MACA-APT: A MACA-based Adaptive Packet Train transmission protocol for Underwater Acoustic Networks

In wireless communications, collision is one of the principal sources of energy wastage, which often makes collision avoidance strategies preferred for medium access control (MAC) protocols. In this paper, we propose a collision avoidance-based MAC protocol called MACA-based Adaptive Packet Train (MACA-APT), which has been designed specifically for underwater acoustic networks (UANs). The design explicitly accounts for prominent characteristics of UANs such as long propagation delays and typically high bit error rates. In particular, the former is compensated via the transmission of multiple consecutive packets to multiple different receivers; the latter, instead, is tackled by embedding a cross-layer Stop&Wait ARQ scheme within MACA-APT. The performance of the proposed protocol is evaluated via simulations and compared to another MAC protocol, also based on MACA, showing that MACA-APT achieves better performance for low to intermediate packet generation rates, and equivalent performance at higher rates. Moreover, we assess the impact of the packet train size on the performance of either protocol. This result is a first step towards the design of adaptive multi-packet multi-receiver MAC protocols for underwater networks.