Exploiting Cooperative Relay for Reliable Communications in Underwater Acoustic Sensor Networks

In this paper, a cooperative transmission scheme is proposed for underwater acoustic sensor networks to enhance the communication reliability. Based on the distinct characteristics of the underwater channel, such as high transmission loss, propagation delay, and ambient noises, this paper presents a cooperative relay scheme, including networking protocol and cooperative transmission at the physical layer to enhance communication reliability through intermediate relay node. The relay is selected from a set of neighbor nodes based on the distance and the channel conditions. The transmissions of ACK-I and ACK-II in consecutive phases significantly reduce the chance of unnecessary redundant transmissions. Through simulations, the proposed scheme is shown to outperform the traditional direct transmission schemes in terms of end-to-end delay, packet delivery ratio, and average energy consumption.