The Applications Of Error Correcting Codes In Underwater Acoustic Communication System

Underwater acoustic channel (UWA) is a complex time-space-frequency varying environment. Multipath channel caused by ray bending and reflection at the boundaries is fundamental mechanism of intersymbol interference (ISI). In order to acquire high information data rate at low bit error rate, efficient modem combined with channel coding techniques are important besides suitable transmission, advanced equalizer, more emissivity and so on.Channel coding can acquire lower bit error rate and insure communication quality in bad channel condition, so it is more important in underwater acoustic communication. The dissertation proposes Reed-Solomon (RS) code, convolution code, Turbo code and LDPC code, on the base of simulation, compare and analyze different parameters, discuss the capabilities of every cedes. Finally, the pivotal matters of how to choose and design correct coding are given.Orthogonal frequency division multiplexing (OFDM) has the performances of high spectrum efficiency, strong anti-multipath and simple implementation without equalizer, which is just the right technique to solve the difficulties of limited bandwidth, strong multipath interference and rapid time-varying in channel structure, OFDM becomes the research priorities in high-speed underwater acoustic communication. In this thesis, combining OFDM with the key technologies of synchronization, channel estimation and low PAR, based on the simulation of OFDM system, COFDM system is constructed with channel coding mentioned above, then simulated and experimented in the pool test.Pattern Time Delay Shift Coding (PDS) scheme can robust against multipath fading and noise interference due to its merits of less duty cycle, lower system power and stronger capability of anty-ISI, which makes it adapt to UWA communication. The time reversal mirror (TRM) in UWA signal processing, can match the acoustic channel automatically without any transcendental knowledge. The performance of single-element passive time reversal mirror PDS system is given by simulation. Finally, CPDS system is constructed by combining PDS with correct coding mentioned above, for different simulation results, capabilities are analyzed, and the communication results are given through pool experiments.