. In this paper the authors is presenting an example of partially integrating Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol and the File Delivery over Unidirectional Transport (FLUTE) protocol. The security concern raised by the proposed algorithm is analysed for satellite network. The proposed algorithm was implemented on a testbed with multicast tunnel between University of Surrey and University of Aberdeen and the results are presented in this paper.

As each type of satellite network has different link features, its data transmission must be designed based on its link features to improve the efficiency of data transferring. The transmission of navigation integrated services information (NISI) in a global navigation satellite system (GNSS) with inter-satellite links (ISLs) is studied by taking the real situation of inter-satellite communication links into account. An on-demand computing and buffering centralized route strategy is proposed based on dynamic grouping and the topology evolution law of the GNSS network within which the satellite nodes are operated in the manner of dynamic grouping. Dynamic grouping is based on satellites spatial relationships and the group role of the satellite node changes by turns due to its spatial relationships. The route strategy provides significant advantages of high efficiency, low complexity, and flexible configuration, by which the established GNSS can possess the features and capabilities of feasible deployment, efficient transmission, convenient management, structural invulnerability and flexible expansion.

Internet over satellites has been a hot research topic for some times. In addition to the development of the Internet applications and services over satellite, there are also significant developments in satellite communication systems and networks with Ka band and high throughput satellites (HTS). These developments enhance greatly the role of satellite in the global Internet infrastructure to allow the satellite to support broadband Internet and services beyond coverage of terrestrial networks, such as air, sea and space an addition to the land with most of the populations.

Broadband satellite will play an important role to provide universal broadband access for the users. In order to lower the cost, the next-generation satellite systems should support IPv6 and seamlessly integrate with terrestrial networks, including wireless local loops. In this paper, a novel network architecture has been proposed as a potential solution to the above problem. Based on the proposed overall network and functional architecture, we have emphasised and presented different aspects of the advanced IPv6-enable networking techniques, such as QoS, multicast, security and mobility. The transport protocols can be used in this network architecture are also studied. © 2007 by SATSIX.

The implementation of SIP signaling over MANET is still a challenging issue, as many routing factors affect SIP performance. Node mobility and dynamic hop number changes between nodes are considered the main routing problems within MANET routing protocols. RFC 6076 proposed end-to-end performance metrics for SIP signaling to provide a standardized method of evaluating SIP performance over different platforms, however, no benchmarking values for these metrics have been proposed yet. In this paper, a cross-layer system designed to enhance the call setup performance of SIP-based VoIP over AODV-based MANET is proposed. The approach used is to employ the SIP performance metric to enhance the call setup time by adjusting the Time-To-Live (TTL) parameter and the Route Request (RREQ) message retries for the AODV route request messages to support the reach ability ratio of SIP INVITE and re-INVITE messages to reduce the call setup time of SIP-based VoIP. The study investigated the Session Request Delay performance metric of SIP signaling as part of the SIP over MANET simulation efforts. Both the call setup time and the number of SIP calls over random waypoint mobility models were enhanced by applying instantaneous modifications to the TTL parameter and RREQ retries, increasing the delivery ratio of route discovery messages to about 35-40% compared with the classic AODV routing protocol.

In this paper, we propose a multihop broadcast protocol for dissemination of time-critical emergency messages (EMs) in vehicular ad hoc networks (VANETs), where the IEEE 802.11p technology is used for communication among the nodes. The proposed trinary partitioned black-burst-based broadcast protocol (3P3B) consists of two primary mechanisms. First, a mini distributed interframe space (DIFS) in a medium access control (MAC) sublayer is introduced to give the time-critical EMs a higher access priority to the communication channel compared with other messages. Second, a trinary partitioning is designed to iteratively partition the communication range into small sectors. The trinary partitioning mechanism allows the farthest possible vehicle in the farthest sector from the sender node to perform forwarding to increase the dissemination speed by reducing the number of forwarding hops. In addition, 3P3B reduces the contention period jitter, which is independent of the density of vehicles, resulting in a more stable contention period. Analytical models are proposed for performance evaluation in conjunction with simulation-based performance analysis. The results demonstrate that 3P3B outperforms benchmarks of the existing broadcast protocols in VANETs in terms of the average message dissemination speed, message progress, communication delay, and packet delivery ratio.

Delay Tolerant Network suffers from lack of resources and disconnected contact nature. In DTN, all possible methods are used to transmit data including the physical transportations means. Aircrafts in commercial routes have been proposed to carry data from ground users along their flying routes. Delivery probability is compared when using aircrafts, buses and ferries. Results show that aircrafts provide higher delivery probability which is up to 62% better compared with buses and ferries. Furthermore, when there is lack of resources, it is difficult to satisfy all users’ demands for traffic. We propose a Fairness and Satisfaction (FS) model to enhance the users’ satisfaction during DTN limited and scarce resources. Various scenarios are tested for the FS model through intense simulations. FS model, when implemented, will improve user’s satisfaction up to 18 % and DTN fairness up to 20 % compared with the same scenario lacking the model.

Advance in digital signal processing and telecommunication technologies has lead to the development of ATM and B-ISDN. Satellite communications systems can play an important role in the development of the initial experimental systems and also in the fully developed networks due to their features of flexible wide coverage, independent of ground distances and geographical constrains, multiple access and multipoint broadcast. This paper presents an implementation structure of ATM via satellite and its capabilities of supporting B-ISDN based on a demonstration system developed within the RACE CATALYST project.

This paper proposes a novel Demand Sensitive Model (DSM) for tuning price service over SDMB (Satellite Digital Multimedia Broadcast) system offering a price discount to large amount of users while maintaining profit for the service provider. The discounted price is determined based on a marginal decision rule using a simple pseudo-linear function of the weight factor and the number of users. For testing the proposed model, an integrated satelliteterrestrial network architecture offering SDMB services to mobile users through the satellite or terrestrial UMTS segment, has been utilized. Simulations have been carried out to show the goodness of the proposed model within the system architecture; moreover the model, based on simple parameters, is very flexible and can be easily integrated in a "Price Adapter" module making the offered service attractive for end users and in the same time profitable for the satellite operator. © 2007 IEEE.

Wireless Sensor Network (WSN) is one of the major research areas in computer network field today. The function of WSN in this paper is to provide sensing services in an un-attended harsh environment. Sensed data need to be delivered to the base station and to cope with the network unreliability problem. Few routing protocol takes into consideration of this problem. It is a great challenge of the hierarchical routing protocol to provide network survivability through redundancy features. In this paper, a short literature review of the existing routing protocol is carried out. Then a novel hierarchical routing protocol, which addresses network survivability and redundancy issues, is introduced. Initial analysis shows promising results of the proposed protocol comparing with LEACH, which is a well known protocol as benchmark. Finally, conclusion was drawn based on the research and future direction for further research is identified.

Significant research and development have been carried out recently in Voice over IP (VoIP) to integrate Internet data services and telephony services based on Public Switched Telephone Network (PSTN). Satellites have been used for many years to provide long distance telephone services and have today an increasing portion of their capacities used to carry IP packets for Internet services. Therefore, convergence of voice and data is happening not only in terrestrial communication links, but also in satellite networks. With their global coverage and reach to remote areas, satellites are well positioned to enable growth of VoIP services. In addition to telephone and Internet services, satellite can also be used for multimedia conference services due to the broadcasting capability. This paper presents the studies of these topics as results of the VIP-TEN project on IP telephony and the ICEBERGS projects on multimedia conference over satellite. © 2002 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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Cloud computing emerges as new computing paradigms in which virtualized resources provide reliable and guarantee service for users demand. Actually, cloud is a service-oriented platform because all kind of virtual resources are treated as service to users. Nowadays, most of data-intensive applications have been developed on cloud system. These applications reaches geographically separated storage or data resource with even cross-continental-networks. Then, the performance degradation of networks will surely affect the cloud application performance and user request. In order to ensure guarantee service of bulk data transfer in cloud computing, the reservation and combined resources utilization become critical issues which include data and network resources. This issue involves reserve and assign combined resources to meet user's QoS requirement. According to this problem, a cloud infrastructure service framework (CISF) is proposed to achieve guarantee service for data-intensive applications in this paper. And a service-oriented resource broker (SRB) based on this framework which is proposed to discovery, select, reserve and assign best combined resources. Finally, under user's QoS constraint dynamic resource selection algorithm has been implemented for optimization of combined resources allocation.

Considering that delay/disruption-tolerant networks (DTNs) suffer from a large variation of network topology, geographic routing is an alternative scheme that utilizes real-time geographic information instead of network topology information. However, the real-time geographic information of mobile destination is likely unavailable due to sparse network density. With this in mind, we propose a geographic routing scheme by relying on historical geographic information to estimate the movement range of destination. The idea is to make efficient message replication toward this estimated range via the proposed Approach Phase to reduce routing overhead. Meanwhile, the effective message replication within this range is guaranteed via the proposed Roam Phase to increase the message delivery ratio. We further propose a novel scheme to handle the local maximum problem for geographic routing in sparse networks. Simulation results obtained assuming the maps of three real world cities, namely, Helsinki, Finland; Karlsruhe, Germany; and Manhattan, New York City, USA, show an advantage of the proposed Approach-and-Roam (AaR) over the compared algorithms in terms of delivery ratio, average delivery latency, and overhead ratio.

The popularity of MANET based applications is on the rise by the day and this includes the use of multimedia application over MANETs. The existing routing protocols provide best effort service, but do not provide any guarantee of Quality of Service (QoS) provisioning. Admission control based approach is desirable and plays a vital role in maintaining QoS for MANET-based applications. In this paper, we present a novel Flow-Aware Admission Control (FAAC) protocol that will maintain guaranteed throughput to the applications requiring QoS. FAAC protocol is designed to utilize the caching mechanism of the Dynamic Source Routing (DSR) protocol. It will be implemented in two stages: the first stage is searching the cache for untested paths from source to destinations and initiating the route search before checking the nodes resources. The second stage will include checking of local and carrier sensing neighbors' resources. The protocol is implemented using C++ within NS-2 simulation environment and validated to check the effect of newly admitting traffic over admitted data traffic. The newly arrival traffic was blocked when there is no enough network resources to support the existing and newly arrival traffic. © 2011 IADIS.

This paper describes the architecture of a proposed multiparty conferencing system for satellites. Different conferencing models are discussed and compared. A session initiation protocol (SIP)-based conference signaling model and an extension to protocol-independent multicast sparse mode that supports quality-of-service (QoS) in DiffServ networks are proposed, as particularly suitable for multiparty conferencing applications over satellite links. The paper also presents key issues and potential solutions of scalable QoS multicast services for multiparty conferences over satellite. End-to-end QoS parameters for voice and video are measured and analyzed on a prototype.

Aircrafts in commercial routes have been proposed in some previous work as a novel DTN bundle carriers [1]. Satellites can be one of the hops in this application. DTN suffers from intermittent disconnections, long delays and has scarce resources. It is a challenge to control the admission to these resources to provide better QoS and ensure optimum resource utilisation. Furthermore, providing fairness to different users who compete to access limited and scarce resources makes the solution even harder. In this paper, we propose a fair novel admission control model for DTN aircrafts applications based on feedback history logging of past admissions. This model will locally estimate the resources and provide fair admissions for users within a group of users in the same area. We will show an analysis of aircrafts fair admission control design for both aircraft initiated and user initiated approaches, which will provide integrated service per flow basis. The paper also presents the initial simulation model using a modified version of DTN2 emulator and DTNperf_2 performance monitoring tool.

Public-key infrastructure (PKI) is based on public-key certificates and is the most widely used mechanism for trust and key management. However, standard PKI validation and revocation mechanisms are considered major reasons for its unsuitability for delay/disruption tolerant networking (DTN). DTN requires mechanism to authenticate messages at each node before forwarding it in the network. So, certificate revocation lists (CRLs) being distributed in DTN network will need to be authenticated and validated for issuer certificate authority (CA) at each node. In this study, the authors propose new validation and revocation mechanism which is compliant with DTN semantics and protocols. This study also proposes a new design for CRL in compliance with standard PKI X.509 standard to make the proposed mechanism easy to implement for DTN. The new designed CRL is of reduced size as it contains fewer entries as compared with standard X.509 CRL and also arranges the revocation list in the form of hash table (map) to increase the searching efficiency.

While TV broadcasting is probably the best known application of satellite technology, satellite service providers are now expanding their services to include Internet data transmission. Consequently, security of satellite data is becoming an important issue. This article examines the current DVB-RCS security standard and identifies the principal gaps in the provision of secure multicast over DVB-RCS. The main contribution of this article is a proposal for adapting the current DVB-RCS two-way satellite standard to provide secure multicast services over satellites.

Location-based Services (LBS) have become a very important area for research with the rapid development of Internet of Things (IoT) technology and the ubiquitous use of smartphones and social networks in our daily lives. Although users can enjoy a lot of flexibility and conveniences from the LBS with IoT, they may also lose their privacy. Untrusted or malicious LBS servers with all users’ information can track users in various ways or release personal data to third parties. In this work, we first analyze the current dummy-location selection (DLS) algorithm—an efficient location privacy preservation approach and design an attack algorithm for DLS (ADLS) for test emerging IoT security. For efficiently preserving user’s location privacy, we propose a novel dummy location privacy-preserving (DLP) algorithm by considering both computational costs and various privacy requirements of different users. Extensive simulation experiments have been carried out to evaluate the efficiency of the proposed schemes. Evaluation results show that the ADLS algorithm has a high probability of identifying the user’s real location out from chosen dummy locations in the DLS algorithm. Our proposed DLP algorithm has clear advantages over the DLS algorithm in term of lower probability of revealing the user’s real location and improved computational cost and efficiency (i.e., time, speed, accuracy, and complexity) while preserve the same privacy level as DLS algorithm.

Optimizing server’s power consumption in content distribution infrastructure has attracted increasing research efforts. The technical challenge is the tradeoff between server power consumption and the content service capability on both the server and the network side. This paper proposes and evaluates a novel approach that optimizes content servers’ power consumptions in large-scale content distribution platforms across multiple ISP domains. Specifically, our approach strategically puts servers to sleep mode without violating load capacities of virtual content delivery links and active servers in the infrastructure. Such a problem can be formulated into a nonlinear programming model. The efficiency of our approach is evaluated in a content distribution topology covering two real interconnected domains. The simulation has shown that our approach is capable of reducing servers’ power consumptions by up to 62.2%, while maintaining the actual service performance in an acceptable scope.

The internetwork system between Future IP Networks and ZigBee Wireless Networks has two main approaches; the SIP Proxy Based approach, and the ZigBee Stack Based approach. Because of the dynamic nature of the ZigBee devices, both approaches need to be improved to support the connectivity system and the Quality of Service (QoS) for different types of sensing and actuating applications. This paper proposes an initial design for a modified version of SIP (Mod-SIP) for ZigBee Stack Based approach. In addition, the paper introduces the Combined Approach which is an enhanced internetwork system used to provide more reliable and flexible connectivity system between ZigBee WPANs, and the IP clouds. An initial design and simulation efforts on OPNET implemented to study the current approaches and compare it with the proposed approaches. It shows that the SIP Proxy Based approach is not efficient for Future IP Networks applications as it has a high rate of End-to-End delays because of the lack of flexibility between SIP signaling system and the ZigBee WPANs. The initial investigations shown that the Combined approach can provide more reliable connectivity system with the support for the QoS for different types of instantaneous applications such as VoIP and video conferencing. © 2012 IEEE.

