Muhammad Ali Imran

Dr Muhammad Imran Fellow IET, Senior Fellow HEA

Professor in Communications
DIC, MSc, PhD, SMIEEE, Fellow of Higher Education Academy

About

University roles and responsibilities

  • Faculty Lead - Curriculum Design for Engineering for Health
  • Coordinator for communications related curriculum and pathways update
  • Post Graduate Admissions Tutor (for Subcontinent Region and Greece)
  • Visiting Tutor to Professional Training Year Placement students
  • Member of course review panel
  • Member of subcommittee for Faculty Learning and Teaching Committee

    Affiliations and memberships

    IEEE
    Senior Member
    Higher Education Academy
    Senior Fellow

    Research

    Research interests

    Research collaborations

    Teaching

    Publications

    Tang W, Shakir M, Imran MA, Tafazolli R, Alouini M (2012) Throughput Analysis for Cognitive Radio Networks with Multiple Primary Users and Imperfect Spectrum Sensing,IET Communications6(17)pp. 2787-2795 IEEE
    DOI: 10.1049/iet-com.2012.0236
    In cognitive radio networks, the licensed frequency bands of the primary users (PUs) are available to the secondary user (SU) provided that they do not cause significant interference to the PUs. In this study, the authors analysed the normalised throughput of the SU with multiple PUs coexisting under any frequency division multiple access communication protocol. The authors consider a cognitive radio transmission where the frame structure consists of sensing and data transmission slots. In order to achieve the maximum normalised throughput of the SU and control the interference level to the legal PUs, the optimal frame length of the SU is found via simulation. In this context, a new analytical formula has been expressed for the achievable normalised throughput of SU with multiple PUs under prefect and imperfect spectrum sensing scenarios. Moreover, the impact of imperfect sensing, variable frame length of SU and the variable PU traffic loads, on the normalised throughput has been critically investigated. It has been shown that the analytical and simulation results are in perfect agreement. The authors analytical results are much useful to determine how to select the frame duration length subject to the parameters of cognitive radio network, such as network traffic load, achievable sensing accuracy and number of coexisting PUs.
    Katranaras E, Imran MA, Hoshyar R (2011) Energy Aware Transmission in Cellular Uplink with Clustered Base Station Cooperation,IEEE Vehicular technology Conference - VTC Spring 2011 IEEE
    DOI: 10.1109/VETECS.2011.5956541
    We provide an analytical formula to evaluate the performance of the uplink of planar cellular networks when joint processing is enabled among limited number of base stations in a generalised fading environment. Focusing on user transmission power allocation techniques to mitigate inter-cluster interference we investigate the system?s spectral-energy efficiency trade-off. The paper addresses the gains in both cell throughput and transmissions energy efficiency due to the combined strategies of base station cooperation and user power management. We assess the effect of the propagation environment and of the key network design parameters of cooperation cluster size and intersite distance on the overall performance providing numerical results for a real-world scenario.
    Katranaras E, Imran MA, Dianati M (2013) Energy-aware clustering for multi-cell joint transmission in LTE networks, 2013 IEEE International Conference on Communications Workshops, ICC 2013pp. 419-424
    DOI: 10.1109/ICCW.2013.6649270
    This paper investigates the energy-aware clustering of cooperating base stations in the downlink of cellular networks. The focus of this work is on static clustering deployments for LTE systems when joint signal precoding is employed at multiple base stations. We demonstrate that properly planned clustering can provide the desired balance between network spectral and energy efficiency. To this end, we compare the overall energy consumption of various clustered cooperation layouts while considering different target performance metrics at user end. Our evaluations for various inter-site distance deployments in a practical macrocell scenario unveil the individual parameters controlling the energy effectiveness of a clustering strategy. In fact, it is shown that the choice of the optimum clustering layout depends on: 1) the specific service demands; 2) the deployment density of the network and; 3) on the ability of the base stations to jointly adjust their transmit power. Ultimately, we provide a general framework for choosing the most appropriate cooperation set of base stations in energy-aware networks. © 2013 IEEE.
    Peyvandi H, Imran A, Imran MA, Tafazolli R (2013) On Pareto-Koopmans Efficiency for Performance-Driven Optimisation in Self-Organising Networks, IET Digital Library
    Onireti OS, Papaioannou C, Imran MA, Arshad K (2015) Self-Optimization of Cell Sizes in Cellular Networks,
    The next generation networks seem to be too dense compared to the existing one, so a self-control mechanism, which determines the optimal cell size will be essential. In this paper, we present self organized cell size control algorithms, which maintain optimum system throughput and power consumption. Particularly, we investigate three different algorithms that control the cells size, while maintaining the optimum power consumption and block allocation in the network. These algorithms differ in terms of their decision area. The first one is based on a centralized control; the second one is a distributed approach; and the final one is based on a group distributed control. In order to evaluate their performance, these algorithms are tested upon two different simulation environment, which approach real scenarios. Our results indicate that the group distributed algorithm is the best approach for future network, since it has a good performance and about 10 times lower computational complexity when compared with the centralized approach.
    Sabagh MR, Dianati M, Imran MA, Tafazolli R (2013) A heuristic energy efficient scheduling scheme for VoIP in 3GPP LTE networks, 2013 IEEE International Conference on Communications Workshops, ICC 2013pp. 413-418
    DOI: 10.1109/ICCW.2013.6649269
    In this paper, first, energy efficiency of well known and principal scheduling schemes, Round Robin (RR), Best Channel Quality Indicator (BCQI), and Proportional Fair (PF) is evaluated. Then, a novel energy efficient scheme in low load traffic conditions is proposed. The proposed scheme trades off bandwidth for energy whenever possible depending on the load of the network. By applying this approach on the principal schedulers, three relevant energy efficient schedulers for Voice over IP (VoIP) traffic, namely, Energy Efficient Round Robin (EERR), Energy Efficient Best Channel Quality Indicator (EE-BCQI), and Energy Efficient Proportional Fair (EEPF) are introduced. The results of performance analysis, which are based on the specifications of the downlink of 3GPP LTE (Long Term Evolution) demonstrate the superior performance of the proposed scheme in terms of energy consumption of the network, while providing required Quality of Service (QoS) for the users. © 2013 IEEE.
    Kaltakis D, Imran MA, Katranaras E, Hoshyar R (2010) Fairness and user rate distribution in joint processing systems,
    DOI: 10.1109/ICC.2010.5502310
    In this paper we provide a geometric and mathematical model that can be used to evaluate the user rate distribution for a cellular system under the notion of a hyper receiver incorporating realistic system parameters. Variable cell sizes and different location-based decoding orders are analysed and the uplink user rate distribution of a cellular system in which each transmitted signal experiences a distance dependent path loss, fast fading and slow fading, is derived. Interestingly enough, among the three different decoding orders examined, the forward one provides the best results both in terms of fairness (larger percentage of users get satisfactory rates) and minimum rate. The difference among the decoding orders becomes even more notable as the cell sizes increase. There has also to be noted that none of these decoding orders affect the sum-rate.
    Saeed A, Katranaras E, Dianati M, Imran MA (2016) Dynamic femtocell resource allocation for managing inter-tier interference in downlink of heterogeneous networks, IET COMMUNICATIONS10(6)pp. 641-650 INST ENGINEERING TECHNOLOGY-IET
    DOI: 10.1049/iet-com.2015.0153
    Qi Y, Imran MA, Tafazolli R (2012) Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-forward Systems,IEEE VTC Fall 2012pp. 1-5 IEEE
    DOI: 10.1109/VTCFall.2012.6399180
    While many studies have concentrated on providing theoretical analysis for the relay assisted compress-and-forward systems little effort has yet been made to the construction and evaluation of a practical system. In this paper a practical CF system incorporating an error-resilient multilevel Slepian-Wolf decoder is introduced and a novel iterative processing structure which allows information exchanging between the Slepian-Wolf decoder and the forward error correction decoder of the main source message is proposed. In addition, a new quantization scheme is incorporated as well to avoid the complexity of the reconstruction of the relay signal at the final decoder of the destination. The results demonstrate that the iterative structure not only reduces the decoding loss of the Slepian-Wolf decoder, it also improves the decoding performance of the main message from the source.
    Akbari I, Onireti O, Imran A, Imran MA, Tafazolli R (2015) Impact of Inaccurate User and Base Station Positioning on Autonomous Coverage Estimation,2015 IEEE 20TH INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELLING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD)pp. 114-118 IEEE
    Jiang J, Dianati M, Imran M, Tafazolli R, Zhang S (2013) Energy Efficiency Analysis and Optimization for Virtual-MIMO Systems,IEEE Transactions on Vehicular Technology63(5)pp. 2272-2283 IEEE
    DOI: 10.1109/TVT.2013.2291435
    Virtual multiple-input-multiple-output (MIMO) systems using multiple antennas at the transmitter and a single antenna at each of the receivers have recently emerged as an alternative to point-to-point MIMO systems. This paper investigates the relationship between energy efficiency (EE) and spectral efficiency (SE) for a virtual-MIMO system that has one destination and one relay using compress-and-forward (CF) cooperation. To capture the cost of cooperation, the power allocation (between the transmitter and the relay) and the bandwidth allocation (between the data and cooperation channels) are studied. This paper derives a tight upper bound for the overall system EE as a function of SE, which exhibits good accuracy for a wide range of SE values. The EE upper bound is used to formulate an EE optimization problem. Given a target SE, the optimal power and bandwidth allocation can be derived such that the overall EE is maximized. Results indicate that the EE performance of virtual-MIMO is sensitive to many factors, including resource-allocation schemes and channel characteristics. When an out-of-band cooperation channel is considered, the performance of virtual-MIMO is close to that of the MIMO case in terms of EE. Considering a shared-band cooperation channel, virtual-MIMO with optimal power and bandwidth allocation is more energy efficient than the noncooperation case under most SE values.
    Onireti OS, Nur F, Imran MA, Arshad K (2015) System Level Power Consumption Model for Mobile Phones As Part of E3F,
    The Global energy consumption and carbon footprint related to operating mobile phones in wireless networks is increasing significantly. In order to determine the overall energy consumption of a wireless network, both the operation of the network infrastructure and the devices connected to that network must be considered. Although the larger part of the global energy consumption of wireless networks is consumed at base station sites and access points, a significant part is consumed from the operation of mobile phones. In this paper, system level power consumption models for mobile phones in terms of 2G, 3G and Wi-Fi are presented. The developed model increases the accuracy of the current power profiles by considering different stages of a single transmission, including the variables affecting each stage. The power states of wireless interfaces, maintenance, network attachment/detachment and network resource allocation policies of different network operators are also considered to obtain a complete model that can accurately predict that power consumption at every stage of connectivity. A comparison between power consumption of different radio access technologies is also included to promote energy efficient use of spectrum. Using the system level power models presented in this paper, the contribution of the operation of mobile phones to overall energy consumption of wireless communication networks can be determined.
    Razavi R, Al-Imari M, Imran MA, Hoshyar R, Chen D (2012) On Receiver Design for Low Density Signature OFDM (LDS-OFDM),IEEE Transactions on Communications60(11)pp. 3499-3508 IEEE
    DOI: 10.1109/TCOMM.2012.082812.110284
    Low density signature orthogonal frequency division multiplexing (LDS-OFDM) is an uplink multi-carrier multiple access scheme that uses low density signatures (LDS) for spreading the symbols in the frequency domain. In this paper, we introduce an effective receiver for the LDS-OFDM scheme. We propose a framework to analyze and design this iterative receiver using extrinsic information transfer (EXIT) charts. Furthermore, a turbo multi-user detector/decoder (MUDD) is proposed for the LDS-OFDM receiver. We show how the turbo MUDD is tuned using EXIT charts analysis. By tuning the turbo-style processing, the turbo MUDD can approach the performance of optimum MUDD with a smaller number of inner iterations. Using the suggested design guidelines in this paper, we show that the proposed structure brings about 2.3 dB performance improvement at a bit error rate (BER) equal to 10^{-5} over conventional LDS-OFDM while keeping the complexity affordable. Simulations for different scenarios also show that the LDS-OFDM outperforms similar well-known multiple access techniques such as multi-carrier code division multiple access (MC-CDMA) and group-orthogonal MC-CDMA.
    Heliot F, Imran MA, tafazolli R (2011) On the Energy Efficiency Gain of MIMO Communication under Various Power Consumption Models,
    Al-Imari M, Xiao P, Imran MA, Tafazolli R (2014) Radio Resource Allocation for Uplink OFDMA Systems with Finite Symbol Alphabet Inputs,IEEE Transactions on Vehicular Technology63(4)pp. 1917-1921 IEEE
    DOI: 10.1109/TVT.2013.2287809
    In this paper, we consider the radio resource allocation problem for uplink OFDMA system. The existing algorithms have been derived under the assumption of Gaussian inputs due to its closed-form expression of mutual information. For the sake of practicality, we consider the system with Finite Symbol Alphabet (FSA) inputs, and solve the problem by capitalizing on the recently revealed relationship between mutual information and Minimum Mean-Square Error (MMSE). We first relax the problem to formulate it as a convex optimization problem, then we derive the optimal solution via decomposition methods. The optimal solution serves as an upper bound on the system performance. Due to the complexity of the optimal solution, a low-complexity suboptimal algorithm is proposed. Numerical results show that the presented suboptimal algorithm can achieve performance very close to the optimal solution and outperforms the existing suboptimal algorithms. Furthermore, using our proposed algorithm, significant power saving can be achieved in comparison to the case when Gaussian input is assumed.
    Sambo Y, Shakir M, Ekti A, Qaraqe K, Serpedin E, Imran MA K-Tier Heterogeneous Small-Cell Networks: Towards Balancing the Spectrum Usage and Power Consumption with Aggressive Frequency Reuse,
    Heliot F, Imran MA, Tafazolli R (2013) Low-Complexity Energy-Efficient Resource Allocation for the Downlink of Cellular Systems,IEEE Transactions on Communications
    DOI: 10.1109/TCOMM.2013.042313.120516
    Energy efficiency (EE) is undoubtedly an important criterion for designing power-limited systems, and yet in a context of global energy saving, its relevance for power-unlimited systems is steadily growing. Equally, resource allocation is a well-known method for improving the performance of cellular systems. In this paper, we propose an EE optimization framework for the downlink of planar cellular systems over frequency-selective channels. Relying on this framework, we design two novel low-complexity resource allocation algorithms for the single-cell and coordinated multi-cell scenarios, which are EE-optimal and EE-suboptimal, respectively. We then utilize our algorithms for comparing the EE performance of the classic non-coordinated, orthogonal and coordinated multi-cell approaches in realistic power and system settings. Our results show that coordination can be a simple and effective method for improving the EE of cellular systems, especially for medium to large cell sizes. Indeed, by using a coordinated rather than a non-coordinated resource allocation approach, the per-sector energy consumption and transmit power can be reduced by up to 15% and more than 90%, respectively.
    Héliot F, Imran MA, Tafazolli R (2012) A Tight Closed-Form Approximation of the SISO Energy Efficiency-Spectral Efficiency Trade-Off,
    Due to the rise of the energy efficiency (EE) as a system performance evaluation criterion, the EE-spectral efficiency (SE) trade-off is becoming a key tool for getting insight on how to efficiently design future communication system. As far as the single-input single-output (SISO) Rayleigh fading channel is concerned, the EE-SE trade-off has been accurately approximated in the past but only at low-SE. In this paper, we propose a novel and more generic closed-form approximation (CFA) of this EE-SE trade-off which is very accurate for any SE values. We compare our CFA with two existing CFAs and show the great accuracy of the former for a wider range of SE in comparison with the latter. As an application, we use our CFA to study the variation of EE-SE trade-off when a realistic power model is assumed and to compare the energy consumption of SISO against a 2x2 multi-input multi-output (MIMO) system over the Rayleigh fading channel.
    Konstantinou K, Imran MA, Tzaras C (2008) Transmit Power Formulation for Relay-enhanced UMTS using Simulation and Theory, IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC?08
    Mohammed A-I, Imran MA, Tafazolli R Low Density Spreading for Next Generation Multicarrier Cellular Systems,FEC1pp. x1-x1
    Imran M, Mohamed A, Tafazolli R (2014) Splitting the data and control functionality: Scalable deployment solution for 5G cellular networks, Proceedings of International Wireless Industry Consortium (IWPC) Workshop 2014 IWPC - The International Wireless Industry Consortium
    Razavi R, Imran M, XIAO P, Tafazolli R (2013) Effect of Forward Error Correction Codes on the Performance of LDS-OFDM,19th European Wireless Conference 2013 VDE
    In this paper, selection criteria of Forward Error Correction (FEC) codes, in particular, the convolutional codes are evaluated for a novel air interface scheme, called Low Density Signature Orthogonal Frequency Division Multiple Access (LDS-OFDM). In this regard, the mutual information transfer characteristics of turbo Multiuser Detector (MUD) are investigated using Extrinsic Information Transfer (EXIT) charts. LDS-OFDM uses Low Density Signature structure for spreading the data symbols in frequency domain. This technique benefits from frequency diversity in addition to its ability of supporting parallel data streams more than the number of subcarriers (overloaded condition). The turbo MUD couples the data symbols? detector of LDS scheme with users? FEC decoders through the message passing principle. Index Terms ? Low density signature, Multiuser detection, Iterative decoding.
    Tang W, Shakir MZ, Qaraqe KA, Serpedin E, Imran MA, Tafazolli R (2014) On the bits per joule optimization in cellular cognitive radio networks, 2014 1st International Workshop on Cognitive Cellular Systems, CCS 2014
    DOI: 10.1109/CCS.2014.6933811
    © 2014 IEEE. Cognitive radio has emerged as a promising paradigm to improve the spectrum usage efficiency and to cope with the spectrum scarcity problem through dynamically detecting and re-allocating white spaces in licensed radio band to unlicensed users. However, cognitive radio may cause extra energy consumption because it relies on new and extra technologies and algorithms. The main objective of this work is to enhance the energy efficiency of proposed cellular cognitive radio network (CRN), which is defined as bits/Joule/Hz. In this paper, a typical frame structure of a secondary user (SU) is considered, which consists of sensing and data transmission slots. We analyze and derive the expression for energy efficiency for the proposed CRN as a function of sensing and data transmission duration. The optimal frame structure for maximum bits per joule is investigated under practical network traffic environments. he impact of optimal sensing time and frame length on the achievable energy efficiency, throughput and interference are investigated and verified by simulation results compared with relevant state of art. Our analytical results are in perfect agreement with the empirical results and provide useful insights on how to select sensing length and frame length subject to network environment and required network performance.
    Qi Y, Hoshyar R, Imran MA, Tafazolli R (2011) The Energy Efficiency Analysis of HARQ in Hybrid Relaying Systems, IEEE Vehicular technology Conference - VTC Spring 2011
    Godor I, Frenger P, Holtkamp H, Imran MA, Vidacs A, Fazekas P, Sabella D, Strinati E, Gupta R, Pirinen P, Fehske A (2012) Green Wireless Access Networks, In: Wu J, Sundeep R, Honggang Z (eds.), Green Communications: Theoretical Fundamentals, Algorithms and Applications CRC Press
    I Godor, P Frenger, H Holtkamp, M Imran, A Vidacs, P Fazekas, D Sabella, E Strinati, R Gupta, P Pirinen and A Fehske
    Heliot F, Imran MA, Tafazolli R (2013) Centre for Communication Systems Research (CCSR), Faculty of Electronics & Physical Sciences, University of Surrey, Guildford GU2 7XH, UK, Online Conference on Green Communications (GreenCom), 2013 IEEEpp. 109-114
    Jaber M, Imran MA, Tafazolli R, Tukmanov A (2016) 5G Backhaul Challenges and Emerging Research Directions: A Survey, IEEE Access4pp. 1743-1766
    DOI: 10.1109/ACCESS.2016.2556011
    5G is the next cellular generation and is expected to quench the growing thirst for taxing data rates and to enable the Internet of Things. Focused research and standardization work have been addressing the corresponding challenges from the radio perspective while employing advanced features, such as network densi cation, massive multiple-input-multiple-output antennae, coordinated multi-point processing, intercell interference mitigation techniques, carrier aggregation, and new spectrum exploration. Nevertheless, a new bottleneck has emerged: the backhaul. The ultra-dense and heavy traf c cells should be connected to the core network through the backhaul, often with extreme requirements in terms of capacity, latency, availability, energy, and cost ef ciency. This pioneering survey explains the 5G backhaul paradigm, presents a critical analysis of legacy, cutting-edge solutions, and new trends in backhauling, and proposes a novel consolidated 5G backhaul framework. A new joint radio access and backhaul perspective is proposed for the evaluation of backhaul technologies which reinforces the belief that no single solution can solve the holistic 5G backhaul problem. This paper also reveals hidden advantages and shortcomings of backhaul solutions, which are not evident when backhaul technologies are inspected as an independent part of the 5G network. This survey is key in identifying essential catalysts that are believed to jointly pave the way to solving the beyond-2020 backhauling challenge. Lessons learned, unsolved challenges, and a new consolidated 5G backhaul vision are thus presented.
    Chatzinotas S, Imran MA, Hoshyar R (2009) The multicell processing capacity of the cellular MIMO uplink channel under correlated fading, IEEE International Conference on Communications
    DOI: 10.1109/ICC.2009.5199517
    In the information-theoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems and that the per-cell sum-rate capacity of multicell processing systems grows linearly with the number of Base Station (BS) receive antennas. However, the majority of results in this area has been produced assuming that the fading coefficients of the MIMO subchannels are totally uncorrelated. In this direction, this paper investigates the ergodic per-cell sum-rate capacity of the MIMO Cellular Multiple-Access Channel under correlated fading and multicell processing. More specifically, the current channel model considers Rayleigh fading, uniformly distributed User Terminals (UTs) over a planar cellular system and power-law path loss. Furthermore, both BSs and Uts are equipped with correlated multiple antennas, which are modelled according to the Kronecker model. The per-cell sum-rate capacity closed form is derived using a Free Probability approach and numerical results are produced by varying the cell density of the system, as well as the level of correlation. ©2009 IEEE.
    Akbari I, Onireti O, Imran MA, Imran A, Tafazolli R (2014) Effect of inaccurate position estimation on self-organising coverage estimation in cellular networks,20th European Wireless Conference, EW 2014pp. 176-180
    © VDE VERLAG GMBH, Berlin, Offenbach, Germany.Requirement for low operating and deployment costs of cellular networks motivate the need for self-organisation in cellular networks. To reduce operational costs, self-organising networks are fast becoming a necessity. One key issue in this context is self-organised coverage estimation that is done based on the signal strength measurement and reported position information of system users. In this paper, the effect of inaccurate position estimation on self-organised coverage estimation is investigated. We derive the signal reliability expression (i.e. probability of the received signal being above a certain threshold) and the cell coverage expressions that take the error in position estimation into consideration. This is done for both the shadowing and non-shadowing channel models. The accuracy of the modified reliability and cell coverage probability expressions are also numerically verified for both cases.
    Sambo Y, Heliot F, Imran MA (2012) Low-complexity energy-efficient coordinated resource allocation in cellular systems,
    Onireti OS, Spathopoulos T, Imran MA, Arshad K (2015) Hybrid Cognitive Satellite Terrestrial Coverage: A case study for 5G deployment strategies,
    The explosion of mobile applications, wireless data traffic and their increasing integration in many aspects of everyday life has raised the need of deploying mobile networks that can support exponentially increasing wireless data traffic. In this paper, we present a Hybrid Satellite Terrestrial network, which achieves higher data rate and lower power consumption in comparison with the current LTE and LTE-Advanced cellular architectures. Furthermore, we present a feasibility study of the proposed architecture, in terms of its compliance with the technical specifications in the current standards.
    Chatzinotas S, Imran MA, Tzaras C (2008) Uplink Capacity of MIMO Cellular Systems with Multicell Processing, 2008 IEEE INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS (ISWCS 2008)pp. 333-337 IEEE
    Al-Imari M, Imran MA, Tafazolli R (2012) Low Density Spreading Multiple Access,Information Technology & Software Engineering2(4) OMICS Publishing Group
    DOI: 10.4172/2165-7866.1000e108
    Multiple access (MA) technique is a major building block of the cellular systems. Through the MA technique, the users can simultaneously access the physical medium and share the finite resources of the system, such as spectrum, time and power. Due to the rapid growth in demand on data applications in mobile communications, there has been extensive research to improve the efficiency of cellular systems. A significant part of this effort focuses on developing and optimizing the MA techniques. As a result, many MA techniques have been proposed systematically over the years, and some of these MA techniques are already been adopted in the cellular system standards such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA) and Code Division Multiple Access (CDMA). There are many factors that determine the efficiency of the MA technique such as spectral efficiency, low complexity implementation as well low envelope fluctuations. Mainly, the MA techniques can be categorized into orthogonal and non-orthogonal MA. In orthogonal MA techniques, the signal dimension is partitioned and allocated exclusively to the users, and there is no Multiple Access Interference (MAI). For non-orthogonal MA techniques, all the users share the entire signal dimension, and there is a MAI. Thus, for non-orthogonal transmission, more complicated receiver is required to deal with the MAI comparing to orthogonal transmission. Non-orthogonal MA is more practical in the uplink scenario because the base station can afford the Multiuser Detection (MUD) complexity. On the other hand, for downlink, orthogonal MA is more suitable due to the limited processing power at the user equipment. Many non-orthogonal MA techniques have been overlooked due to the implementation complexity. Evidently, the recent advancements in signal processing have opened up new possibilities for developing more sophisticated and efficient MA techniques. Thus, more advanced MA techniques has been proposed lately. However, in order to adopt these new MA techniques in the mobile communication systems, many challenges and opportunities need to be studied.
    Khan AH, Imran MA, Evans B (2009) Adaptive beamforming for OFDM based hybrid mobile satellite system,27th AIAA International Communication Satellite Systems Conference (ICSSC 2009)
    DOI: 10.1049/cp.2009.1228
    Global connectivity cannot be guaranteed by terrestrial networks due to the lack of infrastructure in rural areas. Neither can satellite networks assure this due to lack of signal penetration and capacity coverage issues in densely populated areas. To bridge this gap, we propose an orthogonal frequency domain (OFDM) based hybrid architecture where users are provided service by existing mobile networks in urban areas and are served by satellite in the rural areas. In such a system terrestrial and satellite networks can reuse the portion of spectrum dedicated to each of these systems resulting in significant increase in overall capacity, wider coverage and reduced cost. This frequency reuse induces severe cochannel interference (CCI) at the satellite end and our work focuses on its mitigation using OFDM based adaptive beamforming
    Awad J, Imran MA, Tafazolli R (2011) Improving Fairness by Cooperative Communications and Selection of Critical Users,The 7th International Wireless Communication and Mobile Computing Conference-IWCMCpp. 184-188 IEEE
    DOI: 10.1109/IWCMC.2011.5982415
    Cooperative Transmission can be used in a multicell scenario where base stations are connected to a central processing unit. This cooperation can be used to improve the fairness for users with bad channel conditions?critical users. This paper will look into using cooperative transmission alongside the orthogonal OFDM scheme to improve fairness by careful selection of critical users and a resource allocation and resource division between the two schemes. A solution for power and subcarrier allocations is provided together with a solution for the selection of the critical users. Simulation results is provided to show the fairness achieved by the proposed critical users selection method, resource allocation and the resource division method applied under the stated assumptions.
    Kakitani M, Brante G, Souza RD, Munaretto A, Imran MA (2013) Energy efficiency of some non-cooperative, cooperative and hybrid communication schemes in multi-relay WSNs, Wireless Networks19(7)pp. 1769-1781 Springer US
    DOI: 10.1007/s11276-013-0569-x
    In this paper we analyze the energy efficiency of single-hop, multi-hop, cooperative selective decode-and-forward, cooperative incremental decode-and-forward, and even the combination of cooperative and non-cooperative schemes, in wireless sensor networks composed of several nodes. We assume that, as the sensor nodes can experience either non line-of-sight or some line-of-sight conditions, the Nakagami-m fading distribution is used to model the wireless environment. The energy efficiency analysis is constrained by a target outage probability and an end-to-end throughput. Our results show that in most scenarios cooperative incremental schemes are more energy efficient than the other methods.
