Analysis of the Impact of Flow on the Underwater Acoustic Channel

Reliable and power efficient underwater communication systems that can adapt to the mediums changing nature can be designed with knowledge of the physical underwater environment This paper discusses a stochastic model for an underwater acoustic channel that takes into consideration the effects of flow and turbulence on the acoustic signal in environments subject to some of the highest tides in the world. The model that relies fundamentally on ray tracing generates an ensemble of time-varying channel characteristics by capturing the effect of known environmental changes including changes in sound speed due to mean and turbulent flow. The model is used to extract the channel characteristics such as channel gain, delay spread, Doppler spread, and the arrival time of the signal. By validating simulation results with real measurements taken in the Bay of Fundy, it is demonstrated that the mean flow has significant impact on various channel characteristics. In fact, flow causes large variance on the path that is subject to a surface bounce. This effectively induces a channel that has amplitude variation and delay spread variation, as a function of tide height.