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Atta ul Quddus


Lecturer in Wireless Communications

Biography

Biography

Dr. Atta ul Quddus received the MSc degree in Satellite Communications and PhD degree in Mobile Cellular Communications, both from University of Surrey UK in 2000 and 2005, respectively. He is currently a Lecturer in Wireless Communications in the Institute of Communications (ICS), Department of Electrical and Electronic Engineering, University of Surrey UK. During his research career, he has led several successful UK national and international research projects (EU FP7 BeFEMTO, iJOIN), and currently is an active part in the 5GIC research programme of ICS.Dr. Quddus is also principal developer of a professional link-level PHY simulator which has been used in industry by both cellular network operators and chip manufacturers over the years. In 2004, he won the Centre for Communications Systems (CCSR) Research Excellence Prize sponsored by Vodafone for his research on Adaptive Filtering algorithms. His current research interests include Machine Type Communication, Full Duplexing systems, Cloud Radio Access Networks, and Device to Device Communications.

My publications

Publications

Pateromichelakis E, Shariat M, Ul Quddus A, Tafazolli R (2011) On the analysis of co-tier interference in femtocells, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC pp. 122-126
This paper quantifies the impact of co-tier interference in femtocells (i.e. inter-cell interference arising from other neighbouring femtocells) through a semi-analytical approach concluding that without interference mitigation techniques, QoS in the form of acceptable outage probability is not achievable in scenarios representing medium to worst cases of interference. Results obtained from semi-analytical approach are also compared against Monte Carlo simulations for evaluation purposes. Subsequently, some important radio access parameters and deployment configurations, such as path loss model, shadowing, wall penetration loss, location of femtocells and user distribution are further examined as key elements that can potentially affect, positively or negatively, the femtocell-to-femtocell interference in a multi-femtocell deployment. The results can be used as guidelines in the deployments of femtocells. © 2011 IEEE.
Quddus AU, Tafazolli R (2004) SIR estimation on common pilot channel with the knowledge of data to pilot power ratio for closed loop power control in WCDMA FDD downlink, VTC2004-FALL: 2004 IEEE 60TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-7 pp. 865-869 IEEE
Imran A, Imran MA, Atta-ul-Quddus, Tafazolli R (2011) Distributed Spectral Efficiency Optimization At Hotspots Through Self Organisation of BS Tilts, 2011 IEEE GLOBECOM WORKSHOPS (GC WKSHPS) pp. 570-574 IEEE
Ijaz A, Zhang L, Grau M, Mohamed A, Vural S, Quddus A, Imran M, Foh C, Tafazolli R (2016) Enabling Massive IoT in 5G and Beyond Systems: PHY Radio Frame Design Considerations, IEEE Access 4 pp. 3322-3339 IEEE Access
The parameters of Physical (PHY) layer radio frame for 5th Generation (5G) mobile cellular systems are expected to be flexibly configured to cope with diverse requirements of different scenarios and services. This paper presents a frame structure and design which is specifically targeting Internet of Things (IoT) provision in 5G wireless communication systems. We design a suitable radio numerology to support the typical characteristics, that is, massive connection density and small and bursty packet transmissions with the constraint of low cost and low complexity operation of IoT devices. We also elaborate on the design of parameters for Random Access Channel (RACH) enabling massive connection requests by IoT devices to support the required connection density. The proposed design is validated by link level simulation results to show that the proposed numerology can cope with transceiver imperfections and channel impairments. Furthermore, results are also presented to show the impact of different values of guard band on system performance using different subcarrier spacing sizes for data and random access channels, which show the effectiveness of the selected waveform and guard bandwidth. Finally, we present system level simulation results that validate the proposed design under realistic cell deployments and inter-cell interference conditions.
Ijaz A, Zhang L, ul Quddus A, Tafazolli R (2016) HARQ in Relay-Assisted Transmission for Machine Type Communications, IEEE WIRELESS COMMUNICATIONS LETTERS 5 (2) pp. 172-175 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Quddus AU, Tafazolli R, Evans B (2005) Time Diversity in WCDMA FDD Downlink for
Multimedia Broadcast/Multicast Services using Chip Block Interleaving,
Quddus AU, Yang X, Tafazolli R (2008) Link-level analysis of downlink handover regions in UMTS, 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING, VOLS 1-7 pp. 2527-2531 IEEE
Quddus AU, Tafazolli R, Evans B (2005) Interference Suppression in UTRA FDD Downlink
Handover Regions,
Wang D, Katranaras E, Quddus A, Kuo F-C, Rost P, Sapountzis N, Bernardos CJ, Cominardi L, Berberana I (2015) SDN-based Joint Backhaul and Access Design for Efficient Network Layer Operations, 2015 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC) pp. 214-218 IEEE
Touheed H, Quddus AU, Tafazolli R (2009) Impact of MMSE equalization on adaptive modulation and coding in HSDPA, Proceedings of 6th International Bhurban Conference on Applied Sciences and Technology, IBCAST-2009 2 pp. 127-131
High Speed Downlink Packet Access (HSDPA) is the front-line technology within the 3rd Generation Partnership Project (3GPP) and represents mid term evolution of the standard. This paper presents simple equalizer structures based on Minimum Mean Square Error criterion that are suitable for Adaptive Modulation and Coding (AMC), which is one of the key features of HSDPA. Performance of equalizer structures in AMC has been shown to provide significant gain over Rake receiver, in terms of HSDPA throughput, by enabling the use of higher CQI (Channel Quality Indicator) indices whilst showing stability against changing input signal statistics caused by AMC. LMMSE equalizer has been found to roughly double the HSDPA throughput in a variety of radio channels with relatively small increase in complexity. © 2009 IEEE.