    Kaltakis D, Imran MA, Tzaras C (2010) Information Theoretic Capacity of Cellular Multiple Access Channel with Shadow Fading,IEEE Transactions on Communications58(5)pp. 1468-1476 IEEE
    DOI: 10.1109/TCOMM.2010.05.070591
    Evans BG, Khan A, Imran MA (2012) Semi-adaptive beamforming for ofdm based hybrid terestrial-satellite mobile satellite, IEEE Trans Wireless Communications11(10)pp. 3424-3433 IEEE
    DOI: 10.1109/TWC.2012.083112.110130
    Heliot F, Imran MA, Tafazolli R (2013) Near-optimal Energy-efficient Joint Resource Allocation for Multi-hop MIMO-AF Systems,
    Energy efficiency (EE) is becoming an important performance indicator for ensuring both the economical and environmental sustainability of the next generation of communication networks. Equally, cooperative communication is an effective way of improving communication system performances. In this paper, we propose a near-optimal energy-efficient joint resource allocation algorithm for multi-hop multiple-input-multiple-output (MIMO) amplify-and-forward (AF) systems. We first show how to simplify the multivariate unconstrained EE-based problem, based on the fact that this problem has a unique optimal solution, and then solve it by means of a low-complexity algorithm. We compare our approach with classic optimization tools in terms of energy efficiency as well as complexity, and results indicate the near-optimality and low-complexity of our approach. As an application, we use our approach to compare the EE of multihop MIMO-AF with MIMO systems and our results show that the former outperforms the latter mainly when the direct link quality is poor.
    Imran M, Younis M, Haider N, Alnuem MA (2012) Resource efficient connectivity restoration algorithm for mobile sensor/actor networks, EURASIP Journal on Wireless Communications and Networking20121pp. 1-16 Springer International Publishing AG
    Perera R, Fernando A, Arachchi HK, Imran MA (2015) Adaptive Modulation and Coding based Error Resilience for Transmission of Compressed Video,2015 INTERNATIONAL WIRELESS COMMUNICATIONS & MOBILE COMPUTING CONFERENCE (IWCMC)pp. 1127-1132 IEEE
    Ekti AR, Shakir MZ, Serpedin E, Qaraqe KA, Imran MA (2016) On the Traffic Offloading in Wi-Fi Supported Heterogeneous Wireless Networks, Journal of Signal Processing Systems83(2)pp. 225-240
    DOI: 10.1007/s11265-015-1064-7
    Heterogeneous small cell networks (HetSNet) comprise several low power, low cost (SBSa), (D2D) enabled links wireless-fidelity (Wi-Fi) access points (APs) to support the existing macrocell infrastructure, decrease over the air signaling and energy consumption, and increase network capacity, data rate and coverage. This paper presents an active user dependent path loss (PL) based traffic offloading (TO) strategy for HetSNets and a comparative study on two techniques to offload the traffic from macrocell to (SBSs) for indoor environments: PL and signal-to-interference ratio (SIR) based strategies. To quantify the improvements, the PL based strategy against the SIR based strategy is compared while considering various macrocell and (SBS) coverage areas and traffic?types. On the other hand, offloading in a dense urban setting may result in overcrowding the (SBSs). Therefore, hybrid traffic?type driven offloading technologies such as (WiFi) and (D2D) were proposed to en route the delay tolerant applications through (WiFi) (APs) and (D2D) links. It is necessary to illustrate the impact of daily user traffic profile, (SBSs) access schemes and traffic?type while deciding how much of the traffic should be offloaded to (SBSs). In this context, (AUPF) is introduced to account for the population of active small cells which depends on the variable traffic load due to the active users.
    Chatzinotas S, Imran MA, Tzaras C (2009) Capacity Limits in Cooperative Cellular Systems, In: Zhang Y, Chen H-H, Guizani M (eds.), Cooperative Wireless Communicationspp. 25-51 Auerbach Publications, Taylor & Francis Group
    Awad JF, Imran MA, Tafazolli R (2012) Hybrid Transmission Schemes for Grouped Users in Cellular Systems,pp. 561-566 IEEE
    DOI: 10.1109/IWCMC.2012.6314265
    Hybrid systems, where more than one transmission scheme are used within the same cluster, can be used as a way to improve spectral efficiency for the system as a whole and, more importantly, for the cell-edge users. In this paper, we will propose frequency reuse method by grouping the users into two groups, critical and non-critical users. Each user group is served with a transmission scheme, where the most vulnerable users are served by transmission scheme that avoid, make use of, and orthogo-nalise the interference. These schemes include the cooperative maximal ratio transmission and the non-cooperative orthogonal and non-orthogonal schemes. Radio resource allocation is studied and a solution is given for maximal ratio transmission and interference alignment. Simulation results are given, and showing the performance of each scheme when all users are considered critical and one scheme is used. Moreover, results showing the performance of our proposed frequency reuse scheme where different percentage of users considered critical.
    Sambo YA, Shakir MZ, Héliot F, Imran MA, Mumtaz S, Qaraqe KA (2014) Device-to-device communication in heterogeneous networks, In: Smart Device to Smart Device Communicationpp. 219-235
    DOI: 10.1007/978-3-319-04963-2_8
    © 2014 Springer International Publishing Switzerland. All rights are reserved. The increasing popularity of rich multimedia services has resulted in tremendous growth in demand for higher data rates in wireless communication systems. With the spectral performance of the wireless link is fast approaching the theoretical limit due to advances in cellular technologies, researchers have focused on innovative spectral and to support future wireless networks.
    Rashidi L, Leckie C, Rajasegarar S, Palaniswami M, Nati M, Gluhak A, Imran MA (2014) Profiling spatial and temporal behaviour in sensor networks: A case study in energy monitoring,IEEE ISSNIP 2014 - 2014 IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, Conference Proceedingspp. 1-7 IEEE
    DOI: 10.1109/ISSNIP.2014.6827606
    Wireless sensor networks (WSNs) provide a cost-effective platform for monitoring phenomena of interest at fine spatial and temporal resolutions. In this paper, we consider the application of monitoring power usage in an office environment at the resolution of individual users. A key challenge in this context is how to extract meaningful profiles of user behaviour in the large volume of monitoring data collected by the WSN. To manage the complexity of learning such profiles in this context, we propose a query based model for profiling. This query based model provides the ability to characterize the spatial and temporal occurrences of the power usage patterns of interest. We demonstrate the effectiveness of our query-based profiling model for finding relevant electricity usage patterns in a real life data set of power measurements collected by a WSN deployment in an office environment. To the best of our knowledge, this is the first time such a case study has been made on analysing the power usage of users at such a fine scale in an office environment. © 2014 IEEE.
    Muirhead DS, Imran MA (2011) Alamouti Transmit Diversity for Energy Efficient Femtocells, 73rd IEEE Vehicular technology Conference - VTC Spring 2011
    DOI: 10.1109/VETECS.2011.5956320
    With the ever increasing demand for wireless broadband, design of energy efficient systems is paramount. Femtocells, small self installable wireless base stations, are currently being deployed as a solution to the coverage problems faced by mobile operators, particularly in indoor environments. This paper outlines the framework for evaluating the performance of multiple antenna transmit diversity techniques, based on the Alamouti scheme, relevant to minimizing femtocell transmission power. Simulation results for experiments run on appropriate femtocell channel models are provided. The presented material is given in the context of current third generation systems based on the W-CDMA air interface, however the techniques presented can be extended to future OFDM based systems. Appropriate green solutions need to consider issues of implementation complexity and embodiment which are also discussed.
    Al-Imari M, Imran MA, Tafazolli R, Chen D (2011) Subcarrier and Power Allocation for LDS-OFDM System,pp. 1-5 IEEE
    DOI: 10.1109/VETECS.2011.5956554
    Low Density Signature-Orthogonal Frequency Division Multiplexing (LDS-OFDM) has been introduced recently as an efficient multiple access technique. In this paper, we focus on the subcarrier and power allocation scheme for uplink LDS-OFDM system. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solutions is extremely high. We propose a heuristic subcarrier and power allocation algorithm to maximize the weighted sum-rate. The simulation results show that the proposed algorithm can significantly increase the spectral efficiency of the system. Furthermore, it is shown that LDS-OFDM system can achieve an outage probability much less than that for OFDMA system.
    Katranaras E, Kaltakis D, Imran M, Hoshyar R (2010) Interference Allowance in Clustered Joint Processing and Power Allocation,IWCMC 2010, The 6th International Wireless Communication and Mobile Computing Conference
    DOI: 10.1145/1815396.1815433
    We derive an analytical formula for the sum rate of the uplink of a linear network of cells when clustered joint processing is adopted among the base stations in a generalised fading environment. An inter-cluster interference allowance scheme is considered and various user power allocation profiles are investigated in terms of optimal achievable sum rate to highlight that cell-based power allocation is preferable to cluster-based. The contribution of each base station on the cluster sum rate is investigated and its importance is discussed. Numerical results are produced for a real-world scenario showing how medium density systems are the most viable case for clustered system design by achieving > 80% of the global cooperation capacity.
    Imran A, Imran MA, Tafazolli R (2010) A New Performance Characterization Framework for Deployment Architectures of Next Generation Distributed Cellular Networks,IEEE PIMRC 2010pp. 2046-2051 IEEE
    DOI: 10.1109/PIMRC.2010.5671581
    Performance of next generation OFDM/OFDMA based Distributed Cellular Network (ODCN) where no cooperation based interference management schemes are used, is dependent on four major factors: 1) spectrum reuse factor, 2) number of sectors per site, 3) number of relay station per site and 4) modulation and coding efficiency achievable through link adaptation. The combined effect of these factors on the overall performance of a Deployment Architecture (DA) has not been studied in a holistic manner. In this paper we provide a framework to characterize the performance of various DA's by deriving two novel performance metrics for 1) spectral efficiency and 2) fairness among users. These metrics are designed to include the effect of all four contributing factors. We evaluate these metrics for a wide set of DA's through extensive system level simulations. The results provide a comparison of various DA's for both cellular and relay enhanced cellular systems in terms of spectral efficiency and fairness they offer and also provide an interesting insight into the tradeoff between the two performance metrics. Numerical results show that, in interference limited regime, DA's with highest spectrum efficiency are not necessarily those that resort to full frequency reuse. In fact, frequency reuse of 3 with 6 sectors per site is spectrally more efficient than that with full frequency reuse and 3 sectors. In case of relay station enhanced ODCN a DA with full frequency reuse, six sectors and 3 relays per site is spectrally more efficient and can yield around 170% higher spectrum efficiency compared to counterpart DA without RS.
    Imran MA, Hoshyar R (2009) Improving downlink performance by reusing the subcarriers within the cell, ICT-MobileSummit
    Jiang J, Dianati M, Imran MA, Tafazolli R (2013) On the Energy Efficiency of MIMO Channels in Correlated Rayleigh Fading Environment., EW VDE-Verlag
    George R, Aliu OG, Imran MA (2011) Hybrid Spectrum Allocation Scheme in wireless cellular networks,The 7th International Wireless Communication and Mobile Computing Conference-IWCMCpp. 2093-2097 IEEE
    DOI: 10.1109/IWCMC.2011.5982857
    Mobile services have seen a major upswing driven by the bandwidth hungry applications thus leading to higher data rate requirements on the wireless networks. Spectrum being the most precious resource in the wireless industry is of keen interest. Various spectrum assignment and frequency reuse schemes have been proposed in literature. However in future networks, dynamic schemes that adapt to spatio-temporal variation in the environment are desired. We thus present a hybrid spectrum assignment scheme which adapts its allocation strategies depending on user distribution in the system. Results show that the proposed dynamic spectrum assignment strategy improves spectrum utilization thereby providing a higher data rate for the users.
    Qi Y, Imran MA, Demo Souza R, Tafazolli R (2015) On the Optimization of Distributed Compression in Multi-Relay Cooperative Networks,IEEE Transactions on Vehicular Technology IEEE
    In this paper, we consider multi-relay cooperative networks for the Rayleigh fading channel, where each relay, upon receiving its own channel observation, independently compresses it and forwards the compressed information to the destination. Although the compression at each relay is distributed using Wyner-Ziv coding, there exists an opportunity for jointly optimizing compression at multiple relays to maximize the achievable rate. Considering Gaussian signalling, a primal optimization problem is formulated accordingly. We prove that the primal problem can be solved by resorting to its Lagrangian dual problem and an iterative optimization algorithm is proposed. The analysis is further extended to a hybrid scheme, where the employed forwarding scheme depends on the decoding status of each relay. The relays that are capable of successful decoding perform decode-and-forward and the rest conduct distributed compression. The hybrid scheme allows the cooperative network to adapt to the changes of the channel conditions and benefit from an enhanced level of flexibility. Numerical results from both spectrum and energy efficiency perspectives show that the joint optimization improves efficiency of compression and identify the scenarios where the proposed schemes outperform the conventional forwarding schemes. The findings provide important insights into the optimal deployment of relays in a realistic cellular network.
    Khan AH, Imran MA, Evans BG (2012) Iterative turbo beamforming for orthogonal frequency division multiplexing-based hybrid terrestrial-satellite mobile system,IET Communications6(2)pp. 157-164 IET
    DOI: 10.1049/iet-com.2010.1133
    In the context of orthogonal frequency division multiplexing (OFDM)-based systems, pilot-based beamforming (BF) exhibits a high degree of sensitivity to the pilot sub-carriers. Increasing the number of reference pilots significantly improves BF performance as well as system performance. However, this increase comes at the cost of data throughput, which inevitably shrinks due to transmission of additional pilots. Hence an approach where reference signals available to the BF process can be increased without transmitting additional pilots can exhibit superior system performance without compromising throughput. Thus, the authors present a novel three-stage iterative turbo beamforming (ITBF) algorithm for an OFDM-based hybrid terrestrial-satellite mobile system, which utilises both pilots and data to perform interference mitigation. Data sub-carriers are utilised as virtual reference signals in the BF process. Results show that when compared to non-iterative conventional BF, the proposed ITBF exhibits bit error rate gain of up to 2.5 dB with only one iteration.
    Chatzinotas S, Imran MA, Hoshyar R (2009) Reduced-complexity multicell decoding systems with multiple antennas at the base station, Proceedings of the 2009 ACM International Wireless Communications and Mobile Computing Conference, IWCMC 2009pp. 849-853
    DOI: 10.1145/1582379.1582564
    Multicell joint decoding has been proven to greatly enhance the capacity of cellular systems in a range of regimes. However, the complexity of such a joint receiver makes it impossible to implement in practice using current computational capabilities. In this direction, this paper investigates the capacity performance of reduced-complexity communication schemes in order to evaluate their performance with respect to the optimal multicell joint decoding scheme. More specifically, two sub-optimal schemes are considered: 1) intracell user orthogonalization combined with optimal multicell joint decoding and 2) intra-cell user orthogonalization combined with linear MMSE filtering and single-user decoding. The employed cellular multiple-access channel model incorporates flat fading, path loss, distributed users and multiple antennas at the Base Station, while both peak and average transmit power constraints are taken into account. In this context, it is shown that linear MMSE filtering combined with multiple BS antennas and intra-cell orthogonalization can still provide a considerable capacity enhancement. Furthermore, FDMA is shown to be more efficient than TDMA as an intra-cell orthogonalization technique. Copyright 2009 ACM.
    Mehta M, Aliu OG, Karandikar A, Imran MA (2011) Self-Organized Resource Allocation Using Inter-Cell Interference Coordination(ICIC) in Relay-Asisted Cellular Networks,ICT Journal on Communication Technology2(2)pp. 300-313 ICT Academy of Tamil Nadu
    In a multi-cell scenario, the inter-cell interference (ICI) is detrimental in achieving the intended system performance, in particular for the edge users. There is paucity of work available in literature on ICI coordination (ICIC) for relay-assisted cellular networks (RACN). In this paper, we do a survey on the ICIC schemes in cellular networks and RACN. We then propose a self-organized resource allocation plan for RACN to improve the edge user?s performance by ICIC. We compare the performance of reuse-1, reuse-3, soft frequency reuse (SFR) scheme, proposed plan with and without relays. The performance metrics for comparison are edge user?s spectral efficiency, their signal-to-interference-and-noise ratio (SINR) and system?s area spectral efficiency. We show by the simulation results that our proposed plan performs better than the existing resource allocation schemes in static allocation scenario. Next, we propose to make our resource allocation plan dynamic and self-organized. The distinct features of our proposed plan are: One, it achieves a trade-off between the system?s area spectral efficiency and the edge user?s spectral efficiency performance. Secondly, it introduces a novel concept of interfering neighbor set to achieve ICIC by local interaction between the entities.
    Onireti O, Heliot F, imran MA (2011) Closed-form Approximation for the Trade-off between Energy Efficiency and Spectral Efficiency in the Uplink of Cellular Network,
    Héliot F, Imran MA, Tafazolli R (2012) Energy-efficiency based resource allocation for the scalar broadcast channel,IEEE Wireless Communications and Networking Conference, WCNCpp. 193-197
    DOI: 10.1109/WCNC.2012.6214105
    Until recently, link adaptation and resource allocation for communication system relied extensively on the spectral efficiency as an optimization criterion. With the emergence of the energy efficiency (EE) as a key system design criterion, resource allocation based on EE is becoming of great interest. In this paper, we propose an optimal EE-based resource allocation method for the scalar broadcast channel (BC-S). We introduce our EE framework, which includes an EE metric as well as a realistic power consumption model for the base station, and utilize this framework for formulating our EE-based optimization problem subject to a power as well as fairness constraints. We then prove the convexity of this problem and compare our EE-based resource allocation method against two other methods, i.e. one based on sum-rate and one based on fairness optimization. Results indicate that our method provides large EE improvement in comparison with the two other methods by significantly reducing the total consumed power. Moreover, they show that near-optimal EE and average fairness can be simultaneously achieved over the BC-S channel. © 2012 IEEE.
    Kakitani MT, Souza RD, Imran MA (2012) Energy efficiency contours for amplify-and-forward and decode-and-forward cooperative protocols, Proceedings of the 2012 8th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2012
    DOI: 10.1109/CSNDSP.2012.6292728
    In this paper we compare the energy efficiency of different cooperative schemes by means of energy efficiency contours. We consider a three-nodes cooperative scenario, employing either the amplify-and-forward (AF) or the decode-and-forward (DF) protocol. In the case of the DF protocol we analyse the performance of both repetition coding (RC) and parallel coding (PC). Our analysis shows that the maximum energy efficiency operating point is usually related to the allocation of different transmission rates to each user, while enforcing rate fairness leads the system to a sub-optimum operating point in terms of energy efficiency. Depending on the particular topology, the most energy efficient scheme may be AF or DF, with a clear advantage of DF when the two users are close. Moreover, we demonstrate that the exploitation of a return channel may have a large impact in the energy efficiency, being able to almost double it. © 2012 IEEE.
    Sambo Y, Heliot F, Imran MA (2015) A Survey and Tutorial of Electromagnetic Radiation and Reduction in Mobile Communication Systems,Communications Surveys & Tutorials, IEEE17(2)pp. 790-802 IEEE
    DOI: 10.1109/COMST.2014.2364136
    Abstract?This article provides a survey and tutorial of electromagnetic (EM) radiation exposure and reduction in mobile communication systems. EM radiation exposure has received a fair share of interest in literature; however, this work is one of the first to compile the most interesting results and ideas related to EM exposure in mobile communication systems and present possible ways of reducing it. We provide a comprehensive survey of existing literature and also offer a tutorial on the dosimetry, metrics, international projects as well as guidelines and limits on the exposure from EM radiation in mobile communication systems. Based on this survey and given that EM radiation exposure is closely linked with specific absorption rate (SAR) and transmit power usage, we propose possible techniques for reducing EM radiation exposure in mobile communication systems by exploring known concepts related to SAR and transmit power reduction of mobile systems. Thus, this paper serves as an introductory guide for EM radiation exposure in mobile communication systems and provides insights towards the design of future low EM exposure mobile communication networks.
    Riaz M, Imran MA, Hoshyar R (2010) Frequency Planning of Clustered Cellular Network using Particle Swarm Optimization, ISWCS 2010
    Héliot F, Qi Y, Onireti O, Imran MA, Blume O, Ambrosy A, Fazekas P, Bérces M, BME AV, Sabella D, others INFSO-ICT-247733 EARTH,
    Jiang J, Dianati M, Imran MA, Chen Y (2012) Energy Efficiency Analysis and Optimal Power Allocation in Virtual-MIMO Systems,pp. 1-6 IEEE
    DOI: 10.1109/VTCFall.2012.6399002
    This paper investigates energy efficiency (EE) performance of a virtual multiple-input multiple- output (MIMO) wireless system using the receiver- side cooperation with the compress-and-forward protocol. We derive a linear approximation of EE as a function of spectral efficiency (SE) in the low SE operation regime. In addition, we obtain a closed-form lower bound for EE which is valid for both low and high SE regions. This lower bound can be used for optimizing the power allocation between the transmitter and the relay in order to minimize the overall energy per bit consumption in the system. Both analytical and simulation results demonstrate that the virtual MIMO system using the receiver-side cooperation outperforms the multiple- input single-output (MISO) case in terms of energy efficiency. Finally we show that, with the optimal power allocation, the virtual-MIMO system achieves an EE performance close to that of an ideal MIMO system.
    Imran MA, Blume O, EAB PB, BME PF, TUD AF, Ferling D, ETH IG, ETH LH, EAB YJ, Katranaras E, others INFSO-ICT-247733 EARTH,
    Jaber M, Imran MA, Tafazolli R, Tukmanov A (2016) A Distributed SON-based User-Centric Backhaul Provisioning Scheme,IEEE Access4pp. 2314-2330 IEEE
    DOI: 10.1109/ACCESS.2016.2566958
    5G definition and standardization projects are well underway, and governing characteristics and major challenges have been identified. A critical network element impacting the potential performance of 5G networks is the backhaul, which is expected to expand in length and breadth to cater to the exponential growth of small cells while offering high throughput in the order of Gbps and less than one-millisecond latency with high resilience and energy efficiency. Such performance may only be possible with direct optical fibre connections which are often not available countrywide and are cumbersome and expensive to deploy. On the other hand, a prime 5G characteristic is diversity, which describes the radio access network, the backhaul, and also the types of user applications and devices. Thus, we propose a novel, distributed, selfoptimized, end-to-end user-cell-backhaul association scheme that intelligently associates users with potential cells based on corresponding dynamic radio and backhaul conditions while abiding by users? requirements. Radio cells broadcast multiple bias factors, each reflecting a dynamic performance indicator (DPI) of the endto-end network performance such as capacity, latency, resilience, energy consumption, etc. A given user would employ these factors to derive a user-centric cell ranking that motivates it to select the cell with radio and backhaul performance that conforms to the user requirements. Reinforcement learning is used at the radio cell to optimize the bias factors for each DPI in a way that maximizes the system throughput while minimizing the gap between the users? achievable and required end-to-end quality of experience (QoE). Preliminary results show considerable improvement in users QoE and cumulative system throughput when compared to state-of-theart user-cell association schemes.
    Khan AH, Imran MA, Evans BG (2012) Semi-Adaptive Beamforming for OFDM based Hybrid Terrestrial-Satellite Mobile System,IEEE Transactions on Wireless Communications11(10)pp. 3424-3433 IEEE
    DOI: 10.1109/TWC.2012.083112.110130
    Onireti OS, Ahmed Z, Saeed A, Imran A, Imran M, Abu-Dayya A (2016) Outage Detection Framework for Energy Efficient Communication Network, In: Shakir MZ, Imran MA, Qaraqe KA, Alouini M-S, Vasilakos AV (eds.), Energy Management in Wireless Cellular and Ad-hoc Networks1pp. 3-29 Springer
    In this chapter, we present a Cell Outage Detection (COD) framework for Heterogeneous Networks (HetNets) with split control and data planes. COD is a pre-requisite to trigger fully automated self-healing recovery actions following cell outages or network failures not only to ensure reliable recovery of services but also to significantly minimize wastage of energy. To cope with the idiosyncrasies of both the data and control planes, our proposed framework incorporates control COD and data COD mechanisms. The control COD leverage the relatively larger number of UEs in the control cell to gather large scale Minimize Drive Testing (MDT) reports data. These measurements are further pre-processed using multidimensional scaling method and are employed together with state-of-the art machine learning algorithms to detect and localize anomalous network behaviour. On the other hand, for data cells COD, we propose a heuristic Grey-Prediction based approach, which can work with the small number of UEs in the data cell, by exploiting the fact that the control BS manages UE-data BS connectivity, by receiving a periodic update of the Received Signal Reference Power (RSRP) statistic between the UEs and data BSs in its coverage. The detection accuracy of the heuristic data COD algorithm is further improved by exploiting the fourier series of residual error that is inherent to grey prediction model. We validate and demonstrate the effectiveness of our proposed solution for detecting cell outages in both data and control planes via performing network simulations under various operational settings.
    Onireti OS, Imran A, Imran M, Tafazolli R (2016) Impact of Positioning Error on Achievable Spectral Efficiency in Database-aided Networks,
    Database-aided user association, where users are associated with data base stations (BSs) based on a database which stores their geographical location with signal-to-noise-ratio tagging, will play a vital role in the futuristic cellular architecture with separated control and data planes. However, such approach can lead to inaccurate user-data BS association, as a result of the inaccuracies in the positioning technique, thus leading to sub-optimal performance. In this paper, we investigate the impact of database-aided user association approach on the average spectral efficiency (ASE). We model the data plane base stations using its fluid model equivalent and derive the ASE for the channel model with pathloss only and when shadowing is incorporated. Our results show that the ASE in database-aided networks degrades as the accuracy of the user positioning technique decreases. Hence, system specifications for database-aided networks must take account of inaccuracies in positioning techniques.
    Akbari A, Imran MA, Dianati M, Tafazolli R (2013) Weighted average energy efficiency contours for uplink channels, IEEE Vehicular Technology Conference
    DOI: 10.1109/VTCFall.2013.6692457
    The continuous increase in the energy consumption of wireless networks has led to extensive research and development into energy-efficient communications. Towards this objective, this paper employs a novel technique for maximizing the energy efficiency (EE) of wireless networks, using weighted average EE contours with multiple decoding policies (DPs), where users are prioritized based on different criteria such as channel condition. Moreover, our EE based resource allocation method is extended such that other system targets such as rate-fairness and quality of service (QoS) are satisfied. Results indicate that our EE-based resource allocation scheme achieves the highest EE when DP 2 is employed, i.e. the user with the best channel gain achieves its single user bound, whilst other users experience residual interference. Moreover, both the fairness and QoS constraints increase user satisfaction, in terms of achievable data rate, which comes at the cost of a higher transmit power, and therefore lower EE. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.
    Kaltakis D, Imran MA, Tzaras C (2008) Uplink Capacity of Variable-Density Cellular System with Distributed Users and Fading, IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC?08
    Majid I, Imran MA, Hoshyar R (2010) Cell based Fair Resource Allocation in Fixed Clustered Cellular Systems using a Genetic Algorithm, IEEE PIMRC 2010
    Katranaras E, Imran MA, Dianati M, Tafazolli R (2014) Green inter-cluster interference management in uplink of multi-cell processing systems,IEEE Transactions on Wireless Communications13(12)pp. 6580-6592
    DOI: 10.1109/TWC.2014.2363672
    © 2014 IEEE.This paper examines the uplink of cellular systems employing base station cooperation for joint signal processing. We consider clustered cooperation and investigate effective techniques for managing inter-cluster interference to improve users' performance in terms of both spectral and energy efficiency. We use information theoretic analysis to establish general closed form expressions for the system achievable sum rate and the users' Bit-per-Joule capacity while adopting a realistic user device power consumption model. Two main inter-cluster interference management approaches are identified and studied, i.e., through: 1) spectrum re-use; and 2) users' power control. For the former case, we show that isolating clusters by orthogonal resource allocation is the best strategy. For the latter case, we introduce a mathematically tractable user power control scheme and observe that a green opportunistic transmission strategy can significantly reduce the adverse effects of inter-cluster interference while exploiting the benefits from cooperation. To compare the different approaches in the context of real-world systems and evaluate the effect of key design parameters on the users' energy-spectral efficiency relationship, we fit the analytical expressions into a practical macrocell scenario. Our results demonstrate that significant improvement in terms of both energy and spectral efficiency can be achieved by energy-aware interference management.
