Hybrid relay selection in heterogenous relay networks

In this paper heterogenous networks are envisioned where multiple amplify-forward (AF) and decode-forward (DF) relays coexist. Consider a representative case with one source, one destination, and multiple relays, where at each point in time a subset (e.g. two) of the relays can be active simultaneously. The question naturally arises: how can we select relays for service from among the collection of available relays, and what is the performance of each selection scheme. We propose and analyze several selection schemes in a two-relay scenario involving a number of ways to synchronously combine AF and DF relays. Expressions for outage probability in each case are obtained.