Threshold Based Relay Selection for Buffer-Aided Cooperative Relaying Systems

Abstract

In this paper, we propose a novel relay selection strategy for half-duplex decode-and-forward cooperative networks with an arbitrary number of buffer-aided (BA) relays. Unlike most of the existing predetermined relaying protocols, the proposed strategy is adjustable in the sense that it is controlled by K threshold levels. A Markov chain (MC) analysis is adopted for evaluating the outage probability (OP) and average packet delay (APD) of the proposed scheme. Through an asymptotic analysis, we highlight on the impact of the K controlling parameters on the triad of OP, APD and diversity order that can be contemplated. While most of the existing schemes are designed to achieve fixed APD and diversity order values, the proposed scheme can achieve all diversity orders ranging from K to 2K while compromising the asymptotic APD that will range from 2 to 2K+2. We also target the optimization of the buffer size and we prove that a buffer size of three is sufficient for extracting the full capabilities of the BA network. Simulations over Rayleigh fading channels demonstrate the performance gains and the OP-APD tradeoffs that can be attained.