Kosta C, Hunt B, Quddus AU, Tafazolli R (2013) An Improved Inter-cell Interference Coordination (ICIC) for OFDMA multi-cell systems., EW VDE-Verlag
Zhang L, Xiao P, Quddus AU (2016) Cyclic Prefix Based Universal Filtered Multi-carrier System and Performance Analysis, IEEE Signal Processing Letters 23 (9) pp. 1197-1201 IEEE
Recently proposed universal filtered multi-carrier (UFMC) system is not an orthogonal system in multipath channel environments and might cause significant performance loss. In this paper, we propose a cyclic prefix (CP) based UFMC system and first analyze the conditions for interference-free one-tap equalization in the absence of transceiver imperfections. Then the corresponding signal model and output SNR (signal-tonoise ratio) expression are derived. In the presence of carrier frequency offset (CFO), timing offset (TO) and insufficient CP length, we establish an analytical system model as a summation of desired signal, inter-symbol interference (ISI), intercarrier interference (ICI) and noise. New channel equalization algorithms are proposed based on the derived analytical signal model. Numerical results show that the derived model matches the simulation results precisely, and the proposed equalization algorithms improve the UFMC system performance in terms of bit error rate (BER).
Guo T, Quddus AU, Tafazolli R (2012) Seamless handover for LTE macro-femto networks based on reactive data bicasting, IEEE Communications Letters 16 (11) pp. 1788-1791
Seamless mobility support is a key technical requirement to motivate the market acceptance of the femtocells. The current 3GPP handover procedure may cause large downlink service interruption time when users move from a macrocell to a femtocell or vice versa due to the data forwarding operation. In this letter, a practical scheme is proposed to enable seamless handover by reactively bicasting the data to both the source cell and the target cell after the handover is actually initiated. Numerical results show that the proposed scheme can significantly reduce the downlink service interruption time while still avoiding the packet loss with only limited extra resource requirements compared to the standard 3GPP scheme. © 2012 IEEE.
Wang D, Zhang L, Qi Y, Ul Quddus A (2015) Localized Mobility Management for SDN-Integrated LTE Backhaul Networks, 2015 IEEE 81ST VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING) IEEE
Pateromichelakis E, Shariat M, Quddus AU, Tafazolli R (2013) On the evolution of multi-cell scheduling in 3GPP LTE/LTE-A, IEEE Communications Surveys and Tutorials 15 (2) pp. 701-717
This paper provides a holistic overview of multi-cell scheduling strategies in emerging wireless systems. Towards this objective, the evolution of interference management techniques is thoroughly investigated from simple inter-cell interference coordination (ICIC) techniques towards more advanced coordinated multipoint transmissions (CoMP), while comparing and contrasting their common features and differences. Finally CoMP is explored in detail as an advanced and challenging mechanism to fully cooperate between adjacent cells in order to have an efficient resource allocation and inter-cell interference mitigation in multi-cell environments. © 2013 IEEE.
Azizan A, Quddus AU, Evans B (2008) Multipath Interference Canceller and Chip-Level Equalizer
for S-HSDPA,
Touheed H, Quddus AU, Tafazolli R (2008) An improved link adaptation scheme for High Speed Downlink Packet Access, 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING, VOLS 1-7 pp. 2051-2055 IEEE
Guo T, Quddus AU, Wang N, Tafazolli R (2012) Local Mobility Management for Networked Femtocells Based on X2 Traffic Forwarding, IEEE Transactions on Vehicular Technology IEEE
Femtocell is becoming a promising solution to face the explosive growth of mobile broadband usage in cellular networks. While each femtocell only covers a small area, a massive deployment is expected in the near future forming networked femtocells. An immediate challenge is to provide seamless mobility support for networked femtocells with minimal support from mobile core networks. In this paper, we propose efficient local mobility management schemes for networked femtocells based on X2 traffic forwarding under the 3GPP Long Term Evolution Advanced (LTE-A) framework. Instead of implementing the path switch operation at core network entity for each handover, a local traffic forwarding chain is constructed to use the existing Internet backhaul and the local path between the local anchor femtocell and the target femtocell for ongoing session communications. Both analytical studies and simulation experiments are conducted to evaluate the proposed schemes and compare them with the original 3GPP scheme. The results indicate that the proposed schemes can significantly reduce the signaling cost and relieve the processing burden of mobile core networks with the reasonable distributed cost for local traffic forwarding. In addition, the proposed schemes can enable fast session recovery to adapt to the self-deployment nature of the femtocells.
Shariat M, Pateromichelakis E, Quddus A, Tafazolli R (2014) Joint TDD Backhaul and Access Optimization in Dense Small Cell Networks, IEEE Transactions on Vehicular Technology (99) IEEE
This paper addresses the problem of joint backhaul and access links optimization in dense small cell networks with special focus on time division duplexing (TDD) mode of operation in backhaul and access links transmission. Here, we propose a framework for joint radio resource management where we systematically decompose the problem in backhaul and access links. To simplify the analysis, the procedure is tackled in two stages. At the first stage, the joint optimization problem is formulated for a point-to-point scenario where each small cell is simply associated to a single user. It is shown that the optimization can be decomposed into separate power and subchannel allocation in both backhaul and access links where a set of rate-balancing parameters in conjunction with duration of transmission governs the coupling across both links. Moreover, a novel algorithm is proposed based on grouping the cells to achieve rate-balancing in different small cells. Next in the second stage, the problem is generalized for multi access small cells. Here, each small cell is associated to multiple users to provide the service. The optimization is similarly decomposed into separate sub-channel and power allocation by employing auxiliary slicing variables. It is shown that similar algorithms as previous stage are applicable by slight change with the aid of slicing variables. Additionally, for the special case of line-of-sight backhaul links, simplified expressions for sub-channel and power allocation are presented. The developed concepts are evaluated by extensive simulations in different case studies from full orthogonalization to dynamic clustering and full reuse in the downlink and it is shown that proposed framework provides significant improvement over the benchmark cases.
