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)
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.
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.
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.
Zhang R, Wang L, Parr G, Aliu OG, Awoseyila B, Azarmi N, Bhatti S, Bigham J, Bodanese E, Chen H, Dianati M, Dutta A, Fitch M, Giridhar K, Hailes S, Hari KVS, Imran MA, Jagannatham AK, Karandikar A, Kawade S, Khan MZA, Kompalli SC, Langdon P, Narayanan B, Mauthe A, McGeehan J, Mehta N, Millet K, Moessner K, Rajashekar R, Ramkumar B, Ribeiro V, Vasudevan K, Hanzo L (2013) Advances in Base- and Mobile-Station Aided Cooperative Wireless Communications, IEEE VEHICULAR TECHNOLOGY MAGAZINE 8 (1) pp. 57-69 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
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.
Conventional cellular systems are designed to ensure ubiquitous coverage with an always present wireless channel irrespective of the spatial and temporal demand of service. This approach raises several problems due to the tight coupling between network and data access points, as well as the paradigm shift towards data-oriented services, heterogeneous deployments and network densification. A logical separation between control and data planes is seen as a promising solution that could overcome these issues, by providing data services under the umbrella of a coverage layer. This article presents a holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks. As a starting point, we discuss the fundamentals, concept and general structure of the CDSA. Then, we point out limitations of the conventional architecture in futuristic deployment scenarios. In addition, we present and critically discuss the work that has been done to investigate potential benefits of the CDSA, as well as its technical challenges and enabling technologies. Finally, an overview of standardisation proposals related to this research vision is provided.
Auer G, Godor I, Hevizi L, Imran M, Malmodin J, Fazekas P, Biczok G, Zeller D, Blume O, Tafazolli R (2010) The EARTH Project: Towards Energy Efficient Wireless Networks, ICT Future Network and Mobile Summit 2010
Energy consumption has become an increasingly important aspect of wireless communications, from both an economical and environmental point of view. New enhancements are being placed on mobile networks to reduce the power consumption of both mobile terminals and base stations. This paper studies the achievable rate region of AWGN broadcast channels under Time-division, Frequency-division and Superposition coding, and locates the optimal energy-efficient rate-pair according to a comparison metric based on the average energy efficiency of the system. In addition to the transmit power, circuit power and signalling power are also incorporated in the energy efficiency function, with simulation results verifying that the Superposition coding scheme achieves the highest energy efficiency in an ideal, but non-realistic scenario, where the signalling power is zero. With moderate signalling power, the Frequency-division scheme is the most energy-efficient, with Superposition coding and Time-division becoming second and third best. Conversely, when the signalling power is high, both Time-division and Frequency-division schemes outperform Superposition coding. On the other hand, the Superposition coding scheme also incorporates rate-fairness into the system, which allows both users to transmit whilst maximising the energy efficiency.
Alsedairy T, Imran MA (2011) Energy and Spectrum Efficient systems with Adaptive Modulation and Spectrum Sharing for Cellular Systems, IEEE Vehicular technology Conference - VTC Spring 2011
Auer G, Blume O, Giannini V, Godor Istvan, Imran MA, Jading Ylva, Katranaras Efstathios, Olsson Magnus, Sabella Dario, Skillermark Per, Wajda Wieslawa INFSO-ICT-247733 EARTH,
In order to quantify the energy savings in wireless networks, a holistic view of the power
consumption of the entire system needs to be captured. This requires an appropriate energy efficiency
evaluation framework. In this deliverable, we present the necessary enhancements over existing
performance evaluation frameworks for the wireless networks. The main objective is to capture the
factors affecting the energy efficiency at component, node and network level. The most important
additions to the existing frameworks include: (1) a sophisticated power model for various BS types, that
maps the RF output power radiated at the antenna elements to the total supply power necessary to
operate the network; (2) an approach to quantify the energy efficiency of large geographical areas by
using the existing small scale deployment models along with long term traffic models; (3) a suitable set
of metrics that allows quantifying the amount of energy savings capturing the most important trade-offs
between energy savings and maintaining the system capacity, network coverage and quality of service
parameters. After presenting the framework and necessary components of the framework, the
proposed evaluation framework is applied to quantify the base station energy efficiency of 3GPP LTE.
The overall promise of energy efficiency improvement is further investigated qualitatively for different
possible areas of improvement in the system and some fundamental technology potential limits are also
del Aguila FR, Imran MA, Tafazolli R On The Three-Receiver Multilevel Broadcast Channel with Random Parameters,
Al-Imari M, Imran M, Xiao P (2016) Radio Resource Allocation for Multicarrier-Low Density Spreading Multiple Access, IEEE Transactions on Vehicular Technology IEEE
Multicarrier-low density spreading multiple access
(MC-LDSMA) is a promising multiple access technique that
enables near optimum multiuser detection. In MC-LDSMA, each
user?s symbol spread on a small set of subcarriers, and each
subcarrier is shared by multiple users. The unique structure of
MC-LDSMA makes the radio resource allocation more challenging
comparing to some well-known multiple access techniques. In
this paper, we study the radio resource allocation for single-cell
MC-LDSMA system. Firstly, we consider the single-user case, and
derive the optimal power allocation and subcarriers partitioning
schemes. Then, by capitalizing on the optimal power allocation
of the Gaussian multiple access channel, we provide an optimal
solution for MC-LDSMA that maximizes the users? weighted
sum-rate under relaxed constraints. Due to the prohibitive
complexity of the optimal solution, suboptimal algorithms are
proposed based on the guidelines inferred by the optimal solution.
The performance of the proposed algorithms and the effect of
subcarrier loading and spreading are evaluated through Monte
Carlo simulations. Numerical results show that the proposed
algorithms significantly outperform conventional static resource
allocation, and MC-LDSMA can improve the system performance
in terms of spectral efficiency and fairness in comparison with OFDMA.
Multicarrier-Low Density Spreading Multiple Access (MC-LDSMA) is a promising technique for high data rate mobile communications. In this paper, the suitability of using MC-LDSMA in the uplink for next generation cellular systems is investigated. The performance of MC-LDSMA is evaluated and compared with current multiple access techniques, OFDMA and SC-FDMA. Specifically, Peak to Average Power Ratio (PAPR), Bit Error Rate (BER), spectral efficiency and fairness are considered as performance metrics. The link and system-level simulation results show that MC-LDSMA has significant performance improvements over SC-FDMA and OFDMA. It is shown that using MC-LDSMA can significantly improve the system performance in terms of required transmission power, spectral efficiency and fairness among the users.
O Reilly C, Gluhak A, Imran M (2013) Online anomaly detection with an incremental centred kernel hypersphere, Machine Learning for Signal Processing (MLSP), 2013 IEEE International Workshop on pp. 1-6
© 2014 IEEE.Next generation cellular networks require huge capacity, ubiquitous coverage and maximum energy efficiency. In order to meet these targets, Device-to-device (D2D) communication is being considered for future heterogeneous networks (HetNets). In this paper, we consider a three tier hierarchical HetNet by exploiting D2D communication in traditional HetNet. D2D communication is deployed within the HetNet where closely located mobile users are engaged in direct communication without routing the traffic through cellular access network. The proposed configuration mandates to reduce the interference offered by the resultant HetNet by reducing the transmitter-receiver distance and ensuring that the mobile users are transmitting with adaptive power subject to maintaining their desired link quality. In this context, we analyzed and compared the spectral efficiency improvements in hierarchical HetNet against traditional HetNet. Simulation results show that D2D communication offers much higher spectral efficiency as compared to traditional HetNet.
Chatzinotas S, Imran MA, Hoshyar R (2010) Capacity Limits of Base Station Cooperation in Cellular Networks, In: Uysal M (eds.), Cooperative Communications for Improved Wireless Network Transmission: Framework for Virtual Antenna Array Applications
In the information-theoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems. What is more, it has been proved that the per-cell sum-rate capacity of multicell processing systems grows linearly with the number of base station (BS) receive antennas. However, the majority of results in this area have been produced assuming that the fading coefficients of the MIMO subchannels are completely uncorrelated. In this direction, this chapter investigates the ergodic per-cell sum-rate capacity of the Gaussian MIMO cellular channel under correlated fading and BS cooperation (multicell processing). More specifically, the current channel model considers Rayleigh fading, uniformly distributed user terminals (UTs) over a planar cellular system, and power-law path loss. Furthermore, both BSs and UTs are equipped with correlated multiple antennas, which are modelled according to the Kronecker product correlation model. The per-cell sum-rate capacity is evaluated while varying the cell density of the system, as well as the level of receive and transmit correlation. In this context, it is shown that the capacity performance is compromised by correlation at the BS-side, whereas correlation at the UT-side has a negligible effect on the system?s capacity.
Heliot F, Imran MA, Tafazolli R (2012) Energy-Efficiency based Resource Allocation for the Orthogonal Multi-user Channel, IEEE VTC Fall 2012
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.
In this paper we propose a tight closed-form approximation of the Energy Efficiency vs. Spectral Efficiency (EE-SE) trade-off for the uplink of a cellular communication system. We model the uplink of the cellular system by considering the Wyner model with Raleigh fading. We first demonstrate the accuracy of our expression by comparing it with Monte-Carlo simulation and the EE-SE trade-off expression based on lowpower approximation. Results show the great tightness of our expression with Monte-Carlo simulation. We utilize our closed-form for assessing the EE performance of base station (BS) cooperation against non-cooperative system for both a theoretical power model and a realistic power model. The theoretical power model includes only the transmit power, whereas the realistic power model incorporates the backhaul and signal processing powers in addition of the transmit power. Results indicate that BS cooperation is more energy efficient than non cooperative system and the former always outperforms the latter in terms of EE-SE trade-off. This is however no more the case with the realistic power model: the EE performance is then highly dependent on the number of cooperating BSs.
Heliot F, Imran MA, Tafazolli R (2012) On the Energy Efficiency-Spectral Efficiency Trade-Off over the MIMO Rayleigh Fading Channel, IEEE Transactions on Communications 60 (5) pp. 1345-1356 IEEE
Along with spectral efficiency (SE), energy efficiency (EE) is becoming one of the key performance evaluation criteria for communication system. These two criteria, which are conflicting, can be linked through their trade-off. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression has been here utilized for assessing analytically the EE gain of MIMO over single-input single-output (SISO) system for two different types of power consumption models (PCMs): the theoretical PCM, where only the transmit power is considered as consumed power; and a more realistic PCM accounting for the fixed consumed power and amplifier inefficiency. Our analysis unfolds the large mismatch between theoretical and practical MIMO vs. SISO EE gains; the EE gain increases both with the SE and the number of antennas in theory, which indicates that MIMO is a promising EE enabler; whereas it remains small and decreases with the number of transmit antennas when a realistic PCM is considered.
Imran MA, Gurcan MK, Kahn S (2005) Channel Coding for Cooperative Broadcasting, Proc. of Hellenic European Research on Computer Mathematics and its Applications (HERCMA) 2005
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.
With the emergence and continuous growth of wireless data services, the value of a wireless network is not only defined by how many users it can support, but also by its ability to deliver higher data rates. Information theoretic capacity of cellular systems with fading is usually estimated using models originally inspired by Wyner's Gaussian Cellular Multiple Access Channel (GCMAC). In this paper we extend this model to study the cellular system with users distributed over the cellular coverage area. Based on the distance from the cell-site receiver, users are grouped as tiers, and received signals from each tier are scaled using a distance dependent attenuation factor. The optimum capacity in fading environment is then found by calculating the path-loss for users in each tier using a specific path-loss law and some interesting insights are derived. The results correspond to a more realistic model which boils down to Wyner's model with fading, with appropriate substitutions of parameter values. The results are verified using Wyner's model with fading and Monte-Carlo simulations. Insights are provided for the real world scenarios. © 2008 IEEE.
Peyvandi H, Imran A, Imran MA, Tafazolli R (2014) A target-following regime using Similarity Measure for Coverage and Capacity Optimization in Self-Organizing Cellular Networks with hot-spot, 20th European Wireless Conference, EW 2014 pp. 189-194
© VDE VERLAG GMBH, Berlin, Offenbach, Germany.The Self-Organizing Network (SON) has been seen as one of the promising areas to save OPerational EXpenditure (OPEX) and to bring real efficiency to the wireless networks. Though the studies in literature concern with local interaction and distributed structure for SON, study on its coherent pattern has not yet been well-conducted. We consider a targetfollowing regime and propose a novel approach of goal attainment using Similarity Measure (SM) for Coverage & Capacity Optimization (CCO) use-case in SON. The methodology is based on a self-optimization algorithm, which optimizes the multiple objective functions of UE throughput and fairness using performance measure, which is carried out using SM between target and measured KPIs. After certain epochs, the optimum results are used in adjustment and updating modules of goal attainment. To investigate the proposed approach, a simulation in downlink LTE has also been set up. In a scenario including a congested cell with hotspot, the joint antenna parameters of tilt/azimuth using a 3D beam pattern is considered. The final CDF results show a noticeable migration of hot-spot UEs to higher throughputs, while no one worse off.
Reátegui del Águila F, Imran MA, Tafazolli R (2013) On the Three-Receiver Multilevel Broadcast Channel with Random Parameters,
Imran A, Giupponi L, Imran MA, Abu-Dayya A (2014) Joint coverage and backhaul self-optimization in emerging relay enhanced heterogeneous networks, 2014 IEEE International Conference on Communications, ICC 2014 pp. 2671-2677
This paper presents a novel framework for joint self-optimization of backhaul as well as coverage links spectral efficiency in relay enhanced heterogeneous networks. Considering a realistic heterogeneous network deployment, where some cells contain Relay Station (RS), while others do not, we develop an analytical framework for self-optimisation of macrocell Base Station (BS) antenna tilts. Our framework exploits a unique system level perspective to enable dynamic maximization of system-wide spectral efficiency of the BS-RS backhaul links as well as that of the BS-user coverage links. A distributed and practical self-organising solution is obtained by decomposing the large scale system-wide optimization problem into local small scale optimization problems, by mimicking the operational principles of self-organisation in biological systems. The local problems are non-convex but have very small scale and can be solved via appropriate numerical methods, such as sequential quadratic programming. The performance of developed solution is evaluated through extensive system level simulations for LTE-A type networks and compared against conventional tilting benchmarks. Numerical results show that up to 50% gain in average spectral efficiency is achievable through the proposed solution depending on users geographical distributions. © 2014 IEEE.
