Updatable ARQ protocol for distributed space-time coded relay networks

An updatable automatic repeat request (ARQ) protocol for distributed space-time coded cooperative networks is proposed in this paper. We define a decoding relay set (DS), composed of the relays decoding the packet from source correctly. The DS would be expanded as the round of ARQ increasing, because the relays failing to receive correct packet in previous (re)transmission are still possible to decode the packet successfully in future retransmission. Since more and more relays would participate in ARQ process, the possibility that the destination can decode the error-free packet would be improved. Simulation results show that the updatable protocol has a lower packet loss ratio (PLR) and smaller average number of retransmission (N_aver) than conventional protocol. Especially, when the channels between relays are in good condition, the proposed protocol can obtain about 1.6 dB gain at a PLR of 10^-3.