An Adaptive MAC Protocol for Underwater Mobile Ad-hoc Networks

Underwater mobile ad-hoc networks (MANETs) are confronted with several challenges such as node mobility, long and various propagation delay, limited bandwidth and data rate, high transmission power consumption, and so on. Especially, the problem of spatial-temporal uncertainty in underwater acoustic networks causes an unfairness problem [1] and this problem leads to a drastic decline in the network performance. To solve these problems, we proposed a MAC protocol based on a three-way handshaking mechanism with Request-To-Send Waiting Period (RTS-WP) and Data Transmission Waiting Period (DT-WP) in [2]. In this paper, we extend the previously proposed protocol by the ability to schedule a transmission order depending on a distance and to calculate a propagation delay between mobile nodes. The receiver can estimate the distance and the expected propagation delay for intended multiple senders. Using this information, the receiver broadcasts one CTS packet including the transmission order and the beginning of the transmission time which is derived from the mechanisms called Nearest Node First (NNF) and Transmission Time Estimate (TTE). We prove that our proposed protocol is attributed to reducing an end-to-end delay and it would result in improving network performance compared with the original protocol.