Heliot F, Imran MA, Tafazolli R Energy-efficient Coordinated Resource Allocation for the Downlink of Cellular Systems,
Energy efficiency (EE) is growing in importance as a system design crite-
rion for power-unlimited system such as cellular systems. Equally, resource allocation
is a well-known method for improving the performance of the latter. In this paper, we
propose two novel coordinated resource allocation strategies for jointly optimizing
the resources of three sectors/cells in an energy-efficient manner in the downlink of
multi-cell/sector systems. Given that this optimization problem is non-convex, it can
only be optimally solved using high complexity exhaustive search. Here, we propose
two practical approaches for allocating resources in a low complexity manner. We
then compare our novel approaches against other existing non-coordinated and co-
ordinated ones in order to highlight their benefit. Our results indicate that our first
approach performs the best in terms of EE but with a low level of fairness in the user
rate allocation; whereas our second approach provides a good trade-off between EE
and fairness. Overall, base station selection, i.e. allowing only one sector to transmit
at a time, is a very energy-efficient approach when the sleeping power is considered
in the base station power model.
Imran MA (2013) Spectrum Utilization Efficiency Analysis in
Cognitive Radio Networks, Proceedings of the 2013 19th European Wireless Conference (EW) pp. 1-5 IEEE
In cognitive radio network, secondary (unlicensed) users (SUs) are allowed to utilize the licensed spectrum when it is not used by the primary (licensed) users (PUs). Because of the dynamic nature of cognitive radio network, the activities of SUs such as ??how long to sense?? and ??how long to transmit?? significantly affect both the service quality of the cognitive radio networks and protection to PUs. In this work, we formulate and analyze spectrum utilization efficiency problem in the cognitive radio network with various periodic frame structure of SU, which consists of sensing and data transmission slots. Energy detection is considered for spectrum sensing algorithm. To achieve higher spectrum utilization efficiency, the optimal sensing and data transmission length are investigated and found numerically. The simulation results are presented to verify the our analysis and to evaluate the interference to the PU which should be controlled into tolerable level. Index Terms ?? Cognitive radio network; spectrum utilization efficiency; spectrum sensing; energy detection; frame structure.
Khan AH, Imran MA, Evans B (2009) OFDM based Adaptive Beamforming for Hybrid Terrestrial-Satellite Mobile System with Pilot Reallocation, International Workshop on Satellite and Space Communications pp. 201-205 IEEE
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.
Appliance-specific Load Monitoring (LM) provides a possible solution to the problem of energy conservation which is becoming increasingly challenging, due to growing energy demands within offices and residential spaces. It is essential to perform automatic appliance recognition and monitoring for optimal resource utilization. In this paper, we study the use of non-intrusive LM methods that rely on steady-state appliance signatures for classifying most commonly used office appliances, while demonstrating their limitation in terms of accurately discerning the low-power devices due to overlapping load signatures. We propose a multilayer decision architecture that makes use of audio features derived from device sounds and fuse it with load signatures acquired from energy meter. For the recognition of device sounds, we perform feature set selection by evaluating the combination of time-domain and FFT-based audio features on the state of the art machine learning algorithms. The highest recognition performance however is shown by support vector machines, for the device and audio recognition experiments. Further, we demonstrate that our proposed feature set which is a concatenation of device audio feature and load signature significantly improves the device recognition accuracy in comparison to the use of steady-state load signatures only.
Gurcan MK, Abas AEP, Imran MA (2004) Graph theoretic multiple access interference reduction for CDMA based radio LAN, Proc. IEEE International Conference on Communications 7 pp. 4147-4151
Network densification is envisioned as the key enabler for 2020 vision that requires cellular systems to grow in capacity by hundreds of times to cope with unprecedented traffic growth trends being witnessed since advent of broadband on the move. However, increased energy consumption and complex mobility management associated with network densifications remain as the two main challenges to be addressed before further network densification can be exploited on a wide scale. In the wake of these challenges, this paper proposes and evaluates a novel dense network deployment strategy for increasing the capacity of future cellular systems without sacrificing energy efficiency and compromising mobility performance. Our deployment architecture consists of smart small cells, called cloud nodes, which provide data coverage to individual users on a demand bases while taking into account the spatial and temporal dynamics of user mobility and traffic. The decision to activate the cloud nodes, such that certain performance objectives at system level are targeted, is carried out by the overlaying macrocell based on a fuzzy-logic framework. We also compare the proposed architecture with conventional macrocell only deployment and pure microcell-based dense deployment in terms of blocking probability, handover probability and energy efficiency and discuss and quantify the trade-offs therein
Qi Y, Imran M, Tafazolli R (2012) On the Energy Efficiency of Hybrid Relaying Schemes in the Two-way Relay Channel,
In this paper, hybrid relaying schemes are investigated in the two-way relay channel, where the relay node is able to adaptively switch between different forwarding schemes based on the current channel state and its decoding status and thus provides more flexibility as well as improved performance. The analysis is conducted from the energy efficiency perspective for two transmission protocols distinguished by whether exploiting the direct link between two main communicating nodes (the source and destination nodes, and vice versa since it is two way communication) or not. A realistic power model taking circuitry power consumption of all involved nodes into account is employed. The energy efficiency is optimized in terms of consumed energy per bit subject to the Quality of Service (QoS) constraint. Numerical results show that the hybrid schemes are able to achieve the highest energy efficiency due to its capability of adapting to the channel variations and the protocol where the direct link is exploited is more energy efficient.
Imran MA, Chatzinotas S, Hoshyar R (2008) Capacity of the Cellular Uplink using Joint Multi-cell Processing (Hyper-receiver) with OFDM and CDMA, International Research Workshop on LTE-Advanced Technologies
Imran MA, Hoshyar R (2009) Performance of multicell joint processing cellular uplink in the presence of relay nodes, ICT-MobileSummit
Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Results and analysis for the rate limits for Wireless City model,
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.
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
In this paper we carry out an energy efficiency and economic cost analysis of different cellular network designs. Our system model considers the co-channel interference, different amounts of available bandwidths and also the reuse of frequencies. The energy efficiency analysis employs a realistic power consumption model, while the economic analysis focus on infrastructure, spectrum licenses, and energy costs. Our results show that from an economic point of view the bandwidth cost and the number of employed base stations can be the most relevant factors to be balanced, while from an energy efficiency analysis it is more interesting to employ larger bandwidths and to balance the reuse of frequencies and the number of base stations. Moreover, although the system design under these two different points of view can be rather different, we also look into scenarios when the most energy efficient system design may also lead to the best economic option. © 2013 IEEE.
Recent research on Frequency Reuse (FR) schemes for OFDM/OFDMA based cellular networks (OCN) suggest that a single fixed FR cannot be optimal to cope with spatiotemporal dynamics of traffic and cellular environments in a spectral and energy efficient way. To address this issue this paper introduces a novel Self Organizing framework for adaptive Frequency Reuse and Deployment (SO-FRD) for future OCN including both cellular (e.g. LTE) and relay enhanced cellular networks (e.g. LTE Advance). In this paper, an optimization problem is first formulated to find optimal frequency reuse factor, number of sectors per site and number of relays per site. The goal is designed as an adaptive utility function which incorporates three major system objectives; 1) spectral efficiency 2) fairness, and 3) energy efficiency. An appropriate metric for each of the three constituent objectives of utility function is then derived. Solution is provided by evaluating these metrics through a combination of analysis and extensive system level simulations for all feasible FRD's. Proposed SO-FRD framework uses this flexible utility function to switch to particular FRD strategy, which is suitable for system's current state according to predefined or self learned performance criterion. The proposed metrics capture the effect of all major optimization parameters like frequency reuse factor, number of sectors and relay per site, and adaptive coding and modulation. Based on the results obtained, interesting insights into the tradeoff among these factors is also provided.
Mohammed A-I, Imran MA, Tafazolli R, Chen D (2012) Performance Evaluation of Low Density Spreading Multiple Access, FEC 1 pp. x1-x1
Qi Y, Imran MA, Sabella D, Debaillie B, Fatini R, Fernandez Y (2012) On the Deployment Opportunities for Increasing Energy Efficiency,
Saeed A, Imran MA, Aliu OG (2012) Controlling Self-Healing Cellular networks using Fuzzy Logic, pp. 3080-3084 IEEE
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.
Self-Organizing Networks (SONs) have an important role in the development of the next generation mobile networks by introducing automated schemes. Cell outage detection is one of the main functionalities in self-healing mechanism. Outage detection for small cells has not been discussed in literature with greater emphasis yet. The Femtocell Collaborative Outage Detection (FCOD) algorithm with built-in Sleeping Mode Recovery (SMR) is introduced in this paper. The proposed algorithm is mainly based on the femtocell collaborative detection with incorporated sniffer. It compares the current Femtocell Access Points FAPs? Reference Signal Received Power (RSRP) statistics with a benchmark data. An outage decision is autonomously taken by each FAP depending on a certain threshold value. Moreover, the FCOD algorithm is capable of differentiating between the outage and sleeping cells due to the presence of the built-in SMR technique.
Coordination between two or more multiple access channel (MAC) receivers can enlarge the achievable rate region of the whole system. This paper focuses on coordination by sharing the codebooks of the users between the receivers of MACs. We first define the achievable rate region of the time invariant multiple coordinated MAC (MCMAC) and subsequently derive its achievable rate region. We later express the achievable rate region in terms of the dominating points. We base our numerical analysis on the two-user two-receiver Gaussian coordinated MAC and make comparison with the interference channel, full cooperation and the individual MAC performance analysis. It is observed that this approach though suboptimal is less complex in comparison with full cooperation and that the MCMAC rate region is at least equal to the rate region of the uncoordinated approach. Over several channel states, the rate region of MCMAC exceeds that of the uncoordinated approach.
Muirhead D, Imran MA (2012) Determining the Energy Efficiency of Femtocell Basestations with Multiple Antennas,
This paper investigates the radio resource management (RRM) issues in a heterogeneous macro-femto network. The objective of femto deployment is to improve coverage, capacity, and experienced quality of service of indoor users. The location and density of user-deployed femtos is not known a-priori. This makes interference management crucial. In particular, with co-channel allocation (to improve resource utilization efficiency), RRM becomes involved because of both cross-layer and co-layer interference. In this paper, we review the resource allocation strategies available in the literature for heterogeneous macro-femto network. Then, we propose a self-organized resource allocation (SO-RA) scheme for an orthogonal frequency division multiple access based macro-femto network to mitigate co-layer interference in the downlink transmission. We compare its performance with the existing schemes like Reuse-1, adaptive frequency reuse (AFR), and AFR with power control (one of our proposed modification to AFR approach) in terms of 10 percentile user throughput and fairness to femto users. The performance of AFR with power control scheme matches closely with Reuse-1, while the SO-RA scheme achieves improved throughput and fairness performance. SO-RA scheme ensures minimum throughput guarantee to all femto users and exhibits better performance than the existing state-of-the-art resource allocation schemes.
Imran MA, Gurcan MK (2006) Message passing algorithm for iterative decoding of channel codes, HERMIS-mu-pi International Journal of Computer Mathematics and its Applications 8 pp. 1-20-1-20
Onireti O, Imran MA, Tafazolli R, Imran A (2014) Cell outage detection in heterogeneous networks with separated control and data plane, 20th European Wireless Conference, EW 2014 pp. 165-170
In this paper, we propose a data cell outage detection scheme for heterogeneous networks (HetNets) with separated control and data plane. We consider a HetNet where the Control Network Layer (CNL) provides ubiquitous network access while Data Network Layer (DNL) provides high data rate transmission to low mobility User Terminals (UTs) Furthermore, network functionalities such as paging and system information broadcast are provided by the CNL to all active UTs, hence, the CNL is aware of all active UTs association. Based on this observation, we categorize our data cell outage detection scheme into the trigger phase and detection phase. In the former, the CNL monitors all UT-data base station association and triggers detection when irregularities occurs in the association, whUe the later utilizes a grey prediction model on the UTs' reference signal received power (RSRP) statistics to determine the existence of an outage. The simulation results indicate that the proposed scheme can detect the data cell outage problem in a reliable manner.
Katranaras E, Tang J, Imran MA (2013) Energy and spectral efficient inter base station relaying in cellular systems, IEEE Vehicular Technology Conference
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.
