Resource Allocation In Ofdm Based Wireless Relay Networks

The combination of relay transmission with orthogonal frequency division multiplexing (OFDM) technique is deemed as the candidate for the fourth generation (4G) wireless networks. This thesis addresses the resource allocation problem in OFDM based relay networks. Different scenarios of relay networks are considered, e.g., the multi-user relay networks, the multi-relay networks, and the cognitive radio (CR) relay networks. The resource management strategies are developed to analyse: how to optimally distribute available resources among different users, how resource optimization enhances the performance under cooperative communication, how to maximize the lifetime of multi-hop wireless sensor networks (WSNs), and how to improve CR transmission without degrading the performance of the primary network? For each relay transmission scenario, two or more resources are optimized to enhance the system performance under various constraints. The resources include: the power allocation at the source terminal, the power allocation at the relay nodes, the sub-carrier allocation among different users, and the sub-carrier matching over different hops. Multi-user transmission adopts orthogonal frequency division multiple access (OFDMA) technique and is subject to separate power constraint at each terminal. Initially, the resource management issue in multi-user uplink relay transmission is discussed. Then, the similar resource allocation problem is solved when OFDMA multi-user system operates under the bidirectional relay transmission. The multi-relay dual hop transmission is optimized under different transmission schemes, specifically, the non-orthogonal transmission where all the terminals transmit simultaneously in the second time slot and the time division multiple access (TDMA) based transmission where each relay transmits in the pre-defined time slot. The resource allocation in CR relay networks is considered which ensures that the interference caused by the secondary network is not harmful to the primary system. Convex optimization techniques are exploited to solve the problems for each relay transmission and the near optimal solutions are developed. Further, several suboptimal algorithms are also designed to reduce the computational complexity.

Relay systems have become a subject of intensive research interest over the recent years, as it is recognized that they can improve performances and extend the coverage area of wireless communication systems. Special attention has been dedicated to them since the proposal appeared for their implementation in mobile cellular systems. Numerous researches conducted after that proposal have enabled incorporation of OFDM based relay systems in both accepted standards for IMT-Advanced systems. Nowadays, researches are ongoing with the aim to define new solutions for performance improvement of the standardized OFDM relay systems for cellular networks and one of the interesting solutions is implementation of subcarrier permutation (SCP) at the relay (R) station.The book OFDM based relay systems for future wireless communications presents a comprehensive research results in analyzing behavior and performance of the OFDM based relay systems with SCP. Dual-hop relay scenario with three communication terminals, and no direct link between the source (S) and the destination (D) has been analyzed, as it is compliant with the accepted solutions for IMT-Advanced systems. The book includes performance analysis and performance comparison of OFDM based:• amplify-and-forward (AF) relay systems with fixed gain (FG),• amplify-and-forward (AF) relay systems with variable gain (VG),• decode-and-forward (DF) relay systems,each including two SCP schemes, known to maximize the system capacity and/or improve the bit error rate (BER) performances. Performance comparisons have enabled definition of optimal solutions for the future wireless communication systems in a given conditions, and for the given optimality criteria. OFDM based relay systems for future wireless communications contains recent research results in this area and is ideal for the academic staff and master/research students in area of mobile communication systems, as well as for the personnel in communication industry.

This book introduces the sources and historic collection campaigns of resource allocation in wireless communication systems. The unique characteristics of MIMO-OFDMA systems are thoroughly studied and summarized. Remarks on resource allocation and spectrum sharing are also presented, which demonstrate the great value of resource allocation techniques, but also introduce distinct challenges of resource allocation in MIMO-OFDMA systems. Novel resource allocation techniques for OFDMA Systems are surveyed from various applications (e.g., for unicast, or multicast with Guaranteed BER and Rate, subcarrier and power allocation with various detectors, low-complexity energyefficient resource allocation, etc.) in this book. Due to the high mobility and low latency requirements of 5G wireless communications, this book discusses how to deal with the imperfect CSI. It also discusses how to deal with e.g., throughput maximization, outage probabilities maximization and guarantee, energy efficiency, physical-layer security issues with feedback channel capacity constraints, in order to characterize and understand the applications of practical scenes. This book will target professionals & researchers working in the fields of Wireless Communications and Networking, Resource Allocation and Transmissions. Advanced-level students in electrical engineering and computer science will also find this book useful as a secondary textbook.