    Katranaras E, Imran MA, Tzaras C (2008) Capacity of Sectorized Cellular Systems: An Information Theoretic Perspective, In: Vishnevsky V, Vinel A, Koucheryavy Y, Staehle D (eds.), Selected Lectures on Multiple Access and Queuing Systemspp. 130-138 Russian Academy of Science, St Petersburg, Russia
    In this work, we formulate the information theoretic capacity of the sectorized cellular system for the uplink. We model a planar cellular system in which user terminals (UTs) are served by perfect directional antennas dividing the cell coverage area into perfectly non-interfering sectors. Assuming the joint decoding of the signals received at the antennas (hyper-receiver), we find the information theoretic uplink capacity in the presence of a general fading environment. To find the capacity, we apply a known technique to obtain the eigenvalues of a block-circulant matrix with non-circulant blocks. We show how the capacity is increased in comparison to the non-sectorized single antenna system and we investigate the asymptotic behaviour when the number of sectors grows large. We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems.
    Majid MI, Imran MA, Hoshyar R (2013) Frequency planning for clustered jointly processed cellular multiple access channel,IET Communications7(16)pp. 1739-1752 IET Digital Library
    DOI: 10.1049/iet-com.2012.0513
    Owing to limited resources, it is hard to guarantee minimum service levels to all users in conventional cellular systems. Although global cooperation of access points (APs) is considered promising, practical means of enhancing efficiency of cellular systems is by considering distributed or clustered jointly processed APs. The authors present a novel `quality of service (QoS) balancing scheme' to maximise sum rate as well as achieve cell-based fairness for clustered jointly processed cellular multiple access channel (referred to as CC-CMAC). Closed-form cell level QoS balancing function is derived. Maximisation of this function is proved as an NP hard problem. Hence, using power-frequency granularity, a modified genetic algorithm (GA) is proposed. For inter site distance (ISD) <; 500 m, results show that with no fairness considered, the upper bound of the capacity region is achievable. Applying hard fairness restraints on users transmitting in moderately dense AP system, 20% reduction in sum rate contribution increases fairness by upto 10%. The flexible QoS can be applied on a GA-based centralised dynamic frequency planner architecture.
    Aliu OG, Imran MA, Evans B (2010) Self organised cellular networks as the future of wireless communications,11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting
    An introduction into self organizing cellular networks is presented. This topic has generated a lot of research interest over the past few years as operators have identified it as a necessary feature in future wireless communication systems. We review projects which have studied self organization and with knowledge of system model design in computing, we suggest design rules in developing robust and efficient self organizing algorithms. We finally demonstrate a channel assignment example based on the concept of sectorial neighbours where the system autonomously changes its allocation scheme based on external factors in the environment (e.g. geographical location, interfering sectors and demand for resources). Further research directions are also highlighted.
    Gunther A, Giannini V, I Godor PS, Olsson M, Imran MA, Sabella D, Gonzalez M, Desset C, Blume O (2011) Cellular Energy Efficiency Evaluation Framework,IEEE Vehicular technology Conference - VTC Spring 2011pp. 1-6 IEEE
    DOI: 10.1109/VETECS.2011.5956750
    In order to quantify the energy savings in wireless networks, the power consumption of the entire system needs to be captured and an appropriate energy efficiency evaluation framework must be defined. In this paper, the necessary enhancements over existing performance evaluation frameworks are discussed, such that the energy efficiency of the entire network comprising component, node and network level contributions can be quantified. The most important addendums over existing frameworks include a sophisticated power model for various base station (BS) types, which maps the RF output power radiated at the antenna elements to the total supply power of a BS site. We also consider an approach to quantify the energy efficiency of large geographical areas by using the existing small scale deployment models along with long term traffic models. Finally, the proposed evaluation framework is applied to quantify the energy efficiency of the downlink of a 3GPP LTE radio access network.
    Aliu OG, Imran A, Imran MA, Evans B (2012) A survey of self organisation in future cellular networks,IEEE Communications Surveys and Tutorials15(1)pp. 336-361
    DOI: 10.1109/SURV.2012.021312.00116
    This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks. © 1998-2012 IEEE.
    Onireti O, Zoha A, Moysen J, Imran A, Giupponi L, Imran MA, Abu-Dayya A (2015) A Cell Outage Management Framework for Dense Heterogeneous Networks,IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY65(4)pp. 2097-2113 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/TVT.2015.2431371
    Zhang R, Wang L, Parr G, Aliu OG, Awoseyila B, Azarmi N, Bhatti S, Bigham J, Bodanese E, Chen H, Dianati M, Dutta A, Fitch M, Giridhar K, Hailes S, Hari KVS, Imran MA, Jagannatham AK, Karandikar A, Kawade S, Khan MZA, Kompalli SC, Langdon P, Narayanan B, Mauthe A, McGeehan J, Mehta N, Millet K, Moessner K, Rajashekar R, Ramkumar B, Ribeiro V, Vasudevan K, Hanzo L (2013) Advances in Base- and Mobile-Station Aided Cooperative Wireless Communications, IEEE VEHICULAR TECHNOLOGY MAGAZINE8(1)pp. 57-69 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/MVT.2012.2234254
    Imran MA, Imran A, tafazolli R (2011) Relay Station Access Link Spectral Efficiency Optimization through SO of Macro BS Tilts,IEEE Communications Letters15(12)pp. 1326-1328 IEEE
    DOI: 10.1109/LCOMM.2011.103111.1579
    In this paper we present a novel framework for spectral efficiency enhancement on the access link between relay stations and their donor base station through Self Organization (SO) of system-wide BS antenna tilts. Underlying idea of framework is inspired by SO in biological systems. Proposed solution can improve the spectral efficiency by upto 1 bps/Hz.
    Mohamed A, Onireti O, Imran MA, Imran A, Tafazolli R (2015) Control-Data Separation Architecture for Cellular Radio Access Networks: A Survey and Outlook,IEEE Communications Surveys & Tutorials
    DOI: 10.1109/COMST.2015.2451514
    Conventional cellular systems are designed to ensure ubiquitous coverage with an always present wireless channel irrespective of the spatial and temporal demand of service. This approach raises several problems due to the tight coupling between network and data access points, as well as the paradigm shift towards data-oriented services, heterogeneous deployments and network densification. A logical separation between control and data planes is seen as a promising solution that could overcome these issues, by providing data services under the umbrella of a coverage layer. This article presents a holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks. As a starting point, we discuss the fundamentals, concept and general structure of the CDSA. Then, we point out limitations of the conventional architecture in futuristic deployment scenarios. In addition, we present and critically discuss the work that has been done to investigate potential benefits of the CDSA, as well as its technical challenges and enabling technologies. Finally, an overview of standardisation proposals related to this research vision is provided.
    Auer G, Godor I, Hevizi L, Imran M, Malmodin J, Fazekas P, Biczok G, Zeller D, Blume O, Tafazolli R (2010) The EARTH Project: Towards Energy Efficient Wireless Networks, ICT Future Network and Mobile Summit 2010
    Akbari A, Imran MA, Tafazolli R (2011) Maximising Average Energy efficiency for Two-user AWGN Broadcast Channel,Future Network and Mobile Summit IEEE
    Energy consumption has become an increasingly important aspect of wireless communications, from both an economical and environmental point of view. New enhancements are being placed on mobile networks to reduce the power consumption of both mobile terminals and base stations. This paper studies the achievable rate region of AWGN broadcast channels under Time-division, Frequency-division and Superposition coding, and locates the optimal energy-efficient rate-pair according to a comparison metric based on the average energy efficiency of the system. In addition to the transmit power, circuit power and signalling power are also incorporated in the energy efficiency function, with simulation results verifying that the Superposition coding scheme achieves the highest energy efficiency in an ideal, but non-realistic scenario, where the signalling power is zero. With moderate signalling power, the Frequency-division scheme is the most energy-efficient, with Superposition coding and Time-division becoming second and third best. Conversely, when the signalling power is high, both Time-division and Frequency-division schemes outperform Superposition coding. On the other hand, the Superposition coding scheme also incorporates rate-fairness into the system, which allows both users to transmit whilst maximising the energy efficiency.
    Alsedairy T, Imran MA (2011) Energy and Spectrum Efficient systems with Adaptive Modulation and Spectrum Sharing for Cellular Systems, IEEE Vehicular technology Conference - VTC Spring 2011
    Auer G, Blume O, Giannini V, Godor Istvan, Imran MA, Jading Ylva, Katranaras Efstathios, Olsson Magnus, Sabella Dario, Skillermark Per, Wajda Wieslawa INFSO-ICT-247733 EARTH,
    In order to quantify the energy savings in wireless networks, a holistic view of the power consumption of the entire system needs to be captured. This requires an appropriate energy efficiency evaluation framework. In this deliverable, we present the necessary enhancements over existing performance evaluation frameworks for the wireless networks. The main objective is to capture the factors affecting the energy efficiency at component, node and network level. The most important additions to the existing frameworks include: (1) a sophisticated power model for various BS types, that maps the RF output power radiated at the antenna elements to the total supply power necessary to operate the network; (2) an approach to quantify the energy efficiency of large geographical areas by using the existing small scale deployment models along with long term traffic models; (3) a suitable set of metrics that allows quantifying the amount of energy savings capturing the most important trade-offs between energy savings and maintaining the system capacity, network coverage and quality of service parameters. After presenting the framework and necessary components of the framework, the proposed evaluation framework is applied to quantify the base station energy efficiency of 3GPP LTE. The overall promise of energy efficiency improvement is further investigated qualitatively for different possible areas of improvement in the system and some fundamental technology potential limits are also identified.
    del Aguila FR, Imran MA, Tafazolli R On The Three-Receiver Multilevel Broadcast Channel with Random Parameters,
    Al-Imari M, Imran M, Xiao P (2016) Radio Resource Allocation for Multicarrier-Low Density Spreading Multiple Access, IEEE Transactions on Vehicular Technology IEEE
    DOI: 10.1109/TVT.2016.2579168
    Multicarrier-low density spreading multiple access (MC-LDSMA) is a promising multiple access technique that enables near optimum multiuser detection. In MC-LDSMA, each user?s symbol spread on a small set of subcarriers, and each subcarrier is shared by multiple users. The unique structure of MC-LDSMA makes the radio resource allocation more challenging comparing to some well-known multiple access techniques. In this paper, we study the radio resource allocation for single-cell MC-LDSMA system. Firstly, we consider the single-user case, and derive the optimal power allocation and subcarriers partitioning schemes. Then, by capitalizing on the optimal power allocation of the Gaussian multiple access channel, we provide an optimal solution for MC-LDSMA that maximizes the users? weighted sum-rate under relaxed constraints. Due to the prohibitive complexity of the optimal solution, suboptimal algorithms are proposed based on the guidelines inferred by the optimal solution. The performance of the proposed algorithms and the effect of subcarrier loading and spreading are evaluated through Monte Carlo simulations. Numerical results show that the proposed algorithms significantly outperform conventional static resource allocation, and MC-LDSMA can improve the system performance in terms of spectral efficiency and fairness in comparison with OFDMA.
    Al-Imari M, Imran MA, Tafazolli R (2012) Low Density Spreading for next generation multicarrier cellular systems,pp. 52-57 IEEE
    DOI: 10.1109/ICFCN.2012.6206872
    Multicarrier-Low Density Spreading Multiple Access (MC-LDSMA) is a promising technique for high data rate mobile communications. In this paper, the suitability of using MC-LDSMA in the uplink for next generation cellular systems is investigated. The performance of MC-LDSMA is evaluated and compared with current multiple access techniques, OFDMA and SC-FDMA. Specifically, Peak to Average Power Ratio (PAPR), Bit Error Rate (BER), spectral efficiency and fairness are considered as performance metrics. The link and system-level simulation results show that MC-LDSMA has significant performance improvements over SC-FDMA and OFDMA. It is shown that using MC-LDSMA can significantly improve the system performance in terms of required transmission power, spectral efficiency and fairness among the users.
    O Reilly C, Gluhak A, Imran M (2013) Online anomaly detection with an incremental centred kernel hypersphere, Machine Learning for Signal Processing (MLSP), 2013 IEEE International Workshop onpp. 1-6
    Mustafa HA, Shakir MZ, Sambo YA, Qaraqe KA, Imran MA, Serpedin E (2015) Spectral efficiency improvements in HetNets by exploiting device-to-device communications,2014 IEEE Globecom Workshops, GC Wkshps 2014pp. 857-862
    DOI: 10.1109/GLOCOMW.2014.7063540
    © 2014 IEEE.Next generation cellular networks require huge capacity, ubiquitous coverage and maximum energy efficiency. In order to meet these targets, Device-to-device (D2D) communication is being considered for future heterogeneous networks (HetNets). In this paper, we consider a three tier hierarchical HetNet by exploiting D2D communication in traditional HetNet. D2D communication is deployed within the HetNet where closely located mobile users are engaged in direct communication without routing the traffic through cellular access network. The proposed configuration mandates to reduce the interference offered by the resultant HetNet by reducing the transmitter-receiver distance and ensuring that the mobile users are transmitting with adaptive power subject to maintaining their desired link quality. In this context, we analyzed and compared the spectral efficiency improvements in hierarchical HetNet against traditional HetNet. Simulation results show that D2D communication offers much higher spectral efficiency as compared to traditional HetNet.
    Chatzinotas S, Imran MA, Hoshyar R (2010) Capacity Limits of Base Station Cooperation in Cellular Networks, In: Uysal M (eds.), Cooperative Communications for Improved Wireless Network Transmission: Framework for Virtual Antenna Array Applications
    DOI: 10.4018/978-1-60566-665-5.ch004
    In the information-theoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems. What is more, it has been proved that the per-cell sum-rate capacity of multicell processing systems grows linearly with the number of base station (BS) receive antennas. However, the majority of results in this area have been produced assuming that the fading coefficients of the MIMO subchannels are completely uncorrelated. In this direction, this chapter investigates the ergodic per-cell sum-rate capacity of the Gaussian MIMO cellular channel under correlated fading and BS cooperation (multicell processing). More specifically, the current channel model considers Rayleigh fading, uniformly distributed user terminals (UTs) over a planar cellular system, and power-law path loss. Furthermore, both BSs and UTs are equipped with correlated multiple antennas, which are modelled according to the Kronecker product correlation model. The per-cell sum-rate capacity is evaluated while varying the cell density of the system, as well as the level of receive and transmit correlation. In this context, it is shown that the capacity performance is compromised by correlation at the BS-side, whereas correlation at the UT-side has a negligible effect on the system?s capacity.
    Heliot F, Imran MA, Tafazolli R (2012) Energy-Efficiency based Resource Allocation for the Orthogonal Multi-user Channel, IEEE VTC Fall 2012
    DOI: 10.1109/VTCFall.2012.6399243
    Energy efficiency (EE) is emerging as a key design criterion for both power limited, i.e. mobile devices, and power-unlimited, i.e. cellular networks, applications. Whereas, resource allocation is a well-known technique for improving the performance of communication systems. In this paper, we design a simple and optimal EE-based resource allocation method for the orthogonal multi-user channel by adapting the transmit power and rate to the channel condition such that the energy-per-bit consumption is minimized. We present our EE framework, i.e. EE metric and node power consumption model, and utilize it for formulating our EE-based optimization problem with or without constraint. In both cases, we derive explicit formulations of the optimal energy-per-bit consumption as well as optimal power and rate for each user. Our results indicate that EE-based allocation can substantially reduce the consumed power and increase the EE in comparison with spectral efficiency-based allocation.
    Onireti O, Heliot F, Imran M (2011) Closed-form Approximation for the Trade-Off between Energy Efficiency and Spectral Efficiency in the Uplink of Cellular Network,European Wireless IEEE
    In this paper we propose a tight closed-form approximation of the Energy Efficiency vs. Spectral Efficiency (EE-SE) trade-off for the uplink of a cellular communication system. We model the uplink of the cellular system by considering the Wyner model with Raleigh fading. We first demonstrate the accuracy of our expression by comparing it with Monte-Carlo simulation and the EE-SE trade-off expression based on lowpower approximation. Results show the great tightness of our expression with Monte-Carlo simulation. We utilize our closed-form for assessing the EE performance of base station (BS) cooperation against non-cooperative system for both a theoretical power model and a realistic power model. The theoretical power model includes only the transmit power, whereas the realistic power model incorporates the backhaul and signal processing powers in addition of the transmit power. Results indicate that BS cooperation is more energy efficient than non cooperative system and the former always outperforms the latter in terms of EE-SE trade-off. This is however no more the case with the realistic power model: the EE performance is then highly dependent on the number of cooperating BSs.
    Heliot F, Imran MA, Tafazolli R (2012) On the Energy Efficiency-Spectral Efficiency Trade-Off over the MIMO Rayleigh Fading Channel, IEEE Transactions on Communications60(5)pp. 1345-1356 IEEE
    DOI: 10.1109/TCOMM.2012.031712.110215
    Along with spectral efficiency (SE), energy efficiency (EE) is becoming one of the key performance evaluation criteria for communication system. These two criteria, which are conflicting, can be linked through their trade-off. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression has been here utilized for assessing analytically the EE gain of MIMO over single-input single-output (SISO) system for two different types of power consumption models (PCMs): the theoretical PCM, where only the transmit power is considered as consumed power; and a more realistic PCM accounting for the fixed consumed power and amplifier inefficiency. Our analysis unfolds the large mismatch between theoretical and practical MIMO vs. SISO EE gains; the EE gain increases both with the SE and the number of antennas in theory, which indicates that MIMO is a promising EE enabler; whereas it remains small and decreases with the number of transmit antennas when a realistic PCM is considered.
    Imran MA, Gurcan MK, Kahn S (2005) Channel Coding for Cooperative Broadcasting, Proc. of Hellenic European Research on Computer Mathematics and its Applications (HERCMA) 2005
    Heliot F, Imran MA, Tafazolli R (2012) Energy-efficient Power Allocation for Point-to-point MIMO Systems over the Rayleigh Fading Channel,IEEE Wireless Communications Letters1(4)pp. 304-307
    DOI: 10.1109/WCL.2012.042512.120147
    It is well-established that transmitting at full power is the most spectral-efficient power allocation strategy for pointto- point (P2P) multi-input multi-output (MIMO) systems, however, can this strategy be energy efficient as well? In this letter, we address the most energy-efficient power allocation policy for symmetric P2P MIMO systems by accurately approximating in closed-form their optimal transmit power when a realistic MIMO power consumption model is considered. In most cases, being energy efficient implies a reduction in transmit and overall consumed powers at the expense of a lower spectral efficiency.
    Kaltakis D, Katranaras E, Imran MA, Tzaras C (2008) Capacity of cellular uplink with multiple tiers of users and path loss,Proceedings - 4th Advanced International Conference on Telecommunications, AICT 2008pp. 287-292
    DOI: 10.1109/AICT.2008.49
    With the emergence and continuous growth of wireless data services, the value of a wireless network is not only defined by how many users it can support, but also by its ability to deliver higher data rates. Information theoretic capacity of cellular systems with fading is usually estimated using models originally inspired by Wyner's Gaussian Cellular Multiple Access Channel (GCMAC). In this paper we extend this model to study the cellular system with users distributed over the cellular coverage area. Based on the distance from the cell-site receiver, users are grouped as tiers, and received signals from each tier are scaled using a distance dependent attenuation factor. The optimum capacity in fading environment is then found by calculating the path-loss for users in each tier using a specific path-loss law and some interesting insights are derived. The results correspond to a more realistic model which boils down to Wyner's model with fading, with appropriate substitutions of parameter values. The results are verified using Wyner's model with fading and Monte-Carlo simulations. Insights are provided for the real world scenarios. © 2008 IEEE.
    Peyvandi H, Imran A, Imran MA, Tafazolli R (2014) A target-following regime using Similarity Measure for Coverage and Capacity Optimization in Self-Organizing Cellular Networks with hot-spot, 20th European Wireless Conference, EW 2014pp. 189-194
    © VDE VERLAG GMBH, Berlin, Offenbach, Germany.The Self-Organizing Network (SON) has been seen as one of the promising areas to save OPerational EXpenditure (OPEX) and to bring real efficiency to the wireless networks. Though the studies in literature concern with local interaction and distributed structure for SON, study on its coherent pattern has not yet been well-conducted. We consider a targetfollowing regime and propose a novel approach of goal attainment using Similarity Measure (SM) for Coverage & Capacity Optimization (CCO) use-case in SON. The methodology is based on a self-optimization algorithm, which optimizes the multiple objective functions of UE throughput and fairness using performance measure, which is carried out using SM between target and measured KPIs. After certain epochs, the optimum results are used in adjustment and updating modules of goal attainment. To investigate the proposed approach, a simulation in downlink LTE has also been set up. In a scenario including a congested cell with hotspot, the joint antenna parameters of tilt/azimuth using a 3D beam pattern is considered. The final CDF results show a noticeable migration of hot-spot UEs to higher throughputs, while no one worse off.
    Akbari I, Onireti O, Imran A, Imran MA, Tafazolli R (2016) How Reliable is MDT-Based Autonomous Coverage Estimation in the Presence of User and BS Positioning Error?,IEEE WIRELESS COMMUNICATIONS LETTERS5(2)pp. 196-199 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/LWC.2016.2516989
    Reátegui del Águila F, Imran MA, Tafazolli R (2013) On the Three-Receiver Multilevel Broadcast Channel with Random Parameters,
    Imran A, Giupponi L, Imran MA, Abu-Dayya A (2014) Joint coverage and backhaul self-optimization in emerging relay enhanced heterogeneous networks, 2014 IEEE International Conference on Communications, ICC 2014pp. 2671-2677
    DOI: 10.1109/ICC.2014.6883727
    This paper presents a novel framework for joint self-optimization of backhaul as well as coverage links spectral efficiency in relay enhanced heterogeneous networks. Considering a realistic heterogeneous network deployment, where some cells contain Relay Station (RS), while others do not, we develop an analytical framework for self-optimisation of macrocell Base Station (BS) antenna tilts. Our framework exploits a unique system level perspective to enable dynamic maximization of system-wide spectral efficiency of the BS-RS backhaul links as well as that of the BS-user coverage links. A distributed and practical self-organising solution is obtained by decomposing the large scale system-wide optimization problem into local small scale optimization problems, by mimicking the operational principles of self-organisation in biological systems. The local problems are non-convex but have very small scale and can be solved via appropriate numerical methods, such as sequential quadratic programming. The performance of developed solution is evaluated through extensive system level simulations for LTE-A type networks and compared against conventional tilting benchmarks. Numerical results show that up to 50% gain in average spectral efficiency is achievable through the proposed solution depending on users geographical distributions. © 2014 IEEE.
    Heliot F, Imran MA, Tafazolli R Energy-efficient Coordinated Resource Allocation for the Downlink of Cellular Systems,
    Energy efficiency (EE) is growing in importance as a system design crite- rion for power-unlimited system such as cellular systems. Equally, resource allocation is a well-known method for improving the performance of the latter. In this paper, we propose two novel coordinated resource allocation strategies for jointly optimizing the resources of three sectors/cells in an energy-efficient manner in the downlink of multi-cell/sector systems. Given that this optimization problem is non-convex, it can only be optimally solved using high complexity exhaustive search. Here, we propose two practical approaches for allocating resources in a low complexity manner. We then compare our novel approaches against other existing non-coordinated and co- ordinated ones in order to highlight their benefit. Our results indicate that our first approach performs the best in terms of EE but with a low level of fairness in the user rate allocation; whereas our second approach provides a good trade-off between EE and fairness. Overall, base station selection, i.e. allowing only one sector to transmit at a time, is a very energy-efficient approach when the sleeping power is considered in the base station power model.
    Imran MA (2013) Spectrum Utilization Efficiency Analysis in Cognitive Radio Networks, Proceedings of the 2013 19th European Wireless Conference (EW)pp. 1-5 IEEE
    In cognitive radio network, secondary (unlicensed) users (SUs) are allowed to utilize the licensed spectrum when it is not used by the primary (licensed) users (PUs). Because of the dynamic nature of cognitive radio network, the activities of SUs such as ??how long to sense?? and ??how long to transmit?? significantly affect both the service quality of the cognitive radio networks and protection to PUs. In this work, we formulate and analyze spectrum utilization efficiency problem in the cognitive radio network with various periodic frame structure of SU, which consists of sensing and data transmission slots. Energy detection is considered for spectrum sensing algorithm. To achieve higher spectrum utilization efficiency, the optimal sensing and data transmission length are investigated and found numerically. The simulation results are presented to verify the our analysis and to evaluate the interference to the PU which should be controlled into tolerable level. Index Terms ?? Cognitive radio network; spectrum utilization efficiency; spectrum sensing; energy detection; frame structure.
    Khan AH, Imran MA, Evans B (2009) OFDM based Adaptive Beamforming for Hybrid Terrestrial-Satellite Mobile System with Pilot Reallocation, International Workshop on Satellite and Space Communicationspp. 201-205 IEEE
    DOI: 10.1109/IWSSC.2009.5286394
    Next generation networks will have to provide global connectivity to ensure success. Both satellite and terrestrial networks cannot guarantee this on their own. This incapability is attributed to capacity coverage issues in densely populated areas for satellites and lack of infrastructure in rural areas for terrestrial networks. Therefore, we consider a hybrid terrestrial-satellite mobile system based on frequency reuse. However, this frequency reuse introduces severe co-channel interference (CCI) at the satellite end. To mitigate CCI, we propose an OFDM based adaptive beamformer implemented on-board the satellite with pilot reallocation at the transmitter side. Results show that the proposed scheme outperforms the conventional approach.
    Zoha A, Gluhak A, Imran MA, Nati M, Rajasegarar S (2012) Acoustic and Device Feature Fusion for Load Recognition,Proceedings of the 6th IEEE International Conference on Intelligent Systems (IEEE IS)pp. 386-392 IEEE
    DOI: 10.1109/IS.2012.6335166
    Appliance-specific Load Monitoring (LM) provides a possible solution to the problem of energy conservation which is becoming increasingly challenging, due to growing energy demands within offices and residential spaces. It is essential to perform automatic appliance recognition and monitoring for optimal resource utilization. In this paper, we study the use of non-intrusive LM methods that rely on steady-state appliance signatures for classifying most commonly used office appliances, while demonstrating their limitation in terms of accurately discerning the low-power devices due to overlapping load signatures. We propose a multilayer decision architecture that makes use of audio features derived from device sounds and fuse it with load signatures acquired from energy meter. For the recognition of device sounds, we perform feature set selection by evaluating the combination of time-domain and FFT-based audio features on the state of the art machine learning algorithms. The highest recognition performance however is shown by support vector machines, for the device and audio recognition experiments. Further, we demonstrate that our proposed feature set which is a concatenation of device audio feature and load signature significantly improves the device recognition accuracy in comparison to the use of steady-state load signatures only.
