Buffer-Aided Max-Link Relay Selection in Multi-Hop DF Cooperative Networks

Multi-hop relaying is an important strategy for improved link performance and increasing the range of communication, while the buffers at the relays improve the diversity advantage of the system. In this paper, we investigate the performance of multiple clusters of relays with buffers using max-link relay selection scheme for decode-and-forward cooperative networks. A generalized Markov chain is proposed to model the evolution of buffer status for more than one cluster. Construction of the state diagram for two clusters of relays is discussed as an example. Analytical expressions for the outage probability and the average packet delay are derived. It is shown through numerical results that at moderate to high signal-to-noise ratios, the outage improves with increasing number of clusters. Furthermore, closed-form analytical expressions are obtained for the steady-state probability vector by considering different numbers of clusters and relays. Through examples, we observe that states with the same steady-state probabilities can be grouped. The size of the state transition matrix grows with increasing number of clusters and relays in each cluster. Thus, by exploiting the property of grouping the same state probabilities, we provide an approach to reduce the size of the state transition matrix.