Research On The Hybrid Automatic Repeat Request In Underwater Acoustic Communication

Large propagation delay, large bit error rate and the varying underwater acoustic channel are the main characteristics of underwater acoustic communication, which bring great challenge to the underwater acoustic communication. Hence, how to improve the reliability of underwater acoustic communication is very important. Hybrid automatic repeat request (HARQ) schemes in the terrestrial wireless communication can guarantee both the reliability and efficiency. For this reason, combining the characteristics of underwater acoustic communication, the author focuses on the HARQ schemes to carry out the research and pay attention to the specific schemes and performance of HARQ.Firstly, the performance of HARQ for the single hop underwater acoustic communication is discussed. With considering the specific characteristic of underwater acoustic channel, such as large propagation delay and half-duplex nature of acoustic modems, the HARQ schemes for underwater acoustic communication are proposed, and the expressions of various performances are derived. Based on the derivations, several meaningful proposals for designing the real underwater acoustic communication protocol are developed. Then, simulations show the effects of different parameters to the protocols and reveal the optimum protocol and parameters for different underwater acoustic communication environment.After that, the performance of HARQ for the multi-hop underwater acoustic communication will be discussed. Based on the characteristic of the half-duplex modem, the connectivity of underwater acoustic network and the mechanization of time division multiple access, the cooperation scheme of all nodes, in the underwater acoustic network and a distribution scheme for the multi-hop nodes in a convergent type underwater acoustic network, is proposed. The performance of HARQ schemes for the multi-hop underwater acoustic communication is also derived. Simulations about different parameters to the protocols, for the multi-hop underwater acoustic communication, are presented, which reveal that there exists "cask principle" phenomenon in the multi-hop underwater acoustic communication, and type Ⅱ HARQ can adapt to the varying underwater communication environment and ease the "cask principle" phenomenon.