    Gurcan MK, Abas AEP, Imran MA (2004) Graph theoretic multiple access interference reduction for CDMA based radio LAN, Proc. IEEE International Conference on Communications7pp. 4147-4151
    DOI: 10.1109/ICC.2004.1313329
    Alsedairy T, Qi Y, Imran A, Imran MA, Evans B (2014) Self Organising Cloud cells: A Resource Efficient Network Densification Strategy,Transactions on Emerging Telecommunications Technologies Wiley
    DOI: 10.1002/ett.2824
    Network densification is envisioned as the key enabler for 2020 vision that requires cellular systems to grow in capacity by hundreds of times to cope with unprecedented traffic growth trends being witnessed since advent of broadband on the move. However, increased energy consumption and complex mobility management associated with network densifications remain as the two main challenges to be addressed before further network densification can be exploited on a wide scale. In the wake of these challenges, this paper proposes and evaluates a novel dense network deployment strategy for increasing the capacity of future cellular systems without sacrificing energy efficiency and compromising mobility performance. Our deployment architecture consists of smart small cells, called cloud nodes, which provide data coverage to individual users on a demand bases while taking into account the spatial and temporal dynamics of user mobility and traffic. The decision to activate the cloud nodes, such that certain performance objectives at system level are targeted, is carried out by the overlaying macrocell based on a fuzzy-logic framework. We also compare the proposed architecture with conventional macrocell only deployment and pure microcell-based dense deployment in terms of blocking probability, handover probability and energy efficiency and discuss and quantify the trade-offs therein
    Qi Y, Imran M, Tafazolli R (2012) On the Energy Efficiency of Hybrid Relaying Schemes in the Two-way Relay Channel,
    In this paper, hybrid relaying schemes are investigated in the two-way relay channel, where the relay node is able to adaptively switch between different forwarding schemes based on the current channel state and its decoding status and thus provides more flexibility as well as improved performance. The analysis is conducted from the energy efficiency perspective for two transmission protocols distinguished by whether exploiting the direct link between two main communicating nodes (the source and destination nodes, and vice versa since it is two way communication) or not. A realistic power model taking circuitry power consumption of all involved nodes into account is employed. The energy efficiency is optimized in terms of consumed energy per bit subject to the Quality of Service (QoS) constraint. Numerical results show that the hybrid schemes are able to achieve the highest energy efficiency due to its capability of adapting to the channel variations and the protocol where the direct link is exploited is more energy efficient.
    Imran MA, Chatzinotas S, Hoshyar R (2008) Capacity of the Cellular Uplink using Joint Multi-cell Processing (Hyper-receiver) with OFDM and CDMA, International Research Workshop on LTE-Advanced Technologies
    Imran MA, Hoshyar R (2009) Performance of multicell joint processing cellular uplink in the presence of relay nodes, ICT-MobileSummit
    Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Results and analysis for the rate limits for Wireless City model,
    Katranaras E, Imran MA, Tzaras C (2009) Uplink Capacity of a Variable Density Cellular System with Multicell Processing,IEEE TRANSACTIONS ON COMMUNICATIONS57(7)pp. 2098-2108 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/TCOMM.2009.07.070626
    In this work we investigate the information theoretic capacity of the uplink of a cellular system. Assuming centralised processing for all Base Stations, we consider a power-law path loss model along with variable cell size (variable density of Base Stations) and we formulate an average path-loss approximation. Considering a realistic Rician flat fading environment, the analytical result for the per-cell capacity is derived for a large number of users distributed over each cell. We extend this general approach to model the uplink of sectorized cellular system. To this end, we assume that the user terminals are served by perfectly directional receiver antennas, dividing the cell coverage area into perfectly non-interfering sectors. We show how the capacity is increased (due to degrees of freedom gain) in comparison to the single receiving antenna system and we investigate the asymptotic behaviour when the number of sectors grows large. We further extend the analysis to find the capacity when the multiple antennas used for each Base Station are omnidirectional and uncorrelated (power gain on top of degrees of freedom gain). We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems.
    Gruber M, Blume O, Ferling D, Zeller D, Imran MA, Strinati E (2009) EARTH ý Energy Aware Radio and Network Technologies,IEEE PIMRC 2009pp. 1-5 IEEE
    DOI: 10.1109/PIMRC.2009.5449938
    EARTH is a major new European research project starting in 2010 with 15 partners from 10 countries. Its main technical objective is to achieve a reduction of the overall energy consumption of mobile broadband networks by 50%. In contrast to previous efforts, EARTH regards both network aspects and individual radio components from a holistic point of view. Considering that the signal strength strongly decreases with the distance to the base station, small cells are more energy efficient than large cells. EARTH will develop corresponding deployment strategies as well as management algorithms and protocols on the network level. On the component level, the project focuses on base station optimizations as power amplifiers consume the most energy in the system. A power efficient transceiver will be developed that adapts to changing traffic load for an energy efficient operation in mobile radio systems. With these results EARTH will reduce energy costs and carbon dioxide emissions and will thus enable a sustainable increase of mobile data rates
    Kakitani MT, Brante G, Souza RD, Pellenz ME, Imran MA (2013) Energy and cost analysis of cellular networks under co-channel interference,2013 IEEE Latin-America Conference on Communications, LATINCOM 2013 - Conference Proceedings
    DOI: 10.1109/LatinCom.2013.6759815
    In this paper we carry out an energy efficiency and economic cost analysis of different cellular network designs. Our system model considers the co-channel interference, different amounts of available bandwidths and also the reuse of frequencies. The energy efficiency analysis employs a realistic power consumption model, while the economic analysis focus on infrastructure, spectrum licenses, and energy costs. Our results show that from an economic point of view the bandwidth cost and the number of employed base stations can be the most relevant factors to be balanced, while from an energy efficiency analysis it is more interesting to employ larger bandwidths and to balance the reuse of frequencies and the number of base stations. Moreover, although the system design under these two different points of view can be rather different, we also look into scenarios when the most energy efficient system design may also lead to the best economic option. © 2013 IEEE.
    Imran A, Imran MA, Tafazolli R (2010) A Novel Self Organizing Framework for Adaptive Frequency Reuse & Deployment in Future Cellular Networks,IEEE PIMRC 2010pp. 2354-2359 IEEE
    DOI: 10.1109/PIMRC.2010.5671710
    Recent research on Frequency Reuse (FR) schemes for OFDM/OFDMA based cellular networks (OCN) suggest that a single fixed FR cannot be optimal to cope with spatiotemporal dynamics of traffic and cellular environments in a spectral and energy efficient way. To address this issue this paper introduces a novel Self Organizing framework for adaptive Frequency Reuse and Deployment (SO-FRD) for future OCN including both cellular (e.g. LTE) and relay enhanced cellular networks (e.g. LTE Advance). In this paper, an optimization problem is first formulated to find optimal frequency reuse factor, number of sectors per site and number of relays per site. The goal is designed as an adaptive utility function which incorporates three major system objectives; 1) spectral efficiency 2) fairness, and 3) energy efficiency. An appropriate metric for each of the three constituent objectives of utility function is then derived. Solution is provided by evaluating these metrics through a combination of analysis and extensive system level simulations for all feasible FRD's. Proposed SO-FRD framework uses this flexible utility function to switch to particular FRD strategy, which is suitable for system's current state according to predefined or self learned performance criterion. The proposed metrics capture the effect of all major optimization parameters like frequency reuse factor, number of sectors and relay per site, and adaptive coding and modulation. Based on the results obtained, interesting insights into the tradeoff among these factors is also provided.
    Mohammed A-I, Imran MA, Tafazolli R, Chen D (2012) Performance Evaluation of Low Density Spreading Multiple Access, FEC1pp. x1-x1
    Qi Y, Imran MA, Sabella D, Debaillie B, Fatini R, Fernandez Y (2012) On the Deployment Opportunities for Increasing Energy Efficiency,
    Saeed A, Imran MA, Aliu OG (2012) Controlling Self-Healing Cellular networks using Fuzzy Logic, pp. 3080-3084 IEEE
    DOI: 10.1109/WCNC.2012.6214334
    Wireless cellular communication networks is undergoing a transition from being a simply optional voice communication to becoming a necessity in our everyday lives. In order to ensure uninterrupted high Quality of Experience for subscribers, network operators must ensure 100% reliability of their networks without any discontinuity either for planned maintenance or breakdown. This paper demonstrates self healing capability to the fault recovery process for each cell. It is proposed to compensate cells in failure by neighboring cells optimizing their coverage with antenna reconfiguration and power compensation resulting in filling the coverage gap and improving the QoS for users. The right choice of these reconfigured parameters is determined through a process involving fuzzy logic control and reinforcement learning. Results show an improvement in the network performance for the area under outage as perceived by each user in the system.
    Onireti OS, Abouelmaati D, Imran MA, Arshad K, Saeed A (2015) Femtocell Collaborative Outage Detection (FCOD) With Built-In Sleeping Mode Recovery (SMR) Technique,
    Self-Organizing Networks (SONs) have an important role in the development of the next generation mobile networks by introducing automated schemes. Cell outage detection is one of the main functionalities in self-healing mechanism. Outage detection for small cells has not been discussed in literature with greater emphasis yet. The Femtocell Collaborative Outage Detection (FCOD) algorithm with built-in Sleeping Mode Recovery (SMR) is introduced in this paper. The proposed algorithm is mainly based on the femtocell collaborative detection with incorporated sniffer. It compares the current Femtocell Access Points FAPs? Reference Signal Received Power (RSRP) statistics with a benchmark data. An outage decision is autonomously taken by each FAP depending on a certain threshold value. Moreover, the FCOD algorithm is capable of differentiating between the outage and sleeping cells due to the presence of the built-in SMR technique.
    Onireti OST, Imran MA, Heliot F (2011) On Achievable Rate Region of Multiple Coordinated Multiple Access Channels,73rd IEEE Vehicular technology Conference IEEE
    DOI: 10.1109/VETECS.2011.5956549
    Coordination between two or more multiple access channel (MAC) receivers can enlarge the achievable rate region of the whole system. This paper focuses on coordination by sharing the codebooks of the users between the receivers of MACs. We first define the achievable rate region of the time invariant multiple coordinated MAC (MCMAC) and subsequently derive its achievable rate region. We later express the achievable rate region in terms of the dominating points. We base our numerical analysis on the two-user two-receiver Gaussian coordinated MAC and make comparison with the interference channel, full cooperation and the individual MAC performance analysis. It is observed that this approach though suboptimal is less complex in comparison with full cooperation and that the MCMAC rate region is at least equal to the rate region of the uncoordinated approach. Over several channel states, the rate region of MCMAC exceeds that of the uncoordinated approach.
    Muirhead D, Imran MA (2012) Determining the Energy Efficiency of Femtocell Basestations with Multiple Antennas,
    Mehta M, Rane N, Karandikar A, Imran Muhammad Ali, Evans Barry G. (2016) A self-organized resource allocation scheme for heterogeneous macro-femto networks,Wireless Communications and Mobile Computing16(3)pp. 330-342 Wiley
    DOI: 10.1002/wcm.2518
    This paper investigates the radio resource management (RRM) issues in a heterogeneous macro-femto network. The objective of femto deployment is to improve coverage, capacity, and experienced quality of service of indoor users. The location and density of user-deployed femtos is not known a-priori. This makes interference management crucial. In particular, with co-channel allocation (to improve resource utilization efficiency), RRM becomes involved because of both cross-layer and co-layer interference. In this paper, we review the resource allocation strategies available in the literature for heterogeneous macro-femto network. Then, we propose a self-organized resource allocation (SO-RA) scheme for an orthogonal frequency division multiple access based macro-femto network to mitigate co-layer interference in the downlink transmission. We compare its performance with the existing schemes like Reuse-1, adaptive frequency reuse (AFR), and AFR with power control (one of our proposed modification to AFR approach) in terms of 10 percentile user throughput and fairness to femto users. The performance of AFR with power control scheme matches closely with Reuse-1, while the SO-RA scheme achieves improved throughput and fairness performance. SO-RA scheme ensures minimum throughput guarantee to all femto users and exhibits better performance than the existing state-of-the-art resource allocation schemes.
    Imran MA, Gurcan MK (2006) Message passing algorithm for iterative decoding of channel codes, HERMIS-mu-pi International Journal of Computer Mathematics and its Applications8pp. 1-20-1-20
    Onireti O, Imran MA, Tafazolli R, Imran A (2014) Cell outage detection in heterogeneous networks with separated control and data plane, 20th European Wireless Conference, EW 2014pp. 165-170
    In this paper, we propose a data cell outage detection scheme for heterogeneous networks (HetNets) with separated control and data plane. We consider a HetNet where the Control Network Layer (CNL) provides ubiquitous network access while Data Network Layer (DNL) provides high data rate transmission to low mobility User Terminals (UTs) Furthermore, network functionalities such as paging and system information broadcast are provided by the CNL to all active UTs, hence, the CNL is aware of all active UTs association. Based on this observation, we categorize our data cell outage detection scheme into the trigger phase and detection phase. In the former, the CNL monitors all UT-data base station association and triggers detection when irregularities occurs in the association, whUe the later utilizes a grey prediction model on the UTs' reference signal received power (RSRP) statistics to determine the existence of an outage. The simulation results indicate that the proposed scheme can detect the data cell outage problem in a reliable manner.
    Katranaras E, Tang J, Imran MA (2013) Energy and spectral efficient inter base station relaying in cellular systems, IEEE Vehicular Technology Conference
    DOI: 10.1109/VTCSpring.2013.6692537
    This paper considers a classic relay channel which consists of a source, a relay and a destination node and investigates the energy-spectral efficiency tradeoff under three different relay protocols: amplify-and-forward; decode-and-forward; and compress-and-forward. We focus on a cellular scenario where a neighbour base station can potentially act as the relay node to help on the transmissions of the source base station to its assigned mobile device. We employ a realistic power model and introduce a framework to evaluate the performance of different communication schemes for various deployments in a practical macrocell scenario. The results of this paper demonstrate that the proposed framework can be applied flexibly in practical scenarios to identify the pragmatic energy-spectral efficiency tradeoffs and choose the most appropriate scheme optimising the overall performance of inter base station relaying communications. © 2013 IEEE.
    OReilly C, Gluhak A, Imran M, Rajasegarar S (2014) Anomaly Detection in Wireless Sensor Networks in a Non-Stationary Environment,IEEE Surveys and Tutorials IEEE
    Onireti OS, Zaidi ZR, Friderikos V, Gang J, Imran MA (2016) An Integrated Approach for Functional Decomposition of Future RAN (Radio Access Network), In: Shakir MZ, Imran MA, Qaraqe KA, Alouini M-S, Vasilakos AV (eds.), Energy Management in Wireless Cellular and Ad-hoc Networks6pp. 123-144 Springer
    Software-defined radio access networks (SD-RAN), dense deployment of small cells with possible macro-overlay for users with high mobility, decoupled signaling and data transmissions, or beyond cellular green generation (BCG2) architecture for enhanced energy efficiency, etc. are some of the very active research themes and most promising technologies for future RAN architecture. In this chapter, we present the idea of an integrated deployment solution for energy efficient cellular networks combining the strengths of the above mentioned themes. While SD-RAN envisions a decoupled centralized control plane and data forwarding plane for flexible control, the BCG2 architecture calls for decoupling coverage from capacity and coverage is provided through always-on low-power signaling node for a larger geographical area; capacity is catered by various on-demand data nodes or small cells for maximum energy efficiency. We identify that a combined approach bringing in both decompositions together can, not only achieve greater benefits, but also facilitates the faster realization of both technologies. We propose the idea and design of a signaling controller which acts as a signaling node to provide always-on coverage, consuming low power, and at the same time also hosts the control plane functions for the SD-RAN through a general purpose processing platform. Phantom cell concept is also a similar idea where a normal macro cell provides interference control to densely deployed small cells, although, our preliminary results show that the proposed integrated architecture has much greater potential of energy savings in comparison to phantom cells as a signaling controller is supposed to consume minimal power in comparison with the normal macro cell BS.
    Khan A, Imran MA, Evans B (2010) Preamble based Adaptive Beamformer for Hybrid Terrestrial-Satellite Mobile System, 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010)
    Arshad K, Imran MA (2013) Increasing the interaction time in a lecture by integrating flipped classroom and just-in-time teaching concepts, Compass: Journal of Learning and Teaching47
    Majid M, Imran M, Hoshyar R (2010) Optimization of uplink sum-rate for bin based clustered cellular system using a Genetic Algorithm, IWCMC 2010, The 6th International Wireless Communication and Mobile Computing Conference
    Qi Y, Imran MA, Tafazolli R (2010) On the energy aware deployment strategy in cellular systems, Wireless Green Workshop, IEEE PIMRC 2010
    Imran, Muhammad A (2009) Multi-cell Coordination Techniques for OFDMA Multi-hop Cellular Networks,
    Qi Y, Héliot F, Imran MA, Tafazolli R (2012) Green Relay Techniques in Cellular Systems, In: Yu FR, Leung VCM, Zhang X (eds.), Green Communications and Networking CRC Press
    Khan A, Imran MA, Evans B (2010) Ground based and onboard based beamforming for hybrid terrestrial-satellite mobile system, 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010)
    Mustafa HA, Shakir MZ, Imran MA, Imran A, Tafazolli R (2015) Coverage Gain and Device-to-Device User Density: Stochastic Geometry Modeling and Analysis, IEEE COMMUNICATIONS LETTERS19(10)pp. 1742-1745 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/LCOMM.2015.2459677
    Imran A, Imran MA, Abu-Dayya A, Tafazolli R (2014) Self Organization of Tilts in Relay Enhanced Networks: A Distributed Solution,Wireless Communications, IEEE Transactions on13(2)pp. 764-779 IEEE
    DOI: 10.1109/TWC.2014.011614.130299
    Despite years of physical-layer research, the capacity enhancement potential of relays is limited by the additional spectrum required for Base Station (BS)-Relay Station (RS) links. This paper presents a novel distributed solution by exploiting a system level perspective instead. Building on a realistic system model with impromptu RS deployments, we develop an analytical framework for tilt optimization that can dynamically maximize spectral efficiency of both the BS-RS and BS-user links in an online manner. To obtain a distributed self-organizing solution, the large scale system-wide optimization problem is decomposed into local small scale subproblems by applying the design principles of self-organization in biological systems. The local subproblems are non-convex, but having a very small scale, can be solved via standard nonlinear optimization techniques such as sequential quadratic programming. The performance of the developed solution is evaluated through extensive simulations for an LTE-A type system and compared against a number of benchmarks including a centralized solution obtained via brute force, that also gives an upper bound to assess the optimality gap. Results show that the proposed solution can enhance average spectral efficiency by up to 50% compared to fixed tilting, with negligible signaling overheads. The key advantage of the proposed solution is its potential for autonomous and distributed implementation.
    Sambo Y, Heliot F, Imran MA (2015) Electromagnetic Emission-aware Schedulers for the Uplink of OFDM Wireless Communication Systems,2015 IEEE ONLINE CONFERENCE ON GREEN COMMUNICATIONS (ONLINEGREENCOMM)pp. 42-46 IEEE
    DOI: 10.1109/OnlineGreenCom.2015.7387377
    The increasing demand for data and multimedia services, as well as the ubiquitous nature of the current generation of mobile devices have resulted in continuous network upgrades to support an ever-increasing number of users. However, given that wireless communication systems operate on radiofrequency waves, the health effects of electromagnetic (EM) emission from these systems are increasingly becoming a concern. In order to address these concerns, we propose in this paper, an EM emission reduction scheme for the uplink of OFDM wireless systems with base station coordination. We formulate the EM reduction scheme as a convex optimization problem and solve it by iteratively allocating bits to users on their respective subcarriers in each sector. This is based on the assumption that the scheduler can predict the channel state information of all the users for a given transmission window. Simulation results show that, with coordination, our proposed scheme reduces EM emission by over 85% and 99% when compared with a no frequency reuse scheme and an energy efficiency based scheme, respectively.
    Onireti OS, Imran A, Imran MA, Tafazolli R (2014) Cell Outage Detection in Heterogeneous Networks with Separated Control and Data Plane,pp. 1-6 VDE
    In this paper, we propose a data cell outage detection scheme for heterogeneous networks (HetNets) with separated control and data plane. We consider a HetNet where the Control Network Layer (CNL) provides ubiquitous network access while Data Network Layer (DNL) provides high data rate transmission to low mobility User Terminals (UTs). Furthermore, network functionalities such as paging and system information broadcast are provided by the CNL to all active UTs, hence, the CNL is aware of all active UTs association. Based on this observation, we categorize our data cell outage detection scheme into the trigger phase and detection phase. In the former, the CNL monitors all UT-data base station association and triggers detection when irregularities occurs in the association, while the later utilizes a grey prediction model on the UTs? reference signal received power (RSRP) statistics to determine the existence of an outage. The simulation results indicate that the proposed scheme can detect the data cell outage problem in a reliable manner.
    Sambo Y, Héliot F, Imran MA (2012) An interference-aware precoding scheme for the downlink of multi-cell multi-user MIMO communication, Proceedings of the 2012 IEEE 4th International Conference on Adaptive Science and Technology, ICAST 2012pp. 29-32
    DOI: 10.1109/ICASTech.2012.6381061
    In multi-cell communication, users close to the cell boundaries tend to suffer interferences from other-cell users. Other-Cell Interference (OCI) coming from neighbouring cells considerably degrades the overall performance of the system. In this paper, we propose a precoding scheme for the multi-user multi-input multi-output (MIMO) downlink based on the regularized channel inversion algorithm to mitigate the effect of OCI in multi-cell systems. The scheme is designed by taking into account the interference plus noise covariance matrix of each user at the transmitter and the use of an interference suppression filter at each receiver. Unlike traditional OCI-aware Block Diagonalization (BD) based algorithms that experience noise enhancement due to complete elimination of multi-user interference (MUI), this scheme suppresses the MUI while taking the OCI into consideration. Simulation results show that the sum-rate performance of the proposed scheme outperforms the OCI-aware BD algorithm for different OCI settings. © 2012 IEEE.
    Herault L, Strinati E, Zeller D, Blume O, Imran MA, Tafazolli R (2009) Green Communications: A global environmental challenge, 12th WPMC 2009 NICT
    Awad JF, Imran MA, Tafazolli R (2013) Reduced Complexity Interference Avoidance Scheme Based on User Grouping in Dense Cellular Networks, European Wireless 2013 VDE VERLAG GmbH
    Zoha A, Gluhak A, Nati M, Imran MA (2013) Low-power appliance monitoring using Factorial Hidden Markov Models, Proceedings of the 2013 IEEE 8th International Conference on Intelligent Sensors, Sensor Networks and Information Processing: Sensing the Future, ISSNIP 20131pp. 527-532
    DOI: 10.1109/ISSNIP.2013.6529845
    To optimize the energy utilization, intelligent energy management solutions require appliance-specific consumption statistics. One can obtain such information by deploying smart power outlets on every device of interest, however it incurs extra hardware cost and installation complexity. Alternatively, a single sensor can be used to measure total electricity consumption and thereafter disaggregation algorithms can be applied to obtain appliance specific usage information. In such a case, it is quite challenging to discern low-power appliances in the presence of high-power loads. To improve the recognition of low-power appliance states, we propose a solution that makes use of circuit-level power measurements. We examine the use of a specialized variant of Hidden Markov Model (HMM) known as Factorial HMM (FHMM) to recognize appliance specific load patterns from the aggregated power measurements. Further, we demonstrate that feature concatenation can improve the disaggregation performance of the model allowing it to identify device states with an accuracy of 90% for binary and 80% for multi-state appliances. Through experimental evaluations, we show that our solution performs better than the traditional event based approach. In addition, we develop a prototype system that allows real-time monitoring of appliance states. © 2013 IEEE.
    Héliot F, Sambo YA, Imran MA (2014) Energy-efficient interference-aware precoding for the downlink of multi-cell multi-user MIMO systems,EuCNC 2014 - European Conference on Networks and Communications
    DOI: 10.1109/EuCNC.2014.6882646
    Energy efficiency (EE) is fast becoming a key performance indicator for designing future wireless communication systems. Equally, precoding/power allocation has proved to be very effective for improving the spectral efficiency (SE) of multi-user (MU) multi-input multi-output (MIMO) communication systems. In a multi-cell environment, other-cell interference (OCI) degrades both the SE and EE performances of the system. We design here an energy efficient OCI-aware precoding/power allocation algorithm for the downlink of MU-MIMO systems by relying on regularized channel inversion and considering a realistic multi-antenna power consumption model. The performance of our proposed scheme is assessed both in presence and absence of OCI and results demonstrate the effectiveness of our approach for mitigating OCI. In addition, results show that our approach improves the EE of the system by saving transmit power in comparison with a traditional SE-based precoding/power allocation approach. © 2014 IEEE.
    Chatzinotas S, Imran MA, Tzaras C (2008) Spectral efficiency of variable density cellular systems with realistic system models, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
    DOI: 10.1109/PIMRC.2008.4699843
    In the information-theoretic literature, multicell joint processing has been shown to produce high spectral efficiencies. However, the majority of existing results employ simplified models and normalized variables and in addition they consider only the sum-rate capacity, neglecting the individual user rates. In this paper, we investigate a realistic cellular model which incorporates flat fading, path loss and distributed users. Furthermore, the presented results are produced by varying the cell density of the cellular system, while practical values are used for system parameters, such as users per cell, transmitted power, path loss exponent. What is more, we study the effect of sum-rate maximization on the fairness of user rate distribution by comparing channel-dependent and random user orderings within the joint encoding/decoding process. © 2008 IEEE.
    Majid MI, Imran MA, Hoshyar R (2008) Analyzing uplink capacity of partially overlapping channel based WLANs using a hyper-receiver,2008 IEEE INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS (ISWCS 2008)pp. 723-727 IEEE
    DOI: 10.1109/ISWCS.2008.4726151
    Spectrum allocation within the fixed unlicensed band affects performance of wireless networks. Fundamental limitations of spectral efficiency on capacity of wireless local area networks (WLANs) hence needs to be studied. Recently, it was shown that the performance can be increased when both non-overlapping and partially overlapping channels are used. Unlike previous studies, this is the first known attempt on analysis of information theoretic capacity for partially-overlapping channels, as characterized by IEEE 802.11b-type systems using a hyper-receiver. Using Marenko-Pastur law distribution, capacity is approximated for such systems. We implement this by proposing a novel channel model for our analysis. The results conform to Monte Carlo simulations, with an approximate mean error of less than 5%. Fundamental tradeoffs of channel interference and power gain are discussed. We further explore the effect of access point density and find that systems based on partially overlapping channels perform well in high density deployments. We also compute capacity for a range of channel overlaps and conclude that rates close to capacity are achievable for a channel overlap of 90% and above.
    Awad JF, Imran MA, Tafazolli R (2012) Fairness Evaluation in Cooperative Hybrid Cellular Systems,pp. 389-394 IEEE
    DOI: 10.1109/IWCMC.2012.6314236
    Many method has been applied previously to improve the fairness of a wireless communication system. In this paper, we propose using hybrid schemes, where more than one transmission scheme are used in one system, to achieve this objective. These schemes consist of cooperative transmission schemes, maximal ratio transmission and interference alignment, and non-cooperative schemes, orthogonal and non-orthogonal schemes used alongside and in combinations in the same system to improve the fairness. We provide different weight calculation methods to vary the output of the fairness problem. We show the solution of the radio resource allocation problem for the transmission schemes used. Finally, simulation results is provided to show fairness achieved, in terms of Jain's fairness index, by applying the hybrid schemes proposed and the different weight calculation methods at different inter-site distances.
    O Reilly C, Gluhak A, Imran M, Rajasegarar S (2012) Online anomaly rate parameter tracking for anomaly detection in wireless sensor networks, Sensor, Mesh and Ad Hoc Communications and Networks (SECON), 2012 9th Annual IEEE Communications Society Conference onpp. 191 -199-191 -199
    DOI: 10.1109/SECON.2012.6275776
    Heliot F, Imran MA, Tafazolli R (2013) Energy-Efficient Resource Allocation for Orthogonal Multi-antenna Multi-carrier Channel,
    Energy efficiency (EE) is growing in importance as a key performance indicator for designing the next generation of communication systems. Equally, resource allocation is an effective approach for improving the performance of communication systems. In this paper, we propose a low-complexity energyefficient resource allocation method for the orthogonal multiantenna multi-carrier channel. We derive explicit formulations of the optimal rate and energy-per-bit consumption for the per-antenna transmit power constrained and per-antenna rate constrained EE optimization problems as well as provide a lowcomplexity algorithm for optimally allocating resources over the orthogonal multi-antenna multi-carrier channel. We then compare our approach against a classic optimization tool in terms of energy efficiency as well as complexity, and results indicate the optimality and low-complexity of our approach. Comparing EE-optimal with spectral efficiency and power optimal allocation approaches over the orthogonal multi-antenna multi-carrier channel indicates that the former provides a good trade-off between power consumption and sum-rate performances.
