Relay Selection for Cooperative NOMA

Zhiguo Ding,H Vincent Poor,Huaiyu Dai

doi:10.1109/lwc.2016.2574709

Abstract

This letter studies the impact of relay selection (RS) on the performance of cooperative non-orthogonal multiple access (NOMA). In particular, a two-stage RS strategy is proposed, and analytical results are developed to demonstrate that this two-stage strategy can achieve the minimal outage probability among all possible RS schemes, and realize the maximal diversity gain. The provided simulation results show that cooperative NOMA with this two-stage RS scheme outperforms that based on the conventional max-min approach, and can also yield a significant performance gain over orthogonal multiple access.

Highlights

Non-orthogonal multiple access (NOMA) has been recognized as a promising enabling technology to improve the spectral efficiency of the fifth generation (5G) mobile network, and has been recently included into the fourth generation (4G) long term evolution (LTE) system [1]–[3]
We obtain a closed form expression for the outage probability achieved by the twostage relay selection strategy, which shows that this two-stage scheme can realize the maximal diversity gain
We have studied the impact of relay selection on cooperative NOMA

Summary

INTRODUCTION

Non-orthogonal multiple access (NOMA) has been recognized as a promising enabling technology to improve the spectral efficiency of the fifth generation (5G) mobile network, and has been recently included into the fourth generation (4G) long term evolution (LTE) system [1]–[3]. A dedicated relay has been used in [5] to improve the transmission reliability for a user with poor channel conditions. We obtain a closed form expression for the outage probability achieved by the twostage relay selection strategy, which shows that this two-stage scheme can realize the maximal diversity gain. Analytical results are developed to demonstrate that the twostage strategy is outage-optimal, i.e., it achieves the optimal outage probability among all possible relay selection schemes. The max-min relay selection criterion can achieve the same performance as the two-stage one, i.e., realizing the minimal outage probability, for a special case with symmetrical setups, but it suffers a loss of the outage probability in general. H. Dai is with the Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695 USA

SYSTEM MODEL

PERFORMANCE ANALYSIS

NUMERICAL STUDIES

CONCLUSIONS