Low-Earth-Orbit satellite access network (LEO-SAN) can realize real-time and three-dimensional broadband access on the earth anywhere and any time. It has become a major development trend of satellite Internet and mobile communication networks, and has attracted more attention and research from academia and industry. LEO satellites can achieve global coverage through giant constellations. Compared with medium- and high-orbit satellites, LEO satellites have larger communication bandwidth and shorter communication delay, and they are becoming an integrated part of future 6G mobile communication networks. Many countries in the world have planned for LEO satellite constellations and spectrum allocation to support the process of implementation. Differing from traditional terrestrial access networks, LEO-SAN faces many challenges including high-speed mobility of space base stations and highly limited communication and computing resources. LEO satellite constellations are in large scales, where the costs of network management, maintenance, and control increase rapidly. In addition, the high-speed movement of LEO satellites makes the network topology change rapidly, which causes frequent handover for user terminals. Moreover, the beam overlaps between satellites changes with time, resulting in potential interference. In response to the these challenges, researchers have carried out research in the areas including network architecture, beam coverage, resource management, etc. However, the research on LEO-SAN is still in its early stage, and more research is needed for development of comprehensive and systematic theoretical methods and technical standards.

Taking advantage of spontaneous and infrastructure⁃less behaviour, a mobile ad hoc network (MANET) can be integrated with various networks to extend communication for different types of network services. In the integrated system, to provide interconnection between different networks and provide data aggregation, the design of the gateway is vital. In some integrated networks with multiple gateways, proper gateway selection guarantees desirable QoS and optimization of network resource utilization. However, how to select gateway efficiently is still challenging in the integrated MANET systems with distributed behaviour terminals and limited network resources. In this paper, we examine gateway selection problem from different aspects including information discovery behaviour, selection criteria and decision-making entity. The benefits and drawbacks for each method are illustrated and compared. Based on the discussion, points of considerations are highlighted for future studies.

Public Key Infrastructure (PKI) is based on public key certificates and is the most widely used mechanism for trust and key management. However, standard PKI Validation and Revocation mechanisms are considered major reasons for its unsuitability for Delay/Disruption Tolerant Networking (DTN). DTN requires mechanism to authenticate messages at each node before forwarding it in the network. So, Certificate Revocation Lists (CRLs) being distributed in DTN network will need to be authenticated and validated for issuer CA at each node. In this paper we propose new Validation and Revocation mechanism which is compliant with DTN semantics and protocols. The paper also proposes a new design for CRL in compliance with standard PKI X.509 standard to make the proposed mechanism easy to implement for DTN. The new designed CRL is of reduced size as it contains fewer entries as compared to standard X.509 CRL and also arranges the revocation list in the form of Hash Table (Map) to increase the searching efficiency.

Data center has been working as a cost-efficient infrastructure to store a large amount of data and host service applications. With the virtualization technology, a resource request submitted to data center can be abstracted as a virtual data center (VDC) request which consist of virtual machines (VMs) connected through virtual switches, routers and links with guaranteed bandwidth. As one of the challenges, VDC embedding/provisioning focuses on mapping VDC components onto physical nodes and links in data center. In this paper we study the problem of provisioning/embedding for evolving/dynamic VDC request across federated data centers, such that the total operation cost is minimized. We use the VM migration to reconfigure evolving/dynamic VDC for reducing the total operation cost, as well to consolidate the VDCs on as few servers as possible for reducing the number of active servers and thus lowering energy consumption. We design an efficient framework and algorithm for solving the studied NP-Hard problem. Finally, we evaluate and compare the performance of our proposed approach through extensive simulation experiments. The simulation results show that the proposed approach performs better in terms of lowering total operation cost and energy consumption than existing solution does.

Telecommunications networks have migrated from circuit based telephony services to packet based broadband network services. Merging with computer networks, they are being integrated with non-real-time data services on classical Internet integrated multimedia services, including real time voice, video and services on the new generation Internet. Thus, the concepts and requirements of quality of service (QoS) and traffic modelling have also been changed significantly. However, real time services such as voice and video are inelastic, as the transmission bandwidth, transmission time and QoS requirements need to be kept within strict limits and hence are not flexible. On the other hand, elastic services such as file transfer and Web surf are much relaxed with QoS and network resource requirements. Networks need to meet the requirements of both types of services by providing different classes of network services, including best effort service at one end of the spectrum, guaranteed service on the other end, and some others in between, with controlled traffic load. Traffic modelling is one of the important aspects to be considered to meet QoS requirements of services and efficient utilisation of network resources. The paper discusses important QoS issues, techniques for measurement and analysing Internet traffic, and new trends and methodology for Internet traffic modelling. It also presents the results based on the measured Internet traffic to validate the new model and the potential of the model to capture the characteristics of traffic for the Internet.

Secure multicast communication is important for applications such as pay-per-view distribution. LKH has been proposed to distribute a shared secret key in a way that scales efficiently for groups with many members. However, the efficiency of LKH depends critically on whether the key tree remains balanced. For applications such as video streaming or online teaching, several multicast sessions might be related in one way or another. in this paper, we consider the balance of the key tree and treat related multicast sessions as a whole. Our approach shows significant improvement over traditional method and trades off additional rekeying costs for similar computation power at members'. side compared to existing related approach. Two optimisations are also proposed to further enhance the efficiency of our algorithm.

Description This book provides up to date coverage of the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks Satellite Networking: Principles and Protocols, Second Edition provides up to date information of the original topics in satellite networking and protocols focusing on Internet Protocols (IP) over satellites, broadband over satellites, next generation IP (IPv6) over satellites, new generation of DVB-S/S2 and DVB-RCS next generations and new services and applications. It also includes some analytical techniques for evaluation of end to end IP performance and QoS over satellite, reflecting the recent convergence of telecommunication, Internet, broadcasting and mobile networks. Topics new to this edition: Internetworking with MANET, DVB-S/S2 and DVB-RCS/RCS2 (including TCP/IP over DVB-S/RCS), recent developments in broadband satellite systems, convergence of services and network technologies (including Internet, telecom, mobile, TV, etc.), radio resource management, PEP, I-PEP, SCPS, traffic modelling and engineering with analysis and examples, and future developments of satellite networking. • Provides up to date coverage of the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks (e.g. mobile ad hoc networks), including coverage of new services and applications (e.g. Internet, telecom, mobile and TV) •Discusses the real-time protocols including RTP, RTCP and SIP for real-time applications such as VoIP and MMC, and explains TCP/IP over satellite and evolution of IPv6 over satellite and beyond

In order to make Web services operate in a performance optimal status, it is necessary to make an effective decision on selecting the most suitable service provider among a set Web services that provide identical functions. We argue that the network performance between the service container and service consumer can pose a significant influence to the performance of Web service that the consumer actually receive, while current researches have limited emphasis on this issue. In this paper, we propose a cross-layer approach for Web service selection which takes the network performance issue into consideration during the service selection process. A discrete representation of cross-layer performance correlation is proposed. Based on which, a qualitative reasoning method is introduced to predict the performance at the service user side. The integration of the quality driven Web service selection method to Service Oriented Architecture is also considered. Simulation is designed and experiment results suggest that the new approach significantly improves the accuracy of Web service selection and delivers a performance elevation for Web services. ©2008 IEEE.

Reducing energy consumption in the Telecom industry has become a major research challenge to the Internet community. Towards this end, numerous research works have been carried out to mitigate the growth of energy consumption through intelligent network control mechanisms. This paper proposes a novel approach to achieving energy efficiency in ISP backbone networks according to dynamic traffic conditions. The main objective is to enforce as many links as possible to go to sleep during the off-peak time, while in event of traffic volume increase, the minimum number of sleeping links should be required to wake up to handle this dynamicity and in a way that this creates minimal or no traffic disruption. Based on our simulations with the GEANT and Abilene network topologies and their traffic traces respectively, up to 47% and 44% energy gains can be achieved without any obstruction to the network performance. Secondly, we show that the activation of a small number of sleeping links is still sufficient to cope with any traffic surge instead of reverting to the full topology or sacrificing energy savings as seen in some research proposals.

In this paper, we present an end-to-end QoS simulation studies on internetworking of remote LAN and long range communications over LEO-Iridium satellites constellation taking SuperJARING network in Malaysia as an example. A macro level network simulation scenario based on actual network topology in Malaysia is implemented as Diffserv network model using the network simulator-2 (NS-2). Web traffic (HTTP) is used as the internet traffic models in the simulation analysis. All simulations are carried out in error-free and link-loss environment. In error-free simulations, the accumulative network traffic loads are varied from 20%, 50% and 80% while in linkloss environment simulations only 20% traffic load is used with bit error rate (BER) varied from 1x10-5, 1x10-4 and 2x10-4. We compare the empirical TCP throughput traces with analytical model for validation. The results show clearly that QoS can be achieved with IP Diffserv over satellites constellation like Iridium.

IoT emergence has given rise to a new digital experience of payment transactions where physical objects like refrigerators, cars, and wearables will make payments. These physical objects will be storing the cardholder credentials and will directly make payments with the vendors over insecure public networks. For such payment transactions, government regulations and standards organizations require to implement PCI DSS for adapting similar set of security measures at the global level. The current version of PCI DSS is not suitable for IoT-based payment systems due to characteristics of IoT such as resource-constrained nature of devices and updating software/firmware of so many physical devices. Also, there arises an emergent need of implementing PCI DSS requirements and assessments for security of all stakeholders that store or process the user credentials in a payment. This paper is an initial effort to bring the researcher's attention to make upcoming versions of PCI DSS suitable for IoT and thus securing the new ways of IoT-based payment systems. The paper has reviewed the traditional payment process along with considerations for IoT-based payment systems to make recommendations to modify the PCI DSS in a suitable way for IoT.

Whilst TV broadcasting is probably the best-known application of satellite technology, satellite service providers are now expanding their services to include Internet data transmission. Consequently, security of satellite data is becoming an important issue. This article examines the current DVB-RCS security standard and identifies the principal gaps in the provision of secure multicast over DVB-RCS. The main contribution of this article is a proposal for adapting the current DVB-RCS two-way satellite standard to provide secure multicast services over satellites.

Previous geographic routing schemes in Delay/Disruption Tolerant Networks (DTNs) only consider the homogeneous scenario where nodal mobility is identical. Motivated by this gap, we turn to design a DTN based geographic routing scheme in heterogeneous scenario. Systematically, our target is achieved via two steps: 1) We first propose “The-BestGeographic-Relay (TBGR)” routing scheme to relay messages via a limited number of copies, under the homogeneous scenario. We further overcome the local maximum problem of TBGR given a sparse network density, different from those efforts in dense networks like clustered Wireless Sensor Networks (WSNs). 2) We next extend TBGR for heterogeneous scenario, and propose “TheBest-Heterogeneity-Geographic-Relay (TBHGR)” routing scheme considering individual nodal visiting preference (referred to nonidentical nodal mobility). Extensive results under a realistic heterogeneous scenario show the advantage of TBHGR over literature works in terms of reliable message delivery, while with low routing overhead.

Aiming to provide low-cost universal broadband access, this paper describes the strategy that supports the integration of hybrid satellite and WiMAX, based on the network architecture proposed in the IST Satsix project. In this context, WiMAX networks can be used as wireless local loops integrated with a satellite network, lowering the cost of the broadband internet connections and providing a universal access to rural and marine areas. The paper presents the problems concerning the interworking between DVB-RCS and WiMAX technologies and the solutions adopted in the SatSix research project, partially funded by European Commission within the Information Society Technologies (IST) 6th Framework Programme. © Springer 2008.

The concept of Delay Tolerant Networks (DTNs) has been utilized for wireless sensor networks, mobile ad hoc networks, interplanetary networks, pocket switched networks and suburb networks for developing region. Because of these application prospects, DTNs have received attention from academic community. Whereas only a few state of the art routing algorithms in DTNs address the problem of aborted messages due to the insufficient encounter duration. In order to reduce these aborted messages, we propose a routing framework which consists of two optional routing functions. Specifically, only one of them is activated according to the encounter angle between pairwise nodes. Besides, the copies of the undelivered message carried by most of the nodes in the network are more likely to be cleared out after successful transfer, which reduces the number of unnecessary transmissions for message delivery. By means of the priority for message transmission and deletion in case of the limited network resource, the proposed algorithm achieves the high delivery ratio with low overhead as well as less number of aborted messages due to the insufficient encounter duration, thus is more energy efficient.

This paper proposes an e-diagnosis system based on machine learning (ML) algorithms to be implemented on the Internet of Medical Things (IoMT) environment, particularly for diagnosing diabetes mellitus (type 2 diabetes). However, the ML applications tend to be mistrusted because of their inability to show the internal decision-making process, resulting in slow uptake by end-users within certain healthcare sectors. This research delineates the use of three interpretable supervised ML models: Naive Bayes classifier, random forest classifier, and J48 decision tree models to be trained and tested using the Pima Indians diabetes dataset in R programming language. The performance of each algorithm is analyzed to determine the one with the best accuracy, precision, sensitivity, and specificity. An assessment of the decision process is also made to improve the model. It can be concluded that a Naive Bayes model works well with a more fine-tuned selection of features for binary classification, while random forest works better with more features.

In this paper an integrated satellite-terrestrial network architecture offering SDMB (Satellite Digital Multimedia Broadcast) services to mobile users through the satellite or terrestrial UNITS segment, is studied to test a novel Demand Sensitive Model (DSM). The DSM is proposed for tuning price service over SDMB system to offer a price discount to large amount of users while maintaining profit for the service provider. The simulations have been carried out to show the goodness of the proposed model within the system architecture; moreover the model, based on simple parameters, is very flexible and can be easily integrated in a "Price Adapter" module making the offered service attractive for end users and in the same time profitable for the satellite operator.

In the field of reinforcement learning, we propose a Correct Proximal Policy Optimization (CPPO) algorithm based on the modified penalty factor and relative entropy in order to solve the robustness and stationarity of traditional algorithms. Firstly, In the process of reinforcement learning, this paper establishes a strategy evaluation mechanism through the policy distribution function. Secondly, the state space function is quantified by introducing entropy, whereby the approximation policy is used to approximate the real policy distribution, and the kernel function estimation and calculation of relative entropy is used to fit the reward function based on complex problem. Finally, through the comparative analysis on the classic test cases, we demonstrated that our proposed algorithm is effective, has a faster convergence speed and better performance than the traditional PPO algorithm, and the measure of the relative entropy can show the differences. In addition, it can more efficiently use the information of complex environment to learn policies. At the same time, not only can our paper explain the rationality of the policy distribution theory, the proposed framework can also balance between iteration steps, computational complexity and convergence speed, and we also introduced an effective measure of performance using the relative entropy concept.

The satellite network does not have the IP layer where the IPsec [2][3] is designed for. Therefore, a new algorithm is needed to secure the satellite link at link layer or physical layer. This paper will give a short analysis on the advantages and disadvantages of the MPEG-2 TS encryption and present an approach trying to use the extension header of Unidirectional Lightweight Encapsulation (ULE) [6] Protocol Data Unit (PDU) to provide the efficient security solution for satellite networks. This approach is just above the MPEG-2 TS layer and makes the link security as a part of the encapsulation layer. Thanks to a test bed platform named PLATINE developed by France partners and contributed by other partners within the SATSIX project on which the DVB-S and DVB-RCS have been implemented. The Unidirectional Lightweight Encapsulation (ULE) [6] mechanism working together with MPEG 2 Transport Stream (TS) as a part of the encapsulation in PLATINE is for the transport of IPv6 (& IPv4) Datagrams and other network protocol packets directly over the ISO MPEG-2 Transport Stream as TS Private Data. The proposed security approach is implemented within PLATINE to provide integrated security with ULE protocol at the link layer. The approach is based on the security requirements Internet draft [1]

This paper presents studies for the end-to-end QoS of IP over integrated terrestrial and Next Generation Satellite Network (NGSN) using FTP. We compare between LEO and GEO satellites constellations for the QoS parameters (i.e. delay, jitter, loss rate and throughput) of file transfer from a remote server in London and a remote client in Boston. We model the file transfer with multiple connections and file size variation according to Exponential and Pareto distributions respectively. We create the scenario with error model to simulate transmission loss environment using the NS-2 simulation software. A Differentiated Services (Diffserv) queue interface is placed in the server side to regulate the traffic flows across the narrow bandwidth of the satellite links. The results showed the performance evaluation and presented a good comparison of the QoS parameters involved in the data transfer across LEO and GEO satellites systems.

