Resource Allocation in OFDM Based Wireless Relay Networks ...

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1.5 Contribution and Organization of the Thesis of resources by allocating sub-carriers to the nodes with large attenuations. In multi-relay OFDM networks, the optimal relay assignment should also be included in the resource allocation problem. Similar to multi-user diversity, sub-carriers have independent fading for different relaying nodes. In conventional OFDM systems, the system performance is optimized through optimal power allocation among different sub-carriers. However, the resource allocation in OFDM based relaying transmission is more challenging. A deep faded sub-carrier over the first hop for one relay station may be a good candidate over the second hop for the same relay. Thus, a careful power distribution, sub-carrier pairing, and relay assignment policy is required for the guaranteed performance of the system. All these resources are strictly coupled with each other, for example, changing the power distribution will certainly change the sub-carrier pairing over the two hops and this can result in different relay assignments. Thus, designing the joint resource allocation schemes is necessary for the promising advantages of relay networks and is the main aim of this thesis’s work. 1.5 Contribution and Organization of the Thesis The relay networks have gained much interest due to their capability of enhancing the communication reliability and enlarging the transmission range [18], [19]. Meanwhile, multi-carrier transmissions are known to combat the frequency selective fading channels and, when combined with the relay transmission, can provide improved performance through adaptive resource allocation. Hence, various researches on multi-carrier aided relay networks have been carried out during the past few years, for example, channel estimation [20], precoder design [21], and throughput analysis via resource allocation [17]. In this thesis, we study resource allocation problems for relay enhanced networks. The main objective of the research is to develop optimal and computational efficient resource allocation algorithms for various relay transmission schemes. In the context of relay transmission, we consider five different schemes: 1) 11
1.5 Contribution and Organization of the Thesis uplink relay transmission, 2) bidirectional relay transmission, 3) multi-relay dual-hop transmission, 4) multi-hop transmission, and 5) cognitive relay transmission. The detailed description of different schemes will be presented in the next chapters. For each transmission scheme, the aim is to enhance the system performance, for example the system throughput or network lifetime, subject to power and the other transmission specific constraints. Depending on the transmission strategy, different algorithms are developed to optimize two or more resources introduced in section 1.4. In chapter 2, a joint resource allocation problem is formulated for multi-user multi-carrier uplink relay transmission system. The objective function is to maximize the sum-rate over joint sub-carrier allocation, sub-carrier pairing, and power allocation under the individual power constraints at each transmitting node. Asymptomatically optimal and computationally efficient algorithms are developed. Further, the algorithm is extended to multiple relay scenario where the optimal sub-carrier to relay assignment is also obtained. In chapter 3, we develop resource allocation algorithms for OFDMA assisted two-way relay network. The two way relaying promises to overcome the rate loss problem caused due to the half duplex relay transmission, however, makes the resource allocation problem more challenging. We develop a scheme which jointly optimizes the sub-carrier assignment to the pre-defined user pairs, the tone matching over the two phases of the transmission, and the power allocation over the sub-carriers subject to the limited availability of the power budgets at the user/relay nodes and the OFDMA constraints. A low complexity algorithm is also designed which shows its comparable performance via simulation results. In chapter 4, we explore a dual hop multi-relay network where all the relays receive/transmit information on a shared channel. First, a concurrent transmission is considered, where all the relays simultaneously transmit data in the second hop. The resource allocation algorithms are designed such that the power allocation at the source node, the beamforming at the relay nodes, and the sub-carrier pairing over the 12
Page 1 and 2: Resource Allocation in OFDM Based W
Page 3 and 4: Dedications: To my family
Page 5 and 6: Acknowledgment I am greatly thankfu
Page 7 and 8: Contents 2.3.3 Proposed Low-Complex
Page 9 and 10: Abstract The combination of relay t
Page 11 and 12: List of Tables 3.1 Complexity compa
Page 13 and 14: List of Figures 4.1 System model fo
Page 15 and 16: List of Acronyms IEEE MU RS AWGN OW
Page 17 and 18: 1.1 Overview of Relay Networks wire
Page 19 and 20: 1.2 Overview of OFDM Figure 1.2: Th
Page 21 and 22: 1.3 Basics of the Optimization Theo
Page 23 and 24: 1.3 Basics of the Optimization Theo
Page 25: 1.4 Resource Allocation Problem is
Page 29 and 30: 1.5 Contribution and Organization o
Page 31 and 32: 2.1 Introduction allocated to a nod
Page 33 and 34: 2.1 Introduction The main contribut
Page 35 and 36: 2.2 System Model where h m,k denote
Page 37 and 38: 2.3 Resource Allocation Schemes opt
Page 39 and 40: 2.3 Resource Allocation Schemes ( )
Page 41 and 42: 2.3 Resource Allocation Schemes and
Page 43 and 44: 2.3 Resource Allocation Schemes tha
Page 45 and 46: 2.3 Resource Allocation Schemes 2.3
Page 47 and 48: 2.4 Generalization to Multiple Rela
Page 49 and 50: 2.4 Generalization to Multiple Rela
Page 51 and 52: 2.5 Simulation Results • OptSol/J
Page 53 and 54: 2.5 Simulation Results 0.9 0.85 0.8
Page 55 and 56: 2.6 Summary 2.6 2.4 2.2 2 Rate (bit
Page 57 and 58: 2.6 Summary 2.4 2.2 2 1.8 N=4 N=3 N
Page 59 and 60: 3.1 Introduction A new technology c
Page 61 and 62: 3.1 Introduction • Broadcast Phas
Page 63 and 64: 3.2 System Model MU MU 3 8 A 1 2 7
Page 65 and 66: 3.4 Joint Resource Allocation Schem
Page 67 and 68: 3.4 Joint Resource Allocation Schem
Page 69 and 70: 3.5 Step-Wise Low-Complexity Resour
Page 71 and 72: 3.6 Simulation Results and SNR B m,
Page 73 and 74: 3.6 Simulation Results 3 2.5 2 Uppe
Page 75 and 76: 3.7 Summary 1.8 1.6 1.4 JntOpt SubO
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4.1 Introduction • Non-orthogonal
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4.3 Cooperative Non-Orthogonal Tran
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4.4 Optimization under Orthogonal T
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4.4 Optimization under Orthogonal T
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4.5 Simulations Then, the over all
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4.5 Simulations 40 30 20 Sum−ρ S
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4.6 Summary 0.9 0.8 0.7 JPSC Pow EP
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Chapter 5 Lifetime Maximization in
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5.1 Introduction Figure 5.2: Linear
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5.2 System Model antenna that canno
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5.4 Lifetime Maximization Scheme 5.
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5.4 Lifetime Maximization Scheme wh
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5.5 Simulation Results 150 OPT−SO
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5.6 Summary Lifetime (S) 150 100 50
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Chapter 6 Resource Allocation in Co
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7. Conclusions were considered for
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Bibliography [12] A. Peled, and A.
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Bibliography [36] Z. Luo and S. Zha
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Bibliography [61] D. H. N. Nguyen,
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Bibliography [84] A. Goldsmith, S.
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Bibliography [105] Y. Li, W. Wang,
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Appendix A Derivations of Closed-Fo
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B. Derivations of the Optimal Power
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