Onireti OS, Zaidi ZR, Friderikos V, Gang J, Imran MA (2016) An Integrated Approach for Functional Decomposition of Future RAN (Radio Access Network), In: Shakir MZ, Imran MA, Qaraqe KA, Alouini M-S, Vasilakos AV (eds.), Energy Management in Wireless Cellular and Ad-hoc Networks 6 pp. 123-144 Springer
Software-defined radio access networks (SD-RAN), dense deployment of small cells with possible macro-overlay for users with high mobility, decoupled signaling and data transmissions, or beyond cellular green generation (BCG2) architecture for enhanced energy efficiency, etc. are some of the very active research themes and most promising technologies for future RAN architecture. In this chapter, we present the idea of an integrated deployment solution for energy efficient cellular networks combining the strengths of the above mentioned themes. While SD-RAN envisions a decoupled centralized control plane and data forwarding plane for flexible control, the BCG2 architecture calls for decoupling coverage from capacity and coverage is provided through always-on low-power signaling node for a larger geographical area; capacity is catered by various on-demand data nodes or small cells for maximum energy efficiency. We identify that a combined approach bringing in both decompositions together can, not only achieve greater benefits, but also facilitates the faster realization of both technologies. We propose the idea and design of a signaling controller which acts as a signaling node to provide always-on coverage, consuming low power, and at the same time also hosts the control plane functions for the SD-RAN through a general purpose processing platform. Phantom cell concept is also a similar idea where a normal macro cell provides interference control to densely deployed small cells, although, our preliminary results show that the proposed integrated architecture has much greater potential of energy savings in comparison to phantom cells as a signaling controller is supposed to consume minimal power in comparison with the normal macro cell BS.
Khan A, Imran MA, Evans B (2010) Preamble based Adaptive Beamformer for Hybrid Terrestrial-Satellite Mobile System, 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010)
Arshad K, Imran MA (2013) Increasing the interaction time in a lecture by integrating flipped classroom and just-in-time teaching concepts, Compass: Journal of Learning and Teaching 4 7
Majid M, Imran M, Hoshyar R (2010) Optimization of uplink sum-rate for bin based clustered cellular system using a Genetic Algorithm, IWCMC 2010, The 6th International Wireless Communication and Mobile Computing Conference
Qi Y, Imran MA, Tafazolli R (2010) On the energy aware deployment strategy in cellular systems, Wireless Green Workshop, IEEE PIMRC 2010
Imran, Muhammad A (2009) Multi-cell Coordination Techniques for OFDMA Multi-hop Cellular Networks,
Qi Y, Héliot F, Imran MA, Tafazolli R (2012) Green Relay Techniques in Cellular Systems, In: Yu FR, Leung VCM, Zhang X (eds.), Green Communications and Networking CRC Press
Khan A, Imran MA, Evans B (2010) Ground based and onboard based beamforming for hybrid terrestrial-satellite mobile system, 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010)
Mustafa HA, Shakir MZ, Imran MA, Imran A, Tafazolli R (2015) Coverage Gain and Device-to-Device User Density: Stochastic Geometry Modeling and Analysis, IEEE COMMUNICATIONS LETTERS 19 (10) pp. 1742-1745 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
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.
The increasing demand for data and multimedia services, as well as the ubiquitous nature of the current generation of mobile devices have resulted in continuous network upgrades to support an ever-increasing number of users. However, given that wireless communication systems operate on radiofrequency waves, the health effects of electromagnetic (EM) emission from these systems are increasingly becoming a concern. In order to address these concerns, we propose in this paper, an EM emission reduction scheme for the uplink of OFDM wireless systems with base station coordination. We formulate the EM reduction scheme as a convex optimization problem and solve it by iteratively allocating bits to users on their respective subcarriers in each sector. This is based on the assumption that the scheduler can predict the channel state information of all the users for a given transmission window. Simulation results show that, with coordination, our proposed scheme reduces EM emission by over 85% and 99% when compared with a no frequency reuse scheme and an energy efficiency based scheme, respectively.
In this paper, we propose a data cell outage detection scheme for heterogeneous networks (HetNets) with separated control and data plane. We consider a HetNet where the Control Network Layer (CNL) provides ubiquitous network access while Data Network Layer (DNL) provides high data rate transmission to low mobility User Terminals (UTs). Furthermore, network functionalities such as paging and system information broadcast are provided by the CNL to all active UTs, hence, the CNL is aware of all active UTs association. Based on this observation, we categorize our data cell outage detection scheme into the trigger phase and detection phase. In the former, the CNL monitors
all UT-data base station association and triggers detection when irregularities occurs in the association, while the later utilizes
a grey prediction model on the UTs? reference signal received power (RSRP) statistics to determine the existence of an outage. The simulation results indicate that the proposed scheme can detect the data cell outage problem in a reliable manner.
Sambo Y, Héliot F, Imran MA (2012) An interference-aware precoding scheme for the downlink of multi-cell multi-user MIMO communication, Proceedings of the 2012 IEEE 4th International Conference on Adaptive Science and Technology, ICAST 2012 pp. 29-32
In multi-cell communication, users close to the cell boundaries tend to suffer interferences from other-cell users. Other-Cell Interference (OCI) coming from neighbouring cells considerably degrades the overall performance of the system. In this paper, we propose a precoding scheme for the multi-user multi-input multi-output (MIMO) downlink based on the regularized channel inversion algorithm to mitigate the effect of OCI in multi-cell systems. The scheme is designed by taking into account the interference plus noise covariance matrix of each user at the transmitter and the use of an interference suppression filter at each receiver. Unlike traditional OCI-aware Block Diagonalization (BD) based algorithms that experience noise enhancement due to complete elimination of multi-user interference (MUI), this scheme suppresses the MUI while taking the OCI into consideration. Simulation results show that the sum-rate performance of the proposed scheme outperforms the OCI-aware BD algorithm for different OCI settings. © 2012 IEEE.
Herault L, Strinati E, Zeller D, Blume O, Imran MA, Tafazolli R (2009) Green Communications: A global environmental challenge, 12th WPMC 2009 NICT
Awad JF, Imran MA, Tafazolli R (2013) Reduced Complexity Interference Avoidance Scheme Based on User Grouping in Dense Cellular Networks, European Wireless 2013 VDE VERLAG GmbH
Zoha A, Gluhak A, Nati M, Imran MA (2013) Low-power appliance monitoring using Factorial Hidden Markov Models, Proceedings of the 2013 IEEE 8th International Conference on Intelligent Sensors, Sensor Networks and Information Processing: Sensing the Future, ISSNIP 2013 1 pp. 527-532
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.
Energy efficiency (EE) is fast becoming a key performance indicator for designing future wireless communication systems. Equally, precoding/power allocation has proved to be very effective for improving the spectral efficiency (SE) of multi-user (MU) multi-input multi-output (MIMO) communication systems. In a multi-cell environment, other-cell interference (OCI) degrades both the SE and EE performances of the system. We design here an energy efficient OCI-aware precoding/power allocation algorithm for the downlink of MU-MIMO systems by relying on regularized channel inversion and considering a realistic multi-antenna power consumption model. The performance of our proposed scheme is assessed both in presence and absence of OCI and results demonstrate the effectiveness of our approach for mitigating OCI. In addition, results show that our approach improves the EE of the system by saving transmit power in comparison with a traditional SE-based precoding/power allocation approach. © 2014 IEEE.
Chatzinotas S, Imran MA, Tzaras C (2008) Spectral efficiency of variable density cellular systems with realistic system models, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
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.
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.
Many method has been applied previously to improve the fairness of a wireless communication system. In this paper, we propose using hybrid schemes, where more than one transmission scheme are used in one system, to achieve this objective. These schemes consist of cooperative transmission schemes, maximal ratio transmission and interference alignment, and non-cooperative schemes, orthogonal and non-orthogonal schemes used alongside and in combinations in the same system to improve the fairness. We provide different weight calculation methods to vary the output of the fairness problem. We show the solution of the radio resource allocation problem for the transmission schemes used. Finally, simulation results is provided to show fairness achieved, in terms of Jain's fairness index, by applying the hybrid schemes proposed and the different weight calculation methods at different inter-site distances.
O Reilly C, Gluhak A, Imran M, Rajasegarar S (2012) Online anomaly rate parameter tracking for anomaly detection in wireless sensor networks, Sensor, Mesh and Ad Hoc Communications and Networks (SECON), 2012 9th Annual IEEE Communications Society Conference on pp. 191 -199-191 -199
Energy efficiency (EE) is growing in importance as
a key performance indicator for designing the next generation of
communication systems. Equally, resource allocation is an effective
approach for improving the performance of communication
systems. In this paper, we propose a low-complexity energyefficient
resource allocation method for the orthogonal multiantenna
multi-carrier channel. We derive explicit formulations
of the optimal rate and energy-per-bit consumption for the
per-antenna transmit power constrained and per-antenna rate
constrained EE optimization problems as well as provide a lowcomplexity
algorithm for optimally allocating resources over
the orthogonal multi-antenna multi-carrier channel. We then
compare our approach against a classic optimization tool in terms
of energy efficiency as well as complexity, and results indicate
the optimality and low-complexity of our approach. Comparing
EE-optimal with spectral efficiency and power optimal allocation
approaches over the orthogonal multi-antenna multi-carrier
channel indicates that the former provides a good trade-off
between power consumption and sum-rate performances.
Muirhead D, Imran MA (2010) Transmit Diversity and Beamforming for Energy Efficient Femtocells, Annual International Conference on Green Information Technology 2010
© 2015 IEEE. Device-to-device (D2D) communication is being considered an important traffic offloading mechanism for future cellular networks. Coupled with pro-active device caching, it offers huge potential for capacity and coverage enhancements. In order to ensure maximum capacity enhancement, number of nodes for direct communication needs to be identified. In this paper, we derive analytic expression that relates number of D2D nodes (i.e., D2D user density) and average coverage probability of reference D2D receiver. Using stochastic geometry and poisson point process, we introduce retention probability within cooperation region and shortest distance based selection criterion to precisely quantify interference due to D2D pairs in coverage area. The simulation setup and numerical evaluation validates the closed-form expression.
Waqar O, Imran MA, Dianati M (2013) On the error analysis of fixed-gain relay networks over composite multipath/shadowing channels, IEEE Vehicular Technology Conference
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.
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
In the information-theoretic literature, Wyner's model has been the starting point for studying the capacity limits of cellular systems. This simple cellular model was adopted and extended by researchers in order to incorporate flat fading and path loss. However, the majority of these extensions preserved a fundamental assumption of Wyner's model, namely the collocation of User Terminals (UTs). In this paper, we alleviate this assumption and we evaluate the effect of user distribution on the sum-rate capacity. In this context, we show that the effect of user distribution is only considerable in low cell-density systems and we argue that "collocated" models can be utilized to approximate the "distributed" ones in the high cell-density regime. Subsequently, we provide closed forms for the calculation of the interference factors of "collocated" models given the system parameters. In addition, the asymptotics of the per-cell sum-rate capacity are investigated. Finally, the presented results are interpreted in the context of practical cellular systems using appropriate figures of merit.
Murtagh N, nati M, headley WR, gatersleben B, gluhak A, imran MA, uzzell D (2013) Individual energy use and feedback in an office setting: A field trial, Energy Policy
In this paper, we propose a tight closed-form approximation
of the Energy Efficiency vs. Spectral Efficiency (EE-SE)
trade-off for the uplink of a linear cellular communication system
with base station cooperation and uniformly distributed user
terminals. We utilize the doubly-regular property of the channel
to obtain a closed form approximation using the MarÇcenko
Pasture law. We demonstrate the accuracy of our expression
by comparing it with Monte-Carlo simulation and the EE-SE
trade-off expression based on low-power approximation. Results
show the great tightness of our expression with Monte-Carlo
simulation.We utilize our closed form expression for assessing the
EE performance of cooperation for both theoretical and realistic
power models. The theoretical power model includes only the
transmit power, whereas the realistic power model incorporates
the backhaul and signal processing power in addition to the
transmit power. Results indicate that for both power models,
increasing the number of antennas leads to an improvement in
EE performance, whereas, increasing the number of cooperating
BSs results in a loss in EE when considering the realistic power
Kaltakis D, Imran MA, Hoshyar R (2009) Uplink Capacity with Correlated Lognormal Shadow Fading, 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 pp. 3009-3013 IEEE
Auer G, Gódor I, Hévizi L, Imran MA, Malmodin J, Fazekas P, Biczók G, Holtkamp H, Zeller D, Blume O, Tafazolli R (2010) Enablers for energy efficient wireless networks, IEEE Vehicular Technology Conference
Mobile communications are increasingly contributing to global energy consumption. The EARTH (Energy Aware Radio and neTworking tecHnologies) project tackles the important issue of reducing CO2 emissions by enhancing the energy efficiency of cellular mobile networks. EARTH is a holistic approach to develop a new generation of energy efficient products, components, deployment strategies and energy-aware network management solutions. In this paper the holistic EARTH approach to energy efficient mobile communication systems is introduced. Performance metrics are studied to assess the theoretical bounds of energy efficiency as well as the practical achievable limits. A vast potential for energy savings lies in the operation of radio base stations. In particular, base stations consume a considerable amount of the available power budget even when operating at low load. Energy efficient radio resource management (RRM) strategies need to take into account slowly changing daily load patterns, as well as highly dynamic traffic fluctuations. Moreover, various deployment strategies are examined focusing on their potential to reduce energy consumption, whilst providing uncompromised coverage and user experience. This includes heterogeneous networks with a sophisticated mix of different cell sizes, which may be further enhanced by energy efficient relaying and base station cooperation technologies. Finally, scenarios leveraging the capability of advanced terminals to operate on multiple radio access technologies (RAT) are discussed with respect to their energy savings potential. ©2010 IEEE.
The growth in mobile communications has resulted in a significant increase in energy consumption and carbon emissions, which could have serious economic and environmental implications. Consequently, energy consumption has become a key criterion for the design of future mobile communication systems. Device-to-device (D2D) communication has been shown to improve the spectral efficiency and also reduce the power consumption of mobile communication networks. In this paper, we propose a two-tier deployment of D2D communication within a network to reduce the overall power consumption of the network and compared it with full small-cell deployment throughout the network. In this context, we computed the backhaul power consumption of each link in the networks and derived the backhaul energy efficiency expression of the networks. Simulation results show that our proposed network deployment outperforms the network with full small-cell deployment in terms of backhaul power consumption, backhaul energy-efficiency, total power consumption of the tier 2 users and downlink power consumption, thus providing a greener alternative to small-cell deployment.