This paper presents a novel scheduling algorithm to support quality of service (QoS) for multiservice applications over integrated satellite and terrestrial networks using admission control system with multipath selection capabilities. The algorithm exploits the multipath routing paradigm over LEO and GEO satellites constellation in order to achieve optimum end-to-end QoS of the client-server Internet architecture for HTTP web service, file transfer, video streaming and VoIP applications. The proposed multipath scheduler over the satellite networks advocates load balancing technique based on optimum time-bandwidth in order to accommodate the burst of application traffics. The method tries to balance the bandwidth load and queue length on each link over satellite in order to fulfil the optimum QoS level for each traffic type. Each connection of a traffic type will be routed over a link with the least bandwidth load and queue length at current time in order to avoid congestion state. The multipath routing scheduling decision is based on per connection granularity so that packet reordering at the receiver side could be avoided. The performance evaluation of IP over satellites has been carried out using multiple connections, different file sizes and bit-error-rate (BER) variations to measure the packet delay, loss ratio and throughput.

© 2015 IEEE.Wireless sensor networks usually have a massive number of randomly deployed sensor nodes that perform sensing and transmitting data to a base station. This can be a cause of sensor redundancy and data duplication. Sensor scheduling is a solution to reducing the enormous amount of the data load by selecting certain potential sensors to perform the tasks. Meanwhile, the quality of connectivity and coverage is also assured. This paper proposes a sensor scheduling method, called 4-Sqr, which uses a virtual square partition that is composed of consecutive square cells. Based on coordinates upon a monitored area, sensors learn their position on the virtual partition themselves; these are divided into groups of target areas, depending on the sensors' geographical locations. They are then ready for the node selection phase. In order to distribute energy consumption equally, the sensors with the highest residual energy within the same group usually have more chance of being active than the others. Compared to other existing methods, the proposed method is outstanding in many aspects such as the quality of connected coverage, the chance of being selected and the network's lifetime.

It is believed that the deployments of Wireless Sensor Network (WSN) have great long-term economic potential, ability to transform our lives, and pose many new system-building challenges. A typical application domain of WSN is by placing a vast number of multifunctional sensor nodes over a field to sense and collect surrounding environment data. Beside energy conservation concerns, another major challenge for its real deployments is its reliability issue, more precisely the sensing resolution (this being the main service quality we addressed in this paper). In many cases, redundancy of sensors is being made to provide higher sensing resolution when single sensing device is with lower ability. Certain coverage of sensors is required in order to guarantee the sensing data with acceptable degree-of-truth. However, since sensor nodes are mostly powered by batteries and required to remain in inactive state for the longest possible time duration due to save energy. Balancing the trade-off between energyefficiency and sensing quality is a rich area because sensor deaths and sensor replenishments make it difficult to specify the optimum number of sensors that should be activated and sending information at any given time. Through literature survey, we discover that current solutions toward this problem fell into some limitations in configurations or deployments. In this paper, we present a concept for improving the overall performance of the WSNs through local collaborations of neighbour nodes, and provide a more efficient duty-cycle management solution. A framework for distributed duty-cycle management is given, and a control algorithm is generated from the framework. Simulation shows that the new method does work in WSN environments, and gives good results.

Real-time interactive multimedia multiparty communication is becoming a vital part of modern Internet services. As one of its applications, online gaming attracts a huge group of fans playing over the Internet. It has new requirements for relative QoS. This article gives a brief introduction to these new QoS requirements, and then presents an algorithm to satisfy these requirements in the differentiated services network for client-server-topology-based online gaming services. Our simulation results show that this algorithm can provide optimized relative QoS support for online gaming as an example of multiparty communications.

A mobile ad hoc network (MANET) is a self-configuring infrastructure-less network. Taking advantage of spontaneous and infrastructure-less behavior, MANET can be integrated with satellite network to provide world-wide communication for emergency and disaster relieve services and can also be integrated with cellular network for mobile data offloading. To achieve different purposes, different architecture of integrated system, protocols and mechanisms are designed. For emergency services, ubiquitous and robust communications are of paramount importance. For mobile data offloading services, emphasis is amount of offloaded data, limited storage and energy of mobile devices. It is important to study the common features and distinguish of the architecture and service considerations for further research in the two integrated systems. In this paper, we study common issues and distinguish between two systems in terms of routing protocol, QoS provision, energy efficiency, privacy protection and resource management. The future research can benefit from taking advantage of the similarity of two systems and address the relevant issues.

Satellite-based Universal Mobile Telecommunications System (S-UMTS) is used to provide all kinds of Transmission Control Protocol/ Internet Protocol (TCP/IP) based Internet services for global end users. However, due to the high propagation delay and high bit error rates over satellite links, the TCP performance degrades considerably and affects many qualities of TCP based services. In this work, we focus on studying the TCP performance in S-UMTS using radio link control (RLC) with fragmentation and retransmission mechanisms. Analytical and simulation studies have been carried out to study this cross-layer problem. Two scenarios have been studied, i.e., the satellite operates in either transparent mode or with onboard processor (OBP) mode. The results indicate that the TCP performance can be enhanced substantially by employing the relay function using OBP and appropriate configurations of RLC parameters, thus providing useful information to the design the next generation communication satellite with onboard processing.

The concept of sensing-as-a-service is proposed to enable a unified way of accessing and controlling sensing devices for many Internet of Things based applications. Existing techniques for Web service computing are not sufficient for this class of services that are exposed by resource-constrained devices. The vast number of distributed and redundantly deployed sensors necessitate specialised techniques for their discovery and ranking. Current research in this line mostly focuses on discovery, e.g., designing efficient searching methods by exploiting the geographical properties of sensing devices. The problem of ranking, which aims to prioritise semantically equivalent sensor services returned by the discovery process, has not been adequately studied. Existing methods mostly leverage the information directly associated with sensor services, such as detailed service descriptions or quality of service information. However, assuming the availability of such information for sensor services is often unrealistic. We propose a ranking strategy by estimating the cost of accessing sensor services. The computation is based on properties of the sensor nodes as well as the relevant contextual information extracted from the service access process. The evaluation results demonstrate not only the superior performance of the proposed method in terms of ranking quality measure, but also the potential for preserving the energy of the sensor nodes.

Information-centric networking (ICN) is an emerging networking paradigm that places content identifiers rather than host identifiers at the core of the mechanisms and protocols used to deliver content to end-users. Such a paradigm allows routers enhanced with content-awareness to play a direct role in the routing and resolution of content requests from users, without any knowledge of the specific locations of hosted content. However, to facilitate good network traffic engineering and satisfactory user QoS, content routers need to exchange advanced network knowledge to assist them with their resolution decisions. In order to maintain the location-independency tenet of ICNs, such knowledge (known as context information) needs to be independent of the locations of servers. To this end, we propose CAINE — Context-Aware Information-centric Network Ecosystem — which enables context-based operations to be intrinsically supported by the underlying ICN routing and resolution functions. Our approach has been designed to maintain the location-independence philosophy of ICNs by associating context information directly to content rather than to the physical entities such as servers and network elements in the content ecosystem, while ensuring scalability. Through simulation, we show that based on such location-independent context information, CAINE is able to facilitate traffic engineering in the network, while not posing a significant control signalling burden on the network

In aeronautical domain, ARINC-664 Part 7 specification (AFDX) [4] provides the enabling technology for interfacing equipment in Integrated Modular Avionics (IMA) architectures. The complementary part of AFDX for a complete interoperability - Time and Space Partitioning (ARINC 653) concepts [1]-was already studied as part of space domain ESA roadmap (i.e. IMA4Space project) Standardized IMA based architecture is already considered in aeronautical domain as more flexible, reliable and secure. Integration and validation become simple, using a common set of tools and data base and could be done by part on different means with the same definition (hardware and software test benches, flight control or alarm test benches, simulator and flight test installation). In some area, requirements in terms of data processing are quite similar in space domain and the concept could be applicable to take benefit of the technology itself and of the panel of hardware and software solutions and tools available on the market. The Mission project (Methodology and assessment for the applicability of ARINC-664 (AFDX) in Satellite/Spacecraft on-board communication networks), as an FP7 initiative for bringing terrestrial SME research into the space domain started to evaluate the applicability of the standard in space domain.

The high volume of energy consumption has become a great concern to the Internet community because of high energy waste on redundant network devices. One promising scheme for energy savings is to reconfigure network elements to sleep mode when traffic demand is low. However, due to the nature of today's traditional IP routing protocols, network reconfiguration is generally deemed to be harmful because of routing table reconvergence. To make these sleeping network elements, such as links, robust to traffic disruption, we propose a novel online scheme called designate to sleep algorithm that aims to remove network links without causing traffic disruption during energy-saving periods. Considering the nature of diurnal traffic, there could be traffic surge in the network because of reduced network capacity. We therefore propose a complementary scheme called dynamic wake-up algorithm that intelligently wakes up minimum number of sleeping links needed to control such dynamicity. This is contrary to the normal paradigm of either reverting to full topology and sacrificing energy savings or employing on-the-fly link weight manipulation. Using the real topologies of GEANT and Abilene networks respectively, we show that the proposed schemes can save a substantial amount of energy without affecting network performance.

The number of broadband users has beengrowing rapidly during the last years. It is not only the number of users that increases but also the average data volume per user; a consequence of the increased number of users connected via broadband techniques is that the demand for audio and video content is also increasing. In this papel we describe an integrated satellite-terrestrial UMTS architecture investigating on the minimization of the delivery cost. The proposed telecommunication system can offer SDMB (Satellite Digital Multimedia Broadcast) services to mobile users through the satellite or terrestrial UMTS downlink segment. On the inside of this scenario we propose a simple and efficient cost model for choosing the more suitable bearer (satellite or terrestrial) in order to save service delivery cost, moreover we design a new signalling strategy based on users location information for supporting this optimal choice. The simulations performed show the goodness of the proposed strategy also with several mobile operator networks varying the number of users asking for the SDMB service.

Intelligent Automation and Computer Engineering offers the state of the art oftremendous advances in intelligent automation and computer engineering and also ...

The prospect of the Internet as the fastest growing satellite communication application coupled with satellite-based multimedia networks has generated a high level of interest in the performance of TCP over satellite systems. This article presents the network architecture for supporting services based on TCP/IP over satellite. It discusses the key factors that influence TCP performance over satellite links, and compares the benefits and disadvantages of low earth orbit and geostationary earth orbit satellites. The article also discusses the feasibility of using LEO satellites to support and expand the Internet. It presents studies of the TCP behavior over a GEO satellite system and LEO satellite constellation based on computer simulations, where two typical Internet applications are taken into consideration: FTP file transfer and Web browsing. The results show that TCP performs much better over the LEO satellite constellation than over the GEO system; even the standard TCP over LEO is better than enhanced TCP over GEO.

In order to support precision formation flying missions, distributed spacecraft require inter-spacecraft communications with required performance. We present a hierarchical network architecture that supports both time-criticality for updating relative navigation measurements and flexibility for implementing various phases of mission operations. The architecture incorporates a reactive routing protocol with timely topology status, an enhanced IEEE 802.11 media access control protocol meeting the quality of service requirements, and single carrier-frequency domain equalization technique for reducing energy consumption. Our simulation results show that the proposed network architecture provides a fair tradeoff between time-criticality of services and flexibility of network topology among spacecraft. © 2014 Springer Science+Business Media New York.

A delay tolerant network is a highly constrained networking environment which is low in resources such as memory, bandwidth and battery power. In opportunistic DTNs, nodes cooperatively forward packets for each other through the carry-store-and-forward paradigm. Opportunistic data forwarding can be abused by an adversary by injecting spurious packets in order to waste the resources of the network. To guard against such attacks, it is important to authenticate packets at intermediate nodes. Packet authentication in itself comes with overheads such as computation cost and energy consumption which can be exploited by an attacker to mount a denial of service attack. We propose the use of light-weight DTN-cookies to protect this vital security service from such malicious exploitation. We show through simulations that our proposed mechanisms can improve network performance and save considerable amount of power even in the presence of attackers.

In a content delivery network (CDN), the energy cost is dominated by its geographically distributed data centers (DCs). Generally within a DC, the energy consumption is dominated by its server infrastructure and cooling system, with each contributing approximately half. However, existing research work has been addressing energy efficiency on these two sides separately. In this paper, we jointly optimize the energy consumption of both server infrastructures and cooling systems in a holistic manner. Such an objective is achieved through both strategies of: 1) putting idle servers to sleep within individual DCs; and 2) shutting down idle DCs entirely during off-peak hours. Based on these strategies, we develop a heuristic algorithm, which concentrates user request resolution to fewer DCs, so that some DCs may become completely idle and hence have the opportunity to be shut down to reduce their cooling energy consumption. Meanwhile, QoS constraints are respected in the algorithm to assure service availability and end-to-end delay. Through simulations under realistic scenarios, our algorithm is able to achieve an energy-saving gain of up to 62.1% over an existing CDN energy-saving scheme. This result is bound to be near-optimal by our theoretically-derived lower bound on energy-saving performance.

In this paper, we present an end-to-end QoS simulation studies on internetworking of remote LAN and long range communications over LEOIridium satellites constellation taking SuperJARING network in Malaysia as an example. A macro level network simulation scenario based on actual network topology in Malaysia is implemented as Diffserv network model using the Network Simulator-2 (NS-2). Web traffic (HTTP) is used as the internet traffic models in the simulation analysis. All simulations are carried out in error-free and link-loss environment. In error-free simulations, the accumulative network traffic loads are varied from 20%, 50% and 80% while in link-loss environment simulations only 20% traffic load is used with bit error rate (BER) varied from 1x10-5, 1x10-4 and 2x10-4. The results show clearly that QoS can be achieved with IP Diffserv over satellites constellation like Iridium.

Satellites are expected to play an essential role in bridging the “digital divide”; satellite networks are likely to be the only way to provide broadband services to regions that cannot be economically reached by terrestrial networks, in particular the more remote regions of Europe and the rest of the world. Security can be a problem for such global services. This paper presents a link layer security solution and how it is implemented for the Unidirectional Lightweight Encapsulation (ULE). A satellite testbed is constructed where the ULE security implementation is validated. The experiments results are presented in this paper.

Environmental problems, such as pollution, become more serious year after year. One of the major causes is high fossil fuel consumption with CO2 emission. In 2009, 23 percent of CO emission globally came from land transportation systems, which is equal to 7000 million tons of CO. This large amount of gas pollution should be reduced to slow down global environmental problems. Reduction of fuel consumption and CO emission in land transportation systems, which will have immediate positive economical and environmental impact, has become an important part of green technologies to alleviate global warming due to human activity. Intelligent transportation systems, which aim to use information and communication technology in the transportation systems, are considered to be a major enabler for the future green ITS. This article aims to provide a survey of the latest published applications based on vehicular communications as well as the envisaged technical challenges in this research area. © 2012 IEEE.

Security is an important concern in today's information age and particularly so in satellite systems, where eavesdropping can be easily performed. This paper addresses efficient key management for encrypted multicast traffic transmitted via satellite. We consider the topic of encrypting traffic in large multicast groups, where the group size and dynamics have a significant impact on the network load. We consider life cycle key management costs of a multicast connection, and show for a logical key hierarchy (LKH) how member preregistration and periodic admission reduces the initialization cost, and how the optimum outdegree of a hierarchical tree varies with the expected member volatility and rekey factor. This improves network utilization, but encryption at the network layer can pose problems on satellite links. We, therefore, propose and analyze an interworking solution between multilayer Internet protocol security (IPSEC) and LKH that also reduces key management traffic while enabling interworking with performance enhancing modules used on satellite links.

In addition, the book covers hot-button issues such as security, architecture improvement, resource allocation, video networking, and service integration.

