Dr Muhammad Ali Imran

Reader in Communications

Qualifications: DIC, MSc, PhD, SMIEEE, Fellow of Higher Education Academy

Email:

Office hours

Wednesday, 1100-1200 hrs

Further information

Biography

I obtained my BSc in Electrical Engineering (Electronics and Communications) from University of Engineering & Technology Lahore in 1999. I worked in Industry as a senior design engineer in a Systems Design company for a duration of two years. Later, I obtained my MSc degree from Imperial College London in Communications and Signal Processing in 2002. I was awarded the Diploma of Imperial College and the PhD degree from Imperial College and University of London in 2007. My research thesis was entitled "Resource Optimisation for Cooperative Broadcasting in WCDMA Networks".

As a post DOC researcher, I worked on formulation of Information Theoretic fundamental capacity limits of wireless cellular networks. This work was funded by Mobile Virtual Center of Excellence UK (a consortium of selected UK Universities and Industry). I have also worked on a European Commission EC funded project ROCKET where I worked on efficient techniques to design and operate a wireless cellular communication system.

In 2009, I joined the faculty of engineering and physical sciences (FEPS) at the University of Surrey as a Lecturer in Communications. I coordinated the University of Surrey team involved in FP7 EC funded project EARTH - looking at Energy Efficient Next Generation of Cellular Networks. The project has won 2012 Best project for the Future of Internet award. I also lead the Theme 9 of India UK Advanced Technology Centre research - Self Organising Multihop Networks. I also supervised a Huawei funded project on a novel air interface technique: LDS-OFDM.

Currently, I am leading an EPSRC funded project - REDUCE that aims to reshape the energy demand of end users using ICT and economic incentives. REDUCE project has deployed a wireless sensor network in CCSR building to monitor and control energy demand of users using persuasive techniques and communication technology. I am a work package leader for IU-ATC phase II funded by EPSRC. I am co-supervising the Huawei funded Green Communications project and Sony funded Machine to Machine communication projects. I am actively participating in EU funded projects LexNet and iJoin.

Research Interests

Energy Efficiency of Wireless Systems

Interference management for cellular communication

Emission reduction for wireless devices

Smart Spaces and use of technology for energy efficiency

Intelligent and Self-organising cellular networks

Communication techniques for next generation of cellular systems

Fundamental performance limits of wireless cellular networks

Research Collaborations

I have active collaborations with researchers from different parts of the world: Europe, Middle East, China, Brazil, Australia and the Subcontinent (India and Pakistan).

I am also leading the multidisciplinary research collaborating with researchers in Psychology, Environmental Studies, Economic modelling and Scholarship of Teaching.

Further details can be found on my personal web page.

A full list of publications, conference presentations, and patents can be found here.

Publications

Highlights

  • Qi Y, Imran MA, Hoshyar R, Tafazolli R. (2011) 'H2-ARQ Relaying: Spectrum and Energy Efficiency Analysis'. IEEE IEEE Journal on Selected Areas in Communications, 29 (8), pp. 1547-1558.

    Abstract

    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.

  • Kaltakis D, Imran MA, Tzaras C. (2010) 'Information Theoretic Capacity of Cellular Multiple Access Channel with Shadow Fading'. IEEE IEEE Transactions on Communications, 58 (5), pp. 1468-1476.
  • Katranaras E, Imran MA, Tzaras C. (2009) 'Uplink Capacity of a Variable Density Cellular System with Multicell Processing'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON COMMUNICATIONS, 57 (7), pp. 2098-2108.

    Abstract

    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.

  • 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 IEEE Transactions on Wireless Communications, 8 (7), pp. 3704-3715.

    Abstract

    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.

Journal articles

  • del Aguila FR, Imran MA, Tafazolli R. 'On The Three-Receiver Multilevel Broadcast Channel with Random Parameters'.
  • Mohammed A-I, Imran MA, Tafazolli R, Chen D. 'Performance Evaluation of Low Density Spreading Multiple Access'. FEC, 1, pp. x1-x1.
  • Mohammed A-I, Imran MA, Tafazolli R. 'Low Density Spreading for Next Generation Multicarrier Cellular Systems'. FEC, 1, pp. x1-x1.
  • Al-Imari M, Xiao P, Imran MA, Tafazolli R. (2014) 'Radio Resource Allocation for Uplink OFDMA Systems with Finite Symbol Alphabet Inputs'. IEEE IEEE Transactions on Vehicular Technology, 63 (4), pp. 1917-1921.

    Abstract

    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.

  • Imran A, Imran MA, Abu-Dayya A, Tafazolli R. (2014) 'Self Organization of Tilts in Relay Enhanced Networks: A Distributed Solution'. IEEE Wireless Communications, IEEE Transactions on, 13 (2), pp. 764-779.

    Abstract

    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.

  • OReilly C, Gluhak A, Imran M, Rajasegarar S. (2014) 'Anomaly Detection in Wireless Sensor Networks in a Non-Stationary Environment'. IEEE IEEE Surveys and Tutorials,
  • Alsedairy T, Qi Y, Imran A, Imran MA, Evans B. (2014) 'Self Organising Cloud cells: A Resource Efficient Network Densification Strategy'. Wiley Transactions on Emerging Telecommunications Technologies,

    Abstract

    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

  • Waqar O, Imran M, Dianati M, Tafazolli R. (2014) 'Energy Consumption Analysis and Optimization of BER-Constrained Amplify-and-Forward Relay Networks'. IEEE IEEE Transactions on Vehicular Technology,
  • Majid MI, Imran MA, Hoshyar R. (2013) 'Frequency planning for clustered jointly processed cellular multiple access channel'. IET Digital Library IET Communications, 7 (16), pp. 1739-1752.

    Abstract

    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.

  • Jiang J, Dianati M, Imran M, Tafazolli R, Zhang S. (2013) 'Energy Efficiency Analysis and Optimization for Virtual-MIMO Systems'. IEEE IEEE Transactions on Vehicular Technology, 63 (5), pp. 2272-2283.

    Abstract

    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.

  • 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,
  • Heliot F, Imran MA, Tafazolli R. (2013) 'Low-Complexity Energy-Efficient Resource Allocation for the Downlink of Cellular Systems'. IEEE Transactions on Communications,

    Abstract

    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.

  • Shakir MZ, Qaraqe KA, Tabassum H, Alouini M-S, Serpedin E, Imran MA. (2013) 'Green Heterogeneous Small-Cell Networks: Toward Reducing the CO2 Emissions of Mobile Communications Industry Using Uplink Power Adaptation'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE COMMUNICATIONS MAGAZINE, 51 (6), pp. 52-61.
  • Al-Imari M, Xiao P, Imran MA, Tafazolli R. (2013) 'Low complexity subcarrier and power allocation algorithm for uplink OFDMA systems'. Springer Eurasip Journal on Wireless Communications and Networking, April 2013

    Abstract

    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.

  • 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-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE VEHICULAR TECHNOLOGY MAGAZINE, 8 (1), pp. 57-69.
  • Kakitani MT, Imran MA, Brante G, Souza RD. (2013) 'Energy efficiency of transmit diversity systems under a realistic power consumption model'. IEEE Communications Letters, 17 (1), pp. 119-122.

