Resource Allocation in OFDM Based Wireless Relay Networks ...

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3.1 Introduction Figure 3.2: Bidirectional communication with TWRN. three node network, where two user terminals exchange information with the help of a relay node using OFDM transmission, subject to an individual power constraint at each node. The results showed an enhanced system performance from an optimized power allocation via dual decomposition technique and a greedy tone permutation scheme. This scheme is further exploited in [51] under a total power constraint where a two step power allocation strategy was proposed. Joint power allocation and sub-carrier assignment problem in multiple-relay scenario, where two terminals exchange information with the help of more than one intermediate relay nodes, was considered in [52]. The problem is solved by a suboptimal algorithm where each resource is optimized by fixing the other. The authors further applied the idea to the OFDMA based multi-user multi-relay systems in [53] and proposed a sub-carrier allocation algorithm for the known power allocation. The work in [54] studied the power and sub-carrier allocation problem in OFDMA multi-user relay network. More recently, relay power allocation problem in a multi-user system, where a number of user pairs exchange information through a single relay station, was considered in [55]. However a unified resource allocation scheme considering tone permutation, power optimization, and sub-carrier allocation all together has not been designed. Motivation The two phases of transmission in bidirectional relaying are generally categorized as following • Multiple-Access Phase (MAP): In MAP the two end terminals simultaneously transmit information to the relay node. 45
3.1 Introduction • Broadcast Phase (BCP): The relay processes the information according to the relaying mode (AF or DF) and broadcasts the message in BCP. Conventionally, in OFDM based bidirectional communication, the signal received over a sub-carrier in MAP is re-transmitted at the same sub-carrier in BCP. Due to the independent nature of the channels in the two phases, a deep faded sub-carrier in MAP may have high SNR in BCP. Thus, using the same sub-carrier in MAP and BCP is clearly suboptimal and a better utilization of channel dynamics could be achieved with a careful tone-matching strategy. The previous reported works [50]–[55] have shown the enhanced throughput results in OFDM systems by optimizing different units of resources separately. However, due to the nature of types of resources and the multi-user TWRN system model, the different resources are tightly coupled with each other. For example, a bad sub-carrier k in MAP for a pre-assigned user pair (U 1 , U 2 ) may be good for another user pair (U 3 , U 4 ) and a reverse could exist in BCP. Thus, the sub-carriers should not only be carefully matched in the two phases (MAP and BCP) but also be allocated adaptively for different users. Further, the distributed nature of the wireless systems prohibits us to impose a total power constraint over all nodes. Hence, we assume that each node has a limited power supply, which makes our consideration closer to practical scenarios. Contributions The main contributions of this chapter are: • Our target is to maximize the end-to-end system transmission rate of the OFDMA based multi-user bidirectional relay network subject to individual power budget constraint of each transmitting node. We present a new unified framework for jointly optimizing different types of resources, namely, – Power allocation at user and relay terminals such that each user allocates powers to a unique set of sub-carriers allocated to him in MAP and the 46
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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
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 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 ( )
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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: 3.1 Introduction A new technology c
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
Page 89 and 90: 4.4 Optimization under Orthogonal T
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
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
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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
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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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Resource Allocation in OFDM Based Wireless Relay Networks ...

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