For large-scale battery-swapping demands, reserva- tions are utilized to effectively manage battery swapping. To achieve data security, one promising solution is heterogeneous signcryption (i.e. signature + encryption). However, existing heterogeneous signcryption cannot simultaneously support aggre- gation, batch verification, conditional privacy-preserving, bidirec- tional heterogeneous communication, and availability. Besides, to reduce the end-to-end delays, mobile edge computing (MEC) is introduced to reservations, so other challenge is to design an incentive mechanism to encourage mobile edge nodes (MENs) to transmit reservation messages. Seeking to address these chal- lenges, we propose a reservation scheme with conditional privacy- preserving bidirectional heterogeneous aggregate signcryption and incentive mechanism, namely SecBS. More precisely, in status publication (i.e. SecBS-SP), electric vehicles (EVs) obtain status messages released by battery swapping stations (BSSs) via MENs, which is realized via heterogeneous signcryption from certificateless cryptosystem (CLC) to identity-based cryptosystem (IBC). In the reservation (i.e. SecBS-R), under the incentive, MENs transmit reservations sent by EVs to BSSs, which is realized via heterogeneous signcryption from IBC to CLC. Finally, formally security proof and extensive simulations are carried out to manifest the security and feasibility of our SecBS.

The advent of the digital economy and Industry 4.0 enables financial organizations to adapt their processes and mitigate the risks and losses associated with the fraud. Machine learning algorithms facilitate effective predictive models for fraud detection for Industry 4.0. This study aims to identify an efficient and stable model for fraud detection platforms to be adapted for Industry 4.0. By leveraging a real credit card transaction dataset, this study proposes and compares five different learning models: logistic regression, decision tree, k-nearest neighbors, random forest, and autoencoder. Results show that random forest and logistic regression outperform the other algorithms. Besides, the undersampling method and feature reduction using principal component analysis could enhance the results of the proposed models. The outcomes of the studies positively ascertain the effectiveness of using features selection and sampling methods for tackling business problems in the new age of digital economy and industrial 4.0 to detect fraudulent activities.

The fifth generation (5G) Wireless Communication systems development has brought out a paradigm shift using advanced technologies e.g., softwarization, virtualization, Massive MIMO, ultra-densification and introduction of new frequency bands. However, as the societal needs grow, and to satisfy UN's Sustainable Development Goals (SDGs), 6G and beyond systems are envisioned. Non-Terrestrial Networks including satellite systems, Unmanned Aerial Vehicles (UAVs) and High-Altitude Platforms (HAPs) provide the best solutions to connect the unconnected, unserved and underserved in remote and rural areas in particular. Over the past few decades, Geo Synchronous Orbits (GSO) satellite systems have been deployed to support broadband services, backhauling, Disaster Recovery and Continuity of Operations (DR-COOP) and emergency services. Recently, there is a considerable renewed interest in planning and developing non-GSO satellite systems. Within the next few years several thousands of Low Earth Orbit (LEO) satellites and mega LEO constellations will be ready to provide global Internet services. This report is the 2022 Edition of the INGR Satellite Working Group Report, subsequent to the previous two editions [1] [2]. The topics considered in this INGR Satellite WG 2022 Edition of the roadmap are the following taking 6G systems into account: applications and services, reference architectures (both backhaul and direct access), satellite IoT, mmWave use for satellite networks, machine learning and artificial intelligence, edge computing, QoS/QoE, security, network management and standardization. The work on the roadmap will continue towards the next edition of the roadmap addressing new challenges and potential solutions for future networks.

This paper addresses delay/disruption tolerant networking routing under a highly dynamic scenario, envisioned for communication in vehicular sensor networks (VSNs) suffering from intermittent connection. Here, we focus on the design of a high-level routing framework, rather than the dedicated encounter prediction. Based on an analyzed utility metric to predict nodal encounter, our proposed routing framework considers the following three cases. First, messages are efficiently replicated to a better qualified candidate node, based on the analyzed utility metric related to destination. Second, messages are conditionally replicated if the node with a better utility metric has not been met. Third, messages are probabilistically replicated if the information in relation to destination is unavailable in the worst case. With this framework in mind, we propose two routing schemes covering two major technique branches in literature, namely: 1) encounter-based replication routing and 2) encounter-based spraying routing. Results under the scenario applicable to VSNs show that, in addition to achieving high delivery ratio for reliability, our schemes are more efficient in terms of a lower overhead ratio. Our core investigation indicates that apart from what information to use for encounter prediction, how to deliver messages based on the given utility metric is also important.

Communication technology for vehicles has become an important topic for research. IEEE standards including IEEE 802.11p and IEEE P1609.1-4 have emerged to provide a framework for intervehicular communication (IVC). However, due to particular characteristics of IVC, such as high mobility, unstable connectivity, and network partitioning, information routing becomes inevitably challenging. This article reviews the recent research progress to highlight research challenges in vehicular routing protocol as a guideline for future development of IVC applications. The article focuses on the IEEE DSRC/WAVE standard. The state of the art in IVC routing protocols is surveyed, and open issues for further research are highlighted in the article.

Denial of Service (DOS) attacks are a major threat faced by all types of networks. The effect of DOS in a delay tolerant network (DTN) is even more aggravated due to the scarcity of resources. Perpetrators of DOS attacks in DTN-like environments look beyond the objective of rendering a target node useless. The aim of an attacker is to cause a network-wide degradation of resources, service and performance. This can easily be achieved by exhausting node or link resources and partitioning the network. In this paper we seek to provide a proactive approach in making the DTN authentication process robust against DOS. Our aim is to make security protocols which provide mandatory DTN security services resilient to DOS attacks. The overall objective is to make it hard to launch a DOS attack and ensure the availability of DTN services. A DTN-cookie mechanism has been proposed to quickly identify and filter out illegitimate traffic.

In this letter, a non-orthogonal multiple access (NOMA) scheme is employed for irregular repetition slotted ALOHA (IRSA). Specifically, packet replicas are transmitted with discrete power levels which are pre-determined by the NOMA scheme. In this case, most packet collisions can be resolved in the power domain, contributing to a much lower packet loss rate. Density evolution (DE) analysis is formulated and the degree distributions are optimized for different number of power levels. Simulation results validate our analysis and show that the proposed scheme can outperform existing IRSA schemes.

Receiving great interest from the research community, Delay Tolerant Networks (DTNs) are a type of Next Generation Networks (NGNs) proposed to bridge communication in challenged environments. In this paper, the message replication probability is proportionally sprayed for efficient routing mainly under sparse scenario. This methodology is different from the spray based algorithms using message copy tickets to control replication. Our heuristic algorithm aims to overcome the scalability of the spray based algorithms, since to determine the initial value of the copy tickets requires the assumption that either the number of nodes is known in advance, or the underlying mobility model follows the Random WayPoint (RWP) characteristic. Specifically, in combining with the assistance of geographic information to estimate the movement range of destination, the routing decision is based on the encounter angle between pairwise nodes, and is dynamically switched between the designed two routing phases, named as geographic replication and replication probability spray. Furthermore, messages are under prioritized transmission with the consideration of redundancy pruning. Simulation results show our heuristic algorithm outperforms other well known algorithms in terms of delivery ratio, transmission overhead, average latency as well as buffer occupancy time. © 2012 IEEE.

Aiming to provide low-cost universal broadband access, this paper describes the strategy that supports the integration of hybrid satellite and WiMAX, based on the network architecture proposed in the IST Satsix project. In this context, WiMAX networks can be used as wireless local loops integrated with a satellite network, lowering the cost of the broadband internet connections and providing a universal access to rural and marine areas. The paper presents the problems concerning the interworking between DVB-RCS and WiMAX technologies and the solutions adopted in the SatSix research project, partially funded by European Commission within the Information Society Technologies (IST) 6th Framework Programme. © 2007 by SatSix consortium.

How to reduce power consumption within individual data centers has attracted major research efforts in the past decade, as their energy bills have contributed significantly to the overall operating costs. In recent years, increasing research efforts have also been devoted to the design of practical powersaving techniques in content delivery networks (CDNs), as they involve thousands of globally distributed data centers with content server clusters. In this paper, we present a comprehensive survey on existing research works aiming to save power in data centers and content delivery networks that share high degree of commonalities in different aspects. We firstly highlight the necessities of saving power in these two types of networks, followed by the identification of four major power-saving strategies that have been widely exploited in the literature. Furthermore, we present a high-level overview of the literature by categorizing existing approaches with respect to their scopes and research directions. These schemes are later analyzed with respect to their strategies, advantages and imitations. In the end, we summarize several key aspects that are considered to be crucial in effective power-saving schemes. We also highlight a number of our envisaged open research directions in the relevant areas that are of significance and hence require further elaborations.

With the boom of Internet, IP-based applications such as WWW and multimedia have become an essential part of our everyday life, and there is an ever-increasing demand for accessing high-speed Internet services anywhere, anytime and all the times. This trend unavoidably has huge impacts on the design of the next-generation future networks. However, security, privacy and trust systems can be obstacles in the presence of a global and heterogeneous future networks.

This paper presents the QoS performance evaluation studies of IP over integrated terrestrial and Next Generation Satellite Network (NGSN) for HTTP web, file transfer, video streaming and VoIP applications. We compare the QoS parameters (e.g. delay, loss ratio and throughput) of the multiservice applications over Ka-Sat like satellite and the ITU-R standard Hypothetical Reference Digital Path (HRDP). We model the multiservice applications with multiple connections, different files sizes and connection durations variations. We simulate the network scenario with error model for the transmission loss environment using NS-2. A Differentiated Services (Diffserv) queue interface is used in the terrestrial network to regulate and differentiate the traffic flows while a priority queue is used as the satellite on-board-processing unit (OBP). The results showed a better top-down comparison of the QoS parameters involved in each application service across GEO satellite and the standard terrestrial digital data link.

Multicast research has explored the security challenges faced in group communications. Multicast transport and multicast security need to work in close collaboration to realise a multicast service. However, there has been comparatively little work to combine the two technologies. In this paper the authors is presenting an example of partially integrating timed efficient stream loss-tolerant authentication (TESLA) protocol and the file delivery over unidirectional transport (FLUTE) protocol. The security concern raised by the proposed algorithm is analysed for satellite network. The proposed algorithm was implemented on a testbed with multicast tunnel between University of Surrey and University of Aberdeen and the results are presented in this paper.

The growing demand of mobile wireless internet access has prompted rapid growth of wireless data services. The key issue of wireless cloud is to provide complex services by using the available resources within reasonable cost. Accompanying the emergence of integrated wireless and mobile networks (e.g. WLAN, 3G/4G net), it makes a challenge of networks as service to supporting the complete lifecycle of service building and delivery via wireless cloud providers. This paper proposes an agent-based scheme to discover comprehensive service, select and allocate resources for supporting the cloud applications in wireless platforms with respect to efficiency and fairness of resource utilization. This paper presents an optimization resource selection strategy with selection and allocation of network resources based on the agent-based scheme in enabling Quality of Service (QoS) in wireless cloud environment. © 2010 IEEE.

Satellites are popular due to their wide area coverage and for providing connectivity in remote regions of the world. The future development of satellite systems providing services based on the Internet Protocol (IP) needs to be validated on a real satellite network. This paper presents the end-to-end quality of service (QoS) measurements taken at European Space Agency (ESA) testbed over DVB-RCS infrastructure. The applications chosen for these experiments are file transfer (FTP), web browsing (HTTP), video streaming and P2P filesharing. File transfer, web browsing and P2P file-sharing require reliable transport mechanism as a corrupted bit will hinder the intact data delivery. Therefore, these applications use transmission control protocol (TCP) as the transport protocol. TCP involves a three way handshake, which introduces extra delay during data transfer. Video streaming is a real time application, so, it is time-sensitive and requires lesser reliability compared to the other three applications. Hence, it employs user datagram protocol (UDP) at the transport layer, which do not offer any guarantee of reliable data delivery but is fast. The parameters that have been used to evaluate quality of service (QoS) are packet timestamps, file download time, round trip delay, packet sizes and packet loss rate. Also similar applications and results will be measured from a satellite emulation testbed, PLATINE. It is based on Linux operating system, in which most of the DVB-S and DVBRCS satellite network functions have been implemented. These functions include network topology configuration, Quality of Service (QoS), Demand Assigned Multiple Access (DAMA), traffic encapsulation using both Asynchronous Transfer mode (ATM) and ULE/MPEG, satellite network entities configuration and support for both IPv4 and IPv6. The paper concludes with the comparative analysis of the QoS of the applications in both real and emulation environments.

The introduction of intelligent devices with short range wireless communication techniques has motivated the development of Mobile Ad hoc NETworks (MANETs) during the last few years. However, traditional end-to-end based routing algorithms designed for MANETs are not much robust in the challenged networks suffering from frequent disruption, sparse network density and limited device capability. Such challenged networks, also known as Intermittently Connected Networks (ICNs) adopt the Store-Carry-Forward (SCF) behavior arising from the mobility of mobile nodes for message relaying. In this article, we consider the term ICNs as Delay/Disruption Tolerant Networks (DTNs) for the purpose of generalization, since DTNs have been envisioned for different applications with a large number of proposed routing algorithms. Motivated by the great interest from the research community, we firstly review the existing unicasting issue of DTNs because of its extensive research stage. Then, we also address multicasting and anycasting issues in DTNs considering their perspectives. A detail survey based on our taxonomy over the period from 2006 to 2010 is not only provided but also a comparison is given. We further identify the remaining challenges and open issues followed by an evaluation framework proposed for routing in DTNs. Finally, we summarize our contribution with three future research topics highlighted. © 2013 IEEE.

The paper presents the studies of traffic management in the satellite ATM bridge based on RACE II RACE project - CATALYST R2074. The project aims to develop satellite ATM bridge that can support the future B-ISDN services for satellite communications. An ATM bridge can interconnect the ATM network and the existing networks as well as DQDB, FDDI, Ethernet networks. The current interfaces have different bit rates, thus the need to control traffic and manage the resources on the bridge to prevent overload and preserve the quality of the services on the satellite. The satellite ATM bridge will be used in the initial interconnections of B-ISDN islands and the development of B-ISDN for mobile telecommunications and direct broadcast services.

As one of the key elements in an IPv6 supported DVB-RCS satellite network, the multicast architecture design is facing the challenges of interworking between the IPv6 multicast protocols and the satellite signaling while efficiently using the satellite bandwidth. How to enable the multicast group management functions for satellite end users with and without direct IPv6 MLD router support and how to translate the IP multicast routing protocol messages to the satellite lower layer signaling to establish the satellite channels between two spot beams need to be answered. With the regenerating satellite space segment, dynamic multicast routing is possible and making an efficient use of the satellite bandwidth has to be considered. This paper presents the SATSIX approaches of a multicast architecture involving both the IP multicast and the C2P protocols to address and solve these questions. © Springer 2008.

Cloud computing technology facilitates computing-intensive applications by providing virtualized resources which can be dynamically provisioned. However, user’s requests are varied according to different applications’ computation abil- ity needs. These applications can be presented as meta-job of user’s demand. The total processing time of these jobs may need data transmission time over the Internet as well as the completed time of jobs to execute on the virtual ma- chine must be taken into account. In this paper, we presented V-heuristics scheduling algorithm for allocation of virtu- alized network and computing resources under user’s constraint which applied into a service-oriented resource broker for jobs scheduling. This scheduling algorithm takes into account both data transmission time and computation time that related to virtualized network and virtual machine. The simulation results are compared with three different types of heuristic algorithms under conventional network or virtual network conditions such as MCT, Min-Min and Max-Min. e evaluate these algorithms within a simulated cloud environment via an abilene network topology which is real physical core network topology. These experimental results show that V-heuristic scheduling algorithm achieved significant performance gain for a variety of applications in terms of load balance, Makespan, average resource utilization and total processing time.

Multimedia conference is one of the important applications in the Internet. To support such an application over satellite networks, one has to address quality of service (QoS) and performance of IP applications over satellite. Research has been carried to study how satellite networks can support efficiently the IP based multimedia applications including voice, video and data and impacts of satellite networks on these applications. This paper presents the results from the project IP Conferencing with Broadband multimedia over Geostationary Satellites (ICEBERGS), which is within the European 5th Framework IST programme. The networking architecture is based on Internet protocols, including IP, UDP, RTP and RTCP and the Internet signalling protocols such as SIP and SAP. A testbed has been developed to demonstrate the concept of multimedia conference over satellite and evaluate the performance of satellite networks and QoS of applications. The results from this project presented in the paper include IP based multimedia applications over satellite in terms of protocol architecture, satellite network configuration, and performance evaluation. © 2003 by University of Surrey.

