Cooperative ARQ protocols in slotted radio networks

In conventional (non-cooperative) automatic repeat request (ARQ) protocols for radio networks, the corrupted data frames that cannot be correctly decoded at the destination are retransmitted by the source. In cooperative ARQ protocols, data frame retransmissions may be performed by a neighboring node (the relay) that has successfully overheard the source’s frame transmission. One advantage of the latter group of ARQ protocols is the spatial diversity provided by the relay. The first delay model for cooperative ARQ protocols is presented in this paper. The model is analytically derived for a simple set of retransmission rules that make use of both uncoded and coded cooperative communications in slotted radio network. The model estimates the delay experienced by Poisson arriving frames, whose retransmissions (when required) are performed also by a single relay. Saturation throughput, frame latency and buffer occupancy at the source, and relay are quantified and compared against two non-cooperative ARQ protocols.