A fundamental challenge in orthogonal-frequency-division-multiple-access (OFDMA)-based cellular networks is intercell interference coordination, and to meet this challenge, various solutions using fractional frequency reuse (FFR) have been proposed in the literature. However, most of these schemes are either static in nature, dynamic on a large time scale, or require frequent reconfiguration for event-driven changes in the environment. The significant operational cost involved can be minimized with the added functionality that self-organizing networks bring. In this paper, we propose a solution based on the center of gravity of users in each sector. This enables us to have a distributed and adaptive solution for interference coordination. We further enhance our adaptive distributed FFR scheme by employing cellular automata as a step toward achieving an emergent self-organized solution. Our proposed scheme achieves a close performance with strict FFR and better performance than SFR in terms of the edge user's sum rate.
Waqar O, Imran M, Dianati M, Tafazolli R (2014) Energy Consumption Analysis and Optimization of BER-Constrained Amplify-and-Forward Relay Networks, IEEE Transactions on Vehicular Technology IEEE
Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Fundamental limits for practical deployments of wireless cellular networks,
In this paper, hybrid relaying schemes are investigated in the two-way relay channel, where the relay node is able to adaptively switch between different forwarding schemes based on the current channel state and its decoding status and thus provides more flexibility as well as improved performance. The analysis is conducted from the energy efficiency perspective for two transmission protocols distinguished by whether exploiting the direct link between two main communicating nodes (the source and destination nodes, and vice versa since it is two way communication) or not. A realistic power model taking circuitry power consumption of all involved nodes into account is employed. The energy efficiency is optimized in terms of consumed energy per bit subject to the Quality of Service (QoS) constraint. Numerical results show that the hybrid schemes are able to achieve the highest energy efficiency due to its capability of adapting to the channel variations and the protocol where the direct link is exploited is more energy efficient.
Onireti OS, Evans B, Spathopoulos T, Imran MA (2015) THE ROLE OF SATELLITES IN 5G,
The next generation of mobile radio communication systems?so called 5G?will provide some major changes to those generations to date. The ability to cope with huge increases in data traffic at reduced latencies and improved quality of user experience together with major reduction in energy usage are big challenges. In addition future systems will need to embody connections to billions of objects?the so called Internet of Things (IoT) which raise
new challenges. Visions of 5G are now available from
regions across the World and research is ongoing towards new standards. The consensus is a flatter architecture that adds a dense network of small cells operating in the millimetre wave bands and which are adaptable and software controlled. But what place for satellites in such a vision?
The paper examines several potential roles for satellite including coverage extension, content distribution, providing resilience, improved spectrum utilisation and integrated signalling systems.
Alsedairy T, Imran M (2010) Energy Efficiency with Adaptive Modulation and Spectrum Sharing for Cellular Systems, 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting,
Imran MA (2008) Capacity of Variable Density Cellular Systems with Distributed Users, Second International Workshop on Fundamental Capacity Limits for Wireless Cellular Communication Systems
We compare the downlink energy efficiency of spatial diversity multiple transmit antenna schemes. We determine the minimum required transmit power for a given outage probability. Our analysis shows that antenna selection is in general the most energy efficient option as it requires a single radio-frequency chain. We also investigate the limiting distances up to which the antenna selection technique outperforms the transmit beamforming scheme for different numbers of transmit antennas. © 1997-2012 IEEE.
Heliot F, Imran MA, Tafazolli R (2012) Energy-efficient Power Allocation for Point-to-point MIMO System over the Rayleigh Fading Channel, IEEE Wireless Communications Letters 1 (4) pp. 304-307 IEEE
It is well-established that transmitting at full power is the most spectral-efficient power allocation strategy for point-to-point (P2P) multi-input multi-output (MIMO) systems, however, can this strategy be energy efficient as well? In this letter, we address the most energy-efficient power allocation policy for symmetric P2P MIMO systems by accurately approximating in closed-form their optimal transmit power when a realistic MIMO power consumption model is considered. In most cases, being energy efficient implies a reduction in transmit and overall consumed powers at the expense of a lower spectral efficiency.
Navaratnarajah S, Saeed A, Dianati M, Imran ML (2013) Energy efficiency in heterogeneous wireless access networks, IEEE Wireless Communications 20 (5) pp. 37-43
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.
In this article, we consider the joint subcarrier and power allocation problem for uplink orthogonal frequency division multiple access system with the objective of weighted sum-rate maximization. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solution is extremely high. We use the optimality conditions for this problem to propose a suboptimal allocation algorithm. A simplified implementation of the proposed algorithm has been provided, which significantly reduced the algorithm complexity. Numerical results show that the presented algorithm outperforms the existing algorithms and achieves performance very close to the optimal solution.
Datta S, Tzaras C, Imran MA (2007) Impact of Orthogonality Factor on UMTS Capacity Simulation, Proceedings of the 2nd ACM Workshop on Performance Monitoring and Measurement of Heterogenous Wireless and Wired Networks PM2HW2N ?07
Chatzinotas S, Imran MA, Hoshyar R (2009) On the Ergodic Capacity of the Wideband MIMO Channel, 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 pp. 754-758 IEEE
In this paper we compare the uplink performance of various deployment scenarios in the planar (hexagonal) cellular system where the received signals at multiple cells are jointly processed by a central processor. A mathematical model of the planar cellular system is presented and its performance metric is based on information theoretic sum rate, and group rate share. The system deployment is as follows; the density of the base station is decreased, relay node replaces alternate base stations and in the last scenario, alternate bases stations are removed while the left over base stations are equipped with an additional antenna. It is observed that in reduction in the density of base stations resulted in reduction in the achievable sum rate and makes the group rate unfair. The introduction of additional antenna resulted in an improvement in the rate (compared with the reduction in density scenario) without any improvement in group rate fairness to cell user at the cell edge. The replacement of base stations with relay node and the implementation of orthogonal amplify and forward scheme resulted in a reduction in the achievable sum rate however it produced a significant improvement in group rate fairness. The result suggest that relay deployment in multicell joint processing system does not improve the sum rate of the system rather it improves the rate share for cell edge users making the user rate distribution fairer.
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.
Chatzinotas S, Imran MA, Tzaras C (2008) Optimal information theoretic capacity of the planar cellular uplink channel, Proc. IEEE 9th Workshop on Signal Processing Advances in Wireless Communications SPAWC 2008 pp. 196-200
Qi Y, Imran MA, Tafazolli R (2011) Energy-aware adaptive sectorisation in LTE systems, 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications pp. 2402-2406 IEEE
In this paper, we propose a novel energy-aware adaptive sectorisation strategy, where the base stations are able to adapt themselves to the temporal traffic variation by switching off some sectors and changing the beam-width of the remaining sectors. An event based user traffic model is established according to Markov-Modulated Poisson Process (MMPP). Adaptation is performed while taking into account the the target Quality of Service (QoS), in terms of blocking probability. In addition, coverage requirement is also considered. This work targets at future cellular systems, in particular LTE systems. The results show that at least 21% energy consumption can be reduced by using the proposed adaptive sectorisation strategy.
Sambo YA, Shakir MZ, Qaraqe KA, Serpedin E, Imran MA (2014) Expanding Cellular Coverage via Cell-Edge Deployment in Heterogeneous Networks: Spectral Efficiency and Backhaul Power Consumption Perspectives, IEEE COMMUNICATIONS MAGAZINE 52 (6) pp. 140-149 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Lateef HY, Imran A, Imran MA, Giupponi L, Dohler M (2015) LTE-advanced self-organizing network conflicts and coordination algorithms, IEEE Wireless Communications 22 (3) pp. 108-117
© 2015 IEEE.Self-organizing network (SON) functions have been introduced in the LTE and LTEAdvanced standards by the Third Generation Partnership Project as an excellent solution that promises enormous improvements in network performance. However, the most challenging issue in implementing SON functions in reality is the identification of the best possible interactions among simultaneously operating and even conflicting SON functions in order to guarantee robust, stable, and desired network operation. In this direction, the first step is the comprehensive modeling of various types of conflicts among SON functions, not only to acquire a detailed view of the problem, but also to pave the way for designing appropriate Self-Coordination mechanisms among SON functions. In this article we present a comprehensive classification of SON function conflicts, which leads the way for designing suitable conflict resolution solutions among SON functions and implementing SON in reality. Identifying conflicting and interfering relations among autonomous network management functionalities is a tremendously complex task. We demonstrate how analysis of fundamental trade-offs among performance metrics can us to the identification of potential conflicts. Moreover, we present analytical models of these conflicts using reference signal received power plots in multi-cell environments, which help to dig into the complex relations among SON functions. We identify potential chain reactions among SON function conflicts that can affect the concurrent operation of multiple SON functions in reality. Finally, we propose a selfcoordination framework for conflict resolution among multiple SON functions in LTE/LTEAdvanced networks, while highlighting a number of future research challenges for conflict-free operation of SON.
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.
Cooperative communication is an effective approach for increasing the spectral efficiency and/or the coverage of cellular networks as well as reducing the cost of network deployment. However, it remains to be seen how energy efficient it is. In this paper, we assess the energy efficiency of the conventional Amplify-and- forward (AF) scheme in an in-building relaying scenario. This scenario simplifies the mutual information formulation of the AF system and allows us to express its channel capacity with a simple and accurate closed-form approximation. In addition, a framework for the energy efficiency analysis of AF system is introduced, which includes a power consumption model and an energy efficiency metric, i.e. the bit-per-joule capacity. This framework along with our closed-form approximation are utilized for assessing both the channel and bit-per-joule capacities of the AF system in an in-building scenario. Our results indicate that transmitting with maximum power is not energy efficient and that AF system is more energy efficient than point-to-point communication at low transmit powers and signal-to-noise ratios.
Sambo YA, Imran MA, Shakir MZ, Qaraqe KA, Serpedin E (2014) On the capacity bounds of K-tier heterogeneous small-cell networks employing aggressive frequency reuse, IEEE Wireless Communications and Networking Conference, WCNC pp. 2534-2539
With the cell coverage area of current and future mobile networks becoming smaller, heterogeneous small-cell networks (HetSNets), where multiple low-power, low-cost base stations (BSs) complement the existing macrocell infrastructure, are considered constitutive elements of future mobile networks. In this paper, we propose a K-tier HetSNet, where multiple tiers of small-cells are padded between macrocells which in turn expand the network coverage and significantly increase in capacity without compromising the frequency reuse factor. In this context, we derive analytical capacity bounds of the K-tier HetSNets based on the distance of the desired user from its serving BS and all other interfering BSs. It was observed that the upper bound of the capacity becomes tighter as the number of small-cell tiers increases due to the increase in the number of small-cells. Simulation results show the performance of the proposed K-tier HetSNets against the macro-only network in terms of frequency reuse factor, capacity and area spectral efficiency.
Imran, Muhammad A (2009) Cooperation among Base Stations and Relay Stations for OFDMA Multi-hop Cellular Networks,
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.
Tang W, Shakir MZ, Imran MA, Tafazolli R, Alouini M-S (2012) Throughput Analysis for Cognitive Radio Networks with Multiple Primary Users and Imperfect Spectrum Sensing, Communications, IET 6 17 pp. 2787-2795 IET
Energy efficiency (EE) is gradually becoming one of the key criteria, along with the spectral efficiency (SE), for evaluating communication system performances. However, minimizing the EE while maximizing the SE are conflicting objectives and, thus, the main criterion for designing efficient communication systems will become the trade-off between SE and EE. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this EE-SE trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression, which can easily be used for evaluating and comparing the EE-SE trade-off of MIMO communication system, has been utilized in this paper for analyzing the impact of using multiple antennas on the EE and the EE gain of MIMO in comparison with single-input single-output (SISO) system. Our results indicate that EE can be improved predominantly through receive diversity in the low-SE regime and that MIMO is far more energy efficient than SISO at high SE over the Rayleigh fading channel.
Datta S, Imran MA, Tzaras C (2008) Uplink Coverage-Capacity Estimation Using Analysis and Simulation, Proc. Fourth Advanced International Conference on Telecommunications AICT ?08 pp. 151-156
Energy efficiency (EE) is emerging as a key design criterion for both power limited applications, i.e. mobile devices, and power-unlimited applications, i.e. cellular network. Whereas, resource allocation is a well-known technique for improving the performance of communication system. In this paper, we design a
simple and optimal EE-based resource allocation method for the orthogonal multi-user channel by adapting the transmit power and rate to the channel condition such that the energy-per-bit
consumption is minimized. We present our EE framework, i.e. EE metric and node power consumption model, and utilizes it for formulating our EE-based optimization problem with or without constraint. In both cases, we derive explicit formulations of the optimal energy-per-bit consumption as well as optimal power and rate for each user. Our results indicate that EE-based allocation can substantially reduce the consumed power and increase the EE in comparison with spectral efficiency-based allocation.
Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2007) Fundamental limits for wireless cellular networks,
Saeed A, Akbari A, Dianati M, Imran MA (2013) Energy Efficiency Analysis for LTE Macro-Femto HetNets., EW VDE-Verlag
Along with spectral efficiency (SE), energy efficiency (EE) is becoming one of the key performance evaluation criteria for communication system. These two criteria, which are conflicting, can be linked through their trade-off. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression has been here utilized for assessing analytically the EE gain of MIMO over single-input single-output (SISO) system for two different types of power consumption models (PCMs): the theoretical PCM, where only the transmit power is considered as consumed power; and a more realistic PCM accounting for the fixed consumed power and amplifier inefficiency. Our analysis unfolds the large mismatch between theoretical and practical MIMO vs. SISO EE gains; the EE gain increases both with the SE and the number of antennas in theory, which indicates that MIMO is a promising EE enabler; whereas it remains small and decreases with the number of transmit antennas when a realistic PCM is considered. © 2012 IEEE.