In the past, security protocols including key transport protocols are designed with the assumption that there are two parties communication with each other and an adversary tries to intercept this communication. In Delay/Disruption Tolerant Networking (DTN), packet delivery relies on intermediate parties in the communication path to store and forward the packets. DTN security architecture requires that integrity and authentication should be verified at intermediate nodes as well as at end nodes and confidentiality should be maintained for end communicating parties. This requires new security protocols and key management to be defined for DTN as traditional end-to-end security protocols will not work with DTN. To contribute towards solving this problem, we propose a novel Efficient and Scalable Key Transport Scheme (ESKTS) to transport the symmetric key generated at a DTN node to other communicating body securely using public key cryptography and proxy signatures. It is unique effort to design a key transport protocol in compliance with DTN architecture. ESKTS ensures that integrity and authentication is achieved at hop-by-hop level as well as end-to-end level. It also ensures end-to-end confidentiality and freshness for end communicating parties. This scheme provides a secure symmetric key transport mechanism based on public key cryptography to exploit the unique bundle buffering characteristics of DTN to reduce communication and computation cost .

This paper presents studies for the end-to-end QoS of IP over integrated terrestrial and Next Generation Satellite Network (NGSN) using FTP. We compare between LEO and GEO satellites constellations for the QoS parameters (i.e. delay, jitter, loss rate and throughput) of file transfer from a remote server in London and a remote client in Boston. We model the file transfer with multiple connections and file size variation according to Exponential and Pareto distributions respectively. We create the scenario with error model to simulate transmission loss environment using the NS-2 simulation software. A Differentiated Services (Diffserv) queue interface is placed in the server side to regulate the traffic flows across the narrow bandwidth of the satellite links. The results showed the performance evaluation and presented a good comparison of the QoS parameters involved in the data transfer across LEO and GEO satellites systems.

Delay Tolerant Network (DTN) comprises of nodes with small and limited resources including power and memory capacity. We propose the use of DTN as an alternate means of communication for the dissemination of emergency information in a post-disaster evacuation operation. We investigate the performance of DTN in providing emergency communication support services under packet dropping attacks. We consider internally motivated attacks where the nodes that are part of the emergency rescue team are compromised with malicious behaviours thereby dropping packets to disrupt the message dissemination during the evacuation operation. A way to mitigating malicious behaviour and improve network performance of DTN is to use incentives in exchanging information between nodes. Unlike existing schemes, we consider the Basic Watchdog Detection System which detects and acts against misbehaving nodes to reduce their overall impact on the network performance. We design a Collaborative Trust Management Scheme (CTMS) which is based on the Bayesian detection watchdog approach to detect selfish and malicious behaviour in DTN nodes. We have evaluated our proposed CTMS through extensive simulations and compared our results with the other existing schemes. Our evaluations show that the use of adequate collaborative strategies between well behaved nodes could improve the performance of Watchdog schemes taking into account the delivery ratio, routing cost and the message delay from the source node to the destination node.

Satellite networking is an exciting and expanding field that has evolved significantly since the launch of the first telecommunications satellite, from telephone and broadcast to broadband ATM and Internet. With increasing bandwidth and mobility demands on the horizon, satellites have become an integral part of the Global Network Infrastructure (GNI). Satellite Networking: Principles and Protocols provides a balanced coverage of satellite topics from a network point of view, focusing on network aspects, services and applications, quality of service (QoS) and principles and protocols. Introduces the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks Discusses the real-time protocols including RTP, RTCP and SIP for real-time applications such as VoIP and MMC Coverage of new services and applications, internet traffic engineering and MPLS Examines IPv6 over satellite using tunnelling and translation techniques, evolution of earth stations, user terminals and network protocols, and development of satellite networking Includes a Companion Website featuring: Solutions manual, and electronic versions of the figures This text is essential reading for senior undergraduates, postgraduates, and researchers in the fields of satellites, communications and networks. It will also have instant appeal to engineers, managers and operators in these fields. © 2005 John Wiley & Sons, Ltd.

Privacy, Anonymity, pseudonymity are the debatable terms which on one angle restrict the rights but on other angle open doors for malacious activity.This paper propses design for a pseudonymised communication which is optimal solution for the privacy issues, where the real identity is hidden from the outside world by using blind signature in a different way of group commmunication.The protocol is deployed and analysed in extreme environment of Delay Tolerant Networks (DTN), which is overlay on the top of traditional Internet which provides end to end connectivity and charactarised with long delay and disruption. A telemedicine application of rural area network is explored to provide source anonymity.The protocol is finally analysed using Dolev Yao model with two different cases and it preserves the orignal identity of the node.

The characteristics of multiplexed Internet traffic is studied in this paper. On-Off models were developed to represent both voice over IP (VoIP) and HTTP traffic. The main aim of this study is to investigate whether it is possible to characterize multiplexed Internet traffic using simple mathematical terms instead of the current model offerings which are too complex for them to be of any practical use. While the mathematical derivation is not included in this study, the results of the simulation seem to indicate that this is a possibility. © 2002 by University of Surrey.

Transmission Control Protocol (TCP) over satellite IP networks has attracted many researchers' interests for many years because the TCP performance degrades considerably due to the high propagation delay and high bit error rates in satellite links. Many proposals have been produced to enhance TCP performance in satellite IP networks, which are mostly involved of modifying system's architecture or TCP protocol stack. In this paper, we propose a novel on-board link layer relay mechanism. We use both analytical and simulation means to compare the traditional bent-pipe scenario and our on-board link layer relay mechanism. The numerical and simulation results indicate that the TCP performance can be enhanced substantially by employing our on-board link layer relay mechanism.

In this paper, we design and evaluate the proposed geographic-based spray-and-relay (GSaR) routing scheme in delay/disruption-tolerant networks. To the best of our knowledge, GSaR is the first spray-based geographic routing scheme using historical geographic information for making a routing decision. Here, the term spray means that only a limited number of message copies are allowed for replication in the network. By estimating a movement range of destination via the historical geographic information, GSaR expedites the message being sprayed toward this range, meanwhile prevents that away from and postpones that out of this range. As such, the combination of them intends to fast and efficiently spray the limited number of message copies toward this range and effectively spray them within range, to reduce the delivery delay and increase the delivery ratio. Furthermore, GSaR exploits delegation forwarding to enhance the reliability of the routing decision and handle the local maximum problem, which is considered to be the challenges for applying the geographic routing scheme in sparse networks. We evaluate GSaR under three city scenarios abstracted from real world, with other routing schemes for comparison. Results show that GSaR is reliable for delivering messages before the expiration deadline and efficient for achieving low routing overhead ratio. Further observation indicates that GSaR is also efficient in terms of a low and fair energy consumption over the nodes in the network.

Because inter-satellite links (ISLs) among the distributed satellite nodes can be used to support autonomous control in satellite system operation to reduce dependency on the ground stations, it becomes a popular communication paradigm for the future satellite systems. However, this introduces great technical challenges, particularly for routing protocol to support such space communication system. Facing the challenges, we present out study of routing technology in this paper tailored for satellite network of MEO (Table 1) and IGSO with ISLs in addition to satellite-ground links. The study aims to explore the routing strategies and algorithms of satellite network based on the evolution law of network topology to provide reference design for data exchange in autonomous satellite system. A comprehensive investigation, ranging from the analysis of relevant factors affecting data exchange in satellite networks to the primary application and resource constraints in designing satellite routing strategy, has been conducted. Our main contribution is to propose an on-demand computing and caching centralized routing strategy and algorithm on the satellite network. The routing strategy and algorithm is designed for satellite network topology dynamic grouping. The route calculation for user data transmission is divided into three phases: direction estimation, direction enhancement, and congestion avoidance. The strategy and algorithm provide significant advantages of high efficiency, low complexity, and flexible configuration, by which the satellite networks can provide the features of flexible configure, efficient transferring, easy management, structural survivability, and great potential in scalability. Copyright © 2013 John Wiley & Sons, Ltd.

Next-generation broadband satellite systems will have the capability to provide cost-effective universal broadband access for the users. In order to meet users’ requirements on high quality multimedia services, many enhancements have to be made on the existing satellite technologies. One of the promising methods is the introduction of cross-layer design. There are several advantages of a layered approach since modularity, robustness and ease of designs are achieved without difficulty. However the properties of the different layers have substantial interdependencies and a modularised design may therefore be suboptimal with regards to performance and availability in a hybrid satellite and mobile wireless environment. In this paper, we will carry out a review of the cross-layer design in satellite systems. Based on this, a cross-layer architecture for the next-generation broadband satellite system is proposed. The proposed cross-layer architecture has two main components: QoS and resource management and mobility management. In each component, the cross-layer techniques that have been used are described in details.

With the proliferation of the internet, voice over IP has penetrated in both terrestrial and satellite networks. One of the popular protocols responsible for its widespread usage is SIP. SIP is the signalling protocol responsible for the session establishment and termination. By default, it uses UDP as the transport layer protocol. As UDP is an unreliable protocol, the retransmission of the SIP messages is managed by the application layer, using exponential backoff algorithm. In this paper, this retransmission algorithm is studied in satellite environment. Based on the shortcomings of this algorithm, a new algorithm is proposed. The performance of the new algorithm is tested and evaluated on the satellite network testbed at Centre for Communication Systems Research (CCSR), University of Surrey. The results show that the performance of the new algorithm is better than the basic one, in terms of number of retransmissions of SIP messages and their bandwidth consumption, in addition to reduction in call setup time.

Both the academy and industry believe that Intelligent Transportation System (ITS) would be achievable in one decade since modern vehicle and communication technologies advanced apace. Vehicular Communication System (VCS) introduces information technology to the ITS and aims to improve road safety and traffic efficiency. In recent year, security and privacy schemes in VCS are becoming important. However, recovery mechanisms to eliminate the negative effect of security and privacy attacks are still an important topic for research. Therefore, the certificate revocation scheme is considered as a feasible technique to prevent the system from potential attacks. The major challenge of the certificate revocation scheme is to achieve low-cost operation since the communication resources must be capable of carrying various applications apart from the security and privacy purposes. In this paper, we propose an efficient certificate revocation scheme in VCS. The Blockchain concept is introduced to simplify the network structure and distributed maintenance of the Certificate Revocation List (CRL). The proposed scheme embeds part of the certificate revocation functions within the security and privacy applications, aiming to reduce the communication overhead and shorten the processing time cost. Extensive simulations and analysis show the effectiveness and efficiency of the proposed scheme, in which the Blockchain structure costs fewer network resources and gives a more economic solution to against further cybercrime attacks. •Blockchain based certificate revocation scheme helps to listen to the pseudonym ownership changing and timely updates the certificate revocation lists.•Certificate revocation lists are broadcasted along with the sharing of blocks which decreases the overheads.•The scheme can be seamless attached to the blockchain based security and privacy schemes.

Reducing the number of road accidents is a key agenda item for governments across the world. This has led to an increase in the amount of attention given to Vehicular Communication Systems (VCS), which are seen as an important technology that can offer significant improvements in road safety. Using VCS, vehicles can form a dynamic self-configuring network that enables a vehicle to communicate with other vehicles (V2V) and roadside infrastructure (V2I). However, such wireless communication channels are vulnerable to attacks, and therefore an authentication scheme for communications should be designed before the deployment. Prior work has focused on utilising digital signature approaches to achieve the security requirements, but due to the special characteristics of VCS, such approaches are not well suited for safety related applications of VCS, since they incur high communication and computation overheads. To combat this issue, we propose a certificateless and lightweight authentication scheme to provide means of secure communications for VCS. In this work we introduce authentication tokens, which replace digital certificates to reduce the burden of certificate management on a Trusted Authority (TA). In addition, the utilisation of tokens ensures that mutual authentication is achieved for V2I communication. Moreover, we employ TESLA as the underlying broadcast authentication protocol to achieve the required security goals for safety message broadcasting. According to the security analysis and extensive simulation of our scheme, the results show that it can withstands various types of attacks. Also it has better performance in term of verification delay, scalability and communication overhead compared to lightweight authentication schemes that are based on similar techniques. Therefore, the scheme is well suited for VCS

In this paper, we investigate the transmission schemes of space data systems for optimized network capacity in an integrated terrestrial-satellite network (ITSN) with a twolayered space segment. First, a theoretical model of the network capacity is developed to evaluate the strategy of utilizing both direct and relayed transmissions. Second, we consider the ideal and the resource-constrained scenarios in which the corresponding network capacity is modeled with respect to the scheduling scheme. In particular, closed form and semi-closed form solutions to the difficult integer programs are achieved via rigorous mathematical analysis. The proposed model is general for exploring the capacity of various satellite network deployments whose solutions have not been obtained in prior studies. Furthermore, we verify the potential capacity of the different transmission schemes based on the proposed solutions and prove that the system’s network capacity can be significantly improved by the hybrid transmission scheme. The theoretical framework proposed in this paper is expected to provide constructive insights in the design for the future space segments of ITSN.

Node provisioning in wireless sensor networks is very high density and is a cause of data duplication. Therefore, sensors' duty-cycling is a significant process in order to reduce data load and prolong network lifetime, where certain sensors are selected to be active, while some others are pushed into sleep mode. However, quality of service in terms of network connectivity and sensing coverage must be guaranteed. This paper proposes a sensor selection method to guarantee connected coverage by using hexagonal tessellation as a virtual partition which consists of many hexagonal cells across the network. Six pieces of equilateral triangles in each hexagonal cell are target areas in which k sensors are selected to operate. Performance of the method is evaluated in terms of quality of connected coverage, number of active nodes, efficient coverage area and chance of node selection.

The potential of Mobile wireless Ad hoc Networks (MANET) is significantly high. However, MANET applications often happen in infrastructureless or remote regions where remote connectivity to the outside world has to be provided by some other means. Satellite is one of the solutions to provide this and sometimes the only solution. Current expectations dictate that satellite will be seen not only as a component of an alternative routing path but also as part of a unique (really integrated) system. The concept of a hybrid MANET-Satellite network is therefore a natural evolution of considering the problem of providing local and remote connectivity in a highly mobile, dynamic and often remote environment. These composite networks raise significant challenges such as: optimising network resources and link availability; providing Quality of Service (QoS) and Quality of Experience (QoE); minimizing costs and energy. The EC FP7 project MONET will address precisely these issues by considering the end-to-end optimization of resource management in a hybrid network, taking into account its impact on both the MANET and satellite segments. Copyright © 2010 The authors.

Communication technologies are very important for disaster management. Satellite network’s advantage of large coverage and Mobile Ad hoc Network’s (MANET) advantage of high flexibility could be ideal for disaster management. In this paper, the authors propose a novel scheme for providing reliable wireless communications in disaster sites with a hybrid network of terrestrial MANET and satellite network. In comparison with normal wireless routing approaches, i.e. AODV and AOMDV, the proposed scheme could achieve higher packet delivery ratio, higher throughput and lower delay; meanwhile it could also balance traffic loads at gateways to maximum satellite links’ utilization.

Location-based Services (LBS) have gained popularity as a result of the advances in mobile and communication technologies. LBS provide users with relevant information based on their location. In spite of the desirable features provided by LBS, the geographic location of users are not adequately protected. Location privacy is one of the major challenges in vehicular and mobile networks. In this article, we analyse the security and privacy requirements for LBS in vehicular and mobile networks. Specifically, this paper covers privacy enhancing technologies and cryptographic approaches that provide location privacy in vehicular and mobile networks. The different approaches proposed in literature are compared and open research areas are identified.

