Diversity And Doppler Shift Compensation In OFDM Communication Over Underwater Acoustic Channels

The core purpose of the underwater acoustic communication system is to transmit the information efficiently and reliably from the source to the receiver through the water acoustic channel. OFDM(Orthogonal Frequency Division Multiplexing) is a method with many good performances such as high spectrum efficiency, strong anti-multipath and impulse noise abilities, high-speed transmission capacity and simple implementation, OFDM becomes one of the hot spots in researching high-speed underwater acoustic communication in recent years.Doppler estimation and compensation in mobile OFDM underwater acoustic communication system is studied in this thesis as the key part. Two algorithms based on single-frequency real-time tracking signal are designed. Also the outfield experiments on mobile underwater acoustic communication on OFDM are done. And the validity of the two algorithms is verified.Time diversity and frequency diversity in OFDM underwater acoustic communication are also studied. Three kinds of diversity combining methods are analyzed. A MB_TFI_OFDM (Multi-band time-frequency interleaving OFDM) system is designed for underwater acoustic communications combined with OFDM specific technologies and mobile communications features. Also the simulation and the outfield experiments are done. The principles of choosing diversity mode are given througth the simulation and experiment results.