Basic Principles of Underwater Acoustic Communication

Abstract

The transmission characteristics of the underwater acoustic (UWA) channel have an important impact on the performance of UWA communication (UWAC) systems. In the long-range UWA channel, multipath delay of up to several tens of milliseconds may cause tens to hundreds of inter-code element interference, making the received signal serious distortion, which greatly limits the transmission rate of the communication system; according to the direction of propagation and hydrological conditions, the UWA channel will be fast or slow, flat or selective fading process; high-frequency absorption loss and low-frequency environmental noise makes the long-range channel in shallow waters. In the channel, the system available bandwidth is less than a few kilohertz; these factors are challenges to high-speed, high-capacity, and highly reliable UWAC. Therefore, the study of UWA channel transmission characteristics is the basis for the effective design and application of UWAC systems. This chapter first introduces the main characteristics of UWA propagation and its effects, then briefly describes the sound field model of acoustic wave propagation, and finally introduces the mathematical model of channel and noise.