In mobile networks, the User Equipment (UE) secures some of the communication with its serving Radio Access Network (RAN) node ("base station") via a set of keys known as Access Stratum (AS) keys. Unfortunately, the level of secrecy of these keys varies with the mobile procedures re-establishing them. To improve the secrecy of the AS keys, we propose minimal changes to 5G & 4G handovers, i.e., the main AS-key establishment procedures. We show the minimality of our changes also via an implementation of one of our protocol in the 3GPP-compliant Open5GCore 5G testbed. We also cross-compare standard handovers with our amended handovers, systematically via MobTrustCom: a framework to quantify especially trust but also communication complexity in mobile networks. Moreover, we use Tamarin, a formal security-protocol verification tool, to prove no loss of "classical" security yet an increase in AS-keys' secrecy brought by our improvements to handovers.

Satellite Communications can be used when other communication systems are either destroyed or overloaded. Observation satellites and Delay/Disruption Tolerant Networks are technologies that can be interconnected to provide emergency communication for disaster recovery operations. DTNs use a store-carry-forward mechanism to forward messages through intermediary nodes to the destination node. The reliability of relaying messages through multi-hop nodes poses a significant problem in DTNs due to lack of consistent connectivity. These network characteristics make DTNs to heavily rely on the cooperation of neighbouring nodes for the successful delivery of packets. However, the presence of malicious or selfish nodes will have a great impact on the network performance. In this paper, we design a decentralised trust management scheme (DTMS) to filter out malicious nodes in DTNs. First, the number of forwarding evidence are combined with the energy consumption rate of the nodes to formulate direct trust. Then, a recommendation trust is computed from the indirect trust, recommendation credibility and recommendation familiarity. Recommendation credibility and familiarity improve the overall recommendation trust by filtering out dishonest recommendations. A comparative analysis of DTMS is performed against a Cooperative Watchdog Scheme (CWS), Recommendation Based Trust Model (RBTM) and Spray & Wait protocol. The results show that DTMS can effectively deal with malicious behaviours in DTNs including trust related attacks.

Security of satellite data is becoming an important issue. The DVB (TV broadcasting) Conditional Access system used in satellite broadcasting has however been surrounded by controversy for many years due to the spread of counterfeit smart cards, and this paper examines the weaknesses of current DVB-S security. We provide an alternative solution to secure multicast services over satellites using IPSEC and a group key management system called GSAKMP.

Satellite environment provides a whole new spectrum of challenges to communications and networking. The ability to study satellite network conditions in a reproducible and controlled manner has relied mainly on simulations and experimental testbed. Investigations on network protocols and multimedia applications over satellite networks via operational hardware-based testbed are costly and inflexible while results from simulators may be inaccurate due to assumptions made during the modeling process. Hence, a satellite network emulator is proposed to overcome these obstacles as it has complementing properties of both hardware-based testbed and pure software-based simulators. The proposed emulator is to imitate the performance dynamics in IP networks over satellite links. Operating at the Medium Access Control (MAC) of Data Link Layer, the emulator is able to emulate the propagation delay and bit errors of satellite channels. This is a very useful and cost-effective approach to show the impact of satellite link delay and transmission errors on Internet services and applications. Architecturally, the paper describes how the emulator is built upon LINUX IEEE 802.3 bridging facility (brctl) and LINUX firewall (netfilter). As packet level emulation paradigm is used, the emulator is capable of producing precise satellite channel model and thus, put forward itself as a reliable, adaptable and economical alternative for research on satellite communication networking and applications. This paper presents a project on a LINUX-based satellite link emulator, including the design and algorithm of the emulator and performance evaluation of Internet applications (data, voice and video) based on the emulator. It also explains the design and setup of a flexible and expandable testbed to supplement the performance evaluation process. The effects of the satellite emulator on voice, video and data are also studied through the use of Internet applications such as Microsoft Netmeeting and TCP/IP based data transfer. Keywords: satellite emulation, IP over satellite, performance evaluation, Internet protocols. © 2003 by University of Surrey.

Intelligent Transport Systems (ITS) are special applications of Vehicular Ad-hoc Networks (VANETs) for road safety and efficient traffic management. A major challenge for ITS and VANETs in all its flavours is ensuring the privacy of vehicle drivers and the transmitted location information. One attribute of ITS during its early roll-out stage especially in rural areas and challenged environments is low vehicle density and lack of end-to-end connectivity akin to the attribute of Vehicular Delay Tolerant Networks (VDTNs). This means that contact duration between network entities such as vehicles and road-side units (RSUs) are short-lived. Three popular solutions are the use of pseudonyms, mix-zones, and group communication. Privacy schemes based on the mix-zone technique abound for more conventional VANETs. A critical privacy analysis of such scenarios will be key to the design of privacy techniques for intermittent networks. We are not aware of any work that analyse the privacy problem in intermittent VANTEs. In this paper, we add our voice to efforts to characterize the privacy problem in disconnected VANETs.

A new and updated edition of the highly successful comprehensive reference to satellite communications Since publication of the first edition, satellite ...

The goal of this work was to understand the direction of the emerging web technologies and to evaluate their expected impact on satellite networking. Different aspects have been analysed using both real satellite testbeds and emulation platforms in different test sites in Europe. This analysis included an evaluation of those HTTP/2.0 specifications, which were implemented and released as open-source code in the experimental release of the SPDY protocol. SPDY performance was evaluated over satellite testbeds in order to understand the expected interaction with performance-enhancing proxies (including scenarios with a SPDY proxy at a satellite gateway), the impact of security and the effect of satellite capacity allocation mechanisms. The analysis also considered the impact of application protocols and the delay induced by end-system networks, such as a satellite-connected WiFi network. Copyright © 2015 John Wiley & Sons, Ltd.

Avionics Full-Duplex Switched Ethernet (AFDX) is designed for deterministic communications in avionics sensor networks embedded in large aircraft such as the Airbus A380 and Boeing 787. This paper proposes to apply the AFDX concept to the space domain, since there are increasing requirements to develop a similar system in spacecraft. In this paper, the AFDX switch is comprehensively studied and analyzed to tailor the standard for applicability to the space domain. The evaluation results show that AFDX can be efficiently adapted for space onboard data networks to provide deterministic communications even in asynchronous and high-traffic networks.

The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables dynamic host configuration protocol (DHCP) servers to provide configuration parameters to client hosts via IPv6 connections. Security becomes a very important issue. This paper analyses the security issues of the IPv6 DHCP. It then proposes a security solution using the Cryptographically Generated Address (CGA) along with DHCPv6 interaction. It also discusses some further extensions to this mechanism and the security issue for downgrade attacks. Finally it draws conclusions based on the studies and identifies the directions for the future work. © 2011 IEEE.

Satellites are foreseen to be complementary to the future terrestrial networks in deploying multimedia communication systems. The use of Geostationary multi-beams and On-Board Processing (OBP) provides a great opportunity for the speedy deployment of real time services such as IP Voice services over satellites. Voice over IP is a new technology and has the potential to revolutionise telephone communications within the modern enterprise, and promises new integrated services and lower costs. This paper examines the challenges of providing IP telephony, multiparty conference service and using IP multicast to distribute voice conferencing packets over Geostationary satellites. Also this paper analyses the delays in setting/joining audio conferences and proposes to reduce the H.323 signalling messages in order to reduce the audio conference signalling delays.

This paper proposes a reliability enhancement routing protocol in Vehicular Ad hoc Network (VANET) called Priority based Routing Protocol with Reliability Enhancement (PRP-RE). Priority based Routing Protocol (PRP) was previously proposed to provide i) fully distributed routing protocol, ii) different quality of services (QoS) for different types of messages, iii) maximum message dissemination distance per hop of information relay. However, PRP cannot attain high reliability when dissemination distance becomes larger. With the reliability enhancement, implicit acknowledgement and retransmission mechanisms, PRP-RE are able to achieve both higher reliability and further message dissemination distance. PRP-RE is evaluated using network simulation tool named OMNeT++ in terms of average MAC delay as well as percentage of message reception and collision. The results show PRP-RE provides significant improvement in both reception rate and communication distance, with a little impact on MAC delay. In addition, PRP-RE is still able to maintain proportional MAC delay according to priorities of messages in fully distributed environment. Therefore, the PRP-RE presents a good balance of reliability, delay, and dissemination distance. © 2012 IEEE.

Although geographic routing is an alternative approach to topology routing in delay/disruption tolerant networks (DTNs), sparse network density and high mobility result in challenges to obtain the real time geographic information of destination if taking its mobility into account. Furthermore, sparse network density is also in contrast with high-network density, for handling the local maximum problem that the message carrier cannot find a better candidate node to relay a message. In this article, the authors investigate geographic routing in DTNs from another perspective, assuming the real time geographic information of mobile destination is always unavailable. The key insight is to estimate the movement range of the destination using its historical geographic information, to promote message replication reaching the edge of this range using a Reach Phase and spreading within this range using a Spread Phase. Then, these two phases are combined to promote message delivery within the limited message lifetime. The evaluation of results under the Helsinki city scenario show the advantage of our proposed Reach-and-Spread in terms of delivery ratio and average delivery latency as well as overhead ratio.

In the recent year the research in the area of satellite communication has been widen to cover many areas which once considered as higher layer protocols such as TCP/IP, UDP, HTTP, FTP. The main reason is the growing demand for satellite networks to provide wider range of services with Internet service as the fastest growing satellite communication applications. A number of commercial satellite systems have been proposed from all over the world targeting multimedia services. Currently most of the applications and services are based on the existing protocol such as TCP and UDP. It is also possible that in the future B-ISDN services can directly used the ATM. However, TCP is at the moment considered as the main protocol that has to be included. Implementing TCP over satellite links has significant impact on the performance of TCP and its applications due to various reasons as satellite links have many characteristics that differ from terrestrial channels. This paper discusses the Internet protocol architecture and applications over satellite and also evaluates their performance. Simulation results from the study of TCP over satellite networks will be present. This will give a clear indication about the level of effect that satellite networks have over TCP and some applications running over TCP. Also how some of the proposed solutions can be used to enhance and make TCP a more attractive protocol for satellite networks.

Data collection is a fundamental yet challenging task of Wireless Sensor Networks (WSN) to support a variety of applications, due to the inherent distinguish characteristics for sensor networks, such as limited energy supply, self-organizing deployment and QoS requirements for different applications. Mobile sink and virtual MIMO (vMIMO) techniques can be jointly considered to achieve both time efficient and energy efficient for data collection. In this paper, we aim to minimize the overall data collection latency including both sink moving time and sensor data uploading time. We formulate the problem and propose a multihop weighted revenue (MWR) algorithm to approximate the optimal solution. To achieve the trade-off between full utilization of concurrent uploading of vMIMO and the shortest moving tour of mobile sink, the proposed algorithm combines the amount of concurrent uploaded data, the number of neighbours, and the moving tour length of sink in one metric for polling point selection. The simulation results show that the proposed MWR effectively reduces total data collection latency in different network scenarios with less overall network energy consumption.

This paper proposes a novel and adaptive traffic light scheduling scheme via two-way Traffic-Light-to-Vehicle Communication (TLVC) for fuel consumption and CO2 emission reduction, namely CO2Red. In addition to TLVC, a pioneer priority framework is also proposed to give a high priority to heavily-loaded vehicles, which consume and emit larger amount of fuel and CO2 due to breaking and stoppage. The proposed scheme aims to promote a green driving environment in the land transportation sector by increasing green light hit rate for all vehicles, especially for heavily-loaded vehicles, and reduce the total amount of fuel consumption and CO2 emission by reducing the number of stops at traffic lights. The simulation results demonstrate that the green light hit rate of all vehicles is greatly improved, especially of heavily-loaded vehicles, which consequently reduces fuel consumption and CO2 emission in land transportation sector

At the beginning of the 2020s, computing is moving into a new phase from a centralized model to a decentralized one. The first shift from centralized computing to decentralized computing in 1980 was due to personal computing, which formed a foundation for the decentralization method. Since mid-2000, the centralized cloud computing has begun its rise to the outstanding position. Driven by the flourishing of IoT, many new issues have arisen, such as unprecedented data volume, latency control, bandwidth efficiency, reliability of service, and sustainability. These issues limit the development of latency-sensitive IoT-based applications such as unmanned autonomous vehicles (UAV), Machine to Machine (M2M) communications. Hence, various emerging edge-based computing models have been proposed to address these issues related to the post-cloud. This paper first reviews the concepts and challenges of cloud computing. It then explores the driving force from IoT technologies and reveals the relationship between the flourish of IoT and the emerging of post-cloud computing. It also compares several fundamental post-cloud paradigms and propose a new method to meet the challenges using simulations methods. Finally, it concludes the paper and highlights prospects for future research.

The integrated MANET and satellite network is a natural evolution in providing local and remote connectivity. The features of this integrated network, such as requiring no fixed infrastructure, ease of deployment and providing global ubiquitous communication, give advantages of its being popular. However, its unpredictable mobility of nodes, lack of central coordination and limited available resources emphasizes the challenges in networking. A large library of studies has been done in literature, yet some issues are still worth tackling, such as gateway selection mechanisms, satellite link management, resource management and so on. As a basic step of internetworking, the issue of gateway selection is studied specifically and corresponding optimization scheme for achieving load balancing is described.

Quality-of-service in terms of network connectivity and sensing coverage is important in wireless sensor networks. Particularly in sensor scheduling, it must be controlled to meet the required quality. In this paper, we present novel methods of the connected coverage optimization for sensor scheduling using a virtual hexagon partition composed of hexagonal cells. We first investigate the optimum number of active sensors to fully cover an individual hexagonal cell. According to the best case, a sensor selection method called the three-symmetrical area method (3-Sym) is then proposed. Furthermore, we optimize the coverage efficiency by reducing the overlapping coverage degree incurred from the 3-Sym method, which is called the symmetrical area optimization method. This considers coverage redundancy within the particular area, namely, sensor's territory. The simulation results show that we achieve not only complete connected coverage over the entire monitored area with the near-ideal number of active sensors but also the minimum overlapping coverage degree in each scheduling round.

There are great challenges in vehicular networks, i.e., continuous connectivity cannot be guaranteed due to interruptions. This paper proposes a novel multi-hop broadcasting protocol with low signaling overhead in vehicular networks with frequent interruptions named as Trinary Partitioned Black-Burst based Broadcast Protocol (3P3B-DTN). The protocol operates without any infrastructure. It has low overhead supporting different Quality of Service (QoS) levels. Both analysis and comprehensive simulations show that the proposed protocol outperforms the bench mark schemes.

Secure multicast communication is important for both wired and wireless applications. For groups with frequent join or depart requests, a distributed architecture that partitions the group members into several areas is preferred. Inside each area, scalable algorithms such as Logical Key Hierarchy (LKII) can be used to update the group key. However, these algorithms do not consider mobile members traveling in a Mobile Network as a whole. In this paper, we proposed two group key management schemes, which treat mobile members traveling in a Mobile Network as a whole. Both schemes try to reduce the communication costs when the Mobile Network moves in or out of the area. Simulation results show significant reduction in communications costs even for small number of mobile members in the Mobile Network.

The research in this letter focuses on geographic routing in Delay/Disruption Tolerant Networks (DTNs), by considering sparse network density. We explore the Delegation Forwarding (DF) approach to overcome the limitation of the geometric metric which requires mobile node moving towards destination, with the Delegation Geographic Routing (DGR) proposed. Besides, we handle the local maximum problem of DGR, by considering nodal mobility and message lifetime. Analysis and evaluation results show that DGR overcomes the limitation of the algorithm based on the given geometric metric. By overcoming the limited routing decision and handling the local maximum problem, DGR is reliable for delivering messages before expiration lifetime. Meanwhile, the efficiency of DGR regarding low overhead ratio is contributed by utilizing DF. © 2013 IEEE.