Alsedairy T, Imran M, Qi Y, Evans B (2013) Energy-effcient dynamic deployment architecture for future cellular systems, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC pp. 3111-3116
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.
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.
Energy efficiency has become increasingly important in wireless communications, with significant environmental and financial benefits. This paper studies the achievable capacity region of a single carrier uplink channel consisting of two transmitters and a single receiver, and uses average energy efficiency contours to find the optimal rate pair based on four different targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. In addition to the transmit power, circuit power is also accounted for, with the maximum transmit power constrained to a fixed value. Simulation results demonstrate the achievability of the optimal energy-efficient rate pair within the capacity region, and provide the trade-off for energy efficiency, fairness and maximum sum-rate.
Zoha A, Imran MA, Gluhak A, Nati M (2013) A Comparison of Generative and Discriminative Appliance Recognition Models for Load Monitoring, 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013) 51 IOP PUBLISHING LTD
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
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.
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.
This letter addresses energy-efficient design in multi-user, single-carrier uplink channels by employing multiple decoding policies. The comparison metric used in this study is based on average energy efficiency contours, where an optimal rate vector is obtained based on four system targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. The transmit power function is approximated using Taylor series expansion, with simulation results demonstrating the achievability of the optimal rate vector, and negligible performance difference in employing this approximation.
Wang D, Imran MA (2006) Blind Minimum Mean Squared Error (MMSE) Multiuser Detection with Reliable Subspace Estimation (RSE), Proc. International Conference on Wireless and Mobile Communications ICWMC ?06
Desset C, Debaillie B, Giannini V, Fehske A, Richter F, Klessig H, Auer G, Holtkamp H, Wajda W, Ambrosy A, Blume O, Sabella D, Gonzalez MJ, Gódor I, Olsson M, Imran MA (2012) Flexible power modeling of LTE base stations, IEEE Wireless Communications and Networking Conference, WCNC pp. 2858-2862
With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters. © 2012 IEEE.
Imran, Muhammad A (2009) Multi User Cooperative Transmission techniques for OFDMA Multi-hop Cellular Networks,
Héliot F, Imran MA, Tafazolli R (2011) On the Energy Efficiency Gain of MIMO Communication under Various Power Consumption Models,
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
Qi Y, OLSSON M, Imran M (2012) Integration Strategy of
EARTH Energy Efficiency Enablers,
The overall target of the EARTH project is to reduce the power consumption of mobile broadband networks by 50%. For this, solutions acting all the way from components in the base stations, link level improvements, as well as radio network level concepts are developed. This paper presents a strategy for how these energy efficiency enablers can be integrated into an overall solution. The energy efficiency enablers are structured according to their time scale of operation, and mapped to the most suitable application scenarios.
Imran MA, Chatzinotas S, Katranaras E, Kaltakis D, Tzaras C (2006) Book of assumptions and known results for the fundamental limits of wireless networks,
Imran MA, Imran A, Onireti O (2013) Participatory sensing as an enabler for self-organisation in future cellular networks, 1ST INTERNATIONAL CONFERENCE ON SENSING FOR INDUSTRY, CONTROL, COMMUNICATIONS, & SECURITY TECHNOLOGIES (ICSICCST 2013) 51 IOP PUBLISHING LTD
Ul Mustafa HA, Imran MA, Shakir MZ, Imran A, Tafazolli R (2015) Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks, IEEE COMMUNICATIONS SURVEYS AND TUTORIALS 18 (1) pp. 419-445 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Heliot F, Imran MA, Tafazolli R (2011) Energy Efficiency Analysis of Idealized Coordinated Multi-Point Communication System, IEEE Vehicular technology Conference
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.
In this paper we analyse the performance of a
relay based UMTS system in an urban environment using
multiple hops on multiple frequency bands. Measurement
based path loss, fading and shadowing models are used in
the Manhattan grid deployment scenario. Both uplink and
downlink operations of the cellular system are considered
at the same time. Two hop communication links over the
uplink and downlink are operated at four non-overlapping
spectrum bands in order to minimise interference. This results
in several possible frequency schemes. Power solutions
are derived analytically for the selected frequency schemes.
The system performance is evaluated both by simulation and
analysis and improvement by employing relays is shown.
Qi Y, Imran M, Tafazolli R (2012) Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-forward Systems,
While many studies have concentrated on providing theoretical analysis for the relay assisted compress-and-forward systems little effort has yet been made to the construction and evaluation of a practical system. In this paper a practical CF system incorporating an error-resilient multilevel Slepian-Wolf decoder is introduced and a novel iterative processing structure which allows information exchanging between the Slepian-Wolf decoder and the forward error correction decoder of the main source message is proposed. In addition, a new quantization scheme is incorporated as well to avoid the complexity of the reconstruction of the relay signal at the final decoder of the destination. The results demonstrate that the iterative structure not only reduces the decoding loss of the Slepian-Wolf decoder, it also improves the decoding performance of the main message from the source.
Chatzinotas S, Imran M, Hoshyar R, Otterston B (2010) Multicell LMMSE Filtering Capacity under Correlated Multiple BS Antennas, Proc. IEEE VTC Fall 2010
Kakitani MT, Brante G, Souza RD, Imran MA (2013) Downlink energy efficiency analysis of some multiple antenna systems, IEEE Vehicular Technology Conference
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.
In this paper we extend the analysis of two-receiver broadcast channels with random parameters to the three-receivers case. Specifically we base our work on Nair and El Gamal's results for the three-receiver discrete memoryless multilevel broadcast channel and assume that state information is available non-causally at the transmitter. We provide an achievable rate region for this setting and acknowledge its importance in the study of multiuser cognitive radio configurations.
Beside the well-established spectral-efficiency (SE), energy-efficiency (EE) is currently becoming an important performance evaluation metric, which in turn makes the EE-SE trade-off as a prominent criterion for efficiently designing future communication systems. In this letter, we propose a very tight closed-form approximation (CFA) of this trade-off over the single-input single-output (SISO) Rayleigh flat fading channel. We first derive an improved approximation of the SISO ergodic capacity by means of a parametric function and then utilize it for obtaining our novel EE-SE trade-off CFA, which is also generalized for the symmetric multi-input multi-output channel. We compare our CFA with existing CFAs and show its improved accuracy in comparison with the latter.
Auer G, Giannini V, Godor I, Blume O, Fehske A, Rubio J, Frenger P, Olsson M, Sabella D, Gonzalez M, Imran MA, Desset C (2012) How much energy is needed to run a wireless network, In: Hossain E, Bhargava VK, Fettweis GP (eds.), Green Radio Communication Networks
Cambridge University Press
Presenting state-of-the-art research on green radio communications and networking technology by leaders in the field, this book is invaluable for researchers and professionals working in wireless communication.
Kakitani MT, Brante G, Souza RD, Imran MA (2012) Energy efficiency of amplify-and-forward, repetition coding and parallel coding in short range communications, 2012 35th International Conference on Telecommunications and Signal Processing, TSP 2012 - Proceedings pp. 212-216
In this paper we exploit cooperative relaying for energy savings in narrowband short range communication scenarios. The nodes can operate under cooperative decode-and-forward with repetition coding (RC) or with parallel coding (PC), and cooperative amplify-and-forward (AF) protocols. The system is constrained by maximum packet loss and end-to-end throughput requirements. Our results show that, when the relay is closer to the source, AF and RC present similar performance in terms of energy consumption, while PC significantly outperforms the other schemes. On the other hand, when the relay is near the destination, AF offers the best efficiency. © 2012 IEEE.
Imran A, Yaacoub E, Imran MA, Tafazolli R (2012) Distributed Load Balancing through Self Organisation of cell size in cellular systems, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC pp. 1114-1119
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.
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.
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.
The main challenge for a cognitive radio is to detect the existence of primary users reliably in order to minimise the interference to licensed communications. Hence, spectrum sensing is a most important requirement of a cognitive radio. However, due to the channel uncertainties, local observations are not reliable and collaboration among users is required. Selection of fusion rule at a common receiver has a direct impact on the overall spectrum sensing performance. In this paper, optimisation of collaborative spectrum sensing in terms of optimum decision fusion is studied for hard and soft decision combining. It is concluded that for optimum fusion, the fusion centre must incorporate signal-to-noise ratio values of cognitive users and the channel conditions. A genetic algorithm-based weighted optimisation strategy is presented for the case of soft decision combining. Numerical results show that the proposed optimised collaborative spectrum sensing schemes give better spectrum sensing performance.
Saeed A, Katranaras E, Dianati M, Imran MA (2015) Control and Data Channel Resource Allocation in OFDMA Heterogeneous Networks, JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY 85 (2) pp. 183-199 SPRINGER
Rayel OK, Brante G, Rebelatto JL, Souza RD, Imran MA (2014) Energy efficiency-spectral efficiency trade-off of transmit antenna selection, IEEE Transactions on Communications 62 (12) pp. 4293-4303
© 2014 IEEE.We investigate the energy efficiency-spectral efficiency (EE-SE) trade-off of transmit antenna selection/maximum ratio combining (TAS) scheme. A realistic power consumption model (PCM) is considered, and it is shown that using TAS can provide significant energy savings when compared to multiple-input multiple-output (MIMO) in the low to medium SE region, regardless the number of antennas, as well as outperform transmit beamforming scheme (MRT) for the entire SE range. For a fixed number of receive antennas, our results also show that the EE gain of TAS over MIMO becomes even greater as the number of transmit antennas increases. The optimal value of SE that maximizes the EE is obtained analytically, and confirmed by numerical results. Moreover, the influence of receiver correlation is also evaluated and it is shown that considering a non-realistic PCM can lead to mistakes when comparing TAS and MIMO.
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%.
In this paper, using stochastic geometry, we investigate the average energy efficiency (AEE) of the user terminal (UT) in the uplink of a two-tier heterogeneous network (HetNet), where the two tiers are operated on separate carrier frequencies. In such a deployment, a typical UT must periodically perform inter-frequency small cell discovery (ISCD) process in order to discover small cells in its neighborhood and benefit from the high data rate and traffic offloading opportunity that small cells present. We assume that the base stations (BSs) of each tier and UTs are randomly located and we derive the average ergodic rate and UT power consumption, which are later used for our AEE evaluation. The AEE incorporates the percentage of time a typical UT missed small cell offloading opportunity as a result of the periodicity of the ISCD process. In addition to this, the additional power consumed by the UT due to the ISCD measurement is also included. Moreover, we derive the optimal ISCD periodicity based on the UT?s average energy consumption (AEC) and AEE. Our results reveal that ISCD periodicity must be selected with the objective of either minimizing UT?s AEC or maximizing UT?s AEE.
In this paper, we investigate the optimal inter- frequency small cell discovery (ISCD) periodicity for small cells deployed on carrier frequency other than that of the serving macro cell. We consider that the small cells and user terminals (UTs) positions are modeled according to a homogeneous Poisson Point Process (PPP). We utilize polynomial curve fitting to approximate the percentage of time the typical UT misses small cell offloading opportunity, for a fixed small cell density and fixed UT speed. We then derive analytically, the optimal ISCD periodicity that minimizes the average UT energy consumption (EC). Furthermore, we also derive the optimal ISCD periodicity that maximizes the average energy efficiency (EE), i.e. bit- per-joule capacity. Results show that the EC optimal ISCD periodicity always exceeds the EE optimal ISCD periodicity, with the exception of when the average ergodic rate in both tiers are equal, in which the optimal ISCD periodicity in both cases also becomes equal.
Auer G, Giannini V, Desset C, Gódor I, Skillermark P, Olsson M, Imran Muhammad, Sabella D, Gonzalez MJ, Blume O, Fehske A (2011) How much energy is needed to run a wireless network?, IEEE Wireless Communications 18 (5) pp. 40-49
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.
The discrete cosine transform (DCT) based multicarrier system is regarded as one of the complementary multicarrier transmission techniques for 5th Generation (5G) applications in near future. By employing cosine basis as orthogonal functions for multiplexing each real-valued symbol with symbol period of T , it is able to reduce the minimum orthogonal frequency spacing to 1/(2T ) Hz, which is only half of that compared to discrete Fourier transform (DFT) based multicarrier systems. Critical to the optimal DCT-based system design that achieves interference-free single-tap equalization, not only both prefix and suffix are needed as symmetric extension of information block, but also a so-called front-end pre-filter is necessarily introduced at the receiver side. Since the pre-filtering process is essentially a time reversed convolution for continuous inputs, the output signal-to-noise ratio (SNR) for each subcarrier after filtering is enhanced. In this paper, the impact of pre-filtering on the system performance is analyzed in terms of ergodic output SNR per subcarrier. This is followed by reformulated detection criterion where such filtering process is taken into consideration. Numerical results show that under modified detection criteria, the proposed detection algorithms improve the overall bit error rate (BER) performance effectively.
The increasing demand for data and multimedia services, as well as the ubiquitous nature of the current generation of mobile devices have resulted in continuous network upgrades to support an ever-increasing number of users. Given that wireless communication systems rely on radiofrequency waves, the electromagnetic (EM) emissions from these systems are increasingly becoming a concern, especially in terms of adverse health effects. In order to address these concerns, we propose a novel resource allocation scheme for minimizing the EM emission of users in the uplink of multicell OFDM systems, while ensuring quality of service. Our scheme is based on the assumption that long-term channel state information of all the users in the network is available. A new multicell user grouping that uses the received interference powers of the users of different sectors is proposed. Furthermore, we propose two power allocation algorithms to minimize EM emission. The first power allocation algorithm performs multicell iterative optimization to obtain the transmit powers of each user in the system. On the other hand, our second power allocation algorithm uses the average channel gains of the users of different sectors to obtain an approximation of the transmit power of each user without multicell iterative optimization. As a result, this approach has a reduced complexity when compared to our first power allocation algorithm. Simulation results show that our scheme reduces EM emission by up to 70% when compared to a single cell EM emission aware scheme and by over 3 to 4 orders of magnitude when compared to spectral efficiency maximization schemes.
