Hybrid Collision-Free Medium Access (HCFMA) Protocol for Underwater Acoustic Networks: Design and Performance Evaluation

Underwater acoustic channels are typically characterized by long propagation delay, time-varying multipath, as well as very limited bandwidth, thus making it very challenging to develop efficient underwater medium access control (MAC) protocols. In this paper, we propose a new MAC protocol for underwater acoustic networks (UANs), called the hybrid collision-free medium access (HCFMA) scheme. The operation of the HCFMA scheme is based on the combination of the multichannel technique, the channel reservation mechanism, and the juggling-like stop-and-wait (JSW) transmission scheme. With the multichannel technique, the exchange of control signaling and data transmission can be separated, consequently, increasing the throughput of the network. The channel reservation mechanism which is carried out by the temporarily chosen control nodes guarantees no collision in data transmission. This is different from those whose channel reservations rely on a dedicated central controller. The JSW scheme provides an error-control mechanism during data transmission. Together, these approaches greatly improve the performance of UAN in throughput and delay. This paper describes the operation of the HCFMA scheme and analyzes its performance. We further conduct simulation to validate our analytical results. Our results show encouraging throughput and delay performance compared with other popular solutions, especially under heavy load conditions.