Network security protocols such as IPsec have been used for many years to ensure robust end⁃to⁃end communication and are impor⁃ tant in the context of SDN. Despite the widespread installation of IPsec to date, per⁃packet protection offered by the protocol is not very compatible with OpenFlow and flow⁃like behavior. OpenFlow architecture cannot aggregate IPsec⁃ESP flows in transport mode or tunnel mode because layer⁃3 information is encrypted and therefore unreadable. In this paper, we propose using the Secu⁃ rity Parameter Index (SPI) of IPsec within the OpenFlow architecture to identify and direct IPsec flows. This enables IPsec to con⁃ form to the packet⁃based behavior of OpenFlow architecture. In addition, by distinguishing between IPsec flows, the architecture is particularly suited to secure group communication.

Satellites play an important role in the future network due to their wide area coverage and for providing connectivity in remote regions of the world. This paper presents the end-to-end quality of service (QoS) measurements taken employing a European Space Agency (ESA) testbed over DVB-RCS infrastructure, in collaboration with University of Surrey, UK. The applications chosen for these experiments are file transfer (FTP), web browsing (HTTP) and video streaming. File transfer and web browsing require reliable transport mechanism as a corrupted bit will hinder the intact data delivery. Therefore, these applications use transmission control protocol (TCP) as the transport protocol. TCP involves a three way handshake, which introduces extra delay during data transfer. Video streaming is a real time application. It is time-sensitive and requires lesser reliability compared to FTP and Web services. Hence, it employs user datagram protocol (UDP) at the transport layer, which do not offer any guarantee of reliable data delivery but timely. The parameters that have been used to evaluate quality of service (QoS) are packet delivery time, file download time, round trip delay, packet sizes and packet loss. The paper presented measurement results and comparative analysis of the QoS of the applications over the DVB-RCS testbed.

Vehicular Delay Tolerant Networking (VDTN) is a special instance of Vehicular Ad hoc Networking (VANET) and in particular Delay Tolerant Networking (DTN) that utilizes infrastructure to enhance connectivity in challenged environments. While VANETs assume end-to-end connectivity, DTNs and VDTNs do not. Such networks are characterized by dynamic topology, partitioning due to lack of end-to-end connectivity, and opportunistic encounters between nodes. Notably, VDTNs enhances the capabilities DTNs to provide support for delay and intermittent connectivity. Hence, they can easily find applicability in the early stages of the deployment of vehicular networks characterized by low infrastructure deployment as is obtainable in rural areas and in military communications. Privacy implementation and evaluation is a major challenge in VDTNs. Group communication has become one of the well discussed means for achieving effective privacy and packet routing in ad hoc networks including VDTNs. However, most existing privacy schemes lack flexibility in terms of the dynamics of group formation and the level of privacy achievable. Again, it is difficult to evaluate privacy for sparse VDTNs for rural area and early stages of deployment. This paper reports on an improved privacy scheme based on group communication scheme in VDTNs. We analyze the performance of our model in terms of trade-off between privacy and performance based on delivery overhead and message delivery ratio using simulations. While this is a work in progress, we report that our scheme has considerable improvement compared to other similar schemes described in literature.

In the event of a disaster, there is a severe damage/destruction to physical infrastructures such as telecommunication and power lines which result in the disruption of communication in this areas. For such scenarios, Delay Tolerant Network (DTN) provides an alternative means of communication. In Delay Tolerant Networks (DTNs), a message from a source node may be delivered to the destination node despite the non-existence of an infrastructure and an end-to-end connectivity. However DTNs are susceptible to security threats such as DoS attacks targeted at disrupting relayed packets or dropping critical packets during a disaster rescue operation. DoS attacks consist of blackhole, grayhole, wormhole, packet flooding attacks etc. The scope of this paper is to study the impacts of blackhole and packet flooding attacks in a post disaster communication network using DTN. Various performance metrics in DTN have been used to study the impacts of different DoS attacks in DTN and a comprehensive analysis is presented.

This paper proposes a meshed Very Small Aperture Terminal (VSAT) satellite communications network which uses an On Board Processing (OBP) satellite with spot beams and cell switching capabilities. A novel approach is used for maximizing the bandwidth utilization of the satellite by performing statistical multiplexing on-board the satellite. MF-TDMA is used as satellite multiple access protocol since it takes advantage of the flexibility and statistical multiplexing capabilities of ATM. Finally, the cell loss resulting from the limited bandwidth of the satellite link can be prevented by effective traffic control functions. A preventive control scheme has been used for this purpose. The Leaky Bucket (or Generic Cell Rate Algorithm) used as Usage Parameter Control (UPC) controls the source traffic parameters for conformance with the traffic contract. Furthermore a rate-based flow control is used to control ABR services. The results of the performance analysis of the proposed system indicate that a high increase in satellite bandwidth utilization can be achieved, compared to circuit-switched satellite systems.

With the rapid development of the Internet, new technologies and applications are emerging. One of the important applications is voice over IP. Satellites are playing an important role to provide VoIP services with their global coverage and onboard processing ability over IP networks. Satellite network environment, generally characterized by large delay and erroneous link, is considered to be unfriendly to VoIP. The performance of VoIP is adversely influenced by these demerits. The performance metrics of VoIP are signaling, bandwidth, delay, jitter and packet loss. Signaling plays a key role in call establishment and rest of the parameters signifies the quality of service (QoS). In this paper, the performance related issues of SIP-based VoIP over current, IPv4, and next generation, IPv6 satellites is studied. A comparative analysis is performed for different voice codecs. The experimentation is carried out on the satellite network testbed at Centre for Communication Systems Research (CCSR) at University of Surrey. The results show that delay, jitter and packet loss are quite comparable for both current and next generation satellites. SIP signaling performs poorly in IPv6 as compared to IPv4. IPv6 can be adapted for VoIP over next generation satellites, but with some modifications for SIP signaling.

Mobile cloud computing is a new computing paradigm to integrate cloud computing technology into the mobile environment. It takes full advantages of cloud computing with great potential to transform a large part of the IT industry. The objectives of mobile cloud computing are to meet user demand, efficiently utilize a pool of resources, including mobile network, storage, and computation resources, and optimize energy on mobile devices. Here, the authors review the current mobile cloud computing technologies, highlight the main issues and challenges for the future development, and focus on resource management. Then, combining the current agent architectures and resource optimization strategies, they present an agent-based resource management to deal with multiple data and computation intensive applications of user demand. The chapter offers a promising solution of selecting the best service provider and efficiently utilizing mobile network resources given the user's request constraint.

Since the requirements of cross-domain/layer communications, the Space-ground Integrated Information Network (SIIN) becomes a strategic research area. To improve the service sustainability and reduce the latency of data transmission, literature works focus on evaluating the status of channels between ground stations and satellites, but underestimate the power of dynamic data allocation for handover management. This paper explores the relationship of data allocation and seamless handover in SIIN to provide high-reliability and service sustainability. We propose a Channel Perceiving-based Handover Management (CPHM) strategy to optimize the utilization of channels and dynamically adjust the data allocation strategy. Specifically, CPHM perceives the motion status of satellites to accurately evaluate their service time and reconstruct connectivities, e.g., altitude, velocity, motion direction, and location. Furthermore, CPHM evaluates the service capability of satellites to generate the strategy of data allocation and dynamically adjust this strategy. Then, to improve utilization of channels, CPHM manages transmission queues according the strategy of data allocation and length of queues. Extensive simulation results show that CPHM outperforms other baseline algorithms in terms of delivery ratio, average delivery latency, and interruption ratio.

This paper describes the issues that arise when using satellites for IP multicast, with the emphasis on multicast protocols and how their implementation depends on the satellite communications platform. Various link layer standards such as DVB-S, DVB-RCS and ATM can be used in satellites with on-board processing, and applied to meet user and network requirements for IP multicast. The paper provides an overview of the networking issues and their interactions. Specifically, we show how multicast networking protocols have to be modified to take into account the satellite link characteristics: these protocols include IGMP, multicast routing protocols and reliable multicast protocols. We also discuss how security systems support IP multicast.

It has been recognised that satellites can play very important role in supporting B-ISDN services based on ATM technology. There have been several projects to exploit ATM over satellite for broadband services since 1992. These include the European RACE II CATALYST project which developed a satellite ATM demonstrator and the EPSRC project which studied the interconnection of Broadband ATM Islands via satellite. In a broadband network environment, ATM over satellite can be used for inter-network connections as transit link and for terminal access as access link. For transit link a small number of earth stations require a high bit rate link. Static bandwidth reservation based on estimated fixed rates provide a simple solution. However for terminal access a large number of terminals require low bit rate links. Since the traffic is expected to have large fluctuations, a dynamic reservation system is a more efficient but complex solution. Dynamic reservation Time Division Multiple Access (TDMA) appears to be the best solutions, as it takes advantage of the flexibility and statistical multiplexing capabilities of ATM and supports all traffic classes. The paper shows that ATM over satellite can implement a flexible and efficient bandwidth resource management mechanisms which allows the satellite link to be configured to meet the requirements of broadband services from low bit rate to high bit rate. © 1996 The Institution of Electrical Engineers. Printed and published by the IEE.

The flexibility of mobile wireless ad hoc networks (MANET) and global coverage of satellite communications presented an ideal combination to provide emergency and disaster relief services. This paper presented the concept of a hybrid MANET-satellite network developed in the on optimising hybrid ad hoc and satellite networks (MONET) project funded within the EU 7th Framework Programme (FP7). It was considered to be a natural step of providing local and remote connectivity in a highly mobile, dynamic and often remote environment for emergency and disaster relief services, such as forest fire fight, mountain rescue and coast rescue. These composite networks raise significant challenges including: optimising network resources and link availability; providing quality of service (QoS) and quality of experience (QoE); minimising costs and maximising energy efficiency, taking into account its impact on both the MANET and satellite segments.

There is growing interest in providing multimedia and broadband access over satellites. However there are several technical challenges need to be addressed. One challenge is security in terms of understanding threats and providing an effective security system. This paper presents a security solution for the Unidirectional Lightweight Encapsulation (ULE). The security header extensions are presented together with detailed transmitter and receiver processing. Finally, the implementation of this solution is shown over the SATSIX project satellite emulator platform.

In order to enhance the cell coverage performance and achieve the higher spectral efficiency, 3GPP studied the new network deployment of Heterogeneous Networks (HetNets) for LTE-Advanced and has completed relevant work items [1]. In cochannel HetNet, Macros and low power nodes (LPNs), such as Femto, Pico and Relay, are deployed with overlapped coverage. For Macro/Pico scenarios, the Cell Range Expansion (CRE) scheme is utilized to offload heavy traffic from Macro cells [2]. However, due to imbalanced transmitting power, the interference between two layers of nodes is challenging, mainly Pico UEs suffer a severe DL interference. The time-domain enhanced inter-cell interference coordination (eICIC) method is one of the key solutions standardized in 3GPP [3-6], while proper design of almost blank subframes (ABS) pattern is left to implementation. In this paper, a novel configuration scheme is proposed for ABS pattern, particularly applied in TD-LTE-Advanced [7]. Evaluation results show that with the proper configuration of ABS pattern, a minimum 16% gain on throughput can be achieved for Pico. Although resource reduction can affect the throughput of Macros, the average system performance remains increasing under the scenarios of one Pico per Macro cell. © VDE VERLAG GMBH.

DTN environment is characterized by intermittent connectivity, high/variable delay, heterogeneity, high error rate and asymmetric data rate amongst others. These characteristics accounts for the poor behavior of Internet protocols in this environment. To address these problems, DTN was conceived and designed together with specialized protocols to carry out its services. Its emergence called for a new concept in security that was considered at the design stage. The main aim of this paper is to propose a traditional cryptography based authentication scheme that does not depend on network administrator’s availability during post network authentication communication and facilitates bundle processing by the recipient in the absence of connectivity. In this paper, we present and discuss the system model, the proposed credential and the propose authentication scheme. A simulation framework is developed for the implementation of the proposed and referenced schemes. From the simulation results, the proposed scheme was observed to be independent of network administrator’s availability during post network authentication communication and facilitates bundle processing in the absence of connectivity.

The intrinsic property of a MIMC (multi-interface multi-channel) network makes the routing in wireless ad hoc networks more diverse. Traditional ad hoc routing protocols can not make good use of the potential introduced by MIMC. In this paper, a cost-aware multi path routing protocol for MIMC ad hoc networks is proposed. Path cost is measured by link load and interference. The costs spread along the forward direction of RREQ and RREP messages. Then by improving the disjoint path criteria and reverse/forward path process, a RREQ/RREP Waiting Mechanism is proposed. A flow based data forwarding procedure is designed to decrease the interference between different flows. We applied this protocol to some network scenarios. Simulation results show the new protocol can significantly improve flow's throughput. © 2011 IADIS.

As modern vehicle and communication technologies advanced apace, people begin to believe that Intelligent Transportation System (ITS) would be achievable in one decade. ITS introduces information technology to the transportation infrastructures and aims to improve road safety and traffic efficiency. However, security is still a main concern in Vehicular Communication Systems (VCS). This can be addressed through secured group broadcast. Therefore, secure key management schemes are considered as a critical technique for network security. In this paper, we propose a framework for providing secure key management within the heterogeneous network. The security managers (SMs) play a key role in the framework by capturing the vehicle departure information, encapsulating block to transport keys and then executing rekeying to vehicles within the same security domain. The first part of this framework is a novel network topology based on a decentralised blockchain structure. The blockchain concept is proposed to simplify the distributed key management in heterogeneous VCS domains. The second part of the framework uses the dynamic transaction collection period to further reduce the key transfer time during vehicles handover. Extensive simulations and analysis show the effectiveness and efficiency of the proposed framework, in which the blockchain structure performs better in term of key transfer time than the structure with a central manager, while the dynamic scheme allows SMs to flexibly fit various traffic levels.

Description Satellite networking is an exciting and expanding field that has evolved significantly since the launch of the first telecommunications satellite, from telephone and broadcast to broadband ATM and Internet. With increasing bandwidth and mobility demands on the horizon, satellites have become an integral part of the Global Network Infrastructure (GNI). Satellite Networking: Principles and Protocols provides a balanced coverage of satellite topics from a network point of view, focusing on network aspects, services and applications, quality of service (QoS) and principles and protocols. •Introduces the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks •Discusses the real-time protocols including RTP, RTCP and SIP for real-time applications such as VoIP and MMC •Coverage of new services and applications, internet traffic engineering and MPLS •Examines IPv6 over satellite using tunnelling and translation techniques, evolution of earth stations, user terminals and network protocols, and development of satellite networking

This article discusses an effective revocation scheme for disconnected Delay Tolerant Vehicular Ad hoc Networks (VANETs). Malicious vehicles can exhibit various misbehaviour such as dropping packets due to selfish reasons. Selfishness can be due to the need to conserve limited resources such as energy and bandwidth. This forces vehicles to either drop all or some of the packets they receive. This is particularly obtainable in multi-hop forwarding networks where packets are routed from one vehicle to another towards their destination. When some packets are dropped, the usefulness of the system is not fully realised since it affects the quality of information available to vehicles for making driving decisions such as road manoeuvres. Additionally, packet dropping can degrade the routing efficiency of the system. In extreme cases of misbehaviour, it is important to stop such vehicles from further participation in network communication. One way of achieving this is through revocation. However, it is important to establish mechanisms for identifying such vehicles before blacklisting them for revocation. Our objective here is to address the question of how much we can use a trust-based scheme where vehicles cannot always be expected to follow normal protocols for revocation. Revocation or suspension of misbehaving vehicles is essential to avoid havoc and possible economic damage.

Data collection is a fundamental task of Wireless Sensor Networks (WSN) to support a variety of applications, such as remote monitoring, and emergency response, where collected information is relayed to an infrastructure network via packet gateways for processing and decision making. In large-scale monitoring scenarios, data packets need to be relayed over multi-hop paths to the gateways, and sensors are often randomly deployed, causing local node density differences. As a result, imbalance in data traffic load on the gateways is likely to occur. Furthermore, due to dynamic network conditions and differences in sensor data generation rates, congestion on some data paths is also often experienced. Numerous studies have focused on the problem of in-network traffic load balancing, while a few works have aimed at equalizing the loads on gateways. However, there is a potential trade-off between these two problems. In this paper, the dual objective of gateway and in-network load balancing is addressed and the RALB (Reactive and Adaptive Load Balancing) algorithm is presented. RALB is proposed as a generic solution for multihop networks and mesh topologies, especially in large-scale remote monitoring scenarios, to balance traffic loads.

