Opportunistic Multiple Relay Selection for Two-Way Relay Networks with Outdated Channel State Information

Abstract

Outdated Channel State Information (CSI) was proved to have negative effect on performance in two-way relay networks.The diversity order of widely used opportunistic relay selection (ORS) was degraded to unity in networks with outdated CSI.This paper proposed a multiple relay selection scheme for amplify-and-forward (AF) based two-way relay networks (TWRN) with outdated CSI.In this scheme, two sources exchange information through more than one relays.We firstly select N best relays out of all candidate relays with respect to signal-noise ratio (SNR).Then, the ratios of the SNRs on the rest of the candidate relays to that of the Nth highest SNR are tested against a normalized threshold μ∈[0, 1], and only those relays passing this test are selected in addition to the N best relays.Expressions of outage probability, average bit error rate (BER) and ergodic channel capacity were obtained in closed-form for the proposed scheme.Numerical results and Simulations verified our theoretical analyses, and showed that the proposed scheme had significant gains comparing with conventional ORS.