Dong, W.; Yang, Q.; Huang, X.; Chen, Y., and Sun, S., 2022. A MAC protocol for underwater sensor networks using parallel transmission variable time slots. Journal of Coastal Research, 38(2), 449–457. Coconut Creek (Florida), ISSN 0749-0208.

Underwater wireless sensor networks (UWSNs) play an important role in coastal research and ocean utilization. The disadvantages of the long propagation delay in underwater acoustic communication make the MAC protocol based on time slots unsuitable for UWSNs. Thus, a MAC protocol with a variable time slot is proposed to solve this problem. In the proposed protocol, a parallel transmission node selection algorithm realizes the collision-free transmission of multiple nodes in the same time slot according to the delay information between nodes and the duration of the packet. It determines the length of each time slot at the same time. Then, the cluster head node schedules the sending time of each node according to the parallel transmission node selection algorithm. Compared with the Time Division Multiple Access (TDMA) and prescheduling-based MAC, the simulation results show that the throughput is increased by approximately 47% and 25%, respectively, under the same load. When the load is low, variable time slot-MAC also has better performance related to end-to-end delay.