A Fair Relay Selection Based on Mapping Functions in the Dual Hop DF Cooperative Networks

Abstract

We address the load balance, referred as “fairness” in our work, in the relay selection procedure of the dual hop decode-and-forward (DF) cooperative networks. Firstly, the unfairness caused by the known best-path relay selection (BRS) scheme is analyzed by the metric of blocking probability at the relays with equal relay channels. Secondly, aiming to improve the fairness while keeping a satisfied and comparable outage performance, we propose a fair relay selection algorithm based on mapping functions, including the signal to noise ratio (SNR) mapping functions and load mapping functions. It is worth mentioning that BRS scheme can be viewed as a special case of the proposed algorithm. Afterwards, the outage probability of the proposed algorithm is derived. During the derivation, the mixture Gamma distribution is used to model SNRs of wireless fading channels, so this kind of derivation is valid for different fading channels, e.g. Rayleigh, Nakagami-m etc.. Finally, taking the average load and outage probability as performance metrics, we simulated the proposed algorithm and compared it with the proportional fair cooperation (PFC) algorithm in the literature. As observed in the simulation results, the proposed algorithm guarantees fairness well among the relays, especially when the network is heavily burdened