    Abstract

    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.

  • 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 Magazine, , pp. 53-53.
  • 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 Technology, 62 (7), pp. 3463-3469.

    Abstract

    Motivated by the increasing interest in energy-efficient communication systems, the relation between energy efficiency (EE) and spectral efficiency (SE) for multiple-input-multiple-output (MIMO) systems is investigated in this paper. To provide insights into the design of practical MIMO systems, we adopt a realistic power model and consider both independent Rayleigh fading and semicorrelated fading channels. We derived a novel and closed-form upper bound (UB) for the system EE as a function of SE. This UB exhibits great accuracy for a wide range of SE values and, thus, can be utilized for explicit assessment of the influence of SE on EE and for analytically addressing the EE optimization problems. Using this tight EE UB, 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, and given a specific value of SE, the optimal number of antennas is derived for maximizing the system EE. © 2013 IEEE.

  • Navaratnarajah S, Saeed A, Dianati M, Imran ML. (2013) 'Energy efficiency in heterogeneous wireless access networks'. IEEE Wireless Communications, 20 (5), pp. 37-43.

    Abstract

    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.

  • Zoha A, Gluhak A, Imran MA, Rajasegarar S. (2013) 'Non-Intrusive Load Monitoring Approaches for Disaggregated Energy Sensing: A Survey'. MDPI Sensors, 12 (12), pp. 16838-16866.

    Abstract

    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. (2013) 'Increasing the interaction time in a lecture by integrating flipped classroom and just-in-time teaching concepts'. Compass: Journal of Learning and Teaching, 4 Article number 7
  • 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'. Springer US Wireless Networks, , pp. 1-13.
  • Akbari A, Heliot F, Imran MA, Tafazolli R. (2012) 'Energy Efficiency Contours for Broadcast Channels Using Realistic Power Models'. IEEE Transactions on Wireless Communications, 11 (11), pp. 4017-4025.

    Abstract

    Energy savings are becoming a global trend, hence the importance of energy efficiency (EE) as an alternative performance evaluation metric. This paper proposes an EE based resource allocation method for the broadcast channel (BC), where a linear power model is used to characterize the power consumed at the base station (BS). Having formulated our EE based optimization problem and objective function, we utilize standard convex optimization techniques to show the concavity of the latter, and thus, the existence of a unique globally optimal energy-efficient rate and power allocation. Our EE based resource allocation framework is also extended to incorporate fairness, and provide a minimum user satisfaction in terms of spectral efficiency (SE). We then derive the generic equation of the EE contours and use them to get insights about the EE-SE trade-off over the BC. The performances of the aforementioned resource allocation schemes are compared for different metrics against the number of users and cell radius. Results indicate that the highest EE improvement is achieved by using the unconstrained optimization scheme, which is obtained by significantly reducing the total transmit power. Moreover, the network EE is shown to increase with the number of users and decrease as the cell radius increases.

  • Khan AH, Imran MA, Evans BG. (2012) 'Semi-Adaptive Beamforming for OFDM based Hybrid Terrestrial-Satellite Mobile System'. IEEE IEEE Transactions on Wireless Communications, 11 (10), pp. 3424-3433.
  • Al-Imari M, Imran MA, Tafazolli R. (2012) 'Low Density Spreading Multiple Access'. OMICS Publishing Group Information Technology & Software Engineering, 2 (4)

    Abstract

    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.

  • Razavi R, Al-Imari M, Imran MA, Hoshyar R, Chen D. (2012) 'On Receiver Design for Low Density Signature OFDM (LDS-OFDM)'. IEEE IEEE Transactions on Communications, 60 (11), pp. 3499-3508.

    Abstract

    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. (2012) 'Energy-efficient Power Allocation for Point-to-point MIMO Systems over the Rayleigh Fading Channel'. IEEE Wireless Communications Letters, 1 (4), pp. 304-307.

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2012) 'Energy-efficient Power Allocation for Point-to-point MIMO System over the Rayleigh Fading Channel'. IEEE IEEE Wireless Communications Letters, 1 (4), pp. 304-307.

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2012) 'A Very Tight Approximation of the SISO Energy Efficiency-Spectral Efficiency Trade-Off'. IEEE Communications Letters,

    Abstract

    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.

  • Aliu OG, Imran A, Imran MA, Evans B. (2012) 'A survey of self organisation in future cellular networks'. IEEE Communications Surveys and Tutorials, 15 (1), pp. 336-361.

    Abstract

    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, Heliot F, Imran MA. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-Off in the Uplink of CoMP System'. IEEE Transactions on Wireless Communications,
  • Onireti O, Heliot F, Imran MA. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-Off in the Uplink of CoMP System'. IEEE IEEE Transactions on Wireless Communications, 11 (2), pp. 556-561.

    Abstract

    In this paper, we derive a generic closed-form approximation (CFA) of the energy efficiency-spectral efficiency (EE-SE) trade-off for the uplink of coordinated multi-point (CoMP) system and demonstrate its accuracy for both idealistic and realistic power consumption models (PCMs). We utilize our CFA to compare CoMP against conventional non-cooperative system with orthogonal multiple access. In the idealistic PCM, CoMP is more energy efficient than non-cooperative system due to a reduction in power consumption; whereas in the realistic PCM, CoMP can also be more energy efficient but due to an improvement in SE and mainly for cell-edge communication and small cell deployment.

  • Imran M, Younis M, Haider N, Alnuem MA. (2012) 'Resource efficient connectivity restoration algorithm for mobile sensor/actor networks'. Springer International Publishing AG EURASIP Journal on Wireless Communications and Networking, 2012 Article number 1 , pp. 1-16.
  • Heliot F, Imran MA, Tafazolli R. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-Off over the MIMO Rayleigh Fading Channel'. IEEE IEEE Transactions on Communications, 60 (5), pp. 1345-1356.

    Abstract

    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.

  • 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'. IET Communications, IET, 6 Article number 17 , pp. 2787-2795.
  • Evans BG, Khan A, Imran MA. (2012) 'Semi-adaptive beamforming for ofdm based hybrid terestrial-satellite mobile satellite'. IEEE IEEE Trans Wireless Communications, 11 (10), pp. 3424-3433.
  • Khan AH, Imran MA, Evans BG. (2012) 'Iterative turbo beamforming for orthogonal frequency division multiplexing-based hybrid terrestrial-satellite mobile system'. IET IET Communications, 6 (2), pp. 157-164.

    Abstract

    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.

  • Tang W, Shakir MZ, Imran MA, Tafazolli R, Alouini M. (2012) 'Throughput Analysis for Cognitive Radio Networks with Multiple Primary Users and Imperfect Spectrum Sensing'. IEEE IET Communications, 6 (17), pp. 2787-2795.

    Abstract

    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.

  • Imran MA, Imran A, tafazolli R. (2011) 'Relay Station Access Link Spectral Efficiency Optimization through SO of Macro BS Tilts'. IEEE IEEE Communications Letters, 15 (12), pp. 1326-1328.

    Abstract

    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.

