Mathematical Problems in Engineering
Volume 2 (1996), Issue 6, Pages 449-485
doi:10.1155/S1024123X96000439
High-rate wireless data communications: An underwater acoustic communications framework at the physical layer
Department of Electrical Engineering, Harbor Branch Oceanographic Institution, Inc., 5600 U.S. 1 North, Fort Pierce 34946, FL, USA
Received 20 October 1995
Copyright © 1996 Anthony G. Bessios and Frank M. Caimi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
A variety of signal processing functions are performed by Underwater Acoustic Systems. These include: 1) detection to determine presence or absence of information signals in the presence of noise, or an attempt to describe which of a predetermined finite set of possible messages {mi,i,...,M}
the signal represents; 2) estimation of some parameter θˆ
associated with the received signal (i.e. range, depth, bearing angle, etc.); 3)
classification and source identification; 4) dynamics tracking; 5) navigation (collision avoidance and terminal guidance); 6) countermeasures; and 7) communications. The focus of this paper is acoustic communications.
There is a global current need to develop reliable wireless digital communications for the underwater environment, with sufficient performance and efficiency to substitute for costly wired systems. One possible goal
is a wireless system implementation that insures underwater terminal mobility. There is also a vital need to improve the performance of the existing systems in terms of data-rate, noise immunity, operational range, and power consumption, since, in practice, portable high-speed, long range, compact, low-power systems are desired.
We concede the difficulties associated with acoustic systems and concentrate on the development of robust data transmission methods anticipating the eventual need for real time or near real time video transmission. An overview of the various detection techniques and the general statistical digital communication problem is given based on a statistical decision theory framework. The theoretical formulation of the underwater acoustic data communications problem includes modeling of the stochastic channel to incorporate a variety of impairments
and environmental uncertainties, and proposal of new compensation strategies for an efficient and robust receiver design.