Pateromichelakis E, Shariat M, Quddus A, Dianati M, Tafazolli R (2013) Dynamic Clustering Framework for Multi-Cell Scheduling in Dense Small Cell Networks, IEEE Communications Letters 17 (9) pp. 1802-1805
This letter proposes a novel graph-based multi-cell scheduling framework to efficiently mitigate downlink inter-cell interference in small cell OFDMA networks. This framework incorporates dynamic clustering combined with channel-aware resource allocation to provide tunable quality of service measures at different levels. Our extensive evaluation study shows that a significant improvement in user's spectral efficiency is achievable, while also maintaining relatively high cell spectral efficiency via empirical tuning of re-use factor across the cells according to the required QoS constraints.
Pateromichelakis E, Shariat M, Ul Quddus A, Tafazolli R (2012) Dynamic graph-based multi-cell scheduling for femtocell networks, 2012 IEEE Wireless Communications and Networking Conference Workshops, WCNCW 2012 pp. 98-102
This paper proposes a dynamic semi-centralized resource partitioning algorithm to mitigate the problem of co-tier interference in dense femtocell deployments. This algorithm incorporates graph-colouring and network utility concepts to address inter-cell interference in femtocell networks. The aforementioned scheme acts as a multi-cell coordination mechanism on top of intra-cell scheduling by applying a low complexity graph-based algorithm. The objective of the coordination mechanism is the efficient management of resource conflicts due to interference in a multi-cell environment consisting of femtocells. This coordination mechanism defines a novel category of graph-based ICIC algorithms that uses bipartite graph colouring to avoid resource conflicts by randomizing them in time domain. © 2012 IEEE.
Mudugamuwa U, Karaliopolous M, Quddus AU, Narenthiran K, Tafazolli R, Evans B (2004) Link level and System level simulators for the S-DMB system evaluation,
Kosta C, Hunt B, Quddus AU, Tafazolli R (2012) On Interference Avoidance through Inter-Cell Interference Coordination (ICIC) Based on OFDMA Mobile Systems, IEEE Communications Surveys and Tutorials
The widely accepted OFDMA air interface technology has recently been adopted in most mobile standards by the wireless industry. However, similar to other frequency-time multiplexed systems, their performance is limited by inter-cell interference. To address this performance degradation, interference mitigation can be employed to maximize the potential capacity of such interference-limited systems. This paper surveys key issues in mitigating interference and gives an overview of the recent developments of a promising mitigation technique, namely, interference avoidance through inter-cell interference coordination (ICIC). By using optimization theory, an ICIC problem is formulated in a multi-cell OFDMA-based system and some research directions in simplifying the problem and associated challenges are given. Furthermore, we present the main trends of interference avoidance techniques that can be incorporated in the main ICIC formulation. Although this paper focuses on 3GPP LTE/LTE-A mobile networks in the downlink, a similar framework can be applied for any typical multi-cellular environment based on OFDMA technology. Some promising future directions are identified and, finally, the state-of-the-art interference avoidance techniques are compared under LTE-system parameters.
Shariat M, Quddus A, Ghorashi S, Tafazolli R (2009) Scheduling as an important cross-layer operation for emerging broadband wireless systems, IEEE Communications Surveys and Tutorials 11 (2) pp. 74-86
Cross-layer scheduling is a promising solution for improving the efficiency of emerging broadband wireless systems. In this tutorial, various cross-layer design approaches are organized into three main categories namely air interface-centric, user-centric and route-centric and the general characteristics of each are discussed. Thereafter, by focusing on the air interfacecentric approach, it is shown that the resource allocation problem can be formulated as an optimization problem with a certain objective function and some particular constraints. This is illustrated with the aid of a customer-provider model from the field of economics. Furthermore, the possible future evolution of scheduling techniques is described based on the characteristics of traffic and air interface in emerging broadband wireless systems. Finally, some further challenges are identified. © 2009 IEEE.
Shariat M, Quddus AU, Tafazolli R (2008) On the efficiency of interference coordination schemes in emerging cellular wireless networks, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
In this paper, the efficiencies of different interference coordination schemes are evaluated for emerging wireless networks and the possible impact on intra-cell scheduling is studied through extensive simulations. The results show that pure fractional frequency reuse can provide similar improvement in the cell-edge throughput compared to power coordinated counterpart at a less cost in terms of overall throughput. Moreover, it can provide fairer distribution of throughput in both central as well as cell-edge areas. However, this scheme can not mange asymmetrical changes in the distribution of users across different cells in the entire system. As a result, a power coordination mechanism would be still necessary on top of such flexible frequency reuse schemes. © 2008 IEEE.
Kosta C, Hunt B, Quddus AU, Tafazolli R (2013) On interference avoidance through inter-cell interference coordination (ICIC) based on OFDMA mobile systems, IEEE Communications Surveys and Tutorials 15 (3) pp. 973-995
The widely accepted OFDMA air interface technology has recently been adopted in most mobile standards by the wireless industry. However, similar to other frequency-time multiplexed systems, their performance is limited by inter-cell interference. To address this performance degradation, interference mitigation can be employed to maximize the potential capacity of such interference-limited systems. This paper surveys key issues in mitigating interference and gives an overview of the recent developments of a promising mitigation technique, namely, interference avoidance through inter-cell interference coordination (ICIC). By using optimization theory, an ICIC problem is formulated in a multi-cell OFDMA-based system and some research directions in simplifying the problem and associated challenges are given. Furthermore, we present the main trends of interference avoidance techniques that can be incorporated in the main ICIC formulation. Although this paper focuses on 3GPP LTE/LTE-A mobile networks in the downlink, a similar framework can be applied for any typical multi-cellular environment based on OFDMA technology. Some promising future directions are identified and, finally, the state-of-the-art interference avoidance techniques are compared under LTE-system parameters. © 2013 IEEE.
Kosta C, Hunt B, Quddus AU, Tafazolli R (2013) A distributed method of inter-cell interference coordination (ICIC) based on dual decomposition for interference-limited cellular networks, IEEE Communications Letters 17 (6) pp. 1144-1147
In this paper we present a novel distributed Inter-Cell Interference Coordination (ICIC) scheme for interference-limited heterogeneous cellular networks (HetNet). We reformulate our problem in such a way that it can be decomposed into a number of small sub-problems, which can be solved independently through an iterative subgradient method. The proposed dual decomposition method can also address problems with binary-valued variables. The proposed algorithm is compared with some reference schemes in terms of cell-edge and total cell throughput. © 1997-2012 IEEE.
