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Dynamic coded cooperative ARQ for multi-hop underwater acoustic networks

Dynamic coded cooperation (DCC) does not need extra transmission time scheduled for the relay, which is appealing to the bandwidth-limited high-delay underwater acoustic (UWA) environment. In this paper, we propose dynamic coded cooperative automatic repeat request (DCC-ARQ) protocol for multi-hop UWA networks. A transmission packet with multiple blocks is taken as a one-shot unit, where an erasure-correction code is used for inter-block encoding. Adopting the DCC scheme in each hop UWA transmission, the half-duplex cooperative node switches to cooperation phase immediately after it decodes the cooperative message, which provides a more reliable cooperative path for the specific three-node network. Further, if the relay (or destination in the last hop) node sends a negative acknowledgement (NACK) to the upstream cooperative node, the cooperative node only needs to retransmit parts of the packet under DCC-ARQ mechanism, hence a reduced end-to-end transmission latency can be achieved. Simulation results show that for a one-shot transmission, the proposed protocol achieves good balance between the reduced end-to-end delay and decent outage performance, relative to existing protocols.