This book allows readers to gain an in-depth understanding of resource allocation problems in wireless networks and the techniques used to solve them.

Cooperative communication has recently been considered as a key technology for modern wireless standards and next generation wireless networks to improve the quality-of-service (QoS) and extend transmission coverage in a cost-e ective manner. In this thesis, we aim to address the challenges of wireless cooperative communications, and design the e cient OFDM-based relay systems. Starting with the channel accumulation problem in the amplify-and-forward (AF) relay system, we proposed two adaptive guard interval (GI) schemes for single/multiple-relay networks respectively to cover the accumulated delay spread and enhance the transmission e - ciency. Distinct from the traditional adaptive GI, the dynamical GI length can be detected by the destination individually. Numerical results show that the proposed scheme can further save the control signaling overhead without any symbol error rate (SER) performance loss. For multiple-relay systems, a novel relay selection criterion is proposed to achieve the trade-off between the transmission reliability and overhead by considering both the channel gain and the accumulated delay spread. From computer simulations, the proposed relay selection scheme significantly improves the e cient throughput over the multipath channel with variable channel length, Moreover, cooperative systems require an accuracy resource allocation to achieve the high capacity in the two-way decode-and-forward (DF) relay system with time-varying channels and the bidirectional asymmetric tra c. We propose two allocation algorithms, where the total capacity is maximized under a capacity ratio constraint which depends on the tra c-load di erence between the uplink and downlink. The balanced capacity performance shows that the proposed schemes can assure the fairs data rate of the two terminals and improve the overall QoS of the relay network. A low-complexity suboptimal allocation algorithm is proposed for the frequency-division model which separates subcarrier and time/power allocation. Verifying by simulations, the suboptimal scheme can achieve the similar performance with the optimal one with reduced complexity. In order to further enhance the transmission reliability and maintain low processing delay, we propose a novel equalize-and-forward (EF) relay scheme, which can equalizes the channel between source and relay and eliminate the channel accumulation e ect. The relay processing time is reduced by performing the channel estimation and equalization in parallel. In the EF relay, free-delay equalization is realized by presetting the equalizer with the current channel response that is predicted in parallel. Numerical results show that the EF relay can achieve comparable SER performance as the DF relay with much less latency and exhibit low outage probability at the same data rate as compared to traditional AF and DF schemes.

Do you need to design efficient wireless communications systems? This unique text provides detailed coverage of radio resource allocation problems in wireless networks and the techniques that can be used to solve them. Covering basic principles and mathematical algorithms, and with a particular focus on power control and channel allocation, you will learn how to model, analyze, and optimize the allocation of resources in both physical and data link layers, and for a range of different network types. Both established and emerging networks are considered, including CDMA and OFDMA wireless networks, relay-based wireless networks, and cognitive radio networks. Numerous exercises help you put knowledge into practice, and provide the tools needed to address some of the current research problems in the field. This is an essential reference whether you are a graduate student, researcher or industry professional working in the field of wireless communication networks.