In this paper, a novel low-complexity and spectrally efficient modulation scheme for visible light communication (VLC) is proposed. Our new spatial quadrature modulation (SQM) is designed to efficiently adapt traditional complex modulation schemes to VLC; i.e. converting multi-level quadrature amplitude modulation (M-QAM), to real-unipolar symbols, making it suitable for transmission over light intensity. The proposed SQM relies on the spatial domain to convey the orthogonality and polarity of the complex signals, rather than mapping bits to symbol as in existing spatial modulation (SM) schemes. The detailed symbol error analysis of SQM is derived and the derivation is validated with link level simulation results. Using simulation and derived results, we also provide a performance comparison between the proposed SQM and SM. Simulation results demonstrate that SQM could achieve a better symbol error rate (SER) and/or data rate performance compared to the state of the art in SM; for instance a Eb/No gain of at least 5 dB at a SER of 10 4.
Network performance optimization is among the most important tasks within the area of wireless communication networks. In a Self- Organizing Network (SON) with the capability of adaptively changing parameters of a network, the optimization tasks are more feasible than static networks. Yet, with an increase of OPEX and CAPEX in new generation telecommunication networks, the optimization tasks are inevitable. In this paper, it is proven that the similarity among target and network parameters can produce lower Uncertainty Entropy (UEN) in a self-organizing system as a higher degree of organizing is gained. The optimization task is carried out with the Adaptive Simulated Annealing method, which is enhanced with a Similarity Measure (SM) in the proposed approach (EASA). The Markov model of EASA is provided to assess the proposed approach. We also show a higher performance through a simulation, based on a scenario in LTE network.
Internet has shown itself to be a catalyst for economic growth and social equity but its potency is thwarted by the fact that the Internet is off limits for the vast majority of human beings. Mobile phones?the fastest growing technology in the world that now reaches around 80% of humanity?can enable universal Internet access if it can resolve coverage problems that have historically plagued previous cellular architectures (2G, 3G, and 4G). These conventional architectures have not been able to sustain universal service provisioning since these architectures depend on having enough users per cell for their economic viability and thus are not well suited to rural areas (which are by definition sparsely populated). The new generation of mobile cellular technology (5G), currently in a formative phase and expected to be finalized around 2020, is aimed at orders of magnitude performance enhancement. 5G offers a clean slate to network designers and can be molded into an architecture also amenable to universal Internet provisioning. Keeping in mind the great social benefits of democratizing Internet and connectivity, we believe that the time is ripe for emphasizing universal Internet provisioning as an important goal on the 5G research agenda. In this paper, we investigate the opportunities and challenges in utilizing 5G for global access to the Internet for all (GAIA). We have also identified the major technical issues involved in a 5G-based GAIA solution and have set up a future research agenda by defining open research problems.
Motivated by increased interests in energy efficient
communication systems, the relation between energy efficiency
(EE) and spectral efficiency (SE) for multiple-input multipleoutput
(MIMO) systems is investigated in this paper. To provide
insight into the design of practical MIMO systems, we adopt
a realistic power model, as well as consider both independent
Rayleigh fading and semicorrelated fading channels. We derive
a novel and closed-form upper bound for the system EE as a
function of SE. This upper bound exhibits a great accuracy
for a wide range of SE values, and thus can be utilized for
explicitly assessing the influence of SE on EE, and analytically
addressing the EE optimization problems. Using this tight EE
upper bound, our analysis unfolds two EE optimization issues:
Given the number of transmit and receive antennas, an optimum
value of SE is derived such that the overall EE can be maximized;
Given a specific value of SE, the optimal number of antennas is
derived for maximizing the system EE.
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.
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.
Future cellular systems need to cope with a huge amount of data and diverse service
requirements in a flexible, sustainable, green and efficient way with minimal signalling
overhead. This calls for network densification, a short length wireless link,
efficient and proactive control signalling and the ability to switch off the power consuming
devices when they are not in use. In this direction, the conventional alwayson
service and worst-case design approach has been identified as the main source of
inefficiency, and a paradigm shift towards adaptive and on-demand systems is seen
as a promising solution. However, the conventional radio access network (RAN) architecture
limits the achievable gains due to the tight coupling between network and
data access points, which in turn imposes strict coverage and signalling requirements
irrespective of the spatio-temporal service demand, channel conditions or mobility
Nowadays, system architecture of the fifth generation
(5G) cellular system is becoming of increasing interest.
To reach the ambitious 5G targets, a dense base station (BS)
deployment paradigm is being considered. In this case, the
conventional always-on service approach may not be suitable due
to the linear energy/density relationship when the BSs are always
kept on. This suggests a dynamic on/off BS operation to reduce
the energy consumption. However, this approach may create
coverage holes and the BS activation delay in terms of hardware
transition latency and software reloading could result in service
disruption. To tackle these issues, we propose a predictive BS
activation scheme under the control/data separation architecture
(CDSA). The proposed scheme exploits user context information,
network parameters, BS sleep depth and measurement databases
to send timely predictive activation requests in advance before
the connection is switched to the sleeping BS. An analytical model
is developed and closed-form expressions are provided for the
predictive activation criteria. Analytical and simulation results
show that the proposed scheme achieves a high BS activation
accuracy with low errors w.r.t. the optimum activation time.
The popularity and convergence of wireless communications have resulted in continuous network upgrades in order to support the increasing demand for bandwidth. However, given that wireless communication systems operate on radiofrequency waves, the health effects of electromagnetic emission from these systems are increasingly becoming a concern due to the ubiquity of mobile communication devices. In order to address these concerns, we propose two schemes (offline and online) for minimizing the EM emission of users in the uplink of OFDM systems, while maintaining an acceptable quality of service. We formulate our offline EM reduction scheme as a convex optimization problem and solve it through water-filling. This is based on the assumption that the long-term channel state information of all the users is known. Given that, in practice, long-term channel state information of all the users cannot always be available, we propose our online EM emission reduction scheme, which is based on minimizing the instantaneous transmit energy per bit of each user. Simulation results show that both our proposed schemes significantly minimize the EM emission when compared to the benchmark classic greedy spectral efficiency based scheme and an energy efficiency based scheme. Furthermore, our offline scheme proves to be very robust against channel prediction errors.
Coordinated multi-point (CoMP) is a key feature for mitigating inter-cell interference, improve system throughput and cell edge performance. However, CoMP implementation requires complex beamforming/scheduling design, increased backhaul bandwidth, additional pilot overhead and precise synchronisa-tion. Cooperation needs to be limited to a few cells only due to this imposed overhead and complexity. Hence, small CoMP clusters will need to be formed in the network. In this paper, we ?rst present a self organising, user-centric CoMP clustering algorithm in a control/data plane separation architecture (CDSA), proposed for 5G to maximise spectral ef?ciency (SE) for a given maximum cluster size. We further utilise this clustering algorithm and introduce a novel two-stage re-clustering algorithm to reduce high load on cells in hotspot areas and improve user satisfaction. Stage-1 of the algorithm utilises maximum cluster size metric to introduce additional capacity in the system. A novel re-clustering algorithm is introduced in stage-2 to distribute load from highly loaded cells to neighbouring cells with less load for multi-user (MU) joint transmission (JT) CoMP case. We show that unsatis?ed users due to high load can be signi?cantly reduced with minimal impact on SE.
The hype surrounding the 5G mobile networks is well justified in view of the explosive increase in mobile traffic and the inclusion of massive ?non-human? users that form the internet of things. Advanced radio features such as network densification, cloud radio access networks (C-RAN), and untapped frequency bands jointly succeed in increasing the radio capacity to accommodate the increasing traffic demand. However, a new challenge has arisen: the backhaul (BH), the transport network that connects radio cells to the core network. The BH needs to expand in a timely fashion to reach the fast spreading small cells. Moreover, the realistic BH solutions are unable to provide the unprecedented 5G performance requirements to every cell. To this end, this research addresses the gap between the 5G stipulated BH characteristics and the available BH capabilities. On the other hand, heterogeneity is a leading trait in 5G networks. First, the RAN is heterogeneous since it comprises different cell types, radio access technologies, and architectures. Second, the BH is composed of a mix of different wired and wireless technologies with different limitations. In addition, 5G users have a broader range of capabilities and requirements than any incumbent mobile network. We exploit this trait and develop a novel scheme, termed User-Centric-BH (UCB). The UCB targets the user association mechanism which is traditionally blind to users? needs and BH conditions. The UCB builds on the existing concept of cell range extension (CRE) and proposes multiple-offset factors (CREO) whereby each reflects the cell's joint RAN and BH capability with respect to a defined attribute (e.g., throughput, latency, resilience, etc.). In parallel, users associate different weights to different attributes, hence, they can make a user-centric decision. The proposed scheme significantly outperforms the state-of-the-art and unlocks the BH bottleneck by availing existing but misused resources to users in need.
Due to the use of an appropriately designed pulse
shaping prototype filter, filter bank multicarrier (FBMC) system
can achieve low out of band (OoB) emissions and is also robust
to the channel and synchronization errors. However, it comes at
a cost of long filter tails which may reduce the spectral efficiency
significantly when the block size is small. Filter output truncation
(FOT) can reduce the overhead by discarding the filter tails but
may also significantly destroy the orthogonality of FBMC system,
by introducing inter carrier interference (ICI) and inter symbol
interference (ISI) terms in the received signal. As a result, the
signal to interference ratio (SIR) is degraded. In addition, the
presence of intrinsic interference terms in FBMC also proves
to be an obstacle in combining multiple input multiple output
(MIMO) with FBMC. In this paper, we present a theoretical
analysis on the effect of FOT in an MIMO-FBMC system. First,
we derive the matrix model of MIMO-FBMC system which is
subsequently used to analyze the impact of finite filter length and
FOT on the system performance. The analysis reveals that FOT
can avoid the overhead in time domain but also introduces extra
interference in the received symbols. To combat the interference
terms, we then propose a compensation algorithm that considers
odd and even overlapping factors as two separate cases, where
the signals are interfered by the truncation in different ways. The
general form of the compensation algorithm can compensate all
the symbols in a MIMO-FBMC block and can improve the SIR
values of each symbol for better detection at the receiver. It is
also shown that the proposed algorithm requires no overhead
and can still achieve a comparable BER performance to the case
with no filter truncation.
Network densification with small cell deployment
is being considered as one of the dominant themes in the
fifth generation (5G) cellular system. Despite the capacity gains,
such deployment scenarios raise several challenges from mobility
management perspective. The small cell size, which implies a
small cell residence time, will increase the handover (HO) rate
dramatically. Consequently, the HO latency will become a critical
consideration in the 5G era. The latter requires an intelligent, fast
and light-weight HO procedure with minimal signalling overhead.
In this direction, we propose a memory-full context-aware HO
scheme with mobility prediction to achieve the aforementioned
objectives. We consider a dual connectivity radio access network
architecture with logical separation between control and data
planes because it offers relaxed constraints in implementing the
predictive approaches. The proposed scheme predicts future HO
events along with the expected HO time by combining radio
frequency performance to physical proximity along with the user
context in terms of speed, direction and HO history. To minimise
the processing and the storage requirements whilst improving
the prediction performance, a user-specific prediction triggering
threshold is proposed. The prediction outcome is utilised to
perform advance HO signalling whilst suspending the periodic
transmission of measurement reports. Analytical and simulation
results show that the proposed scheme provides promising gains
over the conventional approach.
Video data claims a significant portion of global mobile data communications, currently standing at 55%. This demand outburst has been due to exceptional display technologies, on-demand video, gaming and live video streaming, to name a few. Despite the massive data rates supported by modern mobile communication technologies, video data is starting to overload mobile networks. This is particularly true in links with low connectivity, where repeat requests flood the system. As solutions for this inevitable demand growth, in addition to efficient video compression methods, more video data error resilience must be sought. One reason video traffic is vulnerable to channel errors is the method it is treated at transmission; treatment as any other generic data type. Video is a unique data type because its ultimate user is not a machine but a human, and the contents within the data are interdependent on each other. Based on its properties, video compression, transmission methodology, and the decoding function must be adapted. By considering video communication as a collaborative effort of these three functions, error resilience can be effectively implemented. Analysis of radio resources available for data transmission in a multipath fading channel reveals that some resources are more robust than others. In the first contribution of this thesis, this characteristic is utilised to impose more resilience to more sensitive data within the video. Reliable means of forecasting the relative robustness of each radio resource are designed. Criteria for identifying the sensitivity of different video data segments are formulated. Finally, a technology is presented to map data to radio resources such that maximum received video quality is achieved. While the focus of the first contribution was on harmonising the transmission methods with the features of the compressed video payload, the second contribution takes an alternative route to error resilience by focusing on the decoder. The compressed video payload entails some identifiable syntax elements, some of which follow a predictable pattern. This feature is exploited to improve error recovery at an iterative turbo decoder. An algorithm to identify the video frame boundaries in corrupted compressed sequences is formulated, along with algorithms to deduce the correct values for selected fields in the compressed stream. Modifying the turbo extrinsic information using these corrections act as reinforcements in the turbo decoding iterative process. Most communication protocols transmit data as blocks in an ordered sequence and await the acknowledgement of the receiver to determine the next block to be transmitted. This gives rise to latency issues and the overloading of the network when the link connectivity is poor. A solution is presented for video data in the final contribution, where the concept of a digital fountain is hired. A two-dimensional forward error correction strategy is introduced for a digital fountain, where first, the video payload is LDPC encoded and then turbo encoded. A joint decoding strategy is designed between the turbo decoder and the LDPC decoder to recover the video data in an iterative manner. Taken together, these contributions are solutions for the video data burden on mobile networks; solutions which reduce the necessity for re-transmissions. The presented error resilience techniques are updates to the existing transmission methodology and the decoding function. They explore a new paradigm of improving coverage and channel throughput.