    Muirhead D, Imran MA (2010) Transmit Diversity and Beamforming for Energy Efficient Femtocells, Annual International Conference on Green Information Technology 2010
    Mustafa HA, Shakir MZ, Imran MA, Tafazolli R (2015) Distance based cooperation region for D2D pair,IEEE Vehicular Technology Conference2015
    DOI: 10.1109/VTCSpring.2015.7145780
    © 2015 IEEE. Device-to-device (D2D) communication is being considered an important traffic offloading mechanism for future cellular networks. Coupled with pro-active device caching, it offers huge potential for capacity and coverage enhancements. In order to ensure maximum capacity enhancement, number of nodes for direct communication needs to be identified. In this paper, we derive analytic expression that relates number of D2D nodes (i.e., D2D user density) and average coverage probability of reference D2D receiver. Using stochastic geometry and poisson point process, we introduce retention probability within cooperation region and shortest distance based selection criterion to precisely quantify interference due to D2D pairs in coverage area. The simulation setup and numerical evaluation validates the closed-form expression.
    Waqar O, Imran MA, Dianati M (2013) On the error analysis of fixed-gain relay networks over composite multipath/shadowing channels, IEEE Vehicular Technology Conference
    DOI: 10.1109/VTCSpring.2013.6692666
    In this paper, the analysis for the average bit error probability (ABEP) of a dual-hop fixed-gain relay network is conducted. To this end, we consider two different scenarios: 1) the second hop (relay-destination link) is subject to composite multipath/shadowing and the first hop (source-relay link) experiences only multipath fading; 2) the first hop is perturbed by the composite multipath/shadowing and the second hop undergoes only multipath fading. We develop new and exact closed-form expressions of the ABEP for the first scenario in terms of the Meijer-G and Lommel functions. Since the exact closed-form expressions for the second scenario are mathematically intractable, we derive a new approximation and bounds. These approximation and bounds are shown to be tight for medium to high average signal-to-noise ratio (SNR) regime. In addition, we also provide new and relatively simpler asymptotic expressions of the ABEP for both the scenarios. It is shown that some physical insights (e.g., diversity order) of the system can readily be obtained by using these asymptotic expressions. All our analytical results are corroborated by the Monte-Carlo simulations. © 2013 IEEE.
    Onireti O, Heliot F, Imran MA (2012) On the Energy Efficiency-Spectral Efficiency Trade-Off of the 2BS-DMIMO System,IEEE VTC Fall 2012pp. 1-5 IEEE
    DOI: 10.1109/VTCFall.2012.6399182
    In this paper, we propose a novel closed-form approximation of the Energy Efficiency vs. Spectral Efficiency (EE-SE) trade-off for the uplink/downlink of distributed multipleinput multiple-output (DMIMO) system with two cooperating base stations. Our closed-form expression can be utilized for evaluating the idealistic and realistic EE-SE performances of various antenna configurations as well as assessing how DMIMO compares against MIMO system in terms of EE. Results show a tight match between our closed-form approximation and the Monte-Carlo simulation for both idealistic and realistic EESE trade-off. Our results also show that given a target SE requirement, there exists an optimal antenna setting that maximizes the EE. In addition, DMIMO scheme can offer significant improvement in terms of EE over the MIMO scheme
    Chatzinotas S, Imran MA, Tzaras C (2008) Information Theoretic Uplink Capacity of the Linear Cellular Array,Proc. Fourth Advanced International Conference on Telecommunications AICT ?08pp. 249-254 IEEE
    DOI: 10.1109/AICT.2008.35
    In the information-theoretic literature, Wyner's model has been the starting point for studying the capacity limits of cellular systems. This simple cellular model was adopted and extended by researchers in order to incorporate flat fading and path loss. However, the majority of these extensions preserved a fundamental assumption of Wyner's model, namely the collocation of User Terminals (UTs). In this paper, we alleviate this assumption and we evaluate the effect of user distribution on the sum-rate capacity. In this context, we show that the effect of user distribution is only considerable in low cell-density systems and we argue that "collocated" models can be utilized to approximate the "distributed" ones in the high cell-density regime. Subsequently, we provide closed forms for the calculation of the interference factors of "collocated" models given the system parameters. In addition, the asymptotics of the per-cell sum-rate capacity are investigated. Finally, the presented results are interpreted in the context of practical cellular systems using appropriate figures of merit.
    Murtagh N, nati M, headley WR, gatersleben B, gluhak A, imran MA, uzzell D (2013) Individual energy use and feedback in an office setting: A field trial, Energy Policy
    DOI: 10.1016/j.enpol.2013.07.090
    Onireti O, Héliot F, Imran MA (2011) Trade-off between Energy Efficiency and Spectral Efficiency in the Uplink of a Linear Cellular System with Uniformly Distributed User Terminals,Proc. IEEE PIMRCpp. 2407-2407 IEEE
    DOI: 10.1109/PIMRC.2011.6139952
    In this paper, we propose a tight closed-form approximation of the Energy Efficiency vs. Spectral Efficiency (EE-SE) trade-off for the uplink of a linear cellular communication system with base station cooperation and uniformly distributed user terminals. We utilize the doubly-regular property of the channel to obtain a closed form approximation using the MarÇcenko Pasture law. We demonstrate the accuracy of our expression by comparing it with Monte-Carlo simulation and the EE-SE trade-off expression based on low-power approximation. Results show the great tightness of our expression with Monte-Carlo simulation.We utilize our closed form expression for assessing the EE performance of cooperation for both theoretical and realistic power models. The theoretical power model includes only the transmit power, whereas the realistic power model incorporates the backhaul and signal processing power in addition to the transmit power. Results indicate that for both power models, increasing the number of antennas leads to an improvement in EE performance, whereas, increasing the number of cooperating BSs results in a loss in EE when considering the realistic power model.
    Kaltakis D, Imran MA, Hoshyar R (2009) Uplink Capacity with Correlated Lognormal Shadow Fading, 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5pp. 3009-3013 IEEE
    Akbari A, Imran MA, Tafazolli R, Dianati M (2011) Energy Efficiency Contours for Single-Carrier Downlink Channels,IEEE COMMUNICATIONS LETTERS15(12)pp. 1307-1309
    DOI: 10.1109/LCOMM.2011.103111.111519
    Auer G, Gódor I, Hévizi L, Imran MA, Malmodin J, Fazekas P, Biczók G, Holtkamp H, Zeller D, Blume O, Tafazolli R (2010) Enablers for energy efficient wireless networks,IEEE Vehicular Technology Conference
    DOI: 10.1109/VETECF.2010.5594386
    Mobile communications are increasingly contributing to global energy consumption. The EARTH (Energy Aware Radio and neTworking tecHnologies) project tackles the important issue of reducing CO2 emissions by enhancing the energy efficiency of cellular mobile networks. EARTH is a holistic approach to develop a new generation of energy efficient products, components, deployment strategies and energy-aware network management solutions. In this paper the holistic EARTH approach to energy efficient mobile communication systems is introduced. Performance metrics are studied to assess the theoretical bounds of energy efficiency as well as the practical achievable limits. A vast potential for energy savings lies in the operation of radio base stations. In particular, base stations consume a considerable amount of the available power budget even when operating at low load. Energy efficient radio resource management (RRM) strategies need to take into account slowly changing daily load patterns, as well as highly dynamic traffic fluctuations. Moreover, various deployment strategies are examined focusing on their potential to reduce energy consumption, whilst providing uncompromised coverage and user experience. This includes heterogeneous networks with a sophisticated mix of different cell sizes, which may be further enhanced by energy efficient relaying and base station cooperation technologies. Finally, scenarios leveraging the capability of advanced terminals to operate on multiple radio access technologies (RAT) are discussed with respect to their energy savings potential. ©2010 IEEE.
    Sambo YA, Imran MA, Shakir MZ, Qaraqe KA, Ahmed B, Serpedin E (2014) Energy efficiency improvements in HetNets by exploiting device-to-device communications,European Signal Processing Conferencepp. 151-155 IEEE
    The growth in mobile communications has resulted in a significant increase in energy consumption and carbon emissions, which could have serious economic and environmental implications. Consequently, energy consumption has become a key criterion for the design of future mobile communication systems. Device-to-device (D2D) communication has been shown to improve the spectral efficiency and also reduce the power consumption of mobile communication networks. In this paper, we propose a two-tier deployment of D2D communication within a network to reduce the overall power consumption of the network and compared it with full small-cell deployment throughout the network. In this context, we computed the backhaul power consumption of each link in the networks and derived the backhaul energy efficiency expression of the networks. Simulation results show that our proposed network deployment outperforms the network with full small-cell deployment in terms of backhaul power consumption, backhaul energy-efficiency, total power consumption of the tier 2 users and downlink power consumption, thus providing a greener alternative to small-cell deployment.
    Aliu OG, Mehta M, Imran MA, Karandikar A, Evans B (2014) A New Cellular-Automata-Based Fractional Frequency Reuse Scheme,IEEE Transactions on Vehicular Technology64(4)pp. 1535-1547 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/TVT.2014.2330601
    A fundamental challenge in orthogonal-frequency-division-multiple-access (OFDMA)-based cellular networks is intercell interference coordination, and to meet this challenge, various solutions using fractional frequency reuse (FFR) have been proposed in the literature. However, most of these schemes are either static in nature, dynamic on a large time scale, or require frequent reconfiguration for event-driven changes in the environment. The significant operational cost involved can be minimized with the added functionality that self-organizing networks bring. In this paper, we propose a solution based on the center of gravity of users in each sector. This enables us to have a distributed and adaptive solution for interference coordination. We further enhance our adaptive distributed FFR scheme by employing cellular automata as a step toward achieving an emergent self-organized solution. Our proposed scheme achieves a close performance with strict FFR and better performance than SFR in terms of the edge user's sum rate.
    Waqar O, Imran M, Dianati M, Tafazolli R (2014) Energy Consumption Analysis and Optimization of BER-Constrained Amplify-and-Forward Relay Networks, IEEE Transactions on Vehicular Technology IEEE
    Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Fundamental limits for practical deployments of wireless cellular networks,
    Qi Y, Imran MA, Tafazolli R (2012) On the Energy Efficiency of Hybrid Relaying Schemes in the Two-way Relay Channel,IEEE VTC Fall 2012pp. 1-5 IEEE
    DOI: 10.1109/VTCFall.2012.6399179
    In this paper, hybrid relaying schemes are investigated in the two-way relay channel, where the relay node is able to adaptively switch between different forwarding schemes based on the current channel state and its decoding status and thus provides more flexibility as well as improved performance. The analysis is conducted from the energy efficiency perspective for two transmission protocols distinguished by whether exploiting the direct link between two main communicating nodes (the source and destination nodes, and vice versa since it is two way communication) or not. A realistic power model taking circuitry power consumption of all involved nodes into account is employed. The energy efficiency is optimized in terms of consumed energy per bit subject to the Quality of Service (QoS) constraint. Numerical results show that the hybrid schemes are able to achieve the highest energy efficiency due to its capability of adapting to the channel variations and the protocol where the direct link is exploited is more energy efficient.
    Onireti OS, Evans B, Spathopoulos T, Imran MA (2015) THE ROLE OF SATELLITES IN 5G,
    The next generation of mobile radio communication systems?so called 5G?will provide some major changes to those generations to date. The ability to cope with huge increases in data traffic at reduced latencies and improved quality of user experience together with major reduction in energy usage are big challenges. In addition future systems will need to embody connections to billions of objects?the so called Internet of Things (IoT) which raise new challenges. Visions of 5G are now available from regions across the World and research is ongoing towards new standards. The consensus is a flatter architecture that adds a dense network of small cells operating in the millimetre wave bands and which are adaptable and software controlled. But what place for satellites in such a vision? The paper examines several potential roles for satellite including coverage extension, content distribution, providing resilience, improved spectrum utilisation and integrated signalling systems.
    Alsedairy T, Imran M (2010) Energy Efficiency with Adaptive Modulation and Spectrum Sharing for Cellular Systems, 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting,
    Imran MA (2008) Capacity of Variable Density Cellular Systems with Distributed Users, Second International Workshop on Fundamental Capacity Limits for Wireless Cellular Communication Systems
    Kakitani MT, Brante G, Souza RD, Imran MA (2013) Energy efficiency of transmit diversity systems under a realistic power consumption model,IEEE Communications Letters17(1)pp. 119-122
    DOI: 10.1109/LCOMM.2012.112812.122253
    We compare the downlink energy efficiency of spatial diversity multiple transmit antenna schemes. We determine the minimum required transmit power for a given outage probability. Our analysis shows that antenna selection is in general the most energy efficient option as it requires a single radio-frequency chain. We also investigate the limiting distances up to which the antenna selection technique outperforms the transmit beamforming scheme for different numbers of transmit antennas. © 1997-2012 IEEE.
    Heliot F, Imran MA, Tafazolli R (2012) Energy-efficient Power Allocation for Point-to-point MIMO System over the Rayleigh Fading Channel, IEEE Wireless Communications Letters1(4)pp. 304-307 IEEE
    DOI: 10.1109/WCL.2012.042512.120147
    It is well-established that transmitting at full power is the most spectral-efficient power allocation strategy for point-to-point (P2P) multi-input multi-output (MIMO) systems, however, can this strategy be energy efficient as well? In this letter, we address the most energy-efficient power allocation policy for symmetric P2P MIMO systems by accurately approximating in closed-form their optimal transmit power when a realistic MIMO power consumption model is considered. In most cases, being energy efficient implies a reduction in transmit and overall consumed powers at the expense of a lower spectral efficiency.
    Navaratnarajah S, Saeed A, Dianati M, Imran ML (2013) Energy efficiency in heterogeneous wireless access networks, IEEE Wireless Communications20(5)pp. 37-43
    DOI: 10.1109/MWC.2013.6664472
    In this article, we bring forward the important aspect of energy savings in wireless access networks. We specifically focus on the energy saving opportunities in the recently evolving heterogeneous networks (HetNets), both Single-RAT and Multi-RAT. Issues such as sleep/wakeup cycles and interference management are discussed for co-channel Single-RAT HetNets. In addition to that, a simulation based study for LTE macro-femto HetNets is presented, indicating the need for dynamic energy efficient resource management schemes. Multi-RAT HetNets also come with challenges such as network integration, combined resource management and network selection. Along with a discussion on these challenges, we also investigate the performance of the conventional WLAN-first network selection mechanism in terms of energy efficiency (EE) and suggest that EE can be improved by the application of intelligent call admission control policies. © 2013 IEEE.
    Al-Imari M, Xiao P, Imran MA, Tafazolli R (2013) Low complexity subcarrier and power allocation algorithm for uplink OFDMA systems,Eurasip Journal on Wireless Communications and NetworkingApril 2013 Springer
    DOI: 10.1186/1687-1499-2013-98
    In this article, we consider the joint subcarrier and power allocation problem for uplink orthogonal frequency division multiple access system with the objective of weighted sum-rate maximization. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solution is extremely high. We use the optimality conditions for this problem to propose a suboptimal allocation algorithm. A simplified implementation of the proposed algorithm has been provided, which significantly reduced the algorithm complexity. Numerical results show that the presented algorithm outperforms the existing algorithms and achieves performance very close to the optimal solution.
    Datta S, Tzaras C, Imran MA (2007) Impact of Orthogonality Factor on UMTS Capacity Simulation, Proceedings of the 2nd ACM Workshop on Performance Monitoring and Measurement of Heterogenous Wireless and Wired Networks PM2HW2N ?07
    Chatzinotas S, Imran MA, Hoshyar R (2009) On the Ergodic Capacity of the Wideband MIMO Channel, 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5pp. 754-758 IEEE
    Onireti O, Imran M, Hoshyar R (2011) Performance of Multicell Joint Processing Planar Cellular Uplink in the Presence of Relay Nodes,ICT Future Network and Mobile Summit 2010 IEEE
    In this paper we compare the uplink performance of various deployment scenarios in the planar (hexagonal) cellular system where the received signals at multiple cells are jointly processed by a central processor. A mathematical model of the planar cellular system is presented and its performance metric is based on information theoretic sum rate, and group rate share. The system deployment is as follows; the density of the base station is decreased, relay node replaces alternate base stations and in the last scenario, alternate bases stations are removed while the left over base stations are equipped with an additional antenna. It is observed that in reduction in the density of base stations resulted in reduction in the achievable sum rate and makes the group rate unfair. The introduction of additional antenna resulted in an improvement in the rate (compared with the reduction in density scenario) without any improvement in group rate fairness to cell user at the cell edge. The replacement of base stations with relay node and the implementation of orthogonal amplify and forward scheme resulted in a reduction in the achievable sum rate however it produced a significant improvement in group rate fairness. The result suggest that relay deployment in multicell joint processing system does not improve the sum rate of the system rather it improves the rate share for cell edge users making the user rate distribution fairer.
    Chatzinotas S, Imran MA, Tzaras C (2008) The Effect of User Distribution on a Linear Cellular Multiple-Access Channel,2008 THIRD INTERNATIONAL CONFERENCE ON COMMUNICATIONS AND NETWORKING IN CHINA, VOLS 1-3pp. 90-94 IEEE
    Katranaras E, Imran MA, Tzaras C (2008) Framework to Compare the Uplink Capacity of the Cellular Systems with Variable Inter Site Distance,IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC?08 IEEE
    DOI: 10.1109/PIMRC.2008.4699856
    In this paper we derive the information theoretic capacity of the uplink of a cellular system with variable inter site distance and a generalised fading environment. The capacity is shown to be a direct function of the ratio of total received signal power (from within and outside of a cell) to the AWGN noise power, at any BS. This ratio is defined as the Rise over Thermal (RoT). It is shown that the variation in system parameters like the path loss exponent, number of users, transmit power constraint and the inter site distance, changes the region of operation on a capacity-versus-RoT curve. Results are interpreted for practical channel models and it is shown that RoT provides a useful framework to compare various practical systems.
    Kaltakis D, Katranaras E, Imran MA, Tzaras C (2009) Information theoretic capacity of Gaussian cellular multiple-access MIMO fading channel,IET COMMUNICATIONS3(7)pp. 1201-1207 INST ENGINEERING TECHNOLOGY-IET
    DOI: 10.1049/iet-com.2008.0335
    Chatzinotas S, Imran MA, Tzaras C (2008) Optimal information theoretic capacity of the planar cellular uplink channel, Proc. IEEE 9th Workshop on Signal Processing Advances in Wireless Communications SPAWC 2008pp. 196-200
    DOI: 10.1109/SPAWC.2008.4641597
    Qi Y, Imran MA, Tafazolli R (2011) Energy-aware adaptive sectorisation in LTE systems, 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communicationspp. 2402-2406 IEEE
    DOI: 10.1109/PIMRC.2011.6139951
    In this paper, we propose a novel energy-aware adaptive sectorisation strategy, where the base stations are able to adapt themselves to the temporal traffic variation by switching off some sectors and changing the beam-width of the remaining sectors. An event based user traffic model is established according to Markov-Modulated Poisson Process (MMPP). Adaptation is performed while taking into account the the target Quality of Service (QoS), in terms of blocking probability. In addition, coverage requirement is also considered. This work targets at future cellular systems, in particular LTE systems. The results show that at least 21% energy consumption can be reduced by using the proposed adaptive sectorisation strategy.
    Sambo YA, Shakir MZ, Qaraqe KA, Serpedin E, Imran MA (2014) Expanding Cellular Coverage via Cell-Edge Deployment in Heterogeneous Networks: Spectral Efficiency and Backhaul Power Consumption Perspectives, IEEE COMMUNICATIONS MAGAZINE52(6)pp. 140-149 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    Katranaras E, Imran MA, Hoshyar R (2009) Sum Rate of Linear Cellular Systems with Clustered Joint Processing,2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5pp. 2892-2896 IEEE
    Lateef HY, Imran A, Imran MA, Giupponi L, Dohler M (2015) LTE-advanced self-organizing network conflicts and coordination algorithms, IEEE Wireless Communications22(3)pp. 108-117
    DOI: 10.1109/MWC.2015.7143333
    © 2015 IEEE.Self-organizing network (SON) functions have been introduced in the LTE and LTEAdvanced standards by the Third Generation Partnership Project as an excellent solution that promises enormous improvements in network performance. However, the most challenging issue in implementing SON functions in reality is the identification of the best possible interactions among simultaneously operating and even conflicting SON functions in order to guarantee robust, stable, and desired network operation. In this direction, the first step is the comprehensive modeling of various types of conflicts among SON functions, not only to acquire a detailed view of the problem, but also to pave the way for designing appropriate Self-Coordination mechanisms among SON functions. In this article we present a comprehensive classification of SON function conflicts, which leads the way for designing suitable conflict resolution solutions among SON functions and implementing SON in reality. Identifying conflicting and interfering relations among autonomous network management functionalities is a tremendously complex task. We demonstrate how analysis of fundamental trade-offs among performance metrics can us to the identification of potential conflicts. Moreover, we present analytical models of these conflicts using reference signal received power plots in multi-cell environments, which help to dig into the complex relations among SON functions. We identify potential chain reactions among SON function conflicts that can affect the concurrent operation of multiple SON functions in reality. Finally, we propose a selfcoordination framework for conflict resolution among multiple SON functions in LTE/LTEAdvanced networks, while highlighting a number of future research challenges for conflict-free operation of SON.
    Razavi R, Imran MA, Hoshyar R, Wang Y (2011) Information Theoretic Analysis of LDS Scheme,IEEE Communications Letters15(8)pp. 798-800 IEEE
    DOI: 10.1109/LCOMM.2011.061011.102098
    In this paper, the capacity region of Low Density Signature Multiple Access Channel (LDS-MAC) is calculated through information theoretic analysis. LDS Code Division Multiple Access (LDS-CDMA) uses spreading sequences of low density for spreading the data symbols in time domain. This technique benefits from a less complex Multiuser Detector (MUD) compared to conventional CDMA with optimum MUD; while keeping the performance close to the single user scenario for up to 200% loaded conditions. Also evaluated is the effect of different factors on the capacity of LDS MAC.
    Héliot F, Imran MA, Tafazolli R (2011) Energy Efficiency Analysis of In-Building MIMO AF Communication,IEEE International Wireless Communicatins and Mobile Computing (IWCMC-2011)pp. 912-917 IEEE
    DOI: 10.1109/IWCMC.2011.5982523
    Cooperative communication is an effective approach for increasing the spectral efficiency and/or the coverage of cellular networks as well as reducing the cost of network deployment. However, it remains to be seen how energy efficient it is. In this paper, we assess the energy efficiency of the conventional Amplify-and- forward (AF) scheme in an in-building relaying scenario. This scenario simplifies the mutual information formulation of the AF system and allows us to express its channel capacity with a simple and accurate closed-form approximation. In addition, a framework for the energy efficiency analysis of AF system is introduced, which includes a power consumption model and an energy efficiency metric, i.e. the bit-per-joule capacity. This framework along with our closed-form approximation are utilized for assessing both the channel and bit-per-joule capacities of the AF system in an in-building scenario. Our results indicate that transmitting with maximum power is not energy efficient and that AF system is more energy efficient than point-to-point communication at low transmit powers and signal-to-noise ratios.
    Sambo YA, Imran MA, Shakir MZ, Qaraqe KA, Serpedin E (2014) On the capacity bounds of K-tier heterogeneous small-cell networks employing aggressive frequency reuse, IEEE Wireless Communications and Networking Conference, WCNCpp. 2534-2539
    DOI: 10.1109/WCNC.2014.6952787
    With the cell coverage area of current and future mobile networks becoming smaller, heterogeneous small-cell networks (HetSNets), where multiple low-power, low-cost base stations (BSs) complement the existing macrocell infrastructure, are considered constitutive elements of future mobile networks. In this paper, we propose a K-tier HetSNet, where multiple tiers of small-cells are padded between macrocells which in turn expand the network coverage and significantly increase in capacity without compromising the frequency reuse factor. In this context, we derive analytical capacity bounds of the K-tier HetSNets based on the distance of the desired user from its serving BS and all other interfering BSs. It was observed that the upper bound of the capacity becomes tighter as the number of small-cell tiers increases due to the increase in the number of small-cells. Simulation results show the performance of the proposed K-tier HetSNets against the macro-only network in terms of frequency reuse factor, capacity and area spectral efficiency.
    Imran, Muhammad A (2009) Cooperation among Base Stations and Relay Stations for OFDMA Multi-hop Cellular Networks,
    Onireti O, Imran M, Hoshyar R (2010) Downlink Sum-rate Performance for Cooperation and Coordination between Three Interfering Sectors,11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting
    In this paper we investigate the performance of various transmission schemes for the downlink cellular system. These schemes are either biased towards interference minimisation or the efficient utilisation of the available resources. A mathematical model for the various schemes is presented and the performance measure is based on the information theoretic sum rate and the user rate share. The identified schemes are: avoid intra-cell and tolerate inter-cell interference, full orthogonality, single cell cooperation, cooperation for critical users only and the full cooperation scheme. Two categories of users are identified in this paper: non critical users which are close to the base station and the critical user which are at the cell boundary. It is observed that the full cooperation provides an upper bound on the achievable sum rate and has a user rate distribution whose fairness can be improved by allocating more power to the critical users. The full orthogonality scheme has the fairest user rate distribution and much lower achievable sum rate compared with the full cooperation. The performance of the cooperation of critical user scheme can approach the upper bound of full cooperation scheme with lower complexity.
    Rayel OK, Brante G, Rebelatto JL, Souza RD, Imran MA (2015) Energy Efficiency-Spectral Efficiency Trade-Off of Transmit Antenna Selection (vol 62, pg 4293, 2014),IEEE TRANSACTIONS ON COMMUNICATIONS63(8)pp. 3025-3025 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/TCOMM.2015.2452256
    Tang W, Shakir MZ, Imran MA, Tafazolli R, Alouini M-S (2012) Throughput Analysis for Cognitive Radio Networks with Multiple Primary Users and Imperfect Spectrum Sensing, Communications, IET617pp. 2787-2795 IET
    Imran MA, Tang W, Tafazolli R (2011) Coordination of Energy Efficient Sensing and Transmission in Cognitive Radio Networks,
    Katranaras E, Imran MA, Tzaras C (2008) INFORMATION THEORETIC CAPACITY OF THE CELLULAR UPLINK - AVERAGE PATH LOSS APPROXIMATION,2008 IEEE 9TH WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS, VOLS 1 AND 2pp. 605-609 IEEE
    DOI: 10.1109/SPAWC.2008.4641679
    Héliot F, Onireti O, Imran MA (2011) An accurate closed-form approximation of the energy efficiency-spectral efficiency trade-off over the MIMO Rayleigh fading channel,IEEE International Conference on Communicationspp. 1-6
    DOI: 10.1109/iccw.2011.5963556
    Energy efficiency (EE) is gradually becoming one of the key criteria, along with the spectral efficiency (SE), for evaluating communication system performances. However, minimizing the EE while maximizing the SE are conflicting objectives and, thus, the main criterion for designing efficient communication systems will become the trade-off between SE and EE. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this EE-SE trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression, which can easily be used for evaluating and comparing the EE-SE trade-off of MIMO communication system, has been utilized in this paper for analyzing the impact of using multiple antennas on the EE and the EE gain of MIMO in comparison with single-input single-output (SISO) system. Our results indicate that EE can be improved predominantly through receive diversity in the low-SE regime and that MIMO is far more energy efficient than SISO at high SE over the Rayleigh fading channel.
