ASO-TDMA: ad-hoc self-organizing TDMA protocol for shipborne ad-hoc networks

A shipborne ad-hoc network (SANET), a maritime counterpart of the terrestrial vehicle ad-hoc network, can provide ships with diverse multimedia services by substituting digital maritime VHF communications for expensive satellite communications. This article proposes ad-hoc self-organizing TDMA (ASO-TDMA), a medium access control (MAC) protocol targeting SANETs. Frames in ASO-TDMA are divided into several sub-frames, and based on the proposed rules for assigning time slots, ships can only reserve time slots for data transfers through their available sub-frames. Accordingly, ASO-TDMA provides better performance in terms of reducing receiver collisions from hidden terminal problems compared to self-organizing TDMA (SO-TDMA) and carrier-sensing TDMA (CS-TDMA), two existing MAC protocols for maritime VHF communications. In addition, the article compares the performance of the three MAC protocols in terms of delays and collision rates (CRs). The results suggest that, given the same delay, ASO-TDMA can reduce the CR by as much as 30% in comparison with SO-TDMA and CS-TDMA. Similarly, given the same CR, ASO-TDMA can reduce delays by as much as 26% in comparison with SO-TDMA and CS-TDMA.