  • Akbari A, Imran MA, Tafazolli R, Dianati M. (2011) 'Energy Efficiency Contours for Single-Carrier Downlink Channels'. IEEE COMMUNICATIONS LETTERS, 15 (12), pp. 1307-1309.
  • Qi Y, Imran MA, Hoshyar R, Tafazolli R. (2011) 'H2-ARQ Relaying: Spectrum and Energy Efficiency Analysis'. IEEE IEEE Journal on Selected Areas in Communications, 29 (8), pp. 1547-1558.

    Abstract

    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.

  • Razavi R, Imran MA, Hoshyar R, Wang Y. (2011) 'Information Theoretic Analysis of LDS Scheme'. IEEE IEEE Communications Letters, 15 (8), pp. 798-800.

    Abstract

    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.

  • Mehta M, Aliu OG, Karandikar A, Imran MA. (2011) 'Self-Organized Resource Allocation Using Inter-Cell Interference Coordination(ICIC) in Relay-Asisted Cellular Networks'. Special Issue on Next Generation Wireless Networks and Applications Edition. ICT Academy of Tamil Nadu ICT Journal on Communication Technology, 2 (2), pp. 300-313.

    Abstract

    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.

  • Akbari A, Imran MA, Hoshyar R, Amich A, Tafazolli R. (2011) 'Average Energy Efficiency Contours with Multiple Decoding Policies'. IEEE IEEE Communications Letter, 15 (5), pp. 506-508.

    Abstract

    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.

  • Auer G, Giannini V, Desset C, Gódor I, Skillermark P, Olsson M, Imran MA, Sabella D, Gonzalez MJ, Blume O, Fehske A. (2011) 'How much energy is needed to run a wireless network?'. IEEE Wireless Communications, 18 (5), pp. 40-49.

    Abstract

    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.

  • Kaltakis D, Imran MA, Tzaras C. (2010) 'Information Theoretic Capacity of Cellular Multiple Access Channel with Shadow Fading'. IEEE IEEE Transactions on Communications, 58 (5), pp. 1468-1476.
  • Arshad K, Imran MA, Moessener K. (2010) 'Collaborative Spectrum Sensing Optimisation Algorithms for Cognitive Radio Networks'. Hindawi Publishing Corporation International Journal of Digital Multimedia Broadcasting, 2010 Article number Article ID 424036

    Abstract

    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.

  • Kaltakis D, Katranaras E, Imran MA, Tzaras C. (2009) 'Information theoretic capacity of Gaussian cellular multiple-access MIMO fading channel'. INST ENGINEERING TECHNOLOGY-IET IET COMMUNICATIONS, 3 (7), pp. 1201-1207.
  • 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 IEEE Transactions on Wireless Communications, 8 (7), pp. 3704-3715.

    Abstract

    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.

  • Katranaras E, Imran MA, Tzaras C. (2009) 'Uplink Capacity of a Variable Density Cellular System with Multicell Processing'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE TRANSACTIONS ON COMMUNICATIONS, 57 (7), pp. 2098-2108.

    Abstract

    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.

  • Konstantinou K, Imran MA, Tzaras C. (2008) 'Analysing a Multi-hop UMTS over Multiple Frequency Schemes and an Urban Environment'. ACADEMY PUBLISHER Journal of Networks, 3 Article number 7 , pp. 41-48.

    Abstract

    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.

  • Chatzinotas S, Imran MA, Tzaras C. (2008) 'On the Capacity of Variable Density Cellular Systems under Multicell Decoding'. IEEE IEEE Communications Letters, 12 Article number 7 , pp. 496-498.

    Abstract

    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.

  • Imran MA, Gurcan MK. (2006) 'Message passing algorithm for iterative decoding of channel codes'. HERMIS-mu-pi International Journal of Computer Mathematics and its Applications, 8, pp. 1-20-1-20.

Conference papers

  • Heliot F, Imran MA, Tafazolli R. 'Energy-efficient Coordinated Resource Allocation for the Downlink of Cellular Systems'. Lisbon, Portugal: ICT Future Network & Mobile Summit

    Abstract

    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.

  • Al-Imari M, Xiao P, Imran M, Tafazolli R. 'Uplink Non-Orthogonal Multiple Access for 5G Wireless Networks'. Barcelona, Spain: International Symposium on Wireless Communication Systems (ISWCS'14)
    [ Status: Accepted ]

    Abstract

    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.

  • 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'. Georgia: IEEE International Black Sea Conference on Communications and Networking
  • 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 IEEE ISSNIP 2014 - 2014 IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, Conference Proceedings, Singapore: IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP), pp. 1-7.

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2013) 'Near-optimal Energy-efficient Joint Resource Allocation for Multi-hop MIMO-AF Systems'. London, UK: IEEE PIMRC' 13

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2013) 'Energy-Efficient Resource Allocation for Orthogonal Multi-antenna Multi-carrier Channel'. Online: IEEE OnlineGreenComm 2013

    Abstract

    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.

  • Imran MA. (2013) 'Spectrum Utilization Efficiency Analysis in Cognitive Radio Networks'. IEEE Proceedings of the 2013 19th European Wireless Conference (EW), Guildford, UK: European Wireless 2013, pp. 1-5.

    Abstract

    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.

  • Razavi R, Imran M, XIAO P, Tafazolli R. (2013) 'Effect of Forward Error Correction Codes on the Performance of LDS-OFDM'. VDE 19th European Wireless Conference 2013, Guildford, UK: European Wireless 2013

    Abstract

    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.

  • Reátegui del Águila F, Imran MA, Tafazolli R. (2013) 'On the Three-Receiver Multilevel Broadcast Channel with Random Parameters'. 9th International ITG Conference on Systems, Communications and Coding 2013
  • 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'. VDE VERLAG GmbH European Wireless 2013,
  • 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 2013, 1, pp. 527-532.

    Abstract

    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.

  • Saeed A, Akbari A, Dianati M, Imran MA. (2013) 'Energy Efficiency Analysis for LTE Macro-Femto HetNets.'. VDE-Verlag EW,
  • Kakitani MT, Brante G, Souza RD, Imran MA. (2013) 'Downlink energy efficiency analysis of some multiple antenna systems'. IEEE Vehicular Technology Conference,

    Abstract

    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.

  • Awad JF, Imran MA, Tafazolli R. (2013) 'Reduced Complexity Interference Avoidance Scheme Based on User Grouping in Dense Cellular Networks'. VDE VERLAG GmbH European Wireless 2013,
  • Peyvandi H, Imran A, Imran MA, Tafazolli R. (2013) 'On Pareto-Koopmans Efficiency for Performance-Driven Optimisation in Self-Organising Networks'. IET Digital Library
  • Katranaras E, Tang J, Imran MA. (2013) 'Energy and spectral efficient inter base station relaying in cellular systems'. IEEE Vehicular Technology Conference,

    Abstract

    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.

  • 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, PIMRC, , pp. 3111-3116.

    Abstract

    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.

  • 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 IEEE, , pp. 109-114.
  • 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 2013, , pp. 413-418.

    Abstract

    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.

  • Zoha A, Imran MA, Gluhak A, Nati M, Syed AS. (2013) 'A Comparison of Generative and Discriminative Appliance Recognition Models for Load Monitoring'. IOP PUBLISHING LTD 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013), Indus Univ, Karachi, PAKISTAN: 1st International Conference on Sensing for Industry, Control, Communications, and Security Technologies (ICSICCST) 51
  • 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,

    Abstract

    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.

  • 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 2013, , pp. 419-424.

    Abstract

    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.

  • Imran MA, Imran A, Onireti O, Syed AS. (2013) 'Participatory sensing as an enabler for self-organisation in future cellular networks'. IOP PUBLISHING LTD 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013), Indus Univ, Karachi, PAKISTAN: 1st International Conference on Sensing for Industry, Control, Communications, and Security Technologies (ICSICCST) 51
  • Jiang J, Dianati M, Imran MA, Tafazolli R. (2013) 'On the Energy Efficiency of MIMO Channels in Correlated Rayleigh Fading Environment.'. VDE-Verlag EW,
  • Akbari A, Imran MA, Dianati M, Tafazolli R. (2013) 'Weighted average energy efficiency contours for uplink channels'. IEEE Vehicular Technology Conference,

    Abstract

    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.

  • 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 on, , pp. 1-6.
  • Kakitani MT, Brante G, Souza RD, Pellenz ME, Imran MA. (2013) 'Energy and cost analysis of cellular networks under co-channel interference'. Communications (LATINCOM), 2013 IEEE Latin-America Conference on, , pp. 1-5.
  • Muirhead D, Imran MA. (2012) 'Determining the Energy Efficiency of Femtocell Basestations with Multiple Antennas'. Anaheim, California, USA: IEEE Globecom 2012
  • Qi Y, Imran MA, Sabella D, Debaillie B, Fatini R, Fernandez Y. (2012) 'On the Deployment Opportunities for Increasing Energy Efficiency'. LTE-Advanced with Relay Nodes. In 29h Meeting of WWRF, Berlin, Germany,
  • Zoha A, Gluhak A, Imran MA, Nati M, Rajasegarar S. (2012) 'Acoustic and Device Feature Fusion for Load Recognition'. IEEE Proceedings of the 6th IEEE International Conference on Intelligent Systems (IEEE IS), Sofia, Bulgaria: in Proceedings of the 6th IEEE International Conference on Intelligent Systems (IEEE IS), pp. 386-392.

    Abstract

    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.

  • Awad JF, Imran MA, Tafazolli R. (2012) 'Fairness Evaluation in Cooperative Hybrid Cellular Systems'. IEEE Limassol, Cyprus: 8th International Wireless Communications and Mobile Computing Conference (IWCMC), pp. 389-394.

    Abstract

    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.

  • Awad JF, Imran MA, Tafazolli R. (2012) 'Hybrid Transmission Schemes for Grouped Users in Cellular Systems'. IEEE Limassol, Cyprus: 8th International Wireless Communications and Mobile Computing Conference (IWCMC), pp. 561-566.

    Abstract

    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.

  • Qi Y, Imran M, Tafazolli R. (2012) 'Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-forward Systems'.

    Abstract

    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.

  • Jiang J, Dianati M, Imran M, Chen Y. (2012) 'Energy Efficiency and Optimal Power Allocation in Virtual-MIMO Systems'. Quebec City, Canada: 2012 IEEE 76th Vehicular Technology Conference: VTC2012-Fall, pp. 1-6.

    Abstract

    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.

  • Qi Y, Imran MA, Tafazolli R. (2012) 'On the Energy Efficiency of Hybrid Relaying Schemes in the Two-way Relay Channel'. IEEE IEEE VTC Fall 2012, Quebec City, Canada: IEEE VTC Fall 2012, pp. 1-5.

    Abstract

    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 O, Heliot F, Imran MA. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-Off of the 2BS-DMIMO System'. IEEE IEEE VTC Fall 2012, Quebec City, Canada: IEEE VTC Fall 2012, pp. 1-5.

    Abstract

    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

  • Qi Y, Imran MA, Tafazolli R. (2012) 'Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-forward Systems'. IEEE IEEE VTC Fall 2012, Quebec City, Canada: IEEE VTC Fall 2012, pp. 1-5.

    Abstract

    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.

  • Qi Y, Imran M, Tafazolli R. (2012) 'On the Energy Efficiency of Hybrid Relaying Schemes in the Two-way Relay Channel'. 2012 IEEE 76th Vehicular Technology Conference: VTC2012-Fall

    Abstract

    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.

  • Jiang J, Dianati M, Imran MA, Chen Y. (2012) 'Energy Efficiency Analysis and Optimal Power Allocation in Virtual-MIMO Systems'. IEEE Quebec City, Canada: IEEE VTC Fall 2012, pp. 1-6.

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2012) 'Energy-Efficiency based Resource Allocation for the Orthogonal Multi-user Channel'. IEEE VTC Fall 2012, Quebec City, Canada.: IEEE VTC Fall 2012

    Abstract

    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, Héliot F, Imran MA. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-Off of the 2BS-DMIMO System'. Quebec city, Canada: IEEE VTC-Fall

    Abstract

    In this paper, we propose a novel closed-form approximation of the Energy Efficiency vs. Spectral Efficiency (EESE) 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.

  • Héliot F, Imran MA, Tafazolli R. (2012) 'Energy-Efficiency based Resource Allocation for the Orthogonal Multi-user Channel'. Quebec city, Canada: IEEE VTC-fall

    Abstract

    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.

  • Peyvandi H, Imran MA, Tafazolli R. (2012) 'On Performance Optimization in Self-Organizing Network using Enhanced Simulated Annealing with Similarity Measure'. Cambridge, USA: Recent Research Session, International Symposium on Information Theory (ISIT), Massachusetts Institute of Technology (MIT)
  • Qi Y, OLSSON M, Imran M. (2012) 'Integration Strategy of EARTH Energy Efficiency Enablers'. Berlin: FuNeMS 2012

    Abstract

    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.

  • Héliot F, Imran MA, Tafazolli R. (2012) 'A Tight Closed-Form Approximation of the SISO Energy Efficiency-Spectral Efficiency Trade-Off'. Berlin, Germany: ICT Future & Mobile Summit

    Abstract

    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.

  • Peyvandi H, Imran MA, Tafazolli R. (2012) 'On Performance Optimization in Self-Organizing Network using Enhanced Simulated Annealing with Similarity Measure'. MIT, USA,: International Symposium on Information Theory,
  • Héliot F, Imran MA, Tafazolli R. (2012) 'Energy-efficiency based resource allocation for the scalar broadcast channel'. IEEE Wireless Communications and Networking Conference, WCNC, , pp. 193-197.

    Abstract

    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.

  • Saeed A, Imran MA, Aliu OG. (2012) 'Controlling Self-Healing Cellular networks using Fuzzy Logic'. IEEE Paris, France: IEEE Wireless Communications and Networking Conference (WCNC), pp. 3080-3084.

    Abstract

    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.

