Back-pressure-like mechanisms on relay selection policies for cooperative diversity systems

Abstract: The topic of the current thesis is the reduction of the average packet delay in two-hop wireless cooperative networks with buffer-aided relays. This type of networks is of particular interest since it constitutes the building block for extended networks with multiple hops and numerous relays. Back-pressure-like algorithms are developed for the HRS and max − link relay selection schemes. First, an algorithm is developed and applied for both the HRS and the max − link protocols. It reduces the average delay considerably, but, in the case of the max − link the diversity of the system is reduced resulting in higher outage probabilities. For this reason, a new algorithm is developed that aims at maintaining a high diversity throughout the operation of the network. Distributed implementations of the algorithms are also discussed. The performance of the proposed algorithms is illustrated via simulations.