Abstract

Communication between a set of underwater systems such as remote sensors, autonomous underwater vehicles and control vessels would enhance the effective use of such systems tremendously. As electromagnetic waves do not propagate well underwater, acoustics plays a key role in underwater communication. Although point-to-point acoustic links can be established via numerous modulation schemes, an acoustic communication network demands multi-user communication. In such an environment, orthogonal modulation schemes could provide a solution for multiple simultaneous acoustic links. As an alternative to orthogonal schemes, random shared access technology has proven successful in many wireless networks. Through numerical simulations, we compare the performance of orthogonal and random shared access for underwater networking.

Over the past few decades, numerous networking protocols have been developed for use in wired and wireless networks. Due to significant differences in the characteristics of electromagnetic and acoustic channels, these networking protocols require modifications to perform well in underwater networks. As sound waves are much slower than electromagnetic waves, the latency in communication is typically much higher. Due to the multi-path propagation and ambient noise, the effective data rates are lower and packet loss is much greater. In this paper, we simulate variants of some popular protocols for underwater use, focusing on the Physical and Datalink layers of the OSI protocol stack. The aim is to select an appropriate Physical Layer and Datalink layer model for a small underwater network to be implemented.