  • 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 on, , pp. 191 -199-191 -199.
  • Sambo Y, Heliot F, Imran MA. (2012) 'Low-complexity energy-efficient coordinated resource allocation in cellular systems'. Kumasi, Ghana: IEEE ICAST
  • 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, WCNC, , pp. 737-741.

    Abstract

    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.

  • 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 IEEE Wireless Communications and Networking Conference, WCNC, Shanghai: Wireless Communications and Networking Conference, pp. 2858-2862.

    Abstract

    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.

  • Al-Imari M, Imran MA, Tafazolli R, Chen D. (2012) 'Performance Evaluation of Low Density Spreading Multiple Access'. Limassol, Cyprus: 8th International Wireless Communications and Mobile Computing Conference (IWCMC), pp. 383-388.

    Abstract

    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.

  • 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, PIMRC, , pp. 1114-1119.

    Abstract

    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.

  • Kakitani MT, Imran MA, Souza RD. (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,

    Abstract

    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.

  • Al-Imari M, Imran MA, Tafazolli R. (2012) 'Low Density Spreading for next generation multicarrier cellular systems'. IEEE Baghdad, Iraq: International Conference on Future Communication Networks (ICFCN), pp. 52-57.

    Abstract

    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.

  • 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 - Proceedings, , pp. 212-216.

    Abstract

    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.

  • 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 2012, , pp. 29-32.

    Abstract

    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.

  • 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 on, , pp. 6484-6488.
  • Akbari A, Imran MA, Tafazolli R. (2011) 'Maximising Average Energy efficiency for Two-user AWGN Broadcast Channel'. Warsaw, Poland : IEEE Future Network and Mobile Summit, Warsaw: Future Network & Mobile Summit (FutureNetw), 2011

    Abstract

    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.

  • Qi Y, Imran MA, Tafazolli R. (2011) 'Energy-aware adaptive sectorisation in LTE systems'. IEEE 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, Toronto, Canada: PIMRC'11, pp. 2402-2406.

    Abstract

    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.

  • 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'. IEEE Proc. IEEE PIMRC, Toronto, Canada: IEEE PIMRC, pp. 2407-2407.

    Abstract

    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 Marˇcenko 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.

  • Héliot F, Imran MA, Tafazolli R. (2011) 'Energy Efficiency Analysis of In-Building MIMO AF Communication'. IEEE IEEE International Wireless Communicatins and Mobile Computing (IWCMC-2011), Istanbul, Turkey: IEEE International Wireless Communicatins and Mobile Computing (IWCMC-2011), pp. 912-917.

    Abstract

    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.

  • George R, Aliu OG, Imran MA. (2011) 'Hybrid Spectrum Allocation Scheme in wireless cellular networks'. Istanbul, Turkey : IEEE The 7th International Wireless Communication and Mobile Computing Conference-IWCMC, Istanbul: The 7th International Wireless Communication and Mobile Computing Conference-IWCMC, pp. 2093-2097.

    Abstract

    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.

  • Awad J, Imran MA, Tafazolli R. (2011) 'Improving Fairness by Cooperative Communications and Selection of Critical Users'. Istanbul, Turkey : IEEE The 7th International Wireless Communication and Mobile Computing Conference-IWCMC, Istanbul: The 7th International Wireless Communication and Mobile Computing Conference-IWCMC, pp. 184-188.

    Abstract

    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.

  • 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 Communications, Kyoto, Japan: IEEE ICC'11, pp. 1-6.

    Abstract

    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.

  • Akbari A, Imran MA, Hoshyar R, Tafazolli R. (2011) 'Average Energy Efficiency Contours for Single Carrier AWGN MAC'. IEEE IEEE Vehicular technology Conference - VTC Spring 2011, Budapest, Hungary: 2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), pp. 1-5.

    Abstract

    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.

  • Onireti OST, Imran MA, Heliot F. (2011) 'On Achievable Rate Region of Multiple Coordinated Multiple Access Channels'. IEEE 73rd IEEE Vehicular technology Conference, Budapest, Hungary: IEEE VTC-spring

    Abstract

    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.

  • Razavi R, Imran MA, Tafazolli R. (2011) 'EXIT Chart Analysis for Turbo LDS-OFDM Receivers'. Istanbul, Turkey : IEEE 7th International Wireless Communication and Mobile Computing Conference-IWCMC, Istanbul: 7th International Wireless Communications and Mobile Computing Conference (IWCMC), pp. 354-358.

    Abstract

    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%.

  • Imran MA, Tang W, Tafazolli R. (2011) 'Coordination of Energy Efficient Sensing and Transmission in Cognitive Radio Networks'. Liverpool, UK: PGNET Liverpool
  • Héliot F, Imran MA, Tafazolli R. (2011) 'On the Energy Efficiency Gain of MIMO Communication under Various Power Consumption Models'. Warsaw, Poland: Future Network and Mobile Summit
  • Heliot F, Imran MA, tafazolli R. (2011) 'On the Energy Efficiency Gain of MIMO Communication under Various Power Consumption Models'. Warsaw, Poland: ICT Future Network & Mobile Summit
  • Shakir MZ, Tang W, Rao A, Imran MA, Alouini S. (2011) 'Eigenvalue Ratio Detection Based On Exact Moments of Smallest and Largest Eigenvalues'. Osaka, Japan : IEEE IEEE CrownCom 2011, Osaka, Japan: CrownCom 2011, pp. 46-50.
  • 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'. Budapest, Hungary : IEEE IEEE Vehicular technology Conference - VTC Spring 2011, Yokohama: IEEE 73rd Vehicular Techology Conference, pp. 1-6.

    Abstract

    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.

  • Katranaras E, Imran MA, Hoshyar R. (2011) 'Energy Aware Transmission in Cellular Uplink with Clustered Base Station Cooperation'. Budapest, Hungary : IEEE IEEE Vehicular technology Conference - VTC Spring 2011, Budapest: VTC2011-Spring

    Abstract

    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.

  • Muirhead DS, Imran MA. (2011) 'Alamouti Transmit Diversity for Energy Efficient Femtocells'. Budapest, Hungary : 73rd IEEE Vehicular technology Conference - VTC Spring 2011, Budapest: VTC Spring 2011

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2011) 'Energy Efficiency Analysis of Idealized Coordinated Multi-Point Communication System'. IEEE Vehicular technology Conference, Budapest, Hungary: IEEE VTC-spring
  • 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'. Vienna, Austria: European Wireless Conference
  • 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'. Vienna, Austria : IEEE European Wireless, Vienna: 11th European Wireless Conference 2011 - Sustainable Wireless Technologies (European Wireless)

    Abstract

    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.

  • Onireti O, Imran M, Hoshyar R. (2011) 'Performance of Multicell Joint Processing Planar Cellular Uplink in the Presence of Relay Nodes'. IEEE ICT Future Network and Mobile Summit 2010, Florence Italy: ICT Future Network and Mobile Summit 2010

    Abstract

    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.