Kosta C, Hunt B, Ui Quddus A, Tafazolli R (2013) Distributed energy-efficient inter-cell interference coordination (ICIC) in multi-cell HetNets, IEEE Vehicular Technology Conference
We present a distributed energy-efficient Inter-Cell Interference Coordination (ICIC) scheme for multi-cell HetNets (Heterogeneous Networks) in the downlink. This novel scheme aims to maximize the user fairness performance of the overall system as well as minimizing the total average transmit power at the base station side. We consider a realistic power model to characterize the power consumed (including circuit and transmitted power) at the base station side. We define an energy efficient performance metric in bits/Joule and the user fairness as the 5th percentile of the average user throughput. The proposed scheme is divided into the following three stages: dominant interferences classification, inter-cell radio resource allocation and intra-cell power control. The inter-cell radio resource allocation is formulated as a multidimensional knapsack problem. In order to satisfy the complexity requirements associated with multi-cell networks, we simplify, relax and decompose the original problem into a main master problem and multiple sub-problems. Our simulation results show the proposed scheme significantly increases both the user fairness and the energy efficiency (EE) of the overall network. © 2013 IEEE.
Quddus AU, Seo K, Hoshyar R, Rosmansyah Y, Tafazolli R (2004) SIR estimation for closed loop power control with space time transmit diversity in WCDMA FDD downlink, 2004 IEEE 15TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-4, PROCEEDINGS pp. 249-253 IEEE
Hariyanto H, Quddus AU, Evans B (2007) On-Board Linear Interference Cancellation Multiuser
Detection for Uplink CDMA GEO Satellite Systems,
Zhang L, Quddus A, Katranaras E, Dubben W, Qi Y, Tafazolli R (2016) Performance Analysis and Optimal Cooperative Cluster Size for Randomly Distributed Small Cells under Cloud RAN, IEEE Access 4 pp. 1925-1939 IEEE
One major advantage of cloud/centralized radio access network (C-RAN) is the ease of implementation of multicell coordination mechanisms to improve the system spectrum efficiency (SE). Theoretically, large number of cooperative cells lead to a higher SE, however, it may also cause significant delay due to extra channel state information (CSI) feedback and joint processing computational needs at the cloud data center, which is likely to result in performance degradation. In order to investigate the delay impact on the throughput gains, we divide the network into multiple clusters of cooperative small cells and formulate a throughput optimization problem. We model various delay factors and the sum-rate of the network as a function of cluster size, treating it as the main optimization variable. For our analysis, we consider both base stations? as well as users? geometric locations as random variables for both linear and planar network deployments. The output SINR (signal-tointerference-plus-noise ratio) and ergodic sum-rate are derived based on the homogenous Poisson point processing (PPP) model. The sum-rate optimization problem in terms of the cluster size is formulated and solved. Simulation results show that the proposed analytical framework can be utilized to accurately evaluate the performance of practical cloud-based small cell networks employing clustered cooperation.
Kosta C, Imran A, Quddus AU, Tafazolli R (2011) Flexible soft frequency reuse schemes for heterogeneous networks (macrocell and femtocell), IEEE Vehicular Technology Conference
A mass deployment of femtocells is anticipated to affect a number of areas more adversely, especially in the cell-edge of the macrocell network. In this paper, we propose a flexible frequency-partitioning scheme for OFDMA network based on cyclic difference sets. The cyclic property of these sets allows a quick construction of orthogonal patterns for the macrocell and femtocell networks with an emphasis on tri-sector sites. The impact and the co-deployment of femtocells is also investigated. Unlike, with existing works in the literature, the novel scheme can adaptively control the level of coverage in the cell-edges areas and additionally enables coexistence of femtocells in the network. Simulation results confirm the effectiveness of the proposed scheme in both macrocell and femtocell networks compared to the legacy soft frequency reuse and universal frequency reuse. © 2011 IEEE.
Pateromichelakis E, Shariat M, Quddus A, Tafazolli R (2012) On the Evolution of Multi-cell Scheduling in 3GPP LTE / LTE-A, IEEE Communcations Surveys & Tutorials
Qi Y, Ijaz A, Quddus A, Imran M, Navaratnam P, Ma Y, Tafazolli R, Webb M, Morioka Y (2014) On the Physical Layer Design for Low Cost Machine Type Communication in 3GPP LTE, 2014 IEEE 80TH VEHICULAR TECHNOLOGY CONFERENCE (VTC FALL) IEEE
Salami G, Quddus AU, Thilakawardana D, Tafazolli R (2008) Nonpool based spectrum sharing for two UMTS operators in the UMTS extension band, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
This paper investigates spectrum sharing (in the form of code sharing) between two Universal Mobile Telecommunication System (UMTS) operators in the UMTS extension band (2500-2690MHz) with equal and unequal number of proprietary carriers, respectively. The paper proposes a Dynamic Spectrum Allocation (DSA) algorithm to address the problem of spectrum sharing between two operators on a non-pool basis. It also investigates the impact of Adjacent Channel Interference (ACI) on the spectrum sharing gain. Additionally, an architecture that enables spectrum sharing to take place between two or more UMTS operators is presented. The simulated performance of the proposed DSA algorithm shows that under peak-hour loading, up to 32% increase in capacity can be obtained when compared to currently used Fixed Spectrum Allocation (FSA). © 2008 IEEE.
