A cooperative ARQ scheme for multi-hop underwater acoustic sensor networks

We propose an efficient cooperative ARQ (Automatic Repeat request) scheme for multi-hop underwater acoustic communications, in which cooperative nodes are used to provide more reliable alternative paths for a specific source-relay-destination connection. Based on the knowledge of inter-node distances, a cooperative region is defined to include all possible candidates for cooperative nodes from a given pair of source-relay-destination nodes. When the relay (destination) node receives an erroneous packet, it asks for retransmission from a cooperative node, which is selected in a closest-one-first manner from the nodes in the cooperative region. The selection procedure continues until the retransmission is successful. In addition, during a packet-relay through multiple hops, the typical acknowledgement (ACK) signal is replaced with overhearing data packet returned back from the next hop. In this paper, we evaluate the proposed scheme by comparing it with a conventional S&W ARQ in terms of throughput efficiency. Computer simulation results show that the proposed cooperative retransmission scheme can significantly improve the throughput by increasing the probability of successful retransmission.