  • Heliot F, Imran MA, Tafazolli R. (2011) 'Energy Efficiency Analysis of In-Building MIMO AF Communication'. Istanbul, Turkey : The 7th International Wireless Communication and Mobile Computing Conference-IWCMC,
  • Alsedairy T, Imran MA. (2011) 'Energy and Spectrum Efficient systems with Adaptive Modulation and Spectrum Sharing for Cellular Systems'. Budapest, Hungary : IEEE Vehicular technology Conference - VTC Spring 2011,
  • Shakir MZ, Alouini M-S, Tang W, Imran MA. (2011) 'Collaborative spectrum sensing based on upper bound on joint PDF of extreme eigenvalues'. European Signal Processing Conference, , pp. 1214-1218.

    Abstract

    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.

  • Al-Imari M, Imran MA, Tafazolli R, Chen D. (2011) 'Subcarrier and Power Allocation for LDS-OFDM System'. IEEE IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011, pp. 1-5.

    Abstract

    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.

  • Qi Y, Hoshyar R, Imran MA, Tafazolli R. (2011) 'The Energy Efficiency Analysis of HARQ in Hybrid Relaying Systems'. Budapest, Hungary : IEEE Vehicular technology Conference - VTC Spring 2011,
  • Imran A, Imran MA, Tafazolli R. (2010) 'A New Performance Characterization Framework for Deployment Architectures of Next Generation Distributed Cellular Networks'. Istanbul, Turkey : IEEE IEEE PIMRC 2010, Istanbul: IEEE 21st International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), 2010, pp. 2046-2051.

    Abstract

    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 A, Imran MA, Tafazolli R. (2010) 'A Novel Self Organizing Framework for Adaptive Frequency Reuse & Deployment in Future Cellular Networks'. Istanbul, Turkey : IEEE IEEE PIMRC 2010, Istanbul: IEEE 21st International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), 2010, pp. 2354-2359.

    Abstract

    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.

  • Auer G, Holtkamp H, Gódor I, Hévizi L, Imran MA, Tafazolli R, Malmodin J, Fazekas P, Biczók G, Zeller D, Blume O. (2010) 'Enablers for energy efficient wireless networks'. IEEE Vehicular Technology Conference,

    Abstract

    Mobile communications are increasingly contributing to global energy consumption. The EARTH (Energy Aware Radio and neTworking tecHnologies) project tackles the important issue of reducing CO 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.

  • Kaltakis D, Imran MA, Katranaras E, Hoshyar R. (2010) 'Fairness and user rate distribution in joint processing systems'. Cape Town, South Africa: 2010 IEEE International Conference on Communications (ICC)

    Abstract

    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.

  • Katranaras E, Kaltakis D, Imran M, Hoshyar R. (2010) 'Interference Allowance in Clustered Joint Processing and Power Allocation'. Caen, France : IWCMC 2010, The 6th International Wireless Communication and Mobile Computing Conference, Caen, France: IWCMC 2010

    Abstract

    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.

  • Alsedairy T, Imran M. (2010) 'Energy Efficiency with Adaptive Modulation and Spectrum Sharing for Cellular Systems'. Liverpool, UK : 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting,,
  • Onireti O, Imran M, Hoshyar R. (2010) 'Downlink Sum-rate Performance for Cooperation and Coordination between Three Interfering Sectors'. Liverpool, UK : 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting, Liverpool UK: 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting

    Abstract

    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.

  • Aliu OG, Imran MA, Evans B. (2010) 'Self organised cellular networks as the future of wireless communications'. Liverpool, UK : 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting, 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting

    Abstract

    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.

  • Qi Y, Imran MA, Tafazolli R. (2010) 'On the energy aware deployment strategy in cellular systems'. Istanbul, Turkey : Wireless Green Workshop, IEEE PIMRC 2010,
  • 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'. Florence Italy : ICT Future Network and Mobile Summit 2010,
  • Khan A, Imran MA, Evans B. (2010) 'Preamble based Adaptive Beamformer for Hybrid Terrestrial-Satellite Mobile System'. California, USA : 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010),
  • Majid M, Imran M, Hoshyar R. (2010) 'Optimization of uplink sum-rate for bin based clustered cellular system using a Genetic Algorithm'. Caen, France : IWCMC 2010, The 6th International Wireless Communication and Mobile Computing Conference,
  • Khan A, Imran MA, Evans B. (2010) 'Ground based and onboard based beamforming for hybrid terrestrial-satellite mobile system'. California, USA : 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010),
  • Chatzinotas S, Imran M, Hoshyar R, Otterston B. (2010) 'Multicell LMMSE Filtering Capacity under Correlated Multiple BS Antennas'. Ottawa, Canada : Proc. IEEE VTC Fall 2010,
  • Riaz M, Imran MA, Hoshyar R. (2010) 'Frequency Planning of Clustered Cellular Network using Particle Swarm Optimization'. York, UK : ISWCS 2010,
  • Majid I, Imran MA, Hoshyar R. (2010) 'Cell based Fair Resource Allocation in Fixed Clustered Cellular Systems using a Genetic Algorithm'. Istanbul, Turkey : IEEE PIMRC 2010,
  • Muirhead D, Imran MA. (2010) 'Transmit Diversity and Beamforming for Energy Efficient Femtocells'. Singapore : Annual International Conference on Green Information Technology 2010,
  • Gruber M, Blume O, Ferling D, Zeller D, Imran MA, Strinati E. (2009) 'EARTH � Energy Aware Radio and Network Technologies'. Tokyo, Japan : IEEE IEEE PIMRC 2009, Tokyo: 20th International Symposium on Personal, Indoor and Mobile Radio Communications, pp. 1-5.

    Abstract

    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

  • Khan AH, Imran MA, Evans B. (2009) 'OFDM based Adaptive Beamforming for Hybrid Terrestrial-Satellite Mobile System with Pilot Reallocation'. Siena-Tuscany : IEEE International Workshop on Satellite and Space Communications, Tuscany: International Workshop on Satellite and Space Communications, 2009, pp. 201-205.

    Abstract

    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.

  • Herault L, Strinati E, Zeller D, Blume O, Imran MA, Tafazolli R. (2009) 'Green Communications: A global environmental challenge'. Sendai, Japan : NICT 12th WPMC 2009, Sendai, Japan:
  • Imran MA, Hoshyar R. (2009) 'Performance of multicell joint processing cellular uplink in the presence of relay nodes'. Santander, Spain : ICT-MobileSummit,
  • Imran MA, Hoshyar R. (2009) 'Improving downlink performance by reusing the subcarriers within the cell'. Santander, Spain : ICT-MobileSummit,
  • Khan AH, Imran MA, Evans B. (2009) 'Adaptive beamforming for OFDM based hybrid mobile satellite system'. Edinburgh, UK : 27th AIAA International Communication Satellite Systems Conference (ICSSC 2009), Edinburgh, UK: 27th IET and AIAA International Communications Satellite Systems Conference (ICSSC 2009)

    Abstract

    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

  • Katranaras E, Imran MA, Hoshyar R. (2009) 'Sum Rate of Linear Cellular Systems with Clustered Joint Processing'. IEEE 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, Barcelona, SPAIN: 69th IEEE Vehicular Technology Conference, pp. 2892-2896.
  • Chatzinotas S, Imran MA, Hoshyar R. (2009) 'On the Ergodic Capacity of the Wideband MIMO Channel'. IEEE 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, Barcelona, SPAIN: 69th IEEE Vehicular Technology Conference, pp. 754-758.
  • 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,

    Abstract

    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.

