Research On SC-FDE Underwater Acoustic Communication Technology

Underwater acoustic channel is the most challenging channel in the world for its time varying and frequency-selective characters. These facts obstacle the development of high-speed and reliable underwater data transmission. In the traditional SC-TDE underwater acoustic communication, the adaptive decision feedback equalizer coupled with phase tracking methods is adopted. As the communication rate is increasing, symbol duration is becoming shorter, and the equalizer is more complex with the channel delay spread, the application of traditional methods is hampered in the high-speed underwater acoustic communication. In recent years, OFDM becomes one of the researchful priorities and hotspots in the high-speed underwater acoustic communication due to its high spectral efficiency, high data rate, robustness against multi-path delay and simple implementation, but the high PAPR becomes one bottleneck gradually when the system is implemented and the performance is improved. SC-FDE allows an advantageous of high-speed data transmission in the frequency-selective fading channel, it avoids the complexity of SC-TDE and the high PAPR of OFDM. SC-FDE will become significant technology in the future underwater acoustic communication.In this thesis, key technologies and applications of SC-FDE are researched mainly for the underwater acoustic communication. The works done as follows:1. The advantages and disadvantages of three frame structures as well as the principles of how to choose the frame size are analyzed and studied detailedly.2. Doppler estimation and compensation in the SC-FDE underwater acoustic communication system. Three algorithms are studied and compared which are block doppler estimation and frequency measurement method based on CW pulse and pulse pairing doppler estimation. Based on the performance of different algorithms, two new kinds of combinatorial doppler estimation algorithms are proposed and the algorithm performances are validated through simulation. 3. Channel estimation and equalization. Analysis and comparison of the different types of channel estimation and equalization techniques are made out, and the principles of how to choose the training sequence are pointed out. In addition, noise reduction is a compulsory task in the channel estimation based on LS algorithm, Pilot noise reduction which is adopted in the transform domain is pointed out in this thesis.4. Analysis and comparison of mechanism, error probability, PAPR, and so on for SC-FDE and OFDM over underwater acoustic channel are done in this thesