Resource Allocation in OFDM Based Wireless Relay Networks ...

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Chapter 4 OFDM Resource Allocation for Parallel Relay Communication In this chapter, we explore resource optimization problem in dual hop multi-carrier parallel relay networks. Power allocation at the source and the beamforming at the relay nodes are optimized such that all the relays transmit simultaneously over the second hop. Further, to complete the studies, an orthogonal transmission is also considered where the relays transmit in different time slots. 4.1 Introduction The cooperative communication is known to enhance the performance of wireless systems. In a multi-relay network, different relay nodes coordinate their transmission and transfer the data to destination node which combines all the signals. We consider a parallel relay transmission between the transmitter and the destination. The OFDM based parallel relays can transmit data in different ways, i.e., • The OFDMA transmission where each relay occupies a unique set of orthogonal sub-carrier and transmit simultaneously in the second hop. We have considered this transmission strategy in chapter 2 for multi-user multi-relay scenario. 61
4.1 Introduction • Non-orthogonal transmission where all the relays transmit simultaneously over all the sub-carriers. In this work we consider this scheme of transmission. • The orthogonal transmission such that each relay transmits in exclusive time slot over all OFDM sub-carriers. This resource allocation under this scheme is also discussed in this chapter. The resource optimization in dual hop relay networks has been studied in [56]–[62]. The authors in [56] investigated the power allocation problem in parallel relay networks such that each relay transmits in a pre-assigned time slot under AF protocol. Moreover, a relay selection scheme was also proposed in this work. The power optimization in multi-relay system where the source node and each relay station transmit over orthogonal channels was considered in [57]. In flat fading transmission, the beamforming problem in AF multi-relay networks under an aggregate power constraint has been studied in [58]. The optimal beamforming coefficients under individual power constraints were derived in [59]. Distributed beamforming strategies were developed in [60]. [61] considered the distributive beamforming design in multi-relay network with multiple sources and multiple destinations. Further, [62] investigated the joint power loading and bandwidth allocation strategies for orthogonal and non-orthogonal multi-relay systems. The relay networks with combination of OFDM transmission have been proposed to further enhance the system performance [20]–[21]. The relay power allocation problem to maximize the system throughput in OFDM based parallel relay networks has been considered in [63]. Further, the authors also investigated the relay power allocation in the scenario where each relay transmits in preassigned time slot in [64] and [65]. However, [63]–[65] did not consider the power allocation at the source node. In multi-hop networks the channels over different hops vary independently. With this fact, the sub-carrier paring in multi-relay systems has been considered in [16], [26], and [66]. However, all of these three works assumed an OFDMA based relay selection protocol where each sub-carrier can be assigned to maximum one relay station in each hop and each relay transmits over disjoint set 62
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Resource Allocation in OFDM Based W
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Dedications: To my family
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Acknowledgment I am greatly thankfu
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Contents 2.3.3 Proposed Low-Complex
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Abstract The combination of relay t
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List of Tables 3.1 Complexity compa
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List of Figures 4.1 System model fo
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List of Acronyms IEEE MU RS AWGN OW
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1.1 Overview of Relay Networks wire
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1.2 Overview of OFDM Figure 1.2: Th
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1.3 Basics of the Optimization Theo
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1.3 Basics of the Optimization Theo
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Page 27 and 28: 1.5 Contribution and Organization o
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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 ( )
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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
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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
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Page 69 and 70: 3.5 Step-Wise Low-Complexity Resour
Page 71 and 72: 3.6 Simulation Results and SNR B m,
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Page 91 and 92: 4.5 Simulations Then, the over all
Page 93 and 94: 4.5 Simulations 40 30 20 Sum−ρ S
Page 95 and 96: 4.6 Summary 0.9 0.8 0.7 JPSC Pow EP
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Page 99 and 100: 5.1 Introduction Figure 5.2: Linear
Page 101 and 102: 5.2 System Model antenna that canno
Page 103 and 104: 5.4 Lifetime Maximization Scheme 5.
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Page 107 and 108: 5.5 Simulation Results 150 OPT−SO
Page 109 and 110: 5.6 Summary Lifetime (S) 150 100 50
Page 111 and 112: Chapter 6 Resource Allocation in Co
Page 113 and 114: 7. Conclusions were considered for
Page 115 and 116: Bibliography [12] A. Peled, and A.
Page 117 and 118: Bibliography [36] Z. Luo and S. Zha
Page 119 and 120: Bibliography [61] D. H. N. Nguyen,
Page 121 and 122: Bibliography [84] A. Goldsmith, S.
Page 123 and 124: Bibliography [105] Y. Li, W. Wang,
Page 125 and 126: Appendix A Derivations of Closed-Fo
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B. Derivations of the Optimal Power
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