The rapid growth in the demand for Future Internet services with many emerging group applications has driven the development of satellite, which is the preferred delivery mechanism due to its wide area coverage, multicasting capability and speed to deliver affordable future services. Nevertheless, security has been one of the obstacles for both satellite services as well as smart grid group applications, especially with logical/geographical/cryptographic domains spanning heterogeneous networks and regions. In this paper, adaptive security architecture is implemented to protect satellite services for smart grid group applications. The focus is on key management and policy provisioning. Leveraging Group Domain of Interpretation (GDOI) as the standard for smart grid centralized key/policy management architecture, a single Domain of Interpretation (DOI) is deployed and evaluated critically in terms of the added protocol signaling overhead on the satellite system for a fixed-network scenario. This also partially realizes the growing trend towards the use of TCP/IP technology for smart grid applications.

Routing in delay/disruption-tolerant networks (DTNs) is without the assumption of contemporaneous end-to-end connectivity to relay messages. Geographic routing is an alternative approach using real-time geographic information instead of network topology information. However, if considering the mobility of destination, its real-time geographic information is often unavailable due to sparse network density in DTNs. Using historical geographic information to overcome this problem, we propose the converge-and-diverge (CaD) by combining two routing phases that depend on the proximity to the movement range estimated for destination. The key insight is to promote message replication converging to the edge of this range and diverging to the entire area of this range to achieve fast delivery, given limited message lifetime. Furthermore, the concept of delegation replication (DR) is explored to overcome the limitation of routing decisions and the local maximum problem. Evaluation results under the Helsinki city scenario show an improvement of CaD in terms of delivery ratio, average delivery latency, and overhead ratio. Since geographic routing in DTNs has not received much attention, apart from the design of CaD, our novelty also focuses on exploring DR to overcome the limitation of routing decision and the local maximum problem, in addition to enhancing efficiency, as DR originally intended. © 1967-2012 IEEE.

Energy-aware traffic engineering (ETE) has been gaining increasing research attentions due to the cost reduction benefits that it can offer to network operators and for environmental reasons. While numerous approaches exist which attempt to provide energy reduction benefits by intelligently manipulating network devices and their configurations, most of them suffer from one fundamental shortcoming: however, minor adaptations to a given IP network topology configuration all lead to temporal service disruptions incurred by routing reconvergence, which makes these schemes less appealing to network operators. The more frequently the IP topology reconfigurations take place in order to optimize the network performance against dynamic traffic demands, the more frequently service disruptions will occur to end users. Motivated by the essential requirement for network operators to enable seamless service assurance, we put forward a framework for disruption-free ETE, which leverages on selective link sleeping and wake-up operations in a disruption-free manner. The framework allows for maximizing the opportunities for disruption-free reconfigurations based on intelligent IGP link weight settings, assisted by a dynamic scheme that optimizes the reconfigurations in response to changing traffic conditions. As our simulation-based evaluation show, the framework is capable of achieving significant energy saving gains while at the same time ensuring robustness in terms of disruption avoidance and resilience to congestion.

Network simulator has been acknowledged as one of the most flexible means in studying and developing protocol as it allows virtually endless numbers of simulated network environments to be setup and protocol of interest to be fine-tuned without requiring any real-world complicated and costly network experiment. However, depending on researchers, the same protocol of interest can be developed in different ways and different implementations may yield the outcomes that do not accurately capture the dynamics of the real protocol. In the last decade, TCP, the protocol on which the Internet is based, has been extensively studied in order to study and reevaluate its performance particularly when TCP based applications and services are deployed in an emerging Next Generation Network (NGN) and Next Generation Internet (NGI). As a result, to understand the realistic interaction of TCP with new types of networks and technologies, a combination of a real-world TCP and a network simulator seems very essential. This work presents an integration of real-world TCP implementation of Linux TCP/IP network stack into a network simulator, called INET. Moreover, verification and validation of the integrated Linux TCP are performed within INET framework to ensure the validity of the integration. The results clearly confirm that the integrated Linux TCP displays reasonable and consistent dynamics with respect to the behaviors of the real-world Linux TCP. Finally, to demonstrate the application of the INET with Linux TCP extension, algorithms of other Linux TCP variants and their dynamic over a large-bandwidth long-delay network are briefly presented.

The Internet has become an important part of day to day activities. There is hardly a day without using Internet, such as reading Emails and articles as well as enjoying music and video. Thus, it is very important for the Internet to be provided to anyone anywhere. Terrestrial network has been the underlying infrastructure for the Internet. However, terrestrial network by itself cannot always satisfy all of the growing demands for the Internet, particularly in the remote areas. Thus, the deployment of the Next Generation Satellite Network (NGSN) is needed to fill in the gap and break the digital divide. This paper evaluates how the performances of TCP over NGSN with dynamic bandwidth allocation mechanism. The TCP used in this work is a real-world TCP based on both Linux and Window Vista implementations which have been integrated into a network simulator, INET. The study reveals that the TCP performances in terms of utilization and robustness, friendliness and fairness, and user's perceived Quality of Service are clearly affected by the dynamic bandwidth allocation mechanism. ©2008 IEEE.

Security is an important concern in today's information age and particularly so in satellite systems, where eavesdropping can be easily performed. This paper addresses efficient key management for encrypted multicast traffic transmitted via satellite. We consider the topic of encrypting traffic in large multicast groups, where the group size and dynamics have a significant impact on the network load. We consider life cycle key management costs of a multicast connection, and show for a logical key hierarchy (LKH) how member preregistration and periodic admission reduces the initialization cost, and how the optimum outdegree of a hierarchical tree varies with the expected member volatility and rekey factor. This improves network utilization, but encryption at the network layer can pose problems on satellite links. We, therefore, propose and analyze an interworking solution between multilayer Internet protocol security (IPSEC) and LKH that also reduces key management traffic while enabling interworking with performance enhancing modules used on satellite links.

Abstract Intelligent transportation system (ITS) is proposed as the most effective way to improve road safety and traffic efficiency. However, the future of ITS for large scale transportation infrastructures deployment highly depends on the security level of vehicular communication systems (VCS). Therefore, security key management schemes are considered as a critical research topic for network security. In this paper, we propose a framework for providing secure key management within heterogeneous network. The security managers (SMs ) Play a key role in the framework by retrieving the vehicle departure information, encapsulating block to transport keys and then executing rekeying to vehicles within the same security domain. The first part of this framework is a novel Group Key Management (GKM) scheme basing on (LP) of vehicles to depart current VCS region. Vehicle's LP factor is introduced into GKM scheme to achieve a more efficient rekeying scheme and less rekeying costs. The second component of the framework using the blockchain concept to simplify the distributed key management in Heterogeneous VCS domains. Extensive simulations and analysis are provided to show the effectiveness and efficiency of the proposed framework: Our GKM results demonstrate that probability-based BR reduces rekeying cost compared to the benchmark scheme, while the blockchain decreases the time cost of key transmission over heterogeneous networks.

Wireless Sensor Network (WSN) is one of the major research areas in computer network field today. The function of WSN in this paper is to provide sensing services in an un-attended harsh environment. Sensed data need to be delivered to the sink and to cope with the network unreliability problem. Few routing protocol takes into consideration of this problem. It is a great challenge of the hierarchical routing protocol to provide network survivability and redundancy features. In this paper, a short literature review of the existing routing protocol is carried out. Then a novel hierarchical routing protocol, which addresses network survivability and redundancy issues, is introduced. Initial analysis shows promising results of the proposed protocol over LEACH. Finally, conclusion was drawn based on the research and future direction for further research is identified.

About this bookThe revised and updated sixth edition of Satellite Communications Systems contains information on the most recent advances related to satellite communications systems, technologies, network architectures and new requirements of services and applications. The authors – noted experts on the topic – cover the state-of-the-art satellite communication systems and technologies and examine the relevant topics concerning communication and network technologies, concepts, techniques and algorithms. New to this edition is information on internetworking with the broadband satellite systems, more intensive coverage of Ka band technologies, GEO high throughput satellite (HTS), LEO constellations and the potential to support the current new broadband Internet services as well as future developments for global information infrastructure. The authors offer details on digital communication systems and broadband networks in order to provide high-level researchers and professional engineers an authoritative reference. In addition, the book is designed in a user-friendly format.

This book provides up to date coverage of the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks Satellite Networking: Principles and Protocols, Second Edition provides up to date information of the original topics in satellite networking and protocols focusing on Internet Protocols (IP) over satellites, broadband over satellites, next generation IP (IPv6) over satellites, new generation of DVB-S/S2 and DVB-RCS next generations and new services and applications. It also includes some analytical techniques for evaluation of end to end IP performance and QoS over satellite, reflecting the recent convergence of telecommunication, Internet, broadcasting and mobile networks. Topics new to this edition: Internetworking with MANET, DVB-S/S2 and DVB-RCS/RCS2 (including TCP/IP over DVB-S/RCS), recent developments in broadband satellite systems, convergence of services and network technologies (including Internet, telecom, mobile, TV, etc.), radio resource management, PEP, I-PEP, SCPS, traffic modelling and engineering with analysis and examples, and future developments of satellite networking. • Provides up to date coverage of the basics of ATM and internet protocols, and characteristics of satellite networks and internetworking between satellite and terrestrial networks (e.g. mobile ad hoc networks), including coverage of new services and applications (e.g. Internet, telecom, mobile and TV) • Discusses the real-time protocols including RTP, RTCP and SIP for real-time applications such as VoIP and MMC, and explains TCP/IP over satellite and evolution of IPv6 over satellite and beyond

In recent years, Mobile Ad hoc Networks (MANETs) have been great interest all over the world for its advantage of high mobility and flexibility. It is also among the greatest challenges in wireless communications. As a special type of MANET, Vehicular Ad hoc Networks (VANETs) are considerably important in Next-Generation Networking (NGN). Unlike typical MANETs, VANETs are much more challenging due to high velocity, which makes classic MANET routing protocols cannot fit in such scenarios efficiently. This paper is intended to evaluate performance of two different routing protocols, namely DSDV and AODV, in various realistic scenarios. Thus, a DSDV optimization approach is therefore proposed to improve DSDV's performance in VANETs.

Secure group communication is important for applications such as pay-per-view. Other authors have proposed the key tree approach to distribute a shared group key in a way such that the rekeying cost scales linearly with the logarithm of the group size for a join or depart request. The efficiency of the key tree approach depends critically on whether the key tree remains balanced. Periodic rebalancing can be used to balance the key tree whenever it becomes unbalanced but this adds extra costs to the network. In this paper, we present two Merging Algorithms suitable for batch join events. As the multicast session consists of other events as well, we then show how we can extend our algorithms into existing work to minimise the maximum difference in height without adding extra network costs. Simulation results show our Merging Algorithms not only balance the key tree but their rekeying costs are lower compared to existing algorithms. (C) 2006 Elsevier Ltd. All rights reserved.

In this paper, we investigate the impacts of different radio propagation environments on the performance of emergency message dissemination Vehicular Ad hoc Networks (VANETs). We compared the performances of the benchmark existing broadcast protocols for Emergency Message Dissemination in VANETs. We consider three different propagation models, namely, Log-Normal Shadowing, Longley-Rice, and Nakagami to model six different simulation scenarios of both highway and urban areas. The objective is to provide a qualitative assessment of the protocols applicability in different vehicular scenarios. It is demonstrated that Trinary Partition Black-Burst based Broadcast Protocol (3P3B) reduces the communication delay, increases dissemination speed, increase reliability, and outperforms the well-known existing broadcast protocols for emergency message dissemination in VANETs in all propagation environments. The benchmark protocols achieve high performance in various vehicular scenarios both in highway and urban areas. However, there is still some reliability issue needed to be addressed by all existing protocols, such as communications in a very crowded city where the received communication signal is strongly distorted.

The framework of Delay Tolerant Networks (DTNs) has received an extensive attention from academic community because of its application ranging from Wireless Sensor Networks (WSNs) to interplanetary networks. It has a promising future in military affairs, scientific research and exploration. Due to the characteristic of long delay, intermittent connectivity and limited network resource, the traditional routing algorithms do not perform well in DTNs. In this paper, our proposed algorithm is based on an asymmetric spray mechanism combining with the concept of message classes. For each message class, a corresponding forwarding queue is designed and these queues are scheduled according to their priorities. Together with other designed assistant functions, our proposed algorithm outperforms other state of the art algorithms in terms of delivery ratio, overhead ratio, average latency as well as energy consumption.

Here, the networking aspects of the broadband satellite constellations are discussed, and the suitability of the constellations for multicast is assessed.

In this paper, an evaluation of SIP signaling and voice QoS for SIP based VoIP using GSM voice codec system over IPv6 MANETs with Static, and Random mobility models. This evaluation study considered two types of reactive routing protocols, AODV and DSR. The study examined IPv4, IPv6, and Robust Header Compression (ROHC) as a compression/decompression system for IPv6 headers. The evaluation results show that SIP signaling and VoIP traffic are acting poorly over IPv6 even when applying ROHC. In general, AODV has low performance over different types of Random mobility models for MANET nodes, while DSR shows better performance with Static mobility models and bad performance with Random mobility models. When using ROHC for TCP traffic, a level of enhanced performance had shown for SIP based VoIP calls over IPv6 MANET. However ROHC still has longer delays and poor performance compared with SIP based VoIP over IPv4 MANET. Therefore, the SIP signaling for IPv6 MANET reactive protocols require further enhancements for SIP/TCP registration and retransmission timers to be able to employ the capabilities of IPv6 and ROHC system for SIP based VoIP and real-time applications over MANET.

Ordinary aircrafts rely on point to point wire connection to transmit data. These wires add additional weight to the aircrafts and thus, the fuel cost is increased. Aircrafts released in recent years used AFDX protocol to transfer data within the aircraft. AFDX is a deterministic network transfer protocol used in aircrafts to ensure the quality of service (QoS) on the network and reduce the wiring needed. However, the specification of AFDX only defines the required performance without providing the methods to achieve it and hence there is a room for research. The motivation of this paper is to investigate and analyse impact of different scheduling policies of End System on the performance of a real avionic on-board data network running AFDX protocol.

Next Generation Satellite Network (NGSN) possesses unique characteristics; large coverage area, quick deployment, native broadcasting/multicasting capability, multiple spotbeams, high bandwidth and on-broad processor (OBP). These features enable NGSN to play an important role in providing ubiquitous global Next Generation Internet (NGI). The original Internet is restricted mainly to terrestrial network and supports only best effort service. NGI is to support multiservice applications with service differentiation and extending Internet access beyond the reach of terrestrial network. Based on the integrated satelliteterrestrial network, a main infrastructure for global ubiquitous Internet is envisaged and Internet applications can be accessed anywhere anytime. However, one of the key successes depends mainly on the capabilities of the satellite OBP. Without it, the preservation of end-to-end (e2e) service differentiation has to be dealt with at ground hub stations, thus increasing e2e delay. This paper studies the impacts of different on-board queueing schemes on the quality of multiservice applications on NGI and suggests that the quality of multiservice applications is generally enhanced if the on-board service differentiation is supported. © 2008 IEEE.

Forest fires require huge resources to monitor and fight. It demands for a monitoring system to link all the resources for effective management. Information needs to be delivered to the base station and to cope with the network unreliability problem. Few routing protocol takes into consideration of this problem. It is a great challenge of the hierarchical routing protocol to provide Quality of Service (QoS) in the presence of different data types. This paper is extension work of [2] for QoS issue. A brief review of the existing routing protocol is given, followed by a description of the proposed protocol. Based on simulation results, the proposed routing protocol achieved superior performance about 80% better in terms of end-to-end delay with respect to the network size than selected existing routing protocols. Finally, conclusion was drawn based on the research and future direction for further research is identified. ©2009 IEEE.