Acoustic communication for use in underwater sensor networks

Abstract

In this study an underwater acoustic communications system has been simulated. The simulations has been performed through use of a simulation program called EasyPLR that is based on the PlaneRay propagation model. In the simulations different pulse shapes have been tested for use in underwater communication. Different types of loss have also been studied for different carrier frequencies. Changing the carrier frequency from 20 kHz to 75 kHz gives a huge difference in both absorption loss and reflection loss. This means that there will be a tradeoff between having a high frequency for high data rate and reducing the carrier frequency to reduce the loss. The modulation technique used in this study is Quadrature phase shift keying and different sound speed profiles have been tested to see how this affects the performance. The transmission distance has been tested for several distances up to 3 km. The results show a significant difference in the performances at 1 km and 3 km for the same noise level. Direct sequence spread spectrum with Quadrature phase shift keying has also been simulated for different distances with good performance. The challenge is to get good time synchronization, and the performance is much better at 1 km than at 3 km.