Research On Inter-Carrier Interference Cancellation Technique In OFDM Underwater Acoustic Communication

Orthogonal frequency division multiplexing (OFDM) technology in the application of underwater acoustic communication is one of the hot spots on acoustic field research in recent years. Although the anti-multipath frequency selective fading channel is one of the most prominent advantages about OFDM technology, but due to the complex and changeable of underwater acoustic channel, and any time-varying channel characteristics will affect the performance and stability of OFDM underwater acoustic communication, giving rise to Inter-Symbol Interference and Inter-Carrier Interference. Which, the ISI, can be eliminate by increasing the length of cyclic prefix. However, because of the causes of ICI are more complex, and its impact on the system is also more serious. So it will be priorities that research the cancellation technique of ICI in OFDM underwater acoustic communication.Based on the characteristics of underwater acoustic channel, and introduced the application of OFDM technology in the underwater acoustic communication briefly. Then analyzed the cause of ICI in OFDM underwater acoustic communication and its influence on performance of system, and divided the suppression technique of ICI into three directions, and proposed solutions respectively. and discussed four kinds of methods in detail, Extended Kalman Filter, Maximum Likelihood Estimation, Time-domain windowing and Self-Cancellation. And theoretical derivation of the advantages and disadvantages of methods then validated the performance of various methods by MATLAB simulation. Finally, proposed the ASIZ-VS method, which relatively low implementation complexity, similar as Self-Cancellation, but in the performance of Doppler frequency compensation show more prominent, also, this method reduced the implementation complexity of previous four algorithms, hardware not ask for much, and not only suppressed ICI caused by carrier frequency shift, but also caused by the Doppler frequency extend, so it more suitable for OFDM underwater acoustic communication.To further confirm the feasibility of these methods, various algorithms, which, mentioned in the paper have carried on the tank experiment in the Harbin Engineering University, and through observation test result data, comparative analysis of advantages and disadvantages of each method.