Abstract
In this letter, a buffer-state-based probabilistic relay selection (RS) scheme is proposed for buffer-aided cooperative relay networks with delay constraints. In particular, we first select the source-to-relay (S2R) and relay-to-destination (R2D) links with the smallest and the largest numbers of packets in the corresponding buffer queues, among all S2R and R2D links whose fading channel gains exceed a predefined threshold, respectively. Then, we utilize the outcome of an auxiliary random variable to decide which one between these two links is selected. Furthermore, the outage probability and average packet delay are analyzed, respectively. In addition, a useful definition of the probability mass function for the auxiliary random variable is proposed to enhance the outage performance under delay constraints. Simulation results show that the proposed scheme significantly outperforms existing buffer-aided RS schemes under different delay constraints.