Acoustic communications in shallow waters

The shallow water channel is an environment which is of particular interest to many research workers. An underwater acoustic channel is characterized as a multipath channel. Severe signal degradation can occur in such a channel due to multipath effects and the refractive properties of the channel, which may include multiple interactions with the sea bottom and sea surface. Time-varying multipath propagation is one of the major factors that limit acoustic communication performance in shallow water. In this paper the results of an analysis of broadband shallow water acoustic signal was shown. Linear FM pulses were chosen as the main transmit signal for numerical experiments. The transmitted signal goes through multiple paths in order to reach the receiver. The numerical simulations were performed using the broadband normal mode model. This software channel simulator is capable of simulating the effect of the shallow water propagation channel on an input broadband acoustic signal and can be used for simulations of sound propagation through both a time- and range-varing propagation channel. The received signals were all matched filtered revealing the multipath arrival structure.