Study Based On Underwater Acoustic Communication System Characteristics Of The Channel Model

As ocean environment is complicated and varied, such as UWA (under water acoustic)channel's multi-path propagation with time-,frequency-, space-varying characters makes sound signals strongly distorted and fluctuated during their transmission through UWA channel. In addition, there are many other problems encountered in UWA channels such as larger ambient noise, much-limited bandwidth, and much-extended propagation latency, which severely reduce there liabilities and validity of the UWA communication system. So the research of UWA channel is the foundation of designing UWA communication system.This dissertation focuses on UWA channel modeling and simulation research, researches into the propagation characteristics and communication performances of (UWA) channels based on underwater acoustic modeling, analyzes the error rate of different acoustic signal under fading channel, optimizes the design of UWA communication system in theory.Firstly, the wave equation deduction is introduced amply in theory in the article. Secondly, five modeling techniques based on wave equation are introduced, especially the ray theory model, the normal mode model and the Parabolic Equation model .and their feasibility in given environment. Thirdly, the dissertation derives the propagation losses and eigenrays by use of the Kraken normal wave mode and the Bellhop ray mode.And then two types of modulation technique presented in the paper, which consist of MFSK and PSK , Also presents how to correctly choose the modulation scheme under different system requirements.In the last part, the dissertation relate the time-varying UWA channel to the design of communication systems, presents the method of calculation the performances form the acoustic models. Both the error rate under flat Rayleigh fading channel and the effect of transmission distance and phase noise to error rate are studied by simulation.