Buffer-aided relaying with discrete transmission rates

We consider a slow fading three-node network consisting of a source, a half-duplex decode-and-forward relay, and a destination, where a direct link between the source and the destination does not exist. We assume that the half-duplex relay is equipped with a buffer and employs in each time slot adaptive scheduling of reception and transmission based on the instantaneous qualities of the source-to-relay and relay-to-destination links. Furthermore, as a practical constraint, we assume that in each time slot, the source and the relay can select transmission rates only from a discrete and finite set of available transmission rates. For this network, we design the optimal scheduling of reception and transmission at the relay and the optimal selection of the transmission rates at the source and the relay such that the throughput is maximized. Our numerical results show that the maximum throughput achieved with the proposed buffer-aided protocol for discrete transmission rates is significantly larger than the throughput achieved with conventional relaying protocols with continuous transmission rates.