International Journal of Computer Science Issues

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High data rate acoustic transmission is required for diverse underwater operations such as the retrieval of large amounts of data from bottom packages and real time transmission of signals from underwater sensors. The major obstacle to underwater acoustic communication is the interference of multipath signals due to surface and bottom reflections. High speed acoustic transmission over a shallow water channel characterized by small grazing angles presents formidable difficulties. The reflection losses associated with such small angles are low, causing large amplitudes in multi-path signals. In this paper, based on the results obtained from practical measurements in the Persian Gulf and available data about sound speed variations in different depths, we propose a simple but effective model for shallow water short-range multipath acoustic channel. Based on the Ray theory, mathematical modeling of multipath effects is carried out. Also in channel modeling, the attenuation due to the wave scatterings at the surface and its bottom reflections for deferent grazing angles and bottom types is considered. In addition, we consider the attenuations due to the absorption of different materials and ambient noises such as see-state noise, shipping noise, thermal noise and turbulences. We use a three-dimensional hydrodynamic model (COHERENS) in a fully prognostic mode to study the circulation and water mass properties of the Persian Gulf – a large inverse estuary. Maximum sound speed occurs during the summer in the Persian Gulf which decreases gradually moving from the Strait of Hormuz to the north western part of the Gulf. A gradual decrease in sound speed profiles with depth was commonly observed in almost all parts of the Gulf. However, an exception occurred in the Strait of Hormuz during the winter. The results of the model are in very good agreement with our observations.