Pateromichelakis E, Shariat M, Quddus A, Tafazolli R (2015) Joint Routing and Scheduling in Dense Small Cell Networks using 60GHz backhaul,
Kosta C, Hunt B, Quddus AU, Tafazolli R (2012) A low-complexity distributed inter-cell interference coordination (ICIC) scheme for emerging multi-cell HetNets, IEEE Vehicular Technology Conference
In this paper, we propose a low-complexity distributed Inter-Cell Interference Coordination (ICIC) for emerging multi-cell HetNets (Heterogeneous Networks). The proposed scheme is quickly solved using linear programming tools and aims to maximize both the critical and the overall performance of the multi-cell system. Additionally, a utility measure is used to provide a varying level of user fairness to satisfy the most demanding network providers. Simulation results confirm the low-complexity of the proposed algorithm and its increased effectiveness over a number of state-of-art interference avoidance schemes. © 2012 IEEE.
Shariat M, Quddus AU, Tafazolli R (2009) Joint Opportunistic Scheduling and Spectrum Sharing,
Shariat M, Ul Quddus A, Tafazolli R (2009) IEEE Wireless Communications and Networking Conference, WCNC
In this paper, a novel framework is proposed to integrate spectrum (resource) sharing into multihop scheduling in relay-assisted systems. This approach provides an effective solution to minimize the effect of extra resources that are required in multihop transmission. Particularly, this approach can be combined with different topologies of resource scheduling to provide better performance in terms of throughput and coverage compared to benchmark non-sharing algorithms. © 2009 IEEE.
Quddus AU, Evans BG, Tafazolli R (2009) Blind adaptive multiuser detection for code division multiple access using Cimmino's reflection method, Proceedings of 6th International Bhurban Conference on Applied Sciences and Technology, IBCAST-2009 2 pp. 118-120
This paper investigates adaptive implementation of the linear minimum mean square error (MMSE) detector in code division multiple access (CDMA). From linear algebra, Cimmino's reflection method is proposed as a possible way of achieving the MMSE solution blindly. Simulation results indicate that the proposed method converges four times faster than the blind least mean squares (LMS) algorithm and has roughly the same convergence performance as the blind recursive least squares (RLS) algorithm. Moreover the proposed algorithm is numerically more stable than the RLS algorithm and also exhibits parallelism for pipelined implementation. © 2009 IEEE.
Azizan A, Quddus AU, Evans BG (2008) Satellite high speed downlink packet access physical layer performance analysis, 2008 4th Advanced Satellite Mobile Systems - Proceedings, ASMS 2008 pp. 156-161
The high speed downlink packet access (HSDPA) system has been investigated for adaptation in the GEO satellite environment in order to achieve high packet user throughput and system efficiency. This paper discusses the performance of the so called satellite-HSDPA (S-HSDPA) system, where the impacts of the power amplifier non-linearity, space time transmit diversity (STTD) and multicode transmission, are examined. The S-HSDPA performance is obtained from simulations of a modified terrestrial HSDPA link simulator in a rich multipath urban environment with three intermediate module repeaters (IMR). The results indicate an appropriate choice of system parameters. © 2008 IEEE.
Castro MAV, Bito J, Ebert J, Heder B, Kokkalis NV, Mathiopoulos PT, Koudelka S, Morosi S, Novak C, Quddus AU, Granados GS, Coralli AV (2007) Multiuser Satellite Communications, In: Corazza GE (eds.), Digital satellite communications 10 Springer Verlag
The book provides a unified view of essential topics, including: fundamental theories, channel coding and modulation, synchronization and parameter estimation, ...
Kosta C, Hunt B, Quddus AU, Tafazolli R (2013) A Distributed Method of Inter-Cell Interference Coordination (ICIC) Based on Dual Decomposition for Interference-Limited Cellular Networks, IEEE Communications Letters 17 (6) pp. 1144-1147
In this paper we present a novel distributed Inter-Cell Interference Coordination (ICIC) scheme for interference-limited heterogeneous cellular networks (HetNet). We reformulate our problem in such a way that it can be decomposed into a number of small sub-problems, which can be solved independently through an iterative subgradient method. The proposed dual decomposition method can also address problems with binary-valued variables. The proposed algorithm is compared with some reference schemes in terms of cell-edge and total cell throughput.
Ko Y, Quddus AU, Tafazolli R (2016) Multi-Device Selection Scheduling in Non-Identically Distributed Fading Channels, IET Communications
Multiuser selection scheduling concept has been recently proposed in the literature in order to
increase the multiuser diversity gain and overcome the significant feedback requirements for the opportunistic
scheduling schemes. The main idea is that reducing the feedback overhead saves per-user
power that could potentially be added for the data transmission. In this work, we propose to integrate the
principle of multiuser selection and the proportional fair scheduling scheme. This is aimed especially at
power-limited, multi-device systems in non-identically distributed fading channels. For the performance
analysis, we derive closed-form expressions for the outage probabilities and the average system rate of the
delay-sensitive and the delay-tolerant systems, respectively, and compare them with the full feedback
multiuser diversity schemes. The discrete rate region is analytically presented, where the maximum
average system rate can be obtained by properly choosing the number of partial devices. We optimize
jointly the number of partial devices and the per-device power saving in order to maximize the average
system rate under the power requirement. Through our results, we finally demonstrate that the proposed
scheme leveraging the saved feedback power to add for the data transmission can outperform the full
feedback multiuser diversity, in non-identical Rayleigh fading of devices? channels.
Zhang L, liu W, quddus A, Dianati M, tafazolli R (2015) Adaptive Distributed Beamforming for Relay Networks based on Local Channel State Information, IEEE Transactions on Signal and Information Processing over Networks 1 (2) pp. 117-128 IEEE
Most of the existing distributed beamforming algorithms for relay networks require global channel state information (CSI) at relay nodes and the overall computational complexity is high. In this paper, a new class of adaptive algorithms is proposed which can achieve a globally optimum solution by employing only local CSI. A reference signal based (RSB) scheme is first derived, followed by a constant modulus (CM) based scheme when the reference signal is not available. Considering individual power transmission constraint at each relay node, the corresponding constrained adaptive algorithms are also derived as an extension. An analysis of the overhead and stepsize range for the derived algorithms are then provided and the excess mean square error (EMSE) for the RSB case is studied based on the energy reservation method. As demonstrated by our simulation results, a better performance has been achieved by our proposed algorithms and they have a very low computational complexity and can be implemented on low cost and low processing power devices.