  • 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 2009, , pp. 849-853.

    Abstract

    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.

  • Kaltakis D, Imran MA, Hoshyar R. (2009) 'Uplink Capacity with Correlated Lognormal Shadow Fading'. IEEE 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, Barcelona, SPAIN: 69th IEEE Vehicular Technology Conference, pp. 3009-3013.
  • Majid MI, Imran MA, Hoshyar R. (2008) 'Analyzing uplink capacity of partially overlapping channel based WLANs using a hyper-receiver'. IEEE 2008 IEEE INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS (ISWCS 2008), Reykjavik, ICELAND: 5th International Symposium on Wireless Communication Systems, pp. 723-727.

    Abstract

    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.

  • Katranaras E, Imran MA, Tzaras C. (2008) 'Framework to Compare the Uplink Capacity of the Cellular Systems with Variable Inter Site Distance'. Cannes, France : IEEE IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC’08, Cannes, France: PIMRC’08

    Abstract

    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.

  • Katranaras E, Imran MA, Tzaras C. (2008) 'INFORMATION THEORETIC CAPACITY OF THE CELLULAR UPLINK - AVERAGE PATH LOSS APPROXIMATION'. IEEE 2008 IEEE 9TH WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS, VOLS 1 AND 2, Recife, BRAZIL: 9th IEEE Workshop on Signal Processing Advances in Wireless Communications, pp. 605-609.
  • Imran MA, Chatzinotas S, Hoshyar R. (2008) 'Capacity of the Cellular Uplink using Joint Multi-cell Processing (Hyper-receiver) with OFDM and CDMA'. Newbury, UK : International Research Workshop on LTE-Advanced Technologies,
  • 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 2008, , pp. 287-292.

    Abstract

    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.

  • Chatzinotas S, Imran MA, Tzaras C. (2008) 'Information Theoretic Uplink Capacity of the Linear Cellular Array'. Athens, Greece : IEEE Proc. Fourth Advanced International Conference on Telecommunications AICT ’08, Athens: Fourth Advanced International Conference on Telecommunications, 2008. AICT '08, pp. 249-254.

    Abstract

    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.

  • Datta S, Imran MA, Tzaras C. (2008) 'Uplink Coverage-Capacity Estimation Using Analysis and Simulation'. Proc. Fourth Advanced International Conference on Telecommunications AICT ’08, , pp. 151-156.
  • Imran MA. (2008) 'Capacity of Variable Density Cellular Systems with Distributed Users'. University of Surrey, Guildford, UK : Second International Workshop on Fundamental Capacity Limits for Wireless Cellular Communication Systems,
  • Chatzinotas S, Imran MA, Tzaras C. (2008) 'Uplink Capacity of MIMO Cellular Systems with Multicell Processing'. IEEE 2008 IEEE INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS (ISWCS 2008), Reykjavik, ICELAND: 5th International Symposium on Wireless Communication Systems, pp. 333-337.
  • Kaltakis D, Imran MA, Tzaras C. (2008) 'Uplink Capacity of Variable-Density Cellular System with Distributed Users and Fading'. Cannes, France : IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC’08,
  • Chatzinotas S, Imran MA, Tzaras C. (2008) 'Optimal information theoretic capacity of the planar cellular uplink channel'. Pernambuco, Brazil : Proc. IEEE 9th Workshop on Signal Processing Advances in Wireless Communications SPAWC 2008, , pp. 196-200.
  • Konstantinou K, Imran MA, Tzaras C. (2008) 'Transmit Power Formulation for Relay-enhanced UMTS using Simulation and Theory'. Cannes, France : IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications 2008, PIMRC’08,
  • Chatzinotas S, Imran MA, Tzaras C. (2008) 'The Effect of User Distribution on a Linear Cellular Multiple-Access Channel'. IEEE 2008 THIRD INTERNATIONAL CONFERENCE ON COMMUNICATIONS AND NETWORKING IN CHINA, VOLS 1-3, Hangzhou, PEOPLES R CHINA: 3rd International Conference on Communications and Networking in China, pp. 90-94.
  • 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,

    Abstract

    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.

  • 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,
  • 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,
  • 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,
  • Gurcan MK, Abas AEP, Imran MA. (2004) 'Graph theoretic multiple access interference reduction for CDMA based radio LAN'. Proc. IEEE International Conference on Communications, 7, pp. 4147-4151.

Book chapters

  • 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
  • Qi Y, Heliot F, Imran MA, Tafazolli R. (2012) 'Green Relay Techniques in Cellular Systems'. in Yu FR, Leung V-C, Zhang X (eds.) Green Communications and Networking CRC Press
  • Héliot F, Katranaras E, Onireti O, Imran MA. (2012) 'On the Energy Efficiency-Spectral Efficiency Trade-off in Cellular Systems'. CRC Press , pp. 353-353.
  • 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

    Abstract

    I Godor, P Frenger, H Holtkamp, M Imran, A Vidacs, P Fazekas, D Sabella, E Strinati, R Gupta, P Pirinen and A Fehske

  • 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

    Abstract

    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.

  • Chatzinotas S, Imran MA, Hoshyar R. (2010) 'Capacity Limits of Base Station Cooperation in Cellular Networks'. in Uysal M (ed.) Cooperative Communications for Improved Wireless Network Transmission: Framework for Virtual Antenna Array Applications

    Abstract

    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.

  • Chatzinotas S, Imran MA, Tzaras C. (2009) 'Capacity Limits in Cooperative Cellular Systems'. in Zhang Y, Chen H-H, Guizani M (eds.) Cooperative Wireless Communications 1st Edition. Auerbach Publications, Taylor & Francis Group , pp. 25-51.
  • 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 Systems SAINT-PETERSBURG : Russian Academy of Science, St Petersburg, Russia , pp. 130-138.

    Abstract

    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.

Reports

  • 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.
  • 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.
  • Auer G, Blume O, Giannini V, ETH IG, Imran MA, EAB YJ, Katranaras E, EAB MO, TI DS, EAB PS, others . INFSO-ICT-247733 EARTH.
  • . (2009) Cooperation among Base Stations and Relay Stations for OFDMA Multi-hop Cellular Networks.
  • . (2009) Multi-cell Coordination Techniques for OFDMA Multi-hop Cellular Networks.
  • . (2009) Multi User Cooperative Transmission techniques for OFDMA Multi-hop Cellular Networks.
  • Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C. (2007) Results and analysis for the rate limits for Wireless City model.
  • Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C. (2007) Fundamental limits for wireless cellular networks.
  • Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C. (2007) Fundamental limits for practical deployments of wireless cellular networks.
  • Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C. (2006) Book of assumptions and known results for the fundamental limits of wireless networks.

Teaching

ELEC III (University of Surrey, UK):
2012 Module Coordinator
2nd Year UG course covering Differential Equations, Laplace transforms and applications, Circuit Analysis and Communication Systems for a group of around 80 students

ELEC IV (University of Surrey, UK):
2009/2010/2011/2012/2013
Electronics and Communication Systems: 20 Hours of Lectures for second year undergraduate students. A group of around 70 students.