Regarded as one of the most promising transmission
techniques for future wireless communications, the discrete cosine
transform (DCT) based multicarrier modulation (MCM) system
employs cosine basis as orthogonal functions for real-modulated
symbols multiplexing, by which the minimum orthogonal frequency
spacing can be reduced by half compared to discrete
Fourier transform (DFT) based one. With a time-reversed prefilter
employed at the front of the receiver, interference-free
one-tap equalization is achievable for the DCT-based systems.
However, due to the correlated pre-filtering operation in time
domain, the signal-to-noise ratio (SNR) is enhanced as a result
at the output. This leads to reformulated detection criterion to
compensate for such filtering effect, rendering minimum-meansquare-
error (MMSE) and maximum likelihood (ML) detections
applicable to the DCT-based multicarrier system. In this paper,
following on the pre-filtering based DCT-MCM model that build
in the literature work, we extend the overall system by considering
both transceiver perfections and imperfections, where
frequency offset, time offset and insufficient guard sequence are
included. In the presence of those imperfection errors, the DCTMCM
systems are analysed in terms of desired signal power,
inter-carrier interference (ICI) and inter-symbol interference
(ISI). Thereafter, new detection algorithms based on zero forcing
(ZF) iterative results are proposed to mitigate the imperfection
effect. Numerical results show that the theoretical analysis match
the simulation results, and the proposed iterative detection
algorithms are able to improve the overall system performance
The spatially-incoherent radiators in visible light
communication (VLC) constrain the optical carrier to be only
driven by a real electrical sub-carrier, which cannot be quadrature
modulated as in classic RF-based systems. This restriction,
in turn, severely limits the transmission throughput of VLC
systems. To overcome this technical challenge, we propose a
novel coherent transmission scheme for VLC, in which the
optical carrier is only treated as a purely amplitude-modulated
carrier capable of transmitting two-dimensional (2D) symbols
(e.g. quadrature modulated symbols). The ability of our new
coherent transmission scheme to transmit 2D symbols is validated
through analytical symbol error rate derivation and Matlab
simulations. Results show that our scheme can improve both
the spectral and energy efficiency of VLC systems, i.e. by either
doubling the spectral efficiency or achieving more than 45%
energy efficiency improvement, when compared to its existing
As an advanced non-orthogonal multiple access
(NOMA) technique, the low density signature (LDS) has never
been used in filter bank multicarrier (FBMC) systems. In this
paper, we model a low density weight matrix (LDWM) to utilize
the intrinsic interference in FBMC systems when single-tap
equalization is employed, and propose a LDS-FBMC scheme
which applies LDS to FBMC signals. In addition, a joint sparse
graph for FBMC named JSG-FBMC is proposed to combine
single graphs of LDS, LDWM and low density parity-check
(LDPC) codes which respectively represent techniques of NOMA,
multicarrier modulation and channel coding. By employing the
message passing algorithm (MPA), a joint receiver performing
detection and decoding simultaneously on the joint sparse graph
is designed. Extrinsic information transfer (EXIT) charts and
construction guidelines of the joint sparse graph are studied.
Simulations show the superiority of JSG-FBMC to state-of-theart
techniques such as OFDM, FBMC, LDS-OFDM, LDS-FBMC
and turbo structured LDS-FBMC.
Hybrid networks consisting of both millimeter
wave (mmWave) and microwave (¼W) capabilities are
strongly contested for next generation cellular communications.
A similar avenue of current research is deviceto-
device (D2D) communications, where users establish
direct links with each other rather than using central base
stations (BSs). However, a hybrid network, where D2D
transmissions coexist, requires special attention in terms
of efficient resource allocation. This paper investigates
dynamic resource sharing between network entities in a
downlink (DL) transmission scheme to maximize energy
efficiency (EE) of the cellular users (CUs) served by either
(¼W) macrocells or mmWave small cells, while maintaining
a minimum quality-of-service (QoS) for the D2D
users. To address this problem, firstly a self-adaptive power
control mechanism for the D2D pairs is formulated, subject
to an interference threshold for the CUs while satisfying
their minimum QoS level. Subsequently, a EE optimization
problem, which is aimed at maximizing the EE for both
CUs and D2D pairs, has been solved. Simulation results
demonstrate the effectiveness of our proposed algorithm,
which studies the inherent tradeoffs between system EE,
system sum rate and outage probability for various QoS
levels and varying density of D2D pairs and CUs.
Ultra densification in heterogeneous networks
(HetNets) and the advent of millimeter wave (mmWave) technology
for fifth generation (5G) networks have led the researchers
to redesign the existing resource management techniques. A
salient feature of this activity is to accentuate the importance
of computationally intelligent (CI) resource allocation schemes
offering less complexity and overhead. This paper overviews the
existing literature on resource management in mmWave-based
HetNets with a special emphasis on CI techniques and further
proposes frameworks that ensure quality-of-service requirements
for all network entities. More specifically, HetNets with mmWavebased
small cells pose different challenges as compared to an allmicrowave-
based system. Similarly, various modes of small cell
access policies and operations of base stations in dual mode, i.e.,
operating both mmWave and microwave links simultaneously,
offer unique challenges to resource allocation. Furthermore, the
use of multi-slope path loss models becomes inevitable for analysis
owing to irregular cell patterns and blocking characteristics of
mmWave communications. This paper amalgamates the unique
challenges posed because of the aforementioned recent developments
and proposes various CI-based techniques including game
theory and optimization routines to perform efficient resource
The design of efficient wireless fronthaul connections for future heterogeneous networks incorporating emerging paradigms such as cloud radio access network (C-RAN) has become a challenging task that requires the most effective utilization of fronthaul network resources. In this paper, we propose to use distributed compression to reduce the fronthaul traffic in uplink Coordinated Multi-Point (CoMP) for C-RAN. Unlike the conventional approach where each coordinating point quantizes and forwards its own observation to the processing centre, these observations are compressed before forwarding. At the processing centre, the decompression of the observations and the decoding of the user message are conducted in a successive manner. The essence of this approach is the optimization of the distributed compression using an iterative algorithm to achieve maximal user rate with a given fronthaul rate. In other words, for a target user rate the generated fronthaul traffic is minimized. Moreover, joint decompression and decoding is studied and an iterative optimization algorithm is devised accordingly. Finally, the analysis is extended to multi-user case and our results reveal that, in both dense and ultra-dense urban deployment scenarios, the usage of distributed compression can efficiently reduce the required fronthaul rate and a further reduction is obtained with joint operation.
Non-orthogonal multiple access (NOMA) is an emerging technology for future cellular systems in order to accommodate more users via non-orthogonal resource allocation, especially when the number of users/devices exceeds the available degrees of freedom, resulting in an overloaded condition. To date, low density signature (LDS) and sparse code multiple access (SCMA) are two promising NOMA techniques. However, research in this area is still in its infancy and there are still several open issues in the LDS/SCMA transceiver design. This thesis aims to address some of these challenges. The contributions are summarized as follows.
1:-LDS-OFDM and low density parity check (LDPC) codes both can be represented by a bipartite graph. Inspired by their similar structure, we construct a joint sparse graph combining the single graphs of LDS-OFDM and LDPC codes, namely joint sparse graph for OFDM (JSG-OFDM). A joint detection and decoding scenario is proposed using message passing algorithm (MPA). Design guidelines for the joint sparse graph are derived through extrinsic information transfer (EXIT) chart analysis. Simulation results show that the JSG-OFDM outperforms existing techniques such as GO-MC-CDMA, LDS-OFDM and turbo structured LDS-OFDM.
2:-Due to the higher power and spectral efficiency, the filter-bank multi-carrier (FBMC) technique is a promising alternative to OFDM. We use a low density graph to model the weight matrix of intrinsic interference in the isotropic orthogonal transform algorithm (IOTA) filtered FBMC system. In addition, such graph is combined with LDS and LDPC codes to form a joint sparse graph for FBMC-IOTA (JSG-IOTA). Based on MPA, a joint detection and decoding scheme is designed for JSG-IOTA, and the joint sparse graph is optimized by EXIT chart analysis. Numerical results show the superiority of JSG-IOTA to conventional techniques.
3:-In SCMA, the processes of bit to symbol mapping and LDS spreading are combined together. We investigate multi-dimensional SCMA codebooks, and the design rules are derived to maximize the constellation shaping gain. Moreover, we propose to construct SCMA codebooks by copy-and-permute operation on protographs and three-dimensional (3D) constellation shaping. Simulation results show that SCMA outperforms LDS with high-order constellations, and the proposed optimization methods can further improve the SCMA performance.
Sparse code multiple access (SCMA) is a promising
air interface candidate technique for next generation mobile
networks, especially for massive machine type communications
(mMTC). In this paper, we design a LDPC coded SCMA detector
by combining the sparse graphs of LDPC and SCMA into
one joint sparse graph (JSG). In our proposed scheme, SCMA
sparse graph (SSG) defined by small size indicator matrix is
utilized to construct the JSG, which is termed as sub-graph
based joint sparse graph of SCMA (SG-JSG-SCMA). In this
paper, we first study the binary-LDPC (B-LDPC) coded SGJSG-
SCMA system. To combine the SCMA variable node (SVN)
and LDPC variable node (LVN) into one joint variable node
(JVN), a non-binary LDPC (NB-LDPC) coded SG-JSG-SCMA
is also proposed. Furthermore, to reduce the complexity of NBLDPC
coded SG-JSG-SCMA, a joint trellis representation (JTR)
is introduced to represent the search space of NB-LDPC coded
SG-JSG-SCMA. Based on JTR, a low complexity joint trellis
based detection and decoding (JTDD) algorithm is proposed to
reduce the computational complexity of NB-LDPC coded SGJSG-
SCMA system. According to the simulation results, SG-JSGSCMA
brings significant performance improvement compare to
the conventional receiver using the disjoint approach, and it can
also outperform a Turbo-structured receiver with comparable
complexity. Moreover, the joint approach also has advantages in
terms of processing latency compare to the Turbo approaches.
Energy efficiency (EE) is gradually becoming one of the key criteria, along with the spectral efficiency (SE), for evaluating communication system performances. However, minimizing the energy-per-bit consumption while maximizing the SE are conflicting objectives and, thus, the main criterion for designing efficient communication systems will become the trade-off between SE and EE. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this EE-SE trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression, which can easily be used for evaluating and comparing the EE-SE trade-off of MIMO communication systems, has been utilized in this paper for analyzing the impact of using multiple antennas on the EE and the EE gain of MIMO in comparison with single-input single-output (SISO) system. Our results indicate that EE can be improved predominantly through receive diversity in the very low-SE regime and that MIMO is far more energy efficient than SISO at high SE over the Rayleigh fading channel.
Filter bank based multicarrier (FBMC) systems are one of the promising waveform candidates to satisfy the requirements of future wireless networks. FBMC employs prototype filters with lower side lobe and faster spectral decay, which enables it to have the advantages of reduced out-of-band energy and theoretically higher spectral efficiency (SE) compared to conventional multicarrier scheme i.e., orthogonal frequency division multiplexing (OFDM). These systems also have the ability to facilitate aggregation of non-adjacent bands to acquire higher bandwidths for data transmission. They also support asynchronous transmissions to reduce signaling overhead to meet the ever increasing demand of high data rate transmission in future wireless networks. In this work, the primary research objective is to address some of the critical challenges in FBMC systems to make it viable for practical applications. To this end, the following contributions are provided in this thesis.
First of all, despite numerous advantages, FBMC systems suffers from long filter tails which may reduce the SE of the system. Filter output truncation (FOT) can reduce this overhead by discarding the filter tails but may also destroy the orthogonality in FBMC system. As a result, the signal to interference ratio (SIR) can be significantly degraded. To address this problem, we first presented a theoretical analysis on the effect of FOT in a multiple input multiple output (MIMO) FBMC system, when assuming that transmitter and receiver have the same number of antennas. We derive the matrix model of MIMO-FBMC system which is subsequently used to analyze the impact of finite filter length and FOT on the system performance. The analysis reveals that FOT can avoid the overhead in time domain but also introduces extra interference in the received symbols. To combat the interference terms, we then propose a compensation algorithm that considers odd and even overlapping factors as two separate cases, where the signals are interfered by the truncation in different ways. A general form of the compensation algorithm is then proposed to compensate all the symbols in a MIMO-FBMC block to improve the SIR values of each symbol for better detection at the receiver.
Secondly, transmission of quadrature modulated symbols using FBMC systems has been an issue due to the self-interference between the transmitted symbols both in the time and frequency domain (so-called intrinsic interference). To address this issue, we propose a novel low complexity interference-free FBMC system with QAM modulation (FBMC/QAM) using filter deconvolution. The proposed method is based on inversion of the prototype filters which completely removes the intrinsic interference at the receiver and allows the use of quadrature modulated signaling. The interference terms in FBMC/QAM with and without the proposed system are analyzed and compared in terms of mean square error (MSE). It is shown with theoretical and simulation results that the proposed method cancels the intrinsic interference and improves the output signal to interference plus noise ratio (SINR) at the expense of slight enhancement of residual interferences caused by multipath channel. The complexity of the proposed system is also analyzed along with performance evaluation in an asynchronous multi-service scenario. It is shown that the proposed FBMC/QAM system with filter deconvolution outperforms the conventional OFDM system.
