Energy-efficient resource allocation for OFDMA-based two-way relay channel with physical-layer network coding

Min Zhou,Xiaofeng Tao,Qimei Cui,Mikko Valkama

doi:10.1186/1687-1499-2012-66

Abstract

Physical-layer network coding (PNC) is a novel cooperative technique for two-way relay channel (TRC), where two users exchange information via intermediate relay node(s). On the other hand, the issue of green communications to reduce energy consumption has recently started to arouse much attention. This article studies the energy-efficient resource allocation problem for orthogonal frequency division multiple access (OFDMA)-based TRC with PNC. In particular, resource allocation for multi-user, multi-relay OFDMA systems is vital for the optimization of power allocation, relay selection and subcarrier assignment. By applying convex optimization techniques, an optimal resource allocation scheme is proposed to minimize total transmit power with required rates. Numerical simulations show that the proposed scheme provides diversity gain compared to the single relay network, and PNC gain relative to the TRC without PNC.

Highlights

Wireless relay was introduced in 3GPP-LTE-Advanced [1] for throughput enhancement and coverage extension without requiring large transmit powers
To the best of authors’ knowledge, this problem is considered for the first time in orthogonal frequency division multiple access (OFDMA)-based two-way relay channel (TRC) with physical-layer network coding (PNC) and multiple relay nodes
From Theorem 1, it is known that the proposed opportunistic subcarrier assignment criterion is the optimal energy-efficient criterion in multi-user multi-relay OFDMA-based TRC with PNC-AF

Summary

Introduction

Wireless relay was introduced in 3GPP-LTE-Advanced [1] for throughput enhancement and coverage extension without requiring large transmit powers. Power allocation to maximize the sum-rate under the total power constraint was developed for a TRC exchanging OFDM signals via a single relay in [10,11]. In [13], adaptive subcarrier allocation was proposed to maximize the achievable sum-rate for a multi-user multi-relay OFDMA-based TRC. An energy-efficient resource allocation to minimize transmit power consumption with required link rates is considered for OFDMA-based TRC with PNC. An optimal energy-efficient resource allocation is proposed with joint power allocation, relay selection and subcarrier assignment. To the best of authors’ knowledge, this problem is considered for the first time in OFDMA-based TRC with PNC and multiple relay nodes. The resulting signals at S1 and S2 on the nth subcarrier can be written as h(i n) τiρi(n)αi(n) gi(n) Ps(,n2)x(2n) + u(i n) + v(1n) (7)

Problem formulation

Problem simplification

Conclusion and discussion