In this thesis, we propose several resource allocation strategies for relay networks in the context of joint power and bandwidth allocation and relay selection, and joint power allocation and subchannel assignment for orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) systems. Sharing the two best ordered relays with equal power between the two users over Rayleigh flat fading channels is proposed to establish full diversity order for both users. Closed form expressions for the outage probability, and bit error probability (BEP) performance measures for both amplify and forward (AF) and decode and forward (DF) cooperative communication schemes are developed for different scenarios. To utilize the full potentials of relay-assisted transmission in multi user systems, we propose a mixed strategy of AF relaying and direct transmission, where the user transmits part of the data using the relay, and the other part is transmitted using the direct link. The resource allocation problem is formulated to maximize the sum rate. A recursive algorithm alternating between power allocation and bandwidth allocation steps is proposed to solve the formulated resource allocation problem. Due to the conflict between limited wireless resources and the fast growing wireless demands, Stackelberg game is proposed to allocate the relay resources (power and bandwidth) between competing users, aiming to maximize the relay benefits from selling its resources. We prove the uniqueness of Stackelberg Nash Equilibrium (SNE) for the proposed game. We develop a distributed algorithm to reach SNE, and investigate the conditions for the stability of the proposed algorithm. We propose low complexity algorithms for AF-OFDMA and DF-OFDMA systems to assign the subcarriers to the users based on high SNR approximation aiming to maximize the weighted sum rate. Auction framework is proposed to devise competition based solutions for the resource allocation of AF-OFDMA aiming tomaximize either vi the sum rate or the fairness index. Two auction algorithms are proposed; sequential and one-shot auctions. In sequential auction, the users evaluate the subcarrier based on the rate marginal contribution. In the one-shot auction, the users evaluate the subcarriers based on an estimate of the Shapley value and bids on all subcarriers at once. Acknowledgments All praise and thanks be to Allah, for blessing me with the strength and enthusiasm to seek knowledge and to complete this work. Foremost, I would like to express my sincere appreciation and gratitude to my advisor Dr. Imad Barhumi, for his academic guidance and enthusiastic encouragement throughout this PhD. His constant encouragement was vital in making this dissertation a reality. He spent endless hours proofreading my research papers and giving me excellent suggestions, which always resulted in improved versions of the documents. He also supportedme during the difficult times in my research. He believed in me when I doubted myself, and always preserved his confidence in my ability to complete my PhD. Doing a PhD is always challenging, and I will not forget how Dr. Imad assisted me. I cannot thank him enough for all the encouragement and advice, helping to make it an enjoyable experience. I owemy deepest gratitude to theUnitedArab EmiratesUniversity (UAEU) for its generosity in supporting me financially during my PhD study. I would like to thank Dr. Mohammad Hayajneh, Dr. Qurban Ali, and Prof. Noafal Al-Dahir for serving as my PhD Advisory Committee. I would like to thank Prof. K.J. Ray Liu, Dr. Mohammed Abdel-Hafez, Dr. Khaled Shuaib for serving as my PhD Examining Committee. Iwould like to thank all the faculty and staff in the Electrical Engineering Department in UAEU for their continuous encouragement. I would like to acknowledge the help of all the people who have contributed to my education, especially,my professors in Jordan University and colleagues in Amman Al-Ahliyyah University. I would like to thank friends at UAEU; Salam, Assha, Hanifa, Razan, Shumma, Taghreed, Sawsan, Nedaa, Reem, Maysara, Dr. Maysa, Hanan, Hana, and Swzen. Thank you for the true positive experience we had during my PhD research. I would like to thank my friends Rana, Ymna, Lubna, Lena, Lamiss, Abir, Huda, Maram, Ahlam, and Angham. Your friendship and prayers gave me strength to overcome difficulties throughout this endeavor. All thanks to Alah for blessing me with good friends. My heartiest thanks go to my parents, brothers and their families, thank you for everything, for your support, love, and care.

OFDM-based Broadband Wireless Networks covers the latest technological advances in digital broadcasting, wireless LAN, and mobile networks to achieve high spectral efficiency, and to meet peak requirements for multimedia traffic. The book emphasizes the OFDM modem, air-interface, medium access-control (MAC), radio link protocols, and radio network planning. An Instructor Support FTP site is available from the Wiley editorial department.

The idea of using cooperating relays has been much discussed in the past decade. In a wireless communication system, relaying techniques can offer significant benefits in the throughput enhancement and range extension. On the other hand, cognitive radio is an interesting concept for solving the problem of spectrum availability by reusing the underutilized licensed frequency bands. In a cognitive radio network, relays can be particularly useful for reducing the transmission power at the source and thus reduce the interference to the primary users. In this thesis, we study resource allocation problems for cognitive radio networks that employ relays. In this work, the transmission power of the nodes (users and relays) is the resource that we wish to allocate. The power allocation problems are formulated as non-convex non-linear programs and they do not have a structure that could guarantee the quality of the solution. We present a method of transforming the proposed optimization problems to a new formulation so that f-optimal algorithms can be designed. In general, the transformed problem exhibits certain properties, which enable us to solve the optimization problems to a desirable accuracy by applying known global optimization techniques. We note that the global optimization techniques require significant computations to solve our proposed optimizations. Therefore, we propose low complexity heuristics that provide suboptimal solutions to the given optimization problems. The simulation results show that the performance of the heuristics is close to their respective optimal solutions.