Finally, subcarrier index modulation (SIM) a.k.a., index modulation (IM) has recently emerged as a promising concept for spectrum and energy-efficient next generation wireless communications systems due to the excellent trade-offs they offer among error performance, complexity, and SE. Although IM is well studied for OFDM, FBMC with index modulation (FBMC-IM) has not been thoroughly investigated. To address this topic, we shed light on the potential and implementation of IM technique for FBMC system. We first derived a mathematica
Nowadays, dense network deployment is being
considered as one of the effective strategies to meet capacity
and connectivity demands of the fifth generation (5G) cellular
system. Among several challenges, energy consumption will be a
critical consideration in the 5G era. In this direction, base station
on/off operation, i.e., sleep mode, is an effective technique to
mitigate the excessive energy consumption in ultra-dense cellular
networks. However, current implementation of this technique is
unsuitable for dynamic networks with fluctuating traffic profiles
due to coverage constraints, quality-of-service requirements and
hardware switching latency. In this direction, we propose an
energy/load proportional approach for 5G base stations with
control/data plane separation. The proposed approach depends on
a multi-step sleep mode profiling, and predicts the base station
vacation time in advance. Such a prediction enables selecting
the best sleep mode strategy whilst minimizing the effect of
base station activation/reactivation latency, resulting in significant
energy saving gains.
The rapid growth in mobile communications due to the exponential demand for wireless access is causing the distribution and maintenance of cellular networks to become more complex, expensive and time consuming. Lately, extensive research and standardisation work has been focused on the novel paradigm of self-organising network (SON). SON is an automated technology that allows the planning, deployment, operation, optimisation and healing of the network to become faster and easier by reducing the human involvement in network operational tasks, while optimising the network coverage, capacity and quality of service. However, these SON autonomous features cannot be achieved with the current drive test coverage assessment approach due to its lack of automaticity which results in huge delays and cost. Minimization of drive test (MDT) has recently been standardized by 3GPP as a key self- organising network (SON) feature. MDT allows coverage to be estimated at the base station using user equipment (UE) measurement reports with the objective to eliminate the need for drive tests. However, most MDT based coverage estimation methods recently proposed in literature assume that UE position is known at the base station with 100% accuracy, an assumption that does not hold in reality. In this work, we develop a novel and accurate analytical model that allows the quantification of error in MDT based autonomous coverage estimation (ACE) as a function of error in UE as well as base station (user deployed cell) positioning. We first consider a circular cell with an omnidirectional antenna and then we use a three-sectored cell and see how the system is going to be affected by the UE and the base station (user deployed cell) geographical location information errors. Our model also allows characterization of error in ACE as function of standard deviation of shadowing in addition to the path-loss.
The cognitive interference channel extends the classical two-user interference channel to have unidirectional cooperation at the transmitters. In this model, the cognitive transmitter is assumed to have noncausal knowledge of the other transmitter's current message (primary message). This a priori knowledge is used by the cognitive user to accomplish its two main purposes, i.e., to relay the primary message in order to boost the primary user's data rate and to maximise its own data rate by cancelling the interference at its receiver. The cognitive interference channel is well studied in the literature and capacity results are available for the weak and very strong interference regimes, amongst others. A general solution is still elusive. In this thesis we study the capacity region of cognitive structures that are based in their core on the cognitive interference channel but with the aggregate that an additional node is considered, e.g., an additional receiver node, an additional transmitter node or a relay node.
The cognitive broadcast interference channel consists of the cognitive interference channel with an additional receiver. The cognitive side serves either one or two receivers and the interference goes from the cognitive transmitter to the primary receiver only. In this model we provide a general achievable rate region when the cognitive side serves two receivers. We analyse the discrete memoryless channel and show that the region simplifies to existing results in the literature when certain assumptions are made. An achievable rate region for the Gaussian channel is also provided for the case where the cognitive side sends common information to both receivers. When the cognitive side serves only one receiver, we provide an achievable rate region and an outer bound and show the gap graphically.
The cognitive interference channel with a relay consists of the cognitive interference channel with an additional relay node. In this model we show that as in the interference channel with a relay, interference forwarding is also beneficial. We describe analytically achievable rate regions and show the benefits of interference forwarding. We also provide an achievable rate region with generalised interference forwarding, i.e., the relay forwards the intended message and the interference simultaneously, and show that allowing the relay to allocate part of its power to forward interference is beneficial when we are in the strong but not in the very strong interference regime.
The cognitive interference channel with causal unidirectional destination cooperation is formed by transferring the relaying capabilities of the relay node in the previous model to the cognitive receiver and its operation is causal rather than strictly causal. In this model we show that instantaneous amplify and forward is good enough to achieve the capacity region of the Gaussian channel. We derive analytically an inner and outer bounds and show that they coincide for certain values of the antenna gain at the relay in the very strong interference regime. We also analyse the cognitive interference channel with a relay for the case where the relay operates causally. The capacity region is obtained for a special case of very strong interference.
The cognitive multiple access interference channel consists of the cognitive interference channel with an additional cognitive transmitter. In this model the interference goes from the primary user to the cognitive receiver only. The cognitive users form a MAC channel. We show for this scenario that dirty paper coding achieves the capacity region in the Gaussian case. In the analysis we make use of encoding techniques first utilised for the MAC with state available noncausally at the encoder.
Universal filtered multi-carrier (UFMC) systems offer a flexibility of filtering arbitrary number of subcarriers to suppress out of band (OoB) emission, while keeping the orthogonality between subcarriers and robustness to transceiver imperfections. Such properties enable it as a promising candidate waveform for Internet of Things (IoT) communications. However, subband filtering may affect system performance and capacity in a number of ways. In this paper, we first propose the conditions for interference-free one-tap equalization and corresponding signal model in the frequency domain for UFMC system. The impact of subband filtering on the system performance is analyzed in terms of average signal-to-noise ratio (SNR), capacity and bit error rate (BER) and compared with the orthogonal frequency division multiplexing (OFDM) system. This is followed by filter length selection strategies to provide guidelines for system design. Next, by taking carrier frequency offset (CFO), timing offset (TO), insufficient guard interval between symbols and filter tail cutting (TC) into consideration, an analytical system model is established. In addition, a set of optimization criteria in terms of filter length and guard interval/filter TC length subject to various constraints is formulated to maximize the system capacity. Numerical results show that the analytical and corresponding optimal approaches match the simulation results, and the proposed equalization algorithms can significantly improve the BER performance.
The emerging 5G wireless networks will pose extreme requirements such as high throughput and low latency. Caching as a promising technology can effectively decrease latency and provide customized services based on group users behaviour (GUB). In this paper, we carry out the energy efficiency analysis in the cache-enabled hyper cellular networks (HCNs), where the macro cells and small cells (SCs) are deployed heterogeneously with the control and user plane (C/U) split. Benefiting from the assistance of macro cells, a novel access scheme is proposed according to both user interest and fairness of service, where the SCs can turn into semi- sleep mode. Expressions of coverage probability, throughput and energy efficiency (EE) are derived analytically as the functions of key parameters, including the cache ability, search radius and backhaul limitation. Numerical results show that the proposed scheme in HCNs can increase the network coverage probability by more than 200% compared with the single- tier networks. The network EE can be improved by 54% than the nearest access scheme, with larger research radius and higher SC cache capacity under lower traffic load. Our performance study provides insights into the efficient use of cache in the 5G software defined networking (SDN).
With the worldwide evolution of 4G generation and revolution in the information and communications technology(ICT) field to meet the exponential increase of mobile data traffic in the 2020 era, the hybrid satellite and terrestrial network based on the soft defined features is proposed from a perspective of 5G. In this paper, an end-to-end architecture of hybrid satellite and terrestrial network under the control and user Plane (C/U) split concept is studied and the performances are analysed based on stochastic geometry. The relationship between spectral efficiency (SE) and energy efficiency (EE) is investigated, taking consideration of overhead costs, transmission and circuit power, backhaul of gateway (GW), and density of small cells. Numerical results show that, by optimizing the key parameters, the hybrid satellite and terrestrial network can achieve nearly 90% EE gain with only 3% SE loss in relative dense networks, and achieve both higher EE and SE gain (20% and 5% respectively) in sparse networks toward the future 5G green communication networks.
In order to improve the manageability and adaptability of future 5G wireless networks, the software orchestration mechanism, named software defined networking (SDN) with control and user plane (C/U-plane) decoupling, has become one of the most promising key techniques. Based on these features, the hybrid satellite terrestrial network is expected to support flexible and customized resource scheduling for both massive machine-type- communication (MTC) and high-quality multimedia requests while achieving broader global coverage, larger capacity and lower power consumption. In this paper, an end-to-end hybrid satellite terrestrial network is proposed and the performance metrics, e. g., coverage probability, spectral and energy efficiency (SE and EE), are analysed in both sparse networks and ultra-dense networks. The fundamental relationship between SE and EE is investigated, considering the overhead costs, fronthaul of the gateway (GW), density of small cells (SCs) and multiple quality-ofservice (QoS) requirements. Numerical results show that compared with current LTE networks, the hybrid system with C/U split can achieve approximately 40% and 80% EE improvement in sparse and ultra-dense networks respectively, and greatly enhance the coverage. Various resource management schemes, bandwidth allocation methods, and on-off approaches are compared, and the applications of the satellite in future 5G networks with software defined features are proposed.
Over the last decade, the explosive increase in demand of high-data-rate video services and massive access machine type communication (MTC) requests have become the main challenges for the future 5G wireless network. The hybrid satellite terrestrial network based on the control and user plane (C/U) separation concept is expected to support flexible and customized resource scheduling and management toward global ubiquitous networking and unified service architecture. In this paper, centralized and distributed resource management strategies (CRMS and DRMS) are proposed and compared com- prehensively in terms of throughput, power consumption, spectral and energy efficiency (SE and EE) and coverage probability, utilizing the mature stochastic geometry. Numerical results show that, compared with DRMS strategy, the U-plane cooperation between satellite and terrestrial network under CRMS strategy could improve the throughput and EE by nearly 136% and 60% respectively in ultra-sparse networks and greatly enhance the U-plane coverage probability (approximately 77%). Efficient resource management mechanism is suggested for the hybrid network according to the network deployment for the future 5G wireless network.
Evans B, Onireti O, Spathopoulos T, Imran MA (2015) THE ROLE OF SATELLITES IN 5G, 2015 23rd European Signal Processing Conference (EUSIPCO 2015) pp. 2756-2760
Institute of Electrical and Electronics Engineers (IEEE)
The next generation of mobile radio communication systems?so called 5G?will provide some major changes to
those generations to date. The ability to cope with huge
increases in data traffic at reduced latencies and improved
quality of user experience together with major reduction
in energy usage are big challenges. In addition future
systems will need to embody connections to billions of
objects?the so called Internet of Things (IoT) which raise
new challenges. Visions of 5G are now available from
regions across the World and research is ongoing towards
new standards. The consensus is a flatter architecture that
adds a dense network of small cells operating in the millimetre wave bands and which are adaptable and software
controlled. But what place for satellites in such a vision?
The paper examines several potential roles for satellite
including coverage extension, content distribution, providing resilience, improved spectrum utilisation and integrated signalling systems.
This paper surveys the literature relating to the application of machine learning to fault management in cellular networks from an operational perspective. We summarise the main issues as 5G networks evolve, and their implications for fault management. We describe the relevant machine learning techniques through to deep learning, and survey the progress which has been made in their application, based on the building blocks of a typical fault management system. We review recent work to develop the abilities of deep learning systems to explain and justify their recommendations to network operators. We discuss forthcoming changes in network architecture which are likely to impact fault management and offer a vision of how fault management systems can exploit deep learning in the future. We identify a series of research topics for further study in order to achieve this.
This paper proposes a novel unipolar transceiver for visible light communication (VLC) by using
orthogonal waveforms. The main advantage of our proposed scheme over most of the existing unipolar
schemes in the literature is that the polarity of the real-valued orthogonal frequency division multiplexing
(OFDM) sample determines the pulse shape of the continuous-time signal and thus, the unipolar
conversion is performed directly in the analog instead of the digital domain. Therefore, our proposed
scheme does not require any direct current (DC) biasing or clipping as it is the case with existing schemes
in the literature. The bit error rate (BER) performance of our proposed scheme is analytically derived
and its accuracy is verified by using Matlab simulations. Simulation results also substantiate the potential
performance gains of our proposed scheme against the state-of-the-art OFDM-based systems in VLC; it
indicates that the absence of DC shift and clipping in our scheme supports more reliable communication
and outperforms the asymmetrically clipped optical-OFDM (ACO-OFDM), DC optical-OFDM (DCOOFDM)
and unipolar-OFDM (U-OFDM) schemes. For instance, our scheme outperforms ACO-OFDM
by at least 3 dB (in terms of signal to noise ratio) at a target BER of 10
A clear understanding of mixed-numerology signals multiplexing and isolation in the physical layer is of importance to enable spectrum efficient radio access network (RAN) slicing, where the available access resource is divided into slices to cater to services/users with optimal individual design. In this paper, a RAN slicing framework is proposed and systematically analyzed from a physical layer perspective. According to the baseband and radio frequency (RF) configurations imparities among slices, we categorize four scenarios and elaborate on the numerology relationships of slices configurations. By considering the most generic scenario, system models are established for both uplink and downlink transmissions. Besides, a low out of band emission (OoBE) waveform is implemented in the system for the sake of signal isolation and inter-service/slice-band-interference (ISBI) mitigation. We propose two theorems as the basis of algorithms design in the established system, which generalize the original circular convolution property of discrete Fourier transform (DFT). Moreover, ISBI cancellation algorithms are proposed based on a collaboration detection scheme, where joint slices signal models are implemented. The framework proposed in the paper establishes a foundation to underpin extremely diverse user cases in 5G that implement on a common infrastructure.