Qi Y, Imran MA, Quddus A, Tafazolli R (2014) Achievable rate optimization for coordinated multi-point transmission (CoMP) in cloud-based RAN architecture, 2014 IEEE International Conference on Communications, ICC 2014 pp. 4753-4758
In this paper, we consider Coordinated Multi-Point (CoMP) in a cloud-based radio access network (RAN), where each coordinating access point compresses its observation using distributed Wyner-Ziv compression and forwards the compressed signal to the receiving processing unit. We map this architecture to the multiple-relay compress-and-forward (CF) problem, derive the achievable rate of such a system and then show that the achievable rate can be maximized by optimizing the distributed compression rate at each individual coordinating point in a joint manner. An iterative optimization algorithm is proposed and numerical results indicate that compared with other coordinating schemes, when the channel between the coordinating points and the processing unit is strong, using distributed compression can effectively improve the spectrum efficiency. © 2014 IEEE.
Azizan A, Quddus AU, Evans B (2007) Chip Level Adaptive Equalization for Satellite High Speed
Downlink Packet Access (S-HSDPA),
Shariat M, Quddus AU, Tafazolli R (2009) Distance-incorporated opportunistic scheduling, Proceedings of the 2009 ACM International Wireless Communications and Mobile Computing Conference, IWCMC 2009 pp. 675-680
This paper highlights the deficiencies of classical figures of merit such as throughput and fairness index to evaluate different scheduling algorithms and proposes a new complementary figure of merit called as transport-throughput, which has been inspired from information theory literature to better represent trade-offs among throughput, fairness and coverage associated with a given scheduling algorithm. Furthermore, new objective functions for opportunistic scheduling are proposed that utilize the knowledge about the geographic distance of mobile terminals from the base station. The proposed concept can be easily integrated as an extension to classical scheduling algorithms and provides the ability to control the effective distribution of throughput across the network Copyright © 2009 ACM.
Quddus AU, Guo T, Shariat M, Hunt B, Imran A, Ko Y, Tafazolli R (2010) Next Generation Femtocells: An Enabler for High Efficiency Multimedia Transmission, IEEE Comsoc MMTC E-Letters 5 (5) pp. 27-31 IEEE
The first generation of femtocells is evolving to the next generation with many more capabilities in terms of better utilisation of radio resources and support of high data rates. It is thus logical to conjecture that with these abilities and their inherent suitability for home environment, they stand out as an ideal enabler for delivery of high efficiency multimedia services. This paper presents a comprehensive vision towards this objective and extends the concept of femtocells from indoor to outdoor environments, and strongly couples femtocells to emergency and safety services. It also presents and identifies relevant issues and challenges that have to be overcome in realization of this vision.
Touheed H, Quddus AU, Tafazolli R (2008) Predictive CQI reporting for HSDPA, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
One of the key features of High-Speed Downlink Packet Access (HSDPA) is Adaptive Modulation and Coding (AMC). Link Adaptation at Node-B is done on the basis of Channel Quality Indicator (CQI) reports sent by the User Equipment (IE). However there is a delay of about 10 ms between computation of a CQI report at UE and the corresponding Transport Format and Resource Indicator (TFRI) selection at the Node-B. This delay significantly degrades the performance of link adaptation process. In order to compensate for this loss of performance, we propose predictive CQI reporting by the UE. A simple linear predictor based on NLMS (Normalized Least Mean Square) adaptation is shown through simulations to provide substantial gain in HSDPA link throughput. Results show that predictive CQI reporting provides larger gain in channel environments with medium to high Doppler and lack of multipath diversity. © 2008 IEEE.
Pateromichelakis E, Shariat M, Quddus A, Tafazolli R (2014) Graph-Based Multicell Scheduling in OFDMA-Based Small Cell Networks, IEEE Access 2 pp. 897-908
This paper proposes a novel graph-based multicell scheduling framework to efficiently mitigate downlink intercell interference in OFDMA-based small cell networks. We define a graph-based optimization framework based on interference condition between any two users in the network assuming they are served on similar resources. Furthermore, we prove that the proposed framework obtains a tight lower bound for conventional weighted sum-rate maximization problem in practical scenarios. Thereafter, we decompose the optimization problem into dynamic graph-partitioning-based subproblems across different subchannels and provide an optimal solution using branch-and-cut approach. Subsequently, due to high complexity of the solution, we propose heuristic algorithms that display near optimal performance. At the final stage, we apply cluster-based resource allocation per subchannel to find candidate users with maximum total weighted sum-rate. A case study on networked small cells is also presented with simulation results showing a significant improvement over the state-of-the-art multicell scheduling benchmarks in terms of outage probability as well as average cell throughput.
Azizan A, Quddus AU, Evans BG (2006) Link level performance analysis of Satellite High Speed Downlink Packet Access (S-HSDPA), Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC 2 pp. 1120-1125
We investigate the physical layer performance of HSDPA via GEO satellites for use in S-UMTS and SDMB. The impact of large round trip delay on link adaptation is discussed and link-level results are presented on the performance of HARQ for a variable number of retransmissions and different categories of UE in a rich multipath urban environment with three IMRs. It is shown that the N-channel SAW HARQ protocol can significantly increase the average throughput particularly for 16-QAM but the large round trip delay also requires an increase in the number of parallel HARQ channels resulting in high memory requirements at the UE. Receive antenna diversity with varying degrees of antenna correlation is also investigated as a possible performance enhancing method. The results presented here will help in specifying the physical layer of satellite HSDPA. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Quddus AU, Abedi S, Tafazolli R, Evans B (2003) Blind Multiple Access Interference Suppression
in a Land Mobile Satellite Fading Channel,
Qi Y, Quddus A, Imran M, Tafazolli R (2015) Semi-Persistent RRC Protocol for Machine Type Communication Devices in LTE Networks, IEEE Access 3
In this paper, we investigate the design of a radio resource control (RRC) protocol in the framework of long-term evolution (LTE) of the 3rd Generation Partnership Project regarding provision of low cost/complexity and low energy consumption machine-type communication (MTC), which is an enabling technology for the emerging paradigm of the Internet of Things. Due to the nature and envisaged battery-operated long-life operation of MTC devices without human intervention, energy efficiency becomes extremely important. This paper elaborates the state-of-the-art approaches toward addressing the challenge in relation to the low energy consumption operation of MTC devices, and proposes a novel RRC protocol design, namely, semi-persistent RRC state transition (SPRST), where the RRC state transition is no longer triggered by incoming traffic but depends on pre-determined parameters based on the traffic pattern obtained by exploiting the network memory. The proposed RRC protocol can easily co-exist with the legacy RRC protocol in the LTE. The design criterion of SPRST is derived and the signalling procedure is investigated accordingly. Based upon the simulation results, it is shown that the SPRST significantly reduces both the energy consumption and the signalling overhead while at the same time guarantees the quality of service requirements.
