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4.5 Simulations algorithm converges in 20 iterations, which are four times more than that of FP. Orthogonal transmission Under orthogonal transmission, we compare four different algorithms. The proposed joint power allocation and sub-carrier pairing solution. 1) JPSC: 2) Pow: An algorithm where optimum power allocation is obtained without considering sub-carrier pairing. 3) EPSC: A solution where the sub-carriers are paired according to the proposed algorithm under uniform power distribution such that the available power at each node is equally divided among all the sub-carriers. 4) EP: In this case, without considering sub-carrier pairing, each node equally distribute the available power to the K sub-carriers. The throughput performance of four different methods versus SNR where the relays transmit in preassigned time slots is shown in Fig. 4.4. We have set P = Q n = 10, ∀n. We observe that JPSC yields the best performance over all other algorithms. Further, the optimized power allocation solution (Pow) out performs the uniform power allocation solutions. Optimizing only the sub-carrier pairing also provides performance gain in EPSC over the EP solution which validate the idea of performance achievement from sub-carrier matching over two hops. Finally, as expected, we observe that the system throughput decreases while increasing the number of relay nodes which is due to the lower TDMA factor ( 1 ) for higher N. N+1 Next we examine the performance of the end-to-end rate versus the SNR under the relay selection scenario. The results for different algorithms are shown in Fig. 4.5, where the parameters are same as that of in Fig. 1. Similar to the previous example, JPSC yields the best performance among different methods and the proposed suboptimal methods (Pow, EPSC) also outperform the trivial solution (EP). Comparing the results with Fig. 4.4, all the schemes exhibit performance gain. Further, unlike the previous example, increasing the number of relay nodes improves the performance. This is consistent with the results in [56]. 79
4.6 Summary 0.9 0.8 0.7 JPSC Pow EPSC EP N=4 bits/s/Hz 0.6 0.5 0.4 N=10 0.3 0.2 1 2 3 4 5 6 7 8 9 10 SNR (dB) Figure 4.4: Rate versus SNR with orthogonal transmission. 4.6 Summary In this chapter, a dual hop communication was considered where the multiple relay nodes receive and transmit information over a common frequency band. First a non-orthogonal transmission was assumed where all the relays transmit over all the OFDM sub-carriers to maximize the system throughput. Different variables were optimized to develop a joint resource allocation algorithm, i.e., the power allocation over different sub-carriers at SN, the beamforming coefficients at RNs, and the sub-carrier pairing at the relays. The complexity of the joint resource allocation scheme increases with increasing the number of relay nodes. To reduce the computation burden, a suboptimal algorithm was then designed. Secondly, an orthogonal parallel transmission was studied where the relay nodes transmit in independent time slots. In this scenario, the power allocation at the source/relay nodes and the sub-carrier pairing was optimized to enhance the system throughput. However, this scheme provides much lower performance than the non-orthogonal scheme because of the N + 1 time slots required for a complete transmission. The 80
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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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1.4 Resource Allocation Problem is
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1.5 Contribution and Organization o
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1.5 Contribution and Organization o
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2.1 Introduction allocated to a nod
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2.1 Introduction The main contribut
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2.2 System Model where h m,k denote
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2.3 Resource Allocation Schemes opt
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2.3 Resource Allocation Schemes ( )
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2.3 Resource Allocation Schemes and
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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 75 and 76: 3.7 Summary 1.8 1.6 1.4 JntOpt SubO
Page 77 and 78: 4.1 Introduction • Non-orthogonal
Page 79 and 80: 4.3 Cooperative Non-Orthogonal Tran
Page 87 and 88: 4.4 Optimization under Orthogonal T
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Page 91 and 92: 4.5 Simulations Then, the over all
Page 93: 4.5 Simulations 40 30 20 Sum−ρ S
Page 97 and 98: Chapter 5 Lifetime Maximization in
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
Page 127: B. Derivations of the Optimal Power
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