EE2.COM (University of Surrey, UK):
Spring 2009
Wireless Communications: 12 Hours of Lectures for second year undergraduate students. A group of around 80 students.

EE3.DCM (University of Surrey, UK):
2008 - 2012
Digital Communication and Modulation: 20 Hours of Lectures for final year undergraduate students and MSc students. A group of around 100 students.

Emerging Technologies in Mobile Communications (University of Surrey, Short Course for Modular MSc):
Spring 2010,2011,2012, 2013

Lecture Series (University of Engineering & Technology, Lahore, Pakistan):
Winter 2012
Fundamentals of Wireless Communications - short seminar

Lecture Series (University of Engineering & Technology, Taxila, Pakistan):
Winter 2012
Teaching the teachers: Wireless Communications - 20 Hours of Lectures 

Lecture Series (National Univerity of Science & Technology, Pakistan):
Summer 2008
Wireless Channel Modelling and Simulations - 30 Hours of Lectures and Lab sessions

Demonstrations/Teaching Assistance (Imperial College London):
Fall 2002 - 06
Electronics Laboratory
Compilers Laboratory
First Year and Second Year Tutorials
Computer Programming Helpdesk

Departmental Duties

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

Senior Member IEEE

Fellow of Higher Education Academy

Academic Supervision and Examinations

PhD Graduated
[2008] Dr Konstantinou, Kostas – working in wireless communication consultancy
[2009] Dr Chatzinotas, Symeon – working in academia (Luxemberg)
[2010] Dr Katranaras, Efstathios – working in academia (UK)
[2010] Dr Kaltakis, Dimitrios – working in TFL (UK)
[2010] Dr Datta, Subha – working in chemical industry (optimisation)
[2010] Dr Majid, Muhammad – working in industry
[2011] Dr Khan, Ammar Hussain – Inmarsat, UK
[2011] Dr Shateri, Majid – Communications consultancy
[2011] Dr Imran, Ali – working in academia (Qatar)
[2011] Dr Hassaan Touheed – RIM Blackberry
[2012] Dr Amir Akbari – working in academia (UK)
[2012] Dr Razieh Razavi – working in academia (UK)
[2012] Dr Glenn Aliu – working in Industry as a researcher (Germany)
[2012] Dr Kayode Onireti – working in academia (UK)
[2013] Dr Mohammed Al-Imari - working in academia (UK)
[2013] Juan Awad

Current PhD Supervision

Thesis submitted:

Writing up:
Talal Alsediary

In Progress:
David Muirhead
Ahmed Zoha
Collin O'Reilly
Wuchen Tang
Amine Amich
Sobhan Navaratnarajah
Arsalan Saeed

First Year:
Lei Wen
Iman Akbari
 

PhD Examined
[2010] Dr Sadegh Fazel-Falavarjani
[2010] Dr Mehrdad Shariat
[2010] Dr Mohammed Abaii
[2011] Dr Allahyar Yarmohammed
[2011] Dr Mo Zhu
[2011] Dr Ayesha Ijaz
[2011] Dr Olasunkanmi Durowoju
[2012] Dr Mahdi Pirmoradian – University of Kingston
[2012] Dr Noor I Abdul Razak – King’s College London
[2012] Dr Ibrar Shah – University of Brunel
[2012] Dr Chong Han
[2012] Dr Syed Shah Irfan Hussain – UET Lahore, Pakistan
[2013] Dr Andrew Adekunle - University of Greenwich

MPhil/PhD Confirmation Exam
[2009] Ayesha Ijaz
[2009] Xiabo Yu
[2009] Bruce Mcaleer
[2010] Chong Han
[2010] Juan Awad
[2010] Chrysovalantis Kosta
[2011] Bahareh Jalilli
[2011] Tomasz Mach
[2011] Parisa Chiraghi
[2011] Emmanouil Pateromichelakis
[2012] Jue Cao
[2012] Mohammed Sabagh
[2013] Tengku Faiz Mohamed Noor Izam
[2013] Ricardo Bassoli
 

PhD Thesis Review/Examination in Pakistan
• “Multiuser Communication Techniques based on OFDM” by Mr Habib ur Rehman, CASE UET Taxila, Pakistan
• “Symbol Detection in MIMO systems” by Sajid Bashir, CASE UET Taxila, Pakistan
• “Range sidelobe suppression in phase coded radar applications” by Aamir Hussain, EME College, NUST, Pakistan
• “Performance improvement of downlink beamforming algorithms in wireless channels” by Syed Shah Irfan Hussain – University of Engineering Lahore, Pakistan
 

Research Fellows
Dr Fabien Heliot
Dr Yinan Qi
Dr Efstathios Katranaras
Dr Jing Jiang
Dr Omer Waqar
Dr Amir Akbari
 

MSc/MEng Project Supervision

Charles Acolatse

[2010]
Mr Mohammad Irfan
Ms Panayiota Christodoulaki
Mr Rejoy George
Mr Subhankar Chatterjee
Mr Ali Torajizadeh
Mr M Hosseini
Mr Yogesh Apar

[2011]
Mr Chinaemerem Nwankwo
Mr Zhipeng Chen
Mr Hamel Shah
Mr Rakesh Teja Matta
Mr Naif Aldaafas
Mr Apostolos Papoutsidakis
Mr Danial Ghabra
Mr Aji Valliyathuparampil Philip
Mr Arsalan Saeed
Mr Wenbo Fan
Mr Y Dong
Mr O Ajibawo
Mr Yousaf Sambo

[2012]
Mr Yahya Saeed
Mr Junwei Tang
Mr Maksym Iarovyi

[2013]
Undergraduate Projects:
Firat Nur
Hao Zheng
Rajiv Packiyalingam
Yifan Wu
Shu Liu
Mohammad Devjianie
Quang Nguyen

Professional Training Year Tutor
[2011/2012]
Mr Dominic Lane – CMAC Technology
Mr Fraser Mason – National Grid, Isle of Grain
Mr Alexander Meerman – ACE Axis
Mr William Burris– ACE Axis

[2012/2013]
Mr Luke Testa – Qualcomm Farnborough
Tristian Hughes – ARM Cambridge
Syed Rafique – Qualcomm Farnborough
Andreas Galanomatis – RIM Cambridge

Personal Tutor
[2010/2011]
Nicholas Day
Hoa Do Danh
Ionnis Hadjicharalambous
Reinis Rudzits
Josh Wreford
Ahmed Al-Aidaus

[2011/2012]
Benedict Chapman
Szu-Hsun Chen
Christopher Corris
Ugur Sahbaz
Vijit Rakubala (joining 2012)

[2012/2013]
Samuel Tyler
Jacob Willey
Pawel Zackiewicz

Technical Experience

Service Desk Specialist (part-time)
2003 - 06
Information and Communication Technologies (ICT): IT support at Imperial College London.

Design Engineer
1999 - 2001
And-Or Logic, Inc. Islamabad, Pakistan

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