Shariat M, Quddus AU, Tafazolli R (2011) Opportunistic spectrum reuse for femtocell networks, IEEE Vehicular Technology Conference
Femtocell networks are inherently interferencelimited similar to other cellular networks. However, massive and unplanned roll-outs of femtocells make the classical macro cells more susceptible to the resulting interference. In this paper a novel distributed approach is proposed for resource allocation for femtocells that opportunistically identifies low-cost resources (in terms of interference) in a way that would cause minimal impact on the service level of primary macro users. Simulation study confirms the efficiency of proposed algorithm compared to benchmarking scenario of macro-only network operation. As it is shown, the proposed method enables flexible tuning of femto throughput at the cost of macro users service. © 2011 IEEE.
Pateromichelakis E, Shariat M, Quddus AU, Dianati M, Tafazolli R (2013) Dynamic Clustering Framework for Multi-Cell Scheduling in Dense Small Cell Networks, IEEE Communications Letters 17 (9) pp. 1802-1805 IEEE
This letter proposes a novel graph-based multi-cell scheduling framework to efficiently mitigate downlink inter-cell interference in small cell OFDMA networks. This framework incorporates dynamic clustering combined with channel-aware resource allocation to provide tunable quality of service measures at different levels. Our extensive evaluation study shows that a significant improvement in user's spectral efficiency is achievable, while also maintaining relatively high cell spectral efficiency via empirical tuning of re-use factor across the cells according to the required QoS constraints.
Zhang L, Ijaz A, Xiao P, Quddus AU, Tafazolli R (2017) Subband Filtered Multi-carrier Systems for Multi-service Wireless Communications, IEEE Transactions on Wireless Communications 16 (3) pp. 1893-1907 IEEE
Flexibly supporting multiple services, each with
different communication requirements and frame structure, has
been identified as one of the most significant and promising
characteristics of next generation and beyond wireless communication
systems. However, integrating multiple frame structures
with different subcarrier spacing in one radio carrier may
result in significant inter-service-band-interference (ISBI). In this
paper, a framework for multi-service (MS) systems is established
based on subband filtered multi-carrier system. The subband
filtering implementations and both asynchronous and generalized
synchronous (GS) MS subband filtered multi-carrier (SFMC)
systems have been proposed. Based on the GS-MS-SFMC system,
the system model with ISBI is derived and a number of properties
on ISBI are given. In addition, low-complexity ISBI cancelation
algorithms are proposed by precoding the information symbols
at the transmitter. For asynchronous MS-SFMC system in the
presence of transceiver imperfections including carrier frequency
offset, timing offset and phase noise, a complete analytical
system model is established in terms of desired signal, intersymbol-interference,
inter-carrier-interference, ISBI and noise.
Thereafter, new channel equalization algorithms are proposed
by considering the errors and imperfections. Numerical analysis
shows that the analytical results match the simulation results,
and the proposed ISBI cancelation and equalization algorithms
can significantly improve the system performance in comparison
with the existing algorithms.
Zhang Lei, Xiao Pei, Zafar Adnan, Quddus Atta, Tafazolli Rahim (2016) FBMC System: An Insight into Doubly Dispersive Channel Impact, IEEE Transactions on Vehicular Technology 66 (5) pp. 3942-3956 IEEE
It has been claimed that the filter bank multicarrier (FBMC) systems suffer from negligible performance loss caused by moderate dispersive channels in the absence of guard time protection between symbols. However, a theoretical and systematic explanation/analysis for the statement is missing in the literature to date. In this paper, based on one-tap minimum mean square error (MMSE) and zero-forcing (ZF) channel equalizations, the impact of doubly dispersive channel on the performance of FBMC systems is analyzed in terms of mean square error (MSE) of received symbols. Based on this analytical framework, we prove that the circular convolution property between symbols and the corresponding channel coefficients in the frequency domain holds loosely with a set of inaccuracies. To facilitate analysis, we first model the FBMC system in a vector/matrix form and derive the estimated symbols as a sum of desired signal, noise, inter-symbol interference (ISI), inter-carrier interference (ICI), inter-block interference (IBI) and estimation bias in the MMSE equalizer. Those terms are derived one-by-one and expressed as a function of channel parameters. The numerical results reveal that in harsh channel conditions, e.g., with large Doppler spread or channel delay spread, the FBMC system performance may be severely deteriorated and error floor will occur.