    Datta S, Imran MA, Tzaras C (2008) Uplink Coverage-Capacity Estimation Using Analysis and Simulation, Proc. Fourth Advanced International Conference on Telecommunications AICT ?08pp. 151-156
    DOI: 10.1109/AICT.2008.58
    Héliot F, Imran MA, Tafazolli R (2012) Energy-Efficiency based Resource Allocation for the Orthogonal Multi-user Channel,
    Energy efficiency (EE) is emerging as a key design criterion for both power limited applications, i.e. mobile devices, and power-unlimited applications, i.e. cellular network. Whereas, resource allocation is a well-known technique for improving the performance of communication system. In this paper, we design a simple and optimal EE-based resource allocation method for the orthogonal multi-user channel by adapting the transmit power and rate to the channel condition such that the energy-per-bit consumption is minimized. We present our EE framework, i.e. EE metric and node power consumption model, and utilizes it for formulating our EE-based optimization problem with or without constraint. In both cases, we derive explicit formulations of the optimal energy-per-bit consumption as well as optimal power and rate for each user. Our results indicate that EE-based allocation can substantially reduce the consumed power and increase the EE in comparison with spectral efficiency-based allocation.
    Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Fundamental limits for wireless cellular networks,
    Saeed A, Akbari A, Dianati M, Imran MA (2013) Energy Efficiency Analysis for LTE Macro-Femto HetNets., EW VDE-Verlag
    Heliot F, Imran MA, Tafazolli R (2012) On the energy efficiency-spectral efficiency trade-off over the MIMO rayleigh fading channel,IEEE Transactions on Communications60(5)pp. 1345-1356 IEEE
    DOI: 10.1109/TCOMM.2012.031712.110215
    Along with spectral efficiency (SE), energy efficiency (EE) is becoming one of the key performance evaluation criteria for communication system. These two criteria, which are conflicting, can be linked through their trade-off. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression has been here utilized for assessing analytically the EE gain of MIMO over single-input single-output (SISO) system for two different types of power consumption models (PCMs): the theoretical PCM, where only the transmit power is considered as consumed power; and a more realistic PCM accounting for the fixed consumed power and amplifier inefficiency. Our analysis unfolds the large mismatch between theoretical and practical MIMO vs. SISO EE gains; the EE gain increases both with the SE and the number of antennas in theory, which indicates that MIMO is a promising EE enabler; whereas it remains small and decreases with the number of transmit antennas when a realistic PCM is considered. © 2012 IEEE.
    Alsedairy T, Imran M, Qi Y, Evans B (2013) Energy-effcient dynamic deployment architecture for future cellular systems, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRCpp. 3111-3116
    DOI: 10.1109/PIMRC.2013.6666681
    There is a need to develop energy-effcient adaptive systems for future telecommunication networks. While traffc varies at different times, the power consumption of the radio access network does not scale with it effectively. To make signif-cant energy savings, a dynamic deployment approach is required to allow the system to operate in an energy-effcient mode with respect to traffc load. By deploying small base stations within the area of a conventional macro station, we are able to reduce energy consumption while maintaining QoS. This paper proposes an energy-effcient dynamic deployment architecture based on fuzzy-logic. The algorithm aids in the decision of the architecture layout deployment. Moreover, by implementing the proposed adaptive energy-effcient algorithm, the network gains fexibility that can increase coverage or throughput throughout the same network by adapting its operation to source its requirements better and change them when new requirements arise. © 2013 IEEE.
    Qi Y, Imran MA, Hoshyar R, Tafazolli R (2011) H2-ARQ Relaying: Spectrum and Energy Efficiency Analysis,IEEE Journal on Selected Areas in Communications29(8)pp. 1547-1558 IEEE
    DOI: 10.1109/JSAC.2011.110905
    In this paper, we propose novel Hybrid Automatic Repeat re-Quest (HARQ) strategies used in conjunction with hybrid relaying schemes, named as H^2-ARQ-Relaying. The strategies allow the relay to dynamically switch between amplify-and-forward/compress-and-forward and decode-and-forward schemes according to its decoding status. The performance analysis is conducted from both the spectrum and energy efficiency perspectives. The spectrum efficiency of the proposed strategies, in terms of the maximum throughput, is significantly improved compared with their non-hybrid counterparts under the same constraints. The consumed energy per bit is optimized by manipulating the node activation time, the transmission energy and the power allocation between the source and the relay. The circuitry energy consumption of all involved nodes is taken into consideration. Numerical results shed light on how and when the energy efficiency can be improved in cooperative HARQ. For instance, cooperative HARQ is shown to be energy efficient in long distance transmission only. Furthermore, we consider the fact that the compress-and-forward scheme requires instantaneous signal to noise ratios of all three constituent links. However, this requirement can be impractical in some cases. In this regard, we introduce an improved strategy where only partial and affordable channel state information feedback is needed.
    Akbari A, Imran MA, Hoshyar R, Tafazolli R (2011) Average Energy Efficiency Contours for Single Carrier AWGN MAC,IEEE Vehicular technology Conference - VTC Spring 2011pp. 1-5 IEEE
    DOI: 10.1109/VETECS.2011.5956544
    Energy efficiency has become increasingly important in wireless communications, with significant environmental and financial benefits. This paper studies the achievable capacity region of a single carrier uplink channel consisting of two transmitters and a single receiver, and uses average energy efficiency contours to find the optimal rate pair based on four different targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. In addition to the transmit power, circuit power is also accounted for, with the maximum transmit power constrained to a fixed value. Simulation results demonstrate the achievability of the optimal energy-efficient rate pair within the capacity region, and provide the trade-off for energy efficiency, fairness and maximum sum-rate.
    Zoha A, Imran MA, Gluhak A, Nati M (2013) A Comparison of Generative and Discriminative Appliance Recognition Models for Load Monitoring, 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013)51 IOP PUBLISHING LTD
    DOI: 10.1088/1757-899X/51/1/012002
    Imran M, Alnuem MA, Alsalih W, Younis M (2012) A novel wireless sensor and actor network framework for autonomous monitoring and maintenance of lifeline infrastructures, Communications (ICC), 2012 IEEE International Conference onpp. 6484-6488
    Shakir MZ, Tang W, Imran MA, Alouini MS (2011) Collaborative spectrum sensing based on upper bound on joint PDF of extreme eigenvalues,European Signal Processing Conferencepp. 1214-1218
    Detection based on eigenvalues of received signal covariance matrix is currently one of the most effective solution for spectrum sensing problem in cognitive radios. However, the results of these schemes often depend on asymptotic assumptions since the distribution of ratio of extreme eigenvalues is exceptionally mathematically complex to compute in practice. In this paper, a new approach to determine the distribution of ratio of the largest and the smallest eigenvalues is introduced to calculate the decision threshold and sense the spectrum. In this context, we derive a simple and analytically tractable expression for the distribution of the ratio of the largest and the smallest eigenvalues based on upper bound on the joint probability density function (PDF) of the largest and the smallest eigenvalues of the received covariance matrix. The performance analysis of proposed approach is compared with the empirical results. The decision threshold as a function of a given probability of false alarm is calculated to illustrate the effectiveness of the proposed approach. © 2011 EURASIP.
    Sambo Y, Héliot F, Imran MA (2012) A low-complexity precoding scheme for the downlink of multi-cell multi-user MIMO AF system,IEEE Wireless Communications and Networking Conference, WCNCpp. 737-741
    DOI: 10.1109/WCNC.2012.6214468
    Because of its simplicity, amplify-and-forward (AF) is one of the most popular cooperative relaying technique. Relays are used in cooperative communication to improve reliability, coverage or spectral efficiency of cell-edge users. However, relays tend to increase the interferences seen by users of adjacent cells, particularly by the cell-edge users, when used in multi-cell systems. In this paper, we propose a low-complexity precoding scheme to mitigate the effect of other-cell interference (OCI) in cooperative communication. The scheme is designed by taking into account the interference plus noise covariance matrix of each user for mitigating the interference at each receiver by means of precoding at the relay node. Simulation results show the effectiveness of the proposed scheme, both in terms of sum-rate and computational complexity, when compared to other existing OCI-aware precoding algorithms for AF. © 2012 IEEE.
    Akbari A, Imran MA, Hoshyar R, Amich A, Tafazolli R (2011) Average Energy Efficiency Contours with Multiple Decoding Policies,IEEE Communications Letter15(5)pp. 506-508 IEEE
    DOI: 10.1109/LCOMM.2011.040111.102287
    This letter addresses energy-efficient design in multi-user, single-carrier uplink channels by employing multiple decoding policies. The comparison metric used in this study is based on average energy efficiency contours, where an optimal rate vector is obtained based on four system targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. The transmit power function is approximated using Taylor series expansion, with simulation results demonstrating the achievability of the optimal rate vector, and negligible performance difference in employing this approximation.
    Wang D, Imran MA (2006) Blind Minimum Mean Squared Error (MMSE) Multiuser Detection with Reliable Subspace Estimation (RSE), Proc. International Conference on Wireless and Mobile Communications ICWMC ?06
    DOI: 10.1109/ICWMC.2006.30
    Desset C, Debaillie B, Giannini V, Fehske A, Richter F, Klessig H, Auer G, Holtkamp H, Wajda W, Ambrosy A, Blume O, Sabella D, Gonzalez MJ, Gódor I, Olsson M, Imran MA (2012) Flexible power modeling of LTE base stations,IEEE Wireless Communications and Networking Conference, WCNCpp. 2858-2862 IEEE
    DOI: 10.1109/WCNC.2012.6214289
    With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters. © 2012 IEEE.
    Imran, Muhammad A (2009) Multi User Cooperative Transmission techniques for OFDMA Multi-hop Cellular Networks,
    Héliot F, Imran MA, Tafazolli R (2011) On the Energy Efficiency Gain of MIMO Communication under Various Power Consumption Models,
    Chatzinotas S, Imran MA, Tzaras C (2008) On the Capacity of Variable Density Cellular Systems under Multicell Decoding,IEEE Communications Letters127pp. 496-498 IEEE
    DOI: 10.1109/LCOMM.2008.080439
    The majority of multicell-decoding cellular models preserve a fundamental assumption which has initially appeared in Wyner?s model, namely the collocation of User Terminals (UTs). Although this assumption produces more tractable mathematical models, it is unrealistic w.r.t. current practical cellular systems. In this paper, we alleviate this assumption by assuming uniformly distributed UTs. The model under investigation is the uplink channel of a planar cellular array in the presence of power-law path loss and flat fading. In this context, we employ a free probability approach to evaluate the effect of UT distribution on the optimal sum-rate capacity of a variable-density cellular system.
    Qi Y, OLSSON M, Imran M (2012) Integration Strategy of EARTH Energy Efficiency Enablers,
    The overall target of the EARTH project is to reduce the power consumption of mobile broadband networks by 50%. For this, solutions acting all the way from components in the base stations, link level improvements, as well as radio network level concepts are developed. This paper presents a strategy for how these energy efficiency enablers can be integrated into an overall solution. The energy efficiency enablers are structured according to their time scale of operation, and mapped to the most suitable application scenarios.
    Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2006) Book of assumptions and known results for the fundamental limits of wireless networks,
    Imran MA, Imran A, Onireti O (2013) Participatory sensing as an enabler for self-organisation in future cellular networks, 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013)51 IOP PUBLISHING LTD
    DOI: 10.1088/1757-899X/51/1/012003
    Ul Mustafa HA, Imran MA, Shakir MZ, Imran A, Tafazolli R (2015) Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks, IEEE COMMUNICATIONS SURVEYS AND TUTORIALS18(1)pp. 419-445 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/COMST.2015.2459596
    Heliot F, Imran MA, Tafazolli R (2011) Energy Efficiency Analysis of Idealized Coordinated Multi-Point Communication System, IEEE Vehicular technology Conference
    Jiang J, Dianati M, Imran M, Chen Y (2012) Energy Efficiency and Optimal Power Allocation in Virtual-MIMO Systems,pp. 1-6
    DOI: 10.1109/VTCFall.2012.6399002
    This paper investigates energy efficiency (EE) performance of a virtual multiple-input multiple-output (MIMO) wireless system using the receiver-side cooperation with the compress-and-forward protocol. We derive a linear approximation of EE as a function of spectral efficiency (SE) in the low SE operation regime. In addition, we obtain a closed-form lower bound for EE which is valid for both low and high SE regions. This lower bound can be used for optimizing the power allocation between the transmitter and the relay in order to minimize the overall energy per bit consumption in the system. Both analytical and simulation results demonstrate that the virtual MIMO system using the receiver-side cooperation outperforms the multiple-input single-output (MISO) case in terms of energy efficiency. Finally we show that, with the optimal power allocation, the virtual-MIMO system achieves an EE performance close to that of an ideal MIMO system.
    Konstantinou K, Imran MA, Tzaras C (2008) Analysing a Multi-hop UMTS over Multiple Frequency Schemes and an Urban Environment,Journal of Networks37pp. 41-48 ACADEMY PUBLISHER
    DOI: 10.4304/jnw.3.7.41-48
    In this paper we analyse the performance of a relay based UMTS system in an urban environment using multiple hops on multiple frequency bands. Measurement based path loss, fading and shadowing models are used in the Manhattan grid deployment scenario. Both uplink and downlink operations of the cellular system are considered at the same time. Two hop communication links over the uplink and downlink are operated at four non-overlapping spectrum bands in order to minimise interference. This results in several possible frequency schemes. Power solutions are derived analytically for the selected frequency schemes. The system performance is evaluated both by simulation and analysis and improvement by employing relays is shown.
    Qi Y, Imran M, Tafazolli R (2012) Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-forward Systems,
    While many studies have concentrated on providing theoretical analysis for the relay assisted compress-and-forward systems little effort has yet been made to the construction and evaluation of a practical system. In this paper a practical CF system incorporating an error-resilient multilevel Slepian-Wolf decoder is introduced and a novel iterative processing structure which allows information exchanging between the Slepian-Wolf decoder and the forward error correction decoder of the main source message is proposed. In addition, a new quantization scheme is incorporated as well to avoid the complexity of the reconstruction of the relay signal at the final decoder of the destination. The results demonstrate that the iterative structure not only reduces the decoding loss of the Slepian-Wolf decoder, it also improves the decoding performance of the main message from the source.
    Chatzinotas S, Imran M, Hoshyar R, Otterston B (2010) Multicell LMMSE Filtering Capacity under Correlated Multiple BS Antennas, Proc. IEEE VTC Fall 2010
    Kakitani MT, Brante G, Souza RD, Imran MA (2013) Downlink energy efficiency analysis of some multiple antenna systems, IEEE Vehicular Technology Conference
    DOI: 10.1109/VTCSpring.2013.6692516
    In this paper we compare the energy efficiency of different multiple antenna transmission schemes for longrange wireless networks, assuming a realistic power consumption model. We consider the downlink, between a base station and a mobile station, in which the Alamouti scheme, transmit beamforming, receive diversity, spatial multiplexing, and transmit antenna selection are compared. Our analysis shows that, for different types of base stations, outage probability requirements and spectral efficiencies, the transmit antenna selection scheme is in general the most energy efficient option. Although antenna selection is not the best in terms of outage probability, it becomes the most efficient in terms of overall power consumption as it requires a single radio-frequency chain to obtain spatial diversity. © 2013 IEEE.
    Reategui Del Aguila F, Imran MA, Tafazolli R (2013) On The Three-Receiver Multilevel Broadcast Channel with Random Parameters,VDE Verlag GmBh9
    In this paper we extend the analysis of two-receiver broadcast channels with random parameters to the three-receivers case. Specifically we base our work on Nair and El Gamal's results for the three-receiver discrete memoryless multilevel broadcast channel and assume that state information is available non-causally at the transmitter. We provide an achievable rate region for this setting and acknowledge its importance in the study of multiuser cognitive radio configurations.
    Heliot F, Imran MA, Tafazolli R (2012) A Very Tight Approximation of the SISO Energy Efficiency-Spectral Efficiency Trade-Off,IEEE Communications Letters
    DOI: 10.1109/LCOMM.2012.042512.120253
    Beside the well-established spectral-efficiency (SE), energy-efficiency (EE) is currently becoming an important performance evaluation metric, which in turn makes the EE-SE trade-off as a prominent criterion for efficiently designing future communication systems. In this letter, we propose a very tight closed-form approximation (CFA) of this trade-off over the single-input single-output (SISO) Rayleigh flat fading channel. We first derive an improved approximation of the SISO ergodic capacity by means of a parametric function and then utilize it for obtaining our novel EE-SE trade-off CFA, which is also generalized for the symmetric multi-input multi-output channel. We compare our CFA with existing CFAs and show its improved accuracy in comparison with the latter.
    Auer G, Giannini V, Godor I, Blume O, Fehske A, Rubio J, Frenger P, Olsson M, Sabella D, Gonzalez M, Imran MA, Desset C (2012) How much energy is needed to run a wireless network,In: Hossain E, Bhargava VK, Fettweis GP (eds.), Green Radio Communication Networks Cambridge University Press
    Presenting state-of-the-art research on green radio communications and networking technology by leaders in the field, this book is invaluable for researchers and professionals working in wireless communication.
    Kakitani MT, Brante G, Souza RD, Imran MA (2012) Energy efficiency of amplify-and-forward, repetition coding and parallel coding in short range communications, 2012 35th International Conference on Telecommunications and Signal Processing, TSP 2012 - Proceedingspp. 212-216
    DOI: 10.1109/TSP.2012.6256284
    In this paper we exploit cooperative relaying for energy savings in narrowband short range communication scenarios. The nodes can operate under cooperative decode-and-forward with repetition coding (RC) or with parallel coding (PC), and cooperative amplify-and-forward (AF) protocols. The system is constrained by maximum packet loss and end-to-end throughput requirements. Our results show that, when the relay is closer to the source, AF and RC present similar performance in terms of energy consumption, while PC significantly outperforms the other schemes. On the other hand, when the relay is near the destination, AF offers the best efficiency. © 2012 IEEE.
    Imran A, Yaacoub E, Imran MA, Tafazolli R (2012) Distributed Load Balancing through Self Organisation of cell size in cellular systems, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRCpp. 1114-1119
    DOI: 10.1109/PIMRC.2012.6362512
    Uneven traffic load among the cells increases call blocking rates in some cells and causes low resource utilisation in other cells and thus degrades user satisfaction and overall performance of the cellular system. Various centralised or semi centralised Load Balancing (LB) schemes have been proposed to cope with this time persistent problem, however, a fully distributed Self Organising (SO) LB solution is still needed for the future cellular networks. To this end, we present a novel distributed LB solution based on an analytical framework developed on the principles of nature inspired SO systems. A novel concept of super-cell is proposed to decompose the problem of "system-wide blocking minimization" into the local sub-problems in order to enable a SO distributed solution. Performance of the proposed solution is evaluated through system level simulations for both macro cell and femto cell based systems. Numerical results show that the proposed solution can reduce the blocking in the system close to an Ideal Central Control (ICC) based LB solution. The added advantage of the proposed solution is that it does not require heavy signalling overheads. © 2012 IEEE.
    Chatzinotas C, Imran MA, Hoshyar R (2009) On the Multi-cell Processing Capacity of the Cellular MIMO Uplink Channel in Correlated Rayleigh Fading Environment,IEEE Transactions on Wireless Communications8(7)pp. 3704-3715 IEEE
    DOI: 10.1109/TWC.2009.080922
    In the context of cellular systems, it has been shown that multicell processing can eliminate inter-cell interference and provide high spectral efficiencies with respect to traditional interference-limited implementations. Moreover, it has been proved that the multiplexing sum-rate capacity gain of multicell processing systems is proportional to the number of Base Station (BS) antennas. These results have been also established for cellular systems, where BSs and User Terminals (UTs) are equipped with multiple antennas. Nevertheless, a common simplifying assumption in the literature is the uncorrelated nature of the Rayleigh fading coefficients within the BS-UT MIMO links. In this direction, this paper investigates the ergodic multicell-processing sum-rate capacity of the Gaussian MIMO Cellular Multiple-Access Channel in a correlated fading environment. More specifically, the multiple antennas of both BSs and UTs are assumed to be correlated according to the Kronecker product model. Furthermore, the current system model considers Rayleigh fading, uniformly distributed User Terminals (UTs) over a planar coverage area and powerlaw path loss. Based on free probabilistic arguments, the empirical eigenvalue distribution of the channel covariance matrix is derived and it is used to calculate both Optimal Joint Decoding and Minimum Mean Square Error (MMSE) Filtering capacity. In addition, numerical results are presented, where the per-cell sum-rate capacity is evaluated while varying the cell density of the system, as well as the level of fading correlation. In this context, it is shown that the capacity performance is greatly compromised by BS-side correlation, whereas UT-side correlation has a negligible effect on the system?s performance. Furthermore, MMSE performance is shown to be greatly suboptimal but more resilient to fading correlation in comparison to optimal decoding.
    Zoha A, Gluhak A, Imran MA, Rajasegarar S (2013) Non-Intrusive Load Monitoring Approaches for Disaggregated Energy Sensing: A Survey,Sensors12(12)pp. 16838-16866 MDPI
    DOI: 10.3390/s121216838
    Appliance Load Monitoring (ALM) is essential for energy management solutions, allowing them to obtain appliance-specific energy consumption statistics that can further be used to devise load scheduling strategies for optimal energy utilization. Fine-grained energy monitoring can be achieved by deploying smart power outlets on every device of interest; however it incurs extra hardware cost and installation complexity. Non-Intrusive Load Monitoring (NILM) is an attractive method for energy disaggregation, as it can discern devices from the aggregated data acquired from a single point of measurement. This paper provides a comprehensive overview of NILM system and its associated methods and techniques used for disaggregated energy sensing. We review the state-of-the art load signatures and disaggregation algorithms used for appliance recognition and highlight challenges and future research directions.
    Arshad K, Imran MA, Moessener K (2010) Collaborative Spectrum Sensing Optimisation Algorithms for Cognitive Radio Networks,International Journal of Digital Multimedia Broadcasting2010Article ID 424036 Hindawi Publishing Corporation
    DOI: 10.1155/2010/424036
    The main challenge for a cognitive radio is to detect the existence of primary users reliably in order to minimise the interference to licensed communications. Hence, spectrum sensing is a most important requirement of a cognitive radio. However, due to the channel uncertainties, local observations are not reliable and collaboration among users is required. Selection of fusion rule at a common receiver has a direct impact on the overall spectrum sensing performance. In this paper, optimisation of collaborative spectrum sensing in terms of optimum decision fusion is studied for hard and soft decision combining. It is concluded that for optimum fusion, the fusion centre must incorporate signal-to-noise ratio values of cognitive users and the channel conditions. A genetic algorithm-based weighted optimisation strategy is presented for the case of soft decision combining. Numerical results show that the proposed optimised collaborative spectrum sensing schemes give better spectrum sensing performance.
    Saeed A, Katranaras E, Dianati M, Imran MA (2015) Control and Data Channel Resource Allocation in OFDMA Heterogeneous Networks, JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY85(2)pp. 183-199 SPRINGER
    DOI: 10.1007/s11265-015-1041-1
    Patel A, del Águila FR, Khan ZA, Imran MA, Merchant SN, Desai UB, Tafazolli R (2013) On Capacity and Bounds for the Gaussian CZIC and CBZIC with Linear Coded Approximation,European Wireless 2013 VDE VERLAG GmbH
    Rayel OK, Brante G, Rebelatto JL, Souza RD, Imran MA (2014) Energy efficiency-spectral efficiency trade-off of transmit antenna selection, IEEE Transactions on Communications62(12)pp. 4293-4303
    DOI: 10.1109/TCOMM.2014.2364040
    © 2014 IEEE.We investigate the energy efficiency-spectral efficiency (EE-SE) trade-off of transmit antenna selection/maximum ratio combining (TAS) scheme. A realistic power consumption model (PCM) is considered, and it is shown that using TAS can provide significant energy savings when compared to multiple-input multiple-output (MIMO) in the low to medium SE region, regardless the number of antennas, as well as outperform transmit beamforming scheme (MRT) for the entire SE range. For a fixed number of receive antennas, our results also show that the EE gain of TAS over MIMO becomes even greater as the number of transmit antennas increases. The optimal value of SE that maximizes the EE is obtained analytically, and confirmed by numerical results. Moreover, the influence of receiver correlation is also evaluated and it is shown that considering a non-realistic PCM can lead to mistakes when comparing TAS and MIMO.
    Kakitani MT, Brante GGO, Souza RD, Pellenz ME, Imran MA (2015) Energy Efficiency vs. Economic Cost of Cellular Networks Under Co-channel Interference,IEEE LATIN AMERICA TRANSACTIONS13(2)pp. 422-427 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    Razavi R, Imran MA, Tafazolli R (2011) EXIT Chart Analysis for Turbo LDS-OFDM Receivers,7th International Wireless Communication and Mobile Computing Conference-IWCMCpp. 354-358 IEEE
    DOI: 10.1109/IWCMC.2011.5982559
    In this paper, the mutual information transfer characteristics of turbo Multiuser Detector (MUD) for a novel air interface scheme, called Low Density Signature Orthogonal Frequency Division Multiplexing (LDS-OFDM) are investigated using Extrinsic Information Transfer (EXIT) charts. LDS-OFDM uses Low Density Signature structure for spreading the data symbols in frequency domain. This technique benefits from frequency diversity besides its ability of supporting parallel data streams more than the number of subcarriers (overloaded condition). The turbo MUD couples the data symbols' detector of LDS scheme with users' FEC (Forward Error Correction) decoders through the message passing principle. The effect of overloading on LDS scheme's performance is evaluated using EXIT chart. The results show that at Eb/N0 as low as 0.3, LDS-OFDM can support loads up to 300%.
    Onireti OS, Imran Ali, Imran Muhammad, Tafazolli Rahim (2015) Energy Efficient Inter-Frequency Small Cell Discovery in Heterogeneous Networks,IEEE Transactions on Vehicular Technology65(9)pp. 7122-7135 IEEE
    DOI: 10.1109/TVT.2015.2482818
    In this paper, using stochastic geometry, we investigate the average energy efficiency (AEE) of the user terminal (UT) in the uplink of a two-tier heterogeneous network (HetNet), where the two tiers are operated on separate carrier frequencies. In such a deployment, a typical UT must periodically perform inter-frequency small cell discovery (ISCD) process in order to discover small cells in its neighborhood and benefit from the high data rate and traffic offloading opportunity that small cells present. We assume that the base stations (BSs) of each tier and UTs are randomly located and we derive the average ergodic rate and UT power consumption, which are later used for our AEE evaluation. The AEE incorporates the percentage of time a typical UT missed small cell offloading opportunity as a result of the periodicity of the ISCD process. In addition to this, the additional power consumed by the UT due to the ISCD measurement is also included. Moreover, we derive the optimal ISCD periodicity based on the UT?s average energy consumption (AEC) and AEE. Our results reveal that ISCD periodicity must be selected with the objective of either minimizing UT?s AEC or maximizing UT?s AEE.
    Shakir M, Tang W, Rao A, Imran MA, Alouini S (2011) Eigenvalue Ratio Detection Based On Exact Moments of Smallest and Largest Eigenvalues,IEEE CrownCom 2011pp. 46-50
    DOI: 10.4108/icst.crowncom.2011.246151
    Onireti OS, Imran A, Imran Muhammad, Tafazolli Rahim (2015) On Energy Efficient Inter-Frequency Small Cell Discovery in Heterogeneous Networks,2015 IEEE International Conference on Communications (ICC)pp. 13-18
    DOI: 10.1109/ICC.2015.7248291
    In this paper, we investigate the optimal inter- frequency small cell discovery (ISCD) periodicity for small cells deployed on carrier frequency other than that of the serving macro cell. We consider that the small cells and user terminals (UTs) positions are modeled according to a homogeneous Poisson Point Process (PPP). We utilize polynomial curve fitting to approximate the percentage of time the typical UT misses small cell offloading opportunity, for a fixed small cell density and fixed UT speed. We then derive analytically, the optimal ISCD periodicity that minimizes the average UT energy consumption (EC). Furthermore, we also derive the optimal ISCD periodicity that maximizes the average energy efficiency (EE), i.e. bit- per-joule capacity. Results show that the EC optimal ISCD periodicity always exceeds the EE optimal ISCD periodicity, with the exception of when the average ergodic rate in both tiers are equal, in which the optimal ISCD periodicity in both cases also becomes equal.
