Resource Allocation in OFDM Based Wireless Relay Networks ...

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Chapter 2 Resource Allocation in Multi-User Uplink Systems In this chapter, we propose a joint resource allocation scheme for relay aided uplink multi-user transmission with a single destination node. To reduce the computational complexity, we present a suboptimal algorithm which sacrifices very little on the performance. Moreover, we extend the proposed algorithms to the very general relay network with multi-user and multi-relays. The proposed algorithms could provide improved performance over the existing algorithms. 2.1 Introduction OFDMA is a spectrally efficient multiplexing technique used in various wireless systems such as IEEE 802.11, IEEE 802.16 and is a promising candidate for future cellular networks e.g., accepted for IEEE 802.16j and LTE-Advanced. Disjoint sets of sub-carriers could be formed from OFDM symbol. OFDMA employs OFDM and has an innate feature of exploiting the frequency selectivity enabled multi-user diversity such that the multiple users transmit their information simultaneously using the different sub-carriers without inter-user interference. Based on the quality of wireless channels, the power allocation over sub-carriers and the set of sub-carriers 15
2.1 Introduction allocated to a node can be optimized. Similar to traditional point-to-point multi-user OFDMA system[22], an OFDMA relay network is defined as a broadband relay network where a sub-carrier can be assigned to only one transmitting node at any time. The promise of simple receivers and high system performance has landed OFDMA relay networks as one of the prime multiple-access schemes for future generation broadband wireless networks, e.g., 802.16j. In traditional OFDMA systems, it is possible to optimize the system performance from carefully assigning sub-carriers and power among different users [23, 24]. However, the resource allocation in OFDMA relay networks is more challenging. A sub-carrier with low SNR over the first hop for one node may be a good candidate over the second hop for the same or another node, thus, a careful power distribution and sub-carrier allocation policy is mandatory for promising performance of OFDMA relay networks. The power allocation between source and relay node play an important role in performance enhancement [25]. In OFDM relay networks, the independent nature of the channels over different hops motivates to consider the sub-carrier pairing at relay nodes[15]. In [17], the authors proposed a power allocation and sub-carrier pairing algorithm for single user single relay network under separate power constraints at source and relay nodes. The algorithm follows a step wise approach. In the first step, sub-carriers are paired according to the channel gains assuming an equal power allocation policy. In the second step, an alternate power allocation policy is adopted such that the source (relay) power is optimized for the known relay (source) power. Further, a joint source and relay power allocation scheme is also presented under the total power constraint. On the aspects of the multi-user scenario, resource optimization in relay networks has been studied in [27]–[29] for downlink scenario. For example, the resource allocation in OFDM based multi-user multi-hop relay network was considered in [27]. The joint sub-carrier allocation and power loading in OFDMA based relay networks, with or without fairness, have been studied in [28]. The 16
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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 and 26: 1.4 Resource Allocation Problem is
Page 27 and 28: 1.5 Contribution and Organization o
Page 29: 1.5 Contribution and Organization o
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
Page 77 and 78: 4.1 Introduction • Non-orthogonal
Page 79 and 80: 4.3 Cooperative Non-Orthogonal Tran
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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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