Guo T, Quddus AU, Wang N, Tafazolli R Local Mobility Management for Networked Femtocells Based on X2 Traffic Forwarding, IEEE Transactions on Vehicular Technology Institute of Electrical and Electronics Engineers
Femtocell is becoming a promising solution to face the explosive growth of mobile broadband usage in cellular networks. While each femtocell only covers a small area, a massive deployment is expected in the near future forming networked femtocells. An immediate challenge is to provide seamless mobility support for networked femtocells with minimal support from mobile core networks. In this
paper, we propose efficient local mobility management schemes for networked femtocells based on X2 traffic forwarding under the 3GPP Long Term Evolution Advanced (LTE-A) framework. Instead of implementing the path switch operation at core network entity for each handover, a local traffic forwarding chain is constructed to use the existing Internet backhaul and the local path between the local
anchor femtocell and the target femtocell for ongoing session communications. Both analytical studies and simulation experiments are conducted to evaluate the proposed schemes and compare them with the original 3GPP scheme. The results indicate that the proposed schemes can significantly reduce the signaling cost and relieve the processing burden of mobile core networks with the reasonable distributed cost for local traffic forwarding. In addition, the proposed schemes can enable fast session recovery to adapt to the self-deployment nature of the femtocells.
Zhang Lei, Ijaz A, Xiao Pei, Quddus Atta, Tafazolli Rahim (2016) Single-rate and Multi-rate Multi-service Systems for Next Generation and Beyond Communications, IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications
To flexibly support diverse communication requirements (e.g., throughput, latency, massive connection, etc.) for the next generation wireless communications, one viable solution is to divide the system bandwidth into several service subbands, each for a different type of service. In such a multi-service (MS) system, each service has its optimal frame structure while the services are isolated by subband filtering. In this paper, a framework for multi-service (MS) system is established based on subband filtered multi-carrier (SFMC) modulation. We consider both single-rate (SR) and multi-rate (MR) signal processing as two different MS-SFMC implementations, each having different performance and computational complexity. By comparison, the SR system outperforms the MR system in terms of performance while the MR system has a significantly reduced computational complexity than the SR system. Numerical results show the effectiveness of our analysis and the proposed systems. These proposed SR and MR MS-SFMC systems provide guidelines for next generation wireless system frame structure optimization and algorithm design.
Nwankwo C, Zhang L, Quddus A, Imran M, Tafazolli R (2017) A Survey of Self-Interference Management Techniques for Single Frequency Full Duplex Systems, IEEE Access pp. 1-1 Institute of Electrical and Electronics Engineers (IEEE)
This article presents a comprehensive survey of the literature on self-interference management schemes required to achieve a single frequency full duplex communication in wireless communication networks. A single frequency full duplex system often referred to as in-band full duplex (FD) system has emerged as an interesting solution for the next generation mobile networks where scarcity of available radio spectrum is an important issue. Although studies on the mitigation of self-interference have been documented in the literature, this is the first holistic attempt at presenting not just the various techniques available for handling self-interference that arises when a full duplex device is enabled, as a survey, but it also discusses other system impairments that significantly affect the self-interference management of the system, and not only in terrestrial systems, but also on satellite communication systems. The survey provides a taxonomy of self-interference management schemes and shows by means of comparisons the strengths and limitations of various self-interference management schemes. It also quantifies the amount of self-interference cancellation required for different access schemes from the 1 st generation to the candidate 5 th generation of mobile cellular systems. Importantly, the survey summarises the lessons learnt, identifies and presents open research questions and key research areas for the future. This paper is intended to be a guide and take off point for further work on self-interference management in order to achieve full duplex transmission in mobile networks including heterogeneous cellular networks which is undeniably the network of future wireless systems.
Qi Y, Shakir M, Imran M, Qaraqe K, Quddus A, Tafazolli R (2016) Fronthaul Data Compression for Uplink CoMP in Cloud Radio Access Network (C-RAN), Transactions on Emerging Telecommunications Technologies 27 (10) pp. 1409-1425 Wiley
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.
Chu Zheng, Yu Wenjuan, Xiao Pei, Zhou Fuhui, Al-Dhahir Naofal, ul Quddus Atta, Tafazolli Rahim (2019) Opportunistic Spectrum Sharing for D2D-Based URLLC, IEEE Transactions on Vehicular Technology Institute of Electrical and Electronics Engineers (IEEE)
A device-to-device (D2D) ultra reliable low latency
communications (URLLC) network is investigated in this paper.
Specifically, a D2D transmitter opportunistically accesses the
radio resource provided by a cellular network and directly
transmits short packets to its destination. A novel performance
metric is adopted for finite block-length code. We quantify the
maximum achievable rate for the D2D network, subject to a
probabilistic interference power constraint based on imperfect
channel state information (CSI). First, we perform a convexity
analysis which reveals that the finite block-length rate for the
D2D pair in short-packet transmission is not always concave. To
address this issue, we propose two effective resource allocation
schemes using the successive convex approximation (SCA)-based
iterative algorithm. To gain more insights, we exploit the monotonicity
of the average finite block-length rate. By capitalizing
on this property, an optimal power control policy is proposed,
followed by closed-form expressions and approximations for the
optimal average power and the maximum achievable average rate
in the finite block-length regime. Numerical results are provided
to confirm the effectiveness of the proposed resource allocation
schemes and validate the accuracy of the derived theoretical
results.
Grau Maxime, Foh Chuan Heng, ul Quddus Atta, Tafazolli Rahim (2019) Preamble Barring: A Novel Random Access Scheme for Machine Type Communications with Unpredictable Traffic Bursts, Proceedings of the 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall) Institute of Electrical and Electronics Engineers (IEEE)
In this paper, we present a novel random access
method for future mobile cellular networks that support machine
type communications. Traditionally, such networks establish
connections with the devices using a random access procedure,
however massive machine type communication poses several
challenges to the design of random access for current systems.
State-of-the-art random access techniques rely on predicting
the traffic load to adjust the number of users allowed to
attempt the random access preamble phase, however this delays
network access and is highly dependent on the accuracy of
traffic prediction and fast signalling. We change this paradigm by
using the preamble phase to estimate traffic and then adapt the
network resources to the estimated load. We introduce Preamble
Barring that uses a probabilistic resource separation to allow
load estimation in a wide range of load conditions and combine
it with multiple random access responses. This results in a
load adaptive method that can deliver near-optimal performance
under any load condition without the need for traffic prediction
or signalling, making it a promising solution to avoid network
congestion and achieve fast uplink access for massive MTC.