Performance Evaluation of Spread Spectrum Communication System in some Key Locations of North Western Arabian Sea PDF

Keywords

Underwater acoustic communications, Arabian Sea, Channels, Direct-Sequence, Spread-Spectrum.

Abstract

Multi-path interference due to boundary reflection and variation of sound speed profile in underwater acoustic channel pose a major barrier to dependable underwater acoustic communications. Based on actual data of northwestern Arabian Sea, multipath impulse response profiles of the area were obtained previously. These channel models are used in spread spectrum communication simulation described in this paper. The transmitted signals, which consist of frames of multiple spreading sequences, are modulated using coherent phase shift keying. The use of multiple pseudo noise sequences (PN) in a single frame allows one to achieve robust communication with a relatively simple receiver structure as compared to traditional single spreading sequence approach. This long code multiple sequence approach also helps in realizing low probability of intercept(LPI) communication. On the receiver side, a rake type receiver collects the energy present in multiple propagation paths after synchronization and Doppler compensation. Channel estimation necessary for the correct working of rake receiver is done together with a Doppler tracking that allows an adaptation to the instantaneous shift. The performance of underwater acoustic communication scheme has been evaluated by simulation. Bit error rate (BER) has been used as a performance metric and effects of different channels, types of noises, data rates, chip rates etc. have been evaluated. The results indicate that such communication systems overcome multipath channel distortion and can perform at low signal to noise ratio. This work can be used as a lead for the practical design of underwater acoustic DSSS communication/telemetry system for this area.