    Shakir M, Qaraqe K, Tabassum H, Alouini M, Serpedin E, Imran MA (2013) Green Heterogeneous Small-Cell Networks: Toward Reducing the CO2 Emissions of Mobile Communications Industry Using Uplink Power Adaptation,IEEE COMMUNICATIONS MAGAZINE51(6)pp. 52-61 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    DOI: 10.1109/MCOM.2013.6525595
    Qi Y, Heliot Fabien, Imran Muhammad, Tafazolli Rahim (2012) Green Relay Techniques in Cellular Systems,In: Yu FR, Leung V-C, Zhang X (eds.), Green Communications and Networking CRC Press
    Auer G, Giannini V, Desset C, Gódor I, Skillermark P, Olsson M, Imran Muhammad, Sabella D, Gonzalez MJ, Blume O, Fehske A (2011) How much energy is needed to run a wireless network?,IEEE Wireless Communications18(5)pp. 40-49
    DOI: 10.1109/MWC.2011.6056691
    In order to quantify the energy efficiency of a wireless network, the power consumption of the entire system needs to be captured. In this article, the necessary extensions with respect to existing performance evaluation frameworks are discussed. The most important addenda of the proposed energy efficiency evaluation framework (E3F) are a sophisticated power model for various base station types, as well as large-scale long-term traffic models. The BS power model maps the RF output power radiated at the antenna elements to the total supply power of a BS site. The proposed traffic model emulates the spatial distribution of the traffic demands over large geographical regions, including urban and rural areas, as well as temporal variations between peak and off-peak hours. Finally, the E3F is applied to quantify the energy efficiency of the downlink of a 3GPP LTE radio access network.
    He C, Zhang L, Mao J, Cao A, Xiao P, Imran M (2016) Output SNR Analysis and Detection Criteria for Optimum DCT-Based Multicarrier System,Proceedings of ISWCS'2016 IEEE
    DOI: 10.1109/ISWCS.2016.7600875
    The discrete cosine transform (DCT) based multicarrier system is regarded as one of the complementary multicarrier transmission techniques for 5th Generation (5G) applications in near future. By employing cosine basis as orthogonal functions for multiplexing each real-valued symbol with symbol period of T , it is able to reduce the minimum orthogonal frequency spacing to 1/(2T ) Hz, which is only half of that compared to discrete Fourier transform (DFT) based multicarrier systems. Critical to the optimal DCT-based system design that achieves interference-free single-tap equalization, not only both prefix and suffix are needed as symmetric extension of information block, but also a so-called front-end pre-filter is necessarily introduced at the receiver side. Since the pre-filtering process is essentially a time reversed convolution for continuous inputs, the output signal-to-noise ratio (SNR) for each subcarrier after filtering is enhanced. In this paper, the impact of pre-filtering on the system performance is analyzed in terms of ergodic output SNR per subcarrier. This is followed by reformulated detection criterion where such filtering process is taken into consideration. Numerical results show that under modified detection criteria, the proposed detection algorithms improve the overall bit error rate (BER) performance effectively.
    Sambo Y, Heliot F, Imran M (2017) Electromagnetic Emission-aware Scheduling for the Uplink of Multicell OFDM Wireless Systems,IEEE Transactions on Vehicular Technology66(9)pp. 8212-8222 IEEE
    DOI: 10.1109/TVT.2017.2687127
    The increasing demand for data and multimedia services, as well as the ubiquitous nature of the current generation of mobile devices have resulted in continuous network upgrades to support an ever-increasing number of users. Given that wireless communication systems rely on radiofrequency waves, the electromagnetic (EM) emissions from these systems are increasingly becoming a concern, especially in terms of adverse health effects. In order to address these concerns, we propose a novel resource allocation scheme for minimizing the EM emission of users in the uplink of multicell OFDM systems, while ensuring quality of service. Our scheme is based on the assumption that long-term channel state information of all the users in the network is available. A new multicell user grouping that uses the received interference powers of the users of different sectors is proposed. Furthermore, we propose two power allocation algorithms to minimize EM emission. The first power allocation algorithm performs multicell iterative optimization to obtain the transmit powers of each user in the system. On the other hand, our second power allocation algorithm uses the average channel gains of the users of different sectors to obtain an approximation of the transmit power of each user without multicell iterative optimization. As a result, this approach has a reduced complexity when compared to our first power allocation algorithm. Simulation results show that our scheme reduces EM emission by up to 70% when compared to a single cell EM emission aware scheme and by over 3 to 4 orders of magnitude when compared to spectral efficiency maximization schemes.
    Dawoud DWM, Heliot F, Imran MA, Tafazolli R (2017) Spatial Quadrature Modulation for Visible Light Communication in Indoor Environment,2017 IEEE ICC Conference Proceedings
    In this paper, a novel low-complexity and spectrally efficient modulation scheme for visible light communication (VLC) is proposed. Our new spatial quadrature modulation (SQM) is designed to efficiently adapt traditional complex modulation schemes to VLC; i.e. converting multi-level quadrature amplitude modulation (M-QAM), to real-unipolar symbols, making it suitable for transmission over light intensity. The proposed SQM relies on the spatial domain to convey the orthogonality and polarity of the complex signals, rather than mapping bits to symbol as in existing spatial modulation (SM) schemes. The detailed symbol error analysis of SQM is derived and the derivation is validated with link level simulation results. Using simulation and derived results, we also provide a performance comparison between the proposed SQM and SM. Simulation results demonstrate that SQM could achieve a better symbol error rate (SER) and/or data rate performance compared to the state of the art in SM; for instance a Eb/No gain of at least 5 dB at a SER of 10 4.
    Peyvandi H, Imran MA, Tafazolli R (2012) On Performance Optimization in Self-Organizing Network using Enhanced Simulated Annealing with Similarity Measure,International Symposium on Information Theory (ISIT) IEEE
    Network performance optimization is among the most important tasks within the area of wireless communication networks. In a Self- Organizing Network (SON) with the capability of adaptively changing parameters of a network, the optimization tasks are more feasible than static networks. Yet, with an increase of OPEX and CAPEX in new generation telecommunication networks, the optimization tasks are inevitable. In this paper, it is proven that the similarity among target and network parameters can produce lower Uncertainty Entropy (UEN) in a self-organizing system as a higher degree of organizing is gained. The optimization task is carried out with the Adaptive Simulated Annealing method, which is enhanced with a Similarity Measure (SM) in the proposed approach (EASA). The Markov model of EASA is provided to assess the proposed approach. We also show a higher performance through a simulation, based on a scenario in LTE network.
    Onireti O, Imran MA, Qadir J, Sathiaseelan A (2016) Will 5G See its Blind Side? Evolving 5G for Universal Internet Access,GAIA '16 ACM SIGCOMM conference proceedings
    DOI: 10.1145/2940157.2940158
    Internet has shown itself to be a catalyst for economic growth and social equity but its potency is thwarted by the fact that the Internet is off limits for the vast majority of human beings. Mobile phones?the fastest growing technology in the world that now reaches around 80% of humanity?can enable universal Internet access if it can resolve coverage problems that have historically plagued previous cellular architectures (2G, 3G, and 4G). These conventional architectures have not been able to sustain universal service provisioning since these architectures depend on having enough users per cell for their economic viability and thus are not well suited to rural areas (which are by definition sparsely populated). The new generation of mobile cellular technology (5G), currently in a formative phase and expected to be finalized around 2020, is aimed at orders of magnitude performance enhancement. 5G offers a clean slate to network designers and can be molded into an architecture also amenable to universal Internet provisioning. Keeping in mind the great social benefits of democratizing Internet and connectivity, we believe that the time is ripe for emphasizing universal Internet provisioning as an important goal on the 5G research agenda. In this paper, we investigate the opportunities and challenges in utilizing 5G for global access to the Internet for all (GAIA). We have also identified the major technical issues involved in a 5G-based GAIA solution and have set up a future research agenda by defining open research problems.
    Jiang J, Dianati M, Imran MA, Tafazolli R, Chen Y (2013) On the Relation between Energy Efficiency and Spectral Efficiency of Multiple-Antenna Systems,IEEE Transactions on Vehicular Technology62(7)pp. 3463-3469 IEEE
    DOI: 10.1109/TVT.2013.2253141
    Motivated by increased interests in energy efficient communication systems, the relation between energy efficiency (EE) and spectral efficiency (SE) for multiple-input multipleoutput (MIMO) systems is investigated in this paper. To provide insight into the design of practical MIMO systems, we adopt a realistic power model, as well as consider both independent Rayleigh fading and semicorrelated fading channels. We derive a novel and closed-form upper bound for the system EE as a function of SE. This upper bound exhibits a great accuracy for a wide range of SE values, and thus can be utilized for explicitly assessing the influence of SE on EE, and analytically addressing the EE optimization problems. Using this tight EE upper bound, our analysis unfolds two EE optimization issues: Given the number of transmit and receive antennas, an optimum value of SE is derived such that the overall EE can be maximized; Given a specific value of SE, the optimal number of antennas is derived for maximizing the system EE.
    Al-Imari M, Imran MA, Tafazolli R, Chen D (2012) Performance Evaluation of Low Density Spreading Multiple Access,2012 8th International Wireless Communications and Mobile Computing Conference (IWCMC)pp. 383-388
    DOI: 10.1109/IWCMC.2012.6314235
    In this paper, we evaluate the performance of Multicarrier-Low Density Spreading Multiple Access (MC-LDSMA) as a multiple access technique for mobile communication systems. The MC-LDSMA technique is compared with current multiple access techniques, OFDMA and SC-FDMA. The performance is evaluated in terms of cubic metric, block error rate, spectral efficiency and fairness. The aim is to investigate the expected gains of using MC-LDSMA in the uplink for next generation cellular systems. The simulation results of the link and system-level performance evaluation show that MC-LDSMA has significant performance improvements over SC-FDMA and OFDMA. It is shown that using MC-LDSMA can considerably reduce the required transmission power and increase the spectral efficiency and fairness among the users.
    Al-Imari M, Xiao P, Imran MA, Tafazolli R (2014) Uplink Non-Orthogonal Multiple Access for 5G Wireless Networks,11th International Symposium on Wireless Communications Systems (ISWCS) 2014pp. 781-785 IEEE
    DOI: 10.1109/ISWCS.2014.6933459
    Orthogonal Frequency Division Multiple Access (OFDMA) as well as other orthogonal multiple access techniques fail to achieve the system capacity limit in the uplink due to the exclusivity in resource allocation. This issue is more prominent when fairness among the users is considered in the system. Current Non-Orthogonal Multiple Access techniques (NOMA) introduce redundancy by coding/spreading to facilitate the users' signals separation at the receiver, which degrade the system spectral efficiency. Hence, in order to achieve higher capacity, more efficient NOMA schemes need to be developed. In this paper, we propose a NOMA scheme for uplink that removes the resource allocation exclusivity and allows more than one user to share the same subcarrier without any coding/spreading redundancy. Joint processing is implemented at the receiver to detect the users' signals. However, to control the receiver complexity, an upper limit on the number of users per subcarrier needs to be imposed. In addition, a novel subcarrier and power allocation algorithm is proposed for the new NOMA scheme that maximizes the users' sum-rate. The link-level performance evaluation has shown that the proposed scheme achieves bit error rate close to the single-user case. Numerical results show that the proposed NOMA scheme can significantly improve the system performance in terms of spectral efficiency and fairness comparing to OFDMA.
    Mohamed A, Onireti O, Imran MA (2017) Control data separation and its implications on backhaul networks,In: Imran MA, Zaidi S, Shakir M (eds.), Access, Fronthaul and Backhaul Networks for 5G & Beyond Institution of Engineering and Technology (IET)
    Future cellular systems need to cope with a huge amount of data and diverse service requirements in a flexible, sustainable, green and efficient way with minimal signalling overhead. This calls for network densification, a short length wireless link, efficient and proactive control signalling and the ability to switch off the power consuming devices when they are not in use. In this direction, the conventional alwayson service and worst-case design approach has been identified as the main source of inefficiency, and a paradigm shift towards adaptive and on-demand systems is seen as a promising solution. However, the conventional radio access network (RAN) architecture limits the achievable gains due to the tight coupling between network and data access points, which in turn imposes strict coverage and signalling requirements irrespective of the spatio-temporal service demand, channel conditions or mobility profiles.
    Mohamed A, Onireti O, Imran M, Pervaiz H, Xiao P, Tafazolli R (2017) Predictive Base Station Activation in Futuristic Energy-Efficient Control/Data Separated RAN,IEEE Globecom 2017 Proceedings IEEE
    Nowadays, system architecture of the fifth generation (5G) cellular system is becoming of increasing interest. To reach the ambitious 5G targets, a dense base station (BS) deployment paradigm is being considered. In this case, the conventional always-on service approach may not be suitable due to the linear energy/density relationship when the BSs are always kept on. This suggests a dynamic on/off BS operation to reduce the energy consumption. However, this approach may create coverage holes and the BS activation delay in terms of hardware transition latency and software reloading could result in service disruption. To tackle these issues, we propose a predictive BS activation scheme under the control/data separation architecture (CDSA). The proposed scheme exploits user context information, network parameters, BS sleep depth and measurement databases to send timely predictive activation requests in advance before the connection is switched to the sleeping BS. An analytical model is developed and closed-form expressions are provided for the predictive activation criteria. Analytical and simulation results show that the proposed scheme achieves a high BS activation accuracy with low errors w.r.t. the optimum activation time.
    Sambo Y, Heliot Fabien, Imran Muhammad (2016) Electromagnetic Emission-aware Schedulers for the Uplink of OFDM Wireless Communication Systems,IEEE Transactions on Vehicular Technology66(2)pp. 1313-1323 IEEE
    DOI: 10.1109/TVT.2016.2558838
    The popularity and convergence of wireless communications have resulted in continuous network upgrades in order to support the increasing demand for bandwidth. However, given that wireless communication systems operate on radiofrequency waves, the health effects of electromagnetic emission from these systems are increasingly becoming a concern due to the ubiquity of mobile communication devices. In order to address these concerns, we propose two schemes (offline and online) for minimizing the EM emission of users in the uplink of OFDM systems, while maintaining an acceptable quality of service. We formulate our offline EM reduction scheme as a convex optimization problem and solve it through water-filling. This is based on the assumption that the long-term channel state information of all the users is known. Given that, in practice, long-term channel state information of all the users cannot always be available, we propose our online EM emission reduction scheme, which is based on minimizing the instantaneous transmit energy per bit of each user. Simulation results show that both our proposed schemes significantly minimize the EM emission when compared to the benchmark classic greedy spectral efficiency based scheme and an energy efficiency based scheme. Furthermore, our offline scheme proves to be very robust against channel prediction errors.
    Bassoy S, Jaber Mona, Imran Muhammad, Xiao Pei (2016) Load Aware Self-Organising User-Centric Dynamic CoMP Clustering for 5G Networks,IEEE Access4pp. 2895-2906 IEEE
    DOI: 10.1109/ACCESS.2016.2569824
    Coordinated multi-point (CoMP) is a key feature for mitigating inter-cell interference, improve system throughput and cell edge performance. However, CoMP implementation requires complex beamforming/scheduling design, increased backhaul bandwidth, additional pilot overhead and precise synchronisa-tion. Cooperation needs to be limited to a few cells only due to this imposed overhead and complexity. Hence, small CoMP clusters will need to be formed in the network. In this paper, we ?rst present a self organising, user-centric CoMP clustering algorithm in a control/data plane separation architecture (CDSA), proposed for 5G to maximise spectral ef?ciency (SE) for a given maximum cluster size. We further utilise this clustering algorithm and introduce a novel two-stage re-clustering algorithm to reduce high load on cells in hotspot areas and improve user satisfaction. Stage-1 of the algorithm utilises maximum cluster size metric to introduce additional capacity in the system. A novel re-clustering algorithm is introduced in stage-2 to distribute load from highly loaded cells to neighbouring cells with less load for multi-user (MU) joint transmission (JT) CoMP case. We show that unsatis?ed users due to high load can be signi?cantly reduced with minimal impact on SE.
    Jaber Mona (2017) Realistic 5G backhaul.,
    The hype surrounding the 5G mobile networks is well justified in view of the explosive increase in mobile traffic and the inclusion of massive ?non-human? users that form the internet of things. Advanced radio features such as network densification, cloud radio access networks (C-RAN), and untapped frequency bands jointly succeed in increasing the radio capacity to accommodate the increasing traffic demand. However, a new challenge has arisen: the backhaul (BH), the transport network that connects radio cells to the core network. The BH needs to expand in a timely fashion to reach the fast spreading small cells. Moreover, the realistic BH solutions are unable to provide the unprecedented 5G performance requirements to every cell. To this end, this research addresses the gap between the 5G stipulated BH characteristics and the available BH capabilities. On the other hand, heterogeneity is a leading trait in 5G networks. First, the RAN is heterogeneous since it comprises different cell types, radio access technologies, and architectures. Second, the BH is composed of a mix of different wired and wireless technologies with different limitations. In addition, 5G users have a broader range of capabilities and requirements than any incumbent mobile network. We exploit this trait and develop a novel scheme, termed User-Centric-BH (UCB). The UCB targets the user association mechanism which is traditionally blind to users? needs and BH conditions. The UCB builds on the existing concept of cell range extension (CRE) and proposes multiple-offset factors (CREO) whereby each reflects the cell's joint RAN and BH capability with respect to a defined attribute (e.g., throughput, latency, resilience, etc.). In parallel, users associate different weights to different attributes, hence, they can make a user-centric decision. The proposed scheme significantly outperforms the state-of-the-art and unlocks the BH bottleneck by availing existing but misused resources to users in need.
    Zafar A, Zhang L, Xiao P, Imran M (2017) Spectrum Efficient MIMO-FBMC System using Filter Output Truncation,IEEE Transactions on Vehicular Technology67(3)pp. 2367-2381 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/TVT.2017.2771531
    Due to the use of an appropriately designed pulse shaping prototype filter, filter bank multicarrier (FBMC) system can achieve low out of band (OoB) emissions and is also robust to the channel and synchronization errors. However, it comes at a cost of long filter tails which may reduce the spectral efficiency significantly when the block size is small. Filter output truncation (FOT) can reduce the overhead by discarding the filter tails but may also significantly destroy the orthogonality of FBMC system, by introducing inter carrier interference (ICI) and inter symbol interference (ISI) terms in the received signal. As a result, the signal to interference ratio (SIR) is degraded. In addition, the presence of intrinsic interference terms in FBMC also proves to be an obstacle in combining multiple input multiple output (MIMO) with FBMC. In this paper, we present a theoretical analysis on the effect of FOT in an MIMO-FBMC system. First, we derive the matrix model of MIMO-FBMC system which is subsequently used to analyze the impact of finite filter length and FOT on the system performance. The analysis reveals that FOT can avoid the overhead in time domain but also introduces extra interference in the received symbols. To combat the interference terms, we then propose a compensation algorithm that considers odd and even overlapping factors as two separate cases, where the signals are interfered by the truncation in different ways. The general form of the compensation algorithm can compensate all the symbols in a MIMO-FBMC block and can improve the SIR values of each symbol for better detection at the receiver. It is also shown that the proposed algorithm requires no overhead and can still achieve a comparable BER performance to the case with no filter truncation.
    Mohamed Abdelrahim, Imran Muhammad, Xiao Pei, Tafazolli Rahim (2018) Memory-full Context-aware Predictive Mobility Management in Dual Connectivity 5G Networks,IEEE Access6pp. 9655-9666 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/ACCESS.2018.2796579
    Network densification with small cell deployment is being considered as one of the dominant themes in the fifth generation (5G) cellular system. Despite the capacity gains, such deployment scenarios raise several challenges from mobility management perspective. The small cell size, which implies a small cell residence time, will increase the handover (HO) rate dramatically. Consequently, the HO latency will become a critical consideration in the 5G era. The latter requires an intelligent, fast and light-weight HO procedure with minimal signalling overhead. In this direction, we propose a memory-full context-aware HO scheme with mobility prediction to achieve the aforementioned objectives. We consider a dual connectivity radio access network architecture with logical separation between control and data planes because it offers relaxed constraints in implementing the predictive approaches. The proposed scheme predicts future HO events along with the expected HO time by combining radio frequency performance to physical proximity along with the user context in terms of speed, direction and HO history. To minimise the processing and the storage requirements whilst improving the prediction performance, a user-specific prediction triggering threshold is proposed. The prediction outcome is utilised to perform advance HO signalling whilst suspending the periodic transmission of measurement reports. Analytical and simulation results show that the proposed scheme provides promising gains over the conventional approach.
    Perera G. M. Ryan (2018) Error control for compressed video transmission over next generation mobile networks.,
    Video data claims a significant portion of global mobile data communications, currently standing at 55%. This demand outburst has been due to exceptional display technologies, on-demand video, gaming and live video streaming, to name a few. Despite the massive data rates supported by modern mobile communication technologies, video data is starting to overload mobile networks. This is particularly true in links with low connectivity, where repeat requests flood the system. As solutions for this inevitable demand growth, in addition to efficient video compression methods, more video data error resilience must be sought. One reason video traffic is vulnerable to channel errors is the method it is treated at transmission; treatment as any other generic data type. Video is a unique data type because its ultimate user is not a machine but a human, and the contents within the data are interdependent on each other. Based on its properties, video compression, transmission methodology, and the decoding function must be adapted. By considering video communication as a collaborative effort of these three functions, error resilience can be effectively implemented. Analysis of radio resources available for data transmission in a multipath fading channel reveals that some resources are more robust than others. In the first contribution of this thesis, this characteristic is utilised to impose more resilience to more sensitive data within the video. Reliable means of forecasting the relative robustness of each radio resource are designed. Criteria for identifying the sensitivity of different video data segments are formulated. Finally, a technology is presented to map data to radio resources such that maximum received video quality is achieved. While the focus of the first contribution was on harmonising the transmission methods with the features of the compressed video payload, the second contribution takes an alternative route to error resilience by focusing on the decoder. The compressed video payload entails some identifiable syntax elements, some of which follow a predictable pattern. This feature is exploited to improve error recovery at an iterative turbo decoder. An algorithm to identify the video frame boundaries in corrupted compressed sequences is formulated, along with algorithms to deduce the correct values for selected fields in the compressed stream. Modifying the turbo extrinsic information using these corrections act as reinforcements in the turbo decoding iterative process. Most communication protocols transmit data as blocks in an ordered sequence and await the acknowledgement of the receiver to determine the next block to be transmitted. This gives rise to latency issues and the overloading of the network when the link connectivity is poor. A solution is presented for video data in the final contribution, where the concept of a digital fountain is hired. A two-dimensional forward error correction strategy is introduced for a digital fountain, where first, the video payload is LDPC encoded and then turbo encoded. A joint decoding strategy is designed between the turbo decoder and the LDPC decoder to recover the video data in an iterative manner. Taken together, these contributions are solutions for the video data burden on mobile networks; solutions which reduce the necessity for re-transmissions. The presented error resilience techniques are updates to the existing transmission methodology and the decoding function. They explore a new paradigm of improving coverage and channel throughput.
    He C, Zhang L, Mao J, Cao A, Xiao P, Imran M (2018) Performance Analysis and Optimization of DCT-Based Multicarrier System on Frequency-Selective Fading Channels,IEEE Access6pp. 13075-13089 IEEE
    DOI: 10.1109/ACCESS.2018.2806318
    Regarded as one of the most promising transmission techniques for future wireless communications, the discrete cosine transform (DCT) based multicarrier modulation (MCM) system employs cosine basis as orthogonal functions for real-modulated symbols multiplexing, by which the minimum orthogonal frequency spacing can be reduced by half compared to discrete Fourier transform (DFT) based one. With a time-reversed prefilter employed at the front of the receiver, interference-free one-tap equalization is achievable for the DCT-based systems. However, due to the correlated pre-filtering operation in time domain, the signal-to-noise ratio (SNR) is enhanced as a result at the output. This leads to reformulated detection criterion to compensate for such filtering effect, rendering minimum-meansquare- error (MMSE) and maximum likelihood (ML) detections applicable to the DCT-based multicarrier system. In this paper, following on the pre-filtering based DCT-MCM model that build in the literature work, we extend the overall system by considering both transceiver perfections and imperfections, where frequency offset, time offset and insufficient guard sequence are included. In the presence of those imperfection errors, the DCTMCM systems are analysed in terms of desired signal power, inter-carrier interference (ICI) and inter-symbol interference (ISI). Thereafter, new detection algorithms based on zero forcing (ZF) iterative results are proposed to mitigate the imperfection effect. Numerical results show that the theoretical analysis match the simulation results, and the proposed iterative detection algorithms are able to improve the overall system performance significantly.
    Dawoud D, Heliot F, Imran M, Tafazolli R (2018) A Novel Coherent Transmission Scheme for Visible Light Communication,2018 IEEE ICC Conference Proceedings Institute of Electrical and Electronics Engineers (IEEE)
    The spatially-incoherent radiators in visible light communication (VLC) constrain the optical carrier to be only driven by a real electrical sub-carrier, which cannot be quadrature modulated as in classic RF-based systems. This restriction, in turn, severely limits the transmission throughput of VLC systems. To overcome this technical challenge, we propose a novel coherent transmission scheme for VLC, in which the optical carrier is only treated as a purely amplitude-modulated carrier capable of transmitting two-dimensional (2D) symbols (e.g. quadrature modulated symbols). The ability of our new coherent transmission scheme to transmit 2D symbols is validated through analytical symbol error rate derivation and Matlab simulations. Results show that our scheme can improve both the spectral and energy efficiency of VLC systems, i.e. by either doubling the spectral efficiency or achieving more than 45% energy efficiency improvement, when compared to its existing counterparts.
    Wen Lei, Xiao Pei, Razavi R, Imran Muhammad, AL-Imari M, Maaref A, Lei J (2018) Joint sparse graph for FBMC/OQAM systems,IEEE Transactions on Vehicular Technology67(7)pp. 6098-6112 IEEE
    DOI: 10.1109/TVT.2018.2810638
    As an advanced non-orthogonal multiple access (NOMA) technique, the low density signature (LDS) has never been used in filter bank multicarrier (FBMC) systems. In this paper, we model a low density weight matrix (LDWM) to utilize the intrinsic interference in FBMC systems when single-tap equalization is employed, and propose a LDS-FBMC scheme which applies LDS to FBMC signals. In addition, a joint sparse graph for FBMC named JSG-FBMC is proposed to combine single graphs of LDS, LDWM and low density parity-check (LDPC) codes which respectively represent techniques of NOMA, multicarrier modulation and channel coding. By employing the message passing algorithm (MPA), a joint receiver performing detection and decoding simultaneously on the joint sparse graph is designed. Extrinsic information transfer (EXIT) charts and construction guidelines of the joint sparse graph are studied. Simulations show the superiority of JSG-FBMC to state-of-theart techniques such as OFDM, FBMC, LDS-OFDM, LDS-FBMC and turbo structured LDS-FBMC.
    Raza Naqvi Syed Ahsan, Pervaiz Haris, Ali Hassan Syed, Musavian Leila, Ni Qiang, Imran Muhammad Ali, Ge Xiaohu, Tafazolli Rahim (2018) Energy-Aware Radio Resource Management in D2D-Enabled Multi-Tier HetNets,IEEE Access6pp. 16610-16622 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/ACCESS.2018.2817189
    Hybrid networks consisting of both millimeter wave (mmWave) and microwave (¼W) capabilities are strongly contested for next generation cellular communications. A similar avenue of current research is deviceto- device (D2D) communications, where users establish direct links with each other rather than using central base stations (BSs). However, a hybrid network, where D2D transmissions coexist, requires special attention in terms of efficient resource allocation. This paper investigates dynamic resource sharing between network entities in a downlink (DL) transmission scheme to maximize energy efficiency (EE) of the cellular users (CUs) served by either (¼W) macrocells or mmWave small cells, while maintaining a minimum quality-of-service (QoS) for the D2D users. To address this problem, firstly a self-adaptive power control mechanism for the D2D pairs is formulated, subject to an interference threshold for the CUs while satisfying their minimum QoS level. Subsequently, a EE optimization problem, which is aimed at maximizing the EE for both CUs and D2D pairs, has been solved. Simulation results demonstrate the effectiveness of our proposed algorithm, which studies the inherent tradeoffs between system EE, system sum rate and outage probability for various QoS levels and varying density of D2D pairs and CUs.
    Munir Hamnah, Pervaiz Haris bin, Hassan Syed Ali, Musavian Leila, Ni Qiang, Imran Muhammad Ali, Tafazolli Rahim (2018) Computationally Intelligent Techniques for Resource Management in mmWave Small Cell Networks,IEEE Wireless Communications25(4)pp. 32-39 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/MWC.2018.1700400
    Ultra densification in heterogeneous networks (HetNets) and the advent of millimeter wave (mmWave) technology for fifth generation (5G) networks have led the researchers to redesign the existing resource management techniques. A salient feature of this activity is to accentuate the importance of computationally intelligent (CI) resource allocation schemes offering less complexity and overhead. This paper overviews the existing literature on resource management in mmWave-based HetNets with a special emphasis on CI techniques and further proposes frameworks that ensure quality-of-service requirements for all network entities. More specifically, HetNets with mmWavebased small cells pose different challenges as compared to an allmicrowave- based system. Similarly, various modes of small cell access policies and operations of base stations in dual mode, i.e., operating both mmWave and microwave links simultaneously, offer unique challenges to resource allocation. Furthermore, the use of multi-slope path loss models becomes inevitable for analysis owing to irregular cell patterns and blocking characteristics of mmWave communications. This paper amalgamates the unique challenges posed because of the aforementioned recent developments and proposes various CI-based techniques including game theory and optimization routines to perform efficient resource management.
    Qi Y, Shakir M, Imran M, Qaraqe K, Quddus A, Tafazolli R (2016) Fronthaul Data Compression for Uplink CoMP in Cloud Radio Access Network (C-RAN),Transactions on Emerging Telecommunications Technologies27(10)pp. 1409-1425 Wiley
    DOI: 10.1002/ett.3088
    The design of efficient wireless fronthaul connections for future heterogeneous networks incorporating emerging paradigms such as cloud radio access network (C-RAN) has become a challenging task that requires the most effective utilization of fronthaul network resources. In this paper, we propose to use distributed compression to reduce the fronthaul traffic in uplink Coordinated Multi-Point (CoMP) for C-RAN. Unlike the conventional approach where each coordinating point quantizes and forwards its own observation to the processing centre, these observations are compressed before forwarding. At the processing centre, the decompression of the observations and the decoding of the user message are conducted in a successive manner. The essence of this approach is the optimization of the distributed compression using an iterative algorithm to achieve maximal user rate with a given fronthaul rate. In other words, for a target user rate the generated fronthaul traffic is minimized. Moreover, joint decompression and decoding is studied and an iterative optimization algorithm is devised accordingly. Finally, the analysis is extended to multi-user case and our results reveal that, in both dense and ultra-dense urban deployment scenarios, the usage of distributed compression can efficiently reduce the required fronthaul rate and a further reduction is obtained with joint operation.
    Wen Lei (2016) Non-orthogonal multiple access schemes for future cellular systems.,
    Non-orthogonal multiple access (NOMA) is an emerging technology for future cellular systems in order to accommodate more users via non-orthogonal resource allocation, especially when the number of users/devices exceeds the available degrees of freedom, resulting in an overloaded condition. To date, low density signature (LDS) and sparse code multiple access (SCMA) are two promising NOMA techniques. However, research in this area is still in its infancy and there are still several open issues in the LDS/SCMA transceiver design. This thesis aims to address some of these challenges. The contributions are summarized as follows. 1:-LDS-OFDM and low density parity check (LDPC) codes both can be represented by a bipartite graph. Inspired by their similar structure, we construct a joint sparse graph combining the single graphs of LDS-OFDM and LDPC codes, namely joint sparse graph for OFDM (JSG-OFDM). A joint detection and decoding scenario is proposed using message passing algorithm (MPA). Design guidelines for the joint sparse graph are derived through extrinsic information transfer (EXIT) chart analysis. Simulation results show that the JSG-OFDM outperforms existing techniques such as GO-MC-CDMA, LDS-OFDM and turbo structured LDS-OFDM. 2:-Due to the higher power and spectral efficiency, the filter-bank multi-carrier (FBMC) technique is a promising alternative to OFDM. We use a low density graph to model the weight matrix of intrinsic interference in the isotropic orthogonal transform algorithm (IOTA) filtered FBMC system. In addition, such graph is combined with LDS and LDPC codes to form a joint sparse graph for FBMC-IOTA (JSG-IOTA). Based on MPA, a joint detection and decoding scheme is designed for JSG-IOTA, and the joint sparse graph is optimized by EXIT chart analysis. Numerical results show the superiority of JSG-IOTA to conventional techniques. 3:-In SCMA, the processes of bit to symbol mapping and LDS spreading are combined together. We investigate multi-dimensional SCMA codebooks, and the design rules are derived to maximize the constellation shaping gain. Moreover, we propose to construct SCMA codebooks by copy-and-permute operation on protographs and three-dimensional (3D) constellation shaping. Simulation results show that SCMA outperforms LDS with high-order constellations, and the proposed optimization methods can further improve the SCMA performance.
    Lai K, Wen L, Xiao P, Maaref A, Imran M (2018) Sub-graph based Joint Sparse graph for Sparse Code Multiple Access Systems,IEEE Access6pp. 25066-25080 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/ACCESS.2018.2828126
    Sparse code multiple access (SCMA) is a promising air interface candidate technique for next generation mobile networks, especially for massive machine type communications (mMTC). In this paper, we design a LDPC coded SCMA detector by combining the sparse graphs of LDPC and SCMA into one joint sparse graph (JSG). In our proposed scheme, SCMA sparse graph (SSG) defined by small size indicator matrix is utilized to construct the JSG, which is termed as sub-graph based joint sparse graph of SCMA (SG-JSG-SCMA). In this paper, we first study the binary-LDPC (B-LDPC) coded SGJSG- SCMA system. To combine the SCMA variable node (SVN) and LDPC variable node (LVN) into one joint variable node (JVN), a non-binary LDPC (NB-LDPC) coded SG-JSG-SCMA is also proposed. Furthermore, to reduce the complexity of NBLDPC coded SG-JSG-SCMA, a joint trellis representation (JTR) is introduced to represent the search space of NB-LDPC coded SG-JSG-SCMA. Based on JTR, a low complexity joint trellis based detection and decoding (JTDD) algorithm is proposed to reduce the computational complexity of NB-LDPC coded SGJSG- SCMA system. According to the simulation results, SG-JSGSCMA brings significant performance improvement compare to the conventional receiver using the disjoint approach, and it can also outperform a Turbo-structured receiver with comparable complexity. Moreover, the joint approach also has advantages in terms of processing latency compare to the Turbo approaches.
    Héliot Fabien, Onireti Oluwakayode Onireti, Imran Muhammad Ali (2011) An Accurate Closed-Form Approximation of the Energy Efficiency-Spectral Efficiency Trade-off over the MIMO Rayleigh Fading Channel,IEEE International Conference on Communications ICC2011
    Energy efficiency (EE) is gradually becoming one of the key criteria, along with the spectral efficiency (SE), for evaluating communication system performances. However, minimizing the energy-per-bit consumption while maximizing the SE are conflicting objectives and, thus, the main criterion for designing efficient communication systems will become the trade-off between SE and EE. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this EE-SE trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression, which can easily be used for evaluating and comparing the EE-SE trade-off of MIMO communication systems, has been utilized in this paper for analyzing the impact of using multiple antennas on the EE and the EE gain of MIMO in comparison with single-input single-output (SISO) system. Our results indicate that EE can be improved predominantly through receive diversity in the very low-SE regime and that MIMO is far more energy efficient than SISO at high SE over the Rayleigh fading channel.
    Zafar A (2018) Filter bank based multicarrier systems for future wireless networks.,
    Filter bank based multicarrier (FBMC) systems are one of the promising waveform candidates to satisfy the requirements of future wireless networks. FBMC employs prototype filters with lower side lobe and faster spectral decay, which enables it to have the advantages of reduced out-of-band energy and theoretically higher spectral efficiency (SE) compared to conventional multicarrier scheme i.e., orthogonal frequency division multiplexing (OFDM). These systems also have the ability to facilitate aggregation of non-adjacent bands to acquire higher bandwidths for data transmission. They also support asynchronous transmissions to reduce signaling overhead to meet the ever increasing demand of high data rate transmission in future wireless networks. In this work, the primary research objective is to address some of the critical challenges in FBMC systems to make it viable for practical applications. To this end, the following contributions are provided in this thesis. First of all, despite numerous advantages, FBMC systems suffers from long filter tails which may reduce the SE of the system. Filter output truncation (FOT) can reduce this overhead by discarding the filter tails but may also destroy the orthogonality in FBMC system. As a result, the signal to interference ratio (SIR) can be significantly degraded. To address this problem, we first presented a theoretical analysis on the effect of FOT in a multiple input multiple output (MIMO) FBMC system, when assuming that transmitter and receiver have the same number of antennas. We derive the matrix model of MIMO-FBMC system which is subsequently used to analyze the impact of finite filter length and FOT on the system performance. The analysis reveals that FOT can avoid the overhead in time domain but also introduces extra interference in the received symbols. To combat the interference terms, we then propose a compensation algorithm that considers odd and even overlapping factors as two separate cases, where the signals are interfered by the truncation in different ways. A general form of the compensation algorithm is then proposed to compensate all the symbols in a MIMO-FBMC block to improve the SIR values of each symbol for better detection at the receiver. Secondly, transmission of quadrature modulated symbols using FBMC systems has been an issue due to the self-interference between the transmitted symbols both in the time and frequency domain (so-called intrinsic interference). To address this issue, we propose a novel low complexity interference-free FBMC system with QAM modulation (FBMC/QAM) using filter deconvolution. The proposed method is based on inversion of the prototype filters which completely removes the intrinsic interference at the receiver and allows the use of quadrature modulated signaling. The interference terms in FBMC/QAM with and without the proposed system are analyzed and compared in terms of mean square error (MSE). It is shown with theoretical and simulation results that the proposed method cancels the intrinsic interference and improves the output signal to interference plus noise ratio (SINR) at the expense of slight enhancement of residual interferences caused by multipath channel. The complexity of the proposed system is also analyzed along with performance evaluation in an asynchronous multi-service scenario. It is shown that the proposed FBMC/QAM system with filter deconvolution outperforms the conventional OFDM system. Finally, subcarrier index modulation (SIM) a.k.a., index modulation (IM) has recently emerged as a promising concept for spectrum and energy-efficient next generation wireless communications systems due to the excellent trade-offs they offer among error performance, complexity, and SE. Although IM is well studied for OFDM, FBMC with index modulation (FBMC-IM) has not been thoroughly investigated. To address this topic, we shed light on the potential and implementation of IM technique for FBMC system. We first derived a mathematica
    Pervaiz Haris, Onierti Oluwakayode, Mohamed Abdelrahim, Imran Muhammad, Qiang Ni, Tafazolli Rahim (2018) Energy-Efficient and Load-Proportional eNodeB for 5G User-Centric Networks,IEEE Vehicular Technology Magazine13(4)pp. pp 51-59 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/MVT.2018.2871740
    Nowadays, dense network deployment is being considered as one of the effective strategies to meet capacity and connectivity demands of the fifth generation (5G) cellular system. Among several challenges, energy consumption will be a critical consideration in the 5G era. In this direction, base station on/off operation, i.e., sleep mode, is an effective technique to mitigate the excessive energy consumption in ultra-dense cellular networks. However, current implementation of this technique is unsuitable for dynamic networks with fluctuating traffic profiles due to coverage constraints, quality-of-service requirements and hardware switching latency. In this direction, we propose an energy/load proportional approach for 5G base stations with control/data plane separation. The proposed approach depends on a multi-step sleep mode profiling, and predicts the base station vacation time in advance. Such a prediction enables selecting the best sleep mode strategy whilst minimizing the effect of base station activation/reactivation latency, resulting in significant energy saving gains.
    Heliot Fabien, Katranaras E, Onireti O, Imran Muhammad (2012) On the Energy Efficiency-Spectral Efficiency Trade-off in Cellular Systems,In: Green Communications: Theoretical Fundamentals, Algorithms, and Applicationspp. 353-353 CRC Press
    Akbari Iman (2018) Enabling self organisation for future cellular networks.,
    DOI: 10.15126/thesis.00849661
    The rapid growth in mobile communications due to the exponential demand for wireless access is causing the distribution and maintenance of cellular networks to become more complex, expensive and time consuming. Lately, extensive research and standardisation work has been focused on the novel paradigm of self-organising network (SON). SON is an automated technology that allows the planning, deployment, operation, optimisation and healing of the network to become faster and easier by reducing the human involvement in network operational tasks, while optimising the network coverage, capacity and quality of service. However, these SON autonomous features cannot be achieved with the current drive test coverage assessment approach due to its lack of automaticity which results in huge delays and cost. Minimization of drive test (MDT) has recently been standardized by 3GPP as a key self- organising network (SON) feature. MDT allows coverage to be estimated at the base station using user equipment (UE) measurement reports with the objective to eliminate the need for drive tests. However, most MDT based coverage estimation methods recently proposed in literature assume that UE position is known at the base station with 100% accuracy, an assumption that does not hold in reality. In this work, we develop a novel and accurate analytical model that allows the quantification of error in MDT based autonomous coverage estimation (ACE) as a function of error in UE as well as base station (user deployed cell) positioning. We first consider a circular cell with an omnidirectional antenna and then we use a three-sectored cell and see how the system is going to be affected by the UE and the base station (user deployed cell) geographical location information errors. Our model also allows characterization of error in ACE as function of standard deviation of shadowing in addition to the path-loss.
    Reátegui del Águila Fernando (2015) On the capacity of cognitive interference channel structures.,
    The cognitive interference channel extends the classical two-user interference channel to have unidirectional cooperation at the transmitters. In this model, the cognitive transmitter is assumed to have noncausal knowledge of the other transmitter's current message (primary message). This a priori knowledge is used by the cognitive user to accomplish its two main purposes, i.e., to relay the primary message in order to boost the primary user's data rate and to maximise its own data rate by cancelling the interference at its receiver. The cognitive interference channel is well studied in the literature and capacity results are available for the weak and very strong interference regimes, amongst others. A general solution is still elusive. In this thesis we study the capacity region of cognitive structures that are based in their core on the cognitive interference channel but with the aggregate that an additional node is considered, e.g., an additional receiver node, an additional transmitter node or a relay node. The cognitive broadcast interference channel consists of the cognitive interference channel with an additional receiver. The cognitive side serves either one or two receivers and the interference goes from the cognitive transmitter to the primary receiver only. In this model we provide a general achievable rate region when the cognitive side serves two receivers. We analyse the discrete memoryless channel and show that the region simplifies to existing results in the literature when certain assumptions are made. An achievable rate region for the Gaussian channel is also provided for the case where the cognitive side sends common information to both receivers. When the cognitive side serves only one receiver, we provide an achievable rate region and an outer bound and show the gap graphically. The cognitive interference channel with a relay consists of the cognitive interference channel with an additional relay node. In this model we show that as in the interference channel with a relay, interference forwarding is also beneficial. We describe analytically achievable rate regions and show the benefits of interference forwarding. We also provide an achievable rate region with generalised interference forwarding, i.e., the relay forwards the intended message and the interference simultaneously, and show that allowing the relay to allocate part of its power to forward interference is beneficial when we are in the strong but not in the very strong interference regime. The cognitive interference channel with causal unidirectional destination cooperation is formed by transferring the relaying capabilities of the relay node in the previous model to the cognitive receiver and its operation is causal rather than strictly causal. In this model we show that instantaneous amplify and forward is good enough to achieve the capacity region of the Gaussian channel. We derive analytically an inner and outer bounds and show that they coincide for certain values of the antenna gain at the relay in the very strong interference regime. We also analyse the cognitive interference channel with a relay for the case where the relay operates causally. The capacity region is obtained for a special case of very strong interference. The cognitive multiple access interference channel consists of the cognitive interference channel with an additional cognitive transmitter. In this model the interference goes from the primary user to the cognitive receiver only. The cognitive users form a MAC channel. We show for this scenario that dirty paper coding achieves the capacity region in the Gaussian case. In the analysis we make use of encoding techniques first utilised for the MAC with state available noncausally at the encoder.
    Zhang Lei, Ijaz Ayesha, Xiao Pei, Wang Kezhi, Qiao Deli, Imran Muhammad Ali (2019) Optimal Filter Length and Zero Padding Length Design for Universal Filtered Multi-carrier (UFMC) System,IEEE Access Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/ACCESS.2019.2898322
    Universal filtered multi-carrier (UFMC) systems offer a flexibility of filtering arbitrary number of subcarriers to suppress out of band (OoB) emission, while keeping the orthogonality between subcarriers and robustness to transceiver imperfections. Such properties enable it as a promising candidate waveform for Internet of Things (IoT) communications. However, subband filtering may affect system performance and capacity in a number of ways. In this paper, we first propose the conditions for interference-free one-tap equalization and corresponding signal model in the frequency domain for UFMC system. The impact of subband filtering on the system performance is analyzed in terms of average signal-to-noise ratio (SNR), capacity and bit error rate (BER) and compared with the orthogonal frequency division multiplexing (OFDM) system. This is followed by filter length selection strategies to provide guidelines for system design. Next, by taking carrier frequency offset (CFO), timing offset (TO), insufficient guard interval between symbols and filter tail cutting (TC) into consideration, an analytical system model is established. In addition, a set of optimization criteria in terms of filter length and guard interval/filter TC length subject to various constraints is formulated to maximize the system capacity. Numerical results show that the analytical and corresponding optimal approaches match the simulation results, and the proposed equalization algorithms can significantly improve the BER performance.
    Zhang Jiaxin, Zhang Xing, Imran Muhammad Ali, Evans Barry, Wang Wenbo (2016) Energy Efficiency Analysis of Heterogeneous Cache-Enabled 5G Hyper Cellular Networks,Proceedings of the 2016 IEEE Global Communications Conference (GLOBECOM)pp. 1-6 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/GLOCOM.2016.7841790
    The emerging 5G wireless networks will pose extreme requirements such as high throughput and low latency. Caching as a promising technology can effectively decrease latency and provide customized services based on group users behaviour (GUB). In this paper, we carry out the energy efficiency analysis in the cache-enabled hyper cellular networks (HCNs), where the macro cells and small cells (SCs) are deployed heterogeneously with the control and user plane (C/U) split. Benefiting from the assistance of macro cells, a novel access scheme is proposed according to both user interest and fairness of service, where the SCs can turn into semi- sleep mode. Expressions of coverage probability, throughput and energy efficiency (EE) are derived analytically as the functions of key parameters, including the cache ability, search radius and backhaul limitation. Numerical results show that the proposed scheme in HCNs can increase the network coverage probability by more than 200% compared with the single- tier networks. The network EE can be improved by 54% than the nearest access scheme, with larger research radius and higher SC cache capacity under lower traffic load. Our performance study provides insights into the efficient use of cache in the 5G software defined networking (SDN).
    Zhang Jiaxin, Evans Barry, Imran Muhammad Ali, Zhang Xing, Wang Wenbo (2016) Green Hybrid Satellite Terrestrial Networks: Fundamental Trade-Off Analysis,Proceedings of the 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring 2016)pp. 1-5 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/VTCSpring.2016.7504264
    With the worldwide evolution of 4G generation and revolution in the information and communications technology(ICT) field to meet the exponential increase of mobile data traffic in the 2020 era, the hybrid satellite and terrestrial network based on the soft defined features is proposed from a perspective of 5G. In this paper, an end-to-end architecture of hybrid satellite and terrestrial network under the control and user Plane (C/U) split concept is studied and the performances are analysed based on stochastic geometry. The relationship between spectral efficiency (SE) and energy efficiency (EE) is investigated, taking consideration of overhead costs, transmission and circuit power, backhaul of gateway (GW), and density of small cells. Numerical results show that, by optimizing the key parameters, the hybrid satellite and terrestrial network can achieve nearly 90% EE gain with only 3% SE loss in relative dense networks, and achieve both higher EE and SE gain (20% and 5% respectively) in sparse networks toward the future 5G green communication networks.
    Zhang Jiaxin, Zhang Xing, Imran Muhammad Ali, Evans Barry, Zhang Yan, Wang Wenbo (2017) Energy efficient hybrid satellite terrestrial 5G networks with software defined features,Journal of Communications and Networks19(2)pp. 147-161 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/JCN.2017.000024
    In order to improve the manageability and adaptability of future 5G wireless networks, the software orchestration mechanism, named software defined networking (SDN) with control and user plane (C/U-plane) decoupling, has become one of the most promising key techniques. Based on these features, the hybrid satellite terrestrial network is expected to support flexible and customized resource scheduling for both massive machine-type- communication (MTC) and high-quality multimedia requests while achieving broader global coverage, larger capacity and lower power consumption. In this paper, an end-to-end hybrid satellite terrestrial network is proposed and the performance metrics, e. g., coverage probability, spectral and energy efficiency (SE and EE), are analysed in both sparse networks and ultra-dense networks. The fundamental relationship between SE and EE is investigated, considering the overhead costs, fronthaul of the gateway (GW), density of small cells (SCs) and multiple quality-ofservice (QoS) requirements. Numerical results show that compared with current LTE networks, the hybrid system with C/U split can achieve approximately 40% and 80% EE improvement in sparse and ultra-dense networks respectively, and greatly enhance the coverage. Various resource management schemes, bandwidth allocation methods, and on-off approaches are compared, and the applications of the satellite in future 5G networks with software defined features are proposed.
    Zhang J, Evans Barry, Imran MA, Zhang X, Wang Wenwu (2016) Performance Analysis of C/U Split Hybrid Satellite Terrestrial Network for 5G Systems,Proceedings of the 2015 IEEE 20th International Workshop on Computer Aided Modelling and Design of Communication Links and Networks (CAMAD)pp. 97-102 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/CAMAD.2015.7390488
    Over the last decade, the explosive increase in demand of high-data-rate video services and massive access machine type communication (MTC) requests have become the main challenges for the future 5G wireless network. The hybrid satellite terrestrial network based on the control and user plane (C/U) separation concept is expected to support flexible and customized resource scheduling and management toward global ubiquitous networking and unified service architecture. In this paper, centralized and distributed resource management strategies (CRMS and DRMS) are proposed and compared com- prehensively in terms of throughput, power consumption, spectral and energy efficiency (SE and EE) and coverage probability, utilizing the mature stochastic geometry. Numerical results show that, compared with DRMS strategy, the U-plane cooperation between satellite and terrestrial network under CRMS strategy could improve the throughput and EE by nearly 136% and 60% respectively in ultra-sparse networks and greatly enhance the U-plane coverage probability (approximately 77%). Efficient resource management mechanism is suggested for the hybrid network according to the network deployment for the future 5G wireless network.
    Evans B, Onireti O, Spathopoulos T, Imran MA (2015) THE ROLE OF SATELLITES IN 5G,2015 23rd European Signal Processing Conference (EUSIPCO 2015)pp. 2756-2760 Institute of Electrical and Electronics Engineers (IEEE)
    The next generation of mobile radio communication systems?so called 5G?will provide some major changes to those generations to date. The ability to cope with huge increases in data traffic at reduced latencies and improved quality of user experience together with major reduction in energy usage are big challenges. In addition future systems will need to embody connections to billions of objects?the so called Internet of Things (IoT) which raise new challenges. Visions of 5G are now available from regions across the World and research is ongoing towards new standards. The consensus is a flatter architecture that adds a dense network of small cells operating in the millimetre wave bands and which are adaptable and software controlled. But what place for satellites in such a vision? The paper examines several potential roles for satellite including coverage extension, content distribution, providing resilience, improved spectrum utilisation and integrated signalling systems.
    Mulvey David, Foh Chuan Heng, Imran Muhammad Ali, Tafazolli Rahim (2019) Cell Fault Management Using Machine Learning Techniques,IEEE Access7pp. 124514-124539 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/ACCESS.2019.2938410
    This paper surveys the literature relating to the application of machine learning to fault management in cellular networks from an operational perspective. We summarise the main issues as 5G networks evolve, and their implications for fault management. We describe the relevant machine learning techniques through to deep learning, and survey the progress which has been made in their application, based on the building blocks of a typical fault management system. We review recent work to develop the abilities of deep learning systems to explain and justify their recommendations to network operators. We discuss forthcoming changes in network architecture which are likely to impact fault management and offer a vision of how fault management systems can exploit deep learning in the future. We identify a series of research topics for further study in order to achieve this.
    Dawoud Diana, Heliot Fabien, Imran Muhammad, Tafazolli Rahim (2020) A Novel Unipolar Transmission Scheme for Visible Light Communication,IEEE Transactions on Communicationspp. 1-1 Institute of Electrical and Electronics Engineers
    DOI: 10.1109/TCOMM.2019.2963377
    This paper proposes a novel unipolar transceiver for visible light communication (VLC) by using orthogonal waveforms. The main advantage of our proposed scheme over most of the existing unipolar schemes in the literature is that the polarity of the real-valued orthogonal frequency division multiplexing (OFDM) sample determines the pulse shape of the continuous-time signal and thus, the unipolar conversion is performed directly in the analog instead of the digital domain. Therefore, our proposed scheme does not require any direct current (DC) biasing or clipping as it is the case with existing schemes in the literature. The bit error rate (BER) performance of our proposed scheme is analytically derived and its accuracy is verified by using Matlab simulations. Simulation results also substantiate the potential performance gains of our proposed scheme against the state-of-the-art OFDM-based systems in VLC; it indicates that the absence of DC shift and clipping in our scheme supports more reliable communication and outperforms the asymmetrically clipped optical-OFDM (ACO-OFDM), DC optical-OFDM (DCOOFDM) and unipolar-OFDM (U-OFDM) schemes. For instance, our scheme outperforms ACO-OFDM by at least 3 dB (in terms of signal to noise ratio) at a target BER of 10
    Yang Bowen, Zhang Lei, Onireti Oluwakayode, Xiao Pei, Imran Muhammad Ali, Tafazolli Rahim (2020) Mixed-numerology Signals Transmission and Interference Cancellation for Radio Access Network Slicing,IEEE Transactions on Wireless Communicationspp. 1-14 Institute of Electrical and Electronics Engineers (IEEE)
    DOI: 10.1109/TWC.2020.2989399
    A clear understanding of mixed-numerology signals multiplexing and isolation in the physical layer is of importance to enable spectrum efficient radio access network (RAN) slicing, where the available access resource is divided into slices to cater to services/users with optimal individual design. In this paper, a RAN slicing framework is proposed and systematically analyzed from a physical layer perspective. According to the baseband and radio frequency (RF) configurations imparities among slices, we categorize four scenarios and elaborate on the numerology relationships of slices configurations. By considering the most generic scenario, system models are established for both uplink and downlink transmissions. Besides, a low out of band emission (OoBE) waveform is implemented in the system for the sake of signal isolation and inter-service/slice-band-interference (ISBI) mitigation. We propose two theorems as the basis of algorithms design in the established system, which generalize the original circular convolution property of discrete Fourier transform (DFT). Moreover, ISBI cancellation algorithms are proposed based on a collaboration detection scheme, where joint slices signal models are implemented. The framework proposed in the paper establishes a foundation to underpin extremely diverse user cases in 5G that implement on a common infrastructure.