EASO-TDMA: enhanced ad hoc self-organizing TDMA MAC protocol for shipborne ad hoc networks (SANETs)

As very high frequency (VHF) data links are overloaded due to the rise of Automatic Identification System (AIS) applications, additional VHF channels and the development of corresponding communication technologies are necessary. For this reason, shipborne ad hoc networks (SANETs) and the medium access (MAC) protocol for SANETs, ad hoc self-organizing-time division multiple access (ASO-TDMA), have been proposed, which provide ocean-going ships with diverse data services cost-effectively. In this paper, a new MAC protocol for SANETs, enhanced ASO-TDMA (EASO-TDMA), is proposed in order to manage the bottleneck and under-utilization problems resulting fromASO-TDMA and thus enhances the overall performance of SANETs. To accomplish this, in EASO-TDMA, a ship adaptively allocates its time slots according to the number of subscribing ships, which make their communication route to a base station at the shore via the ship, by referring to the routing table. The performance of EASO-TDMA is investigated through simulations and compared with that of ASO-TDMA. The simulation results indicate that EASO-TDMA outperforms ASO-TDMA, regardless of the network conditions, with 25 % higher reception success rate, 25 % lower collision rate, and 21 % higher channel utilization at maximum. In particular, the end-to-end delay of EASO-TDMA is on average 1/12 of that of ASO-TDMA, and this implies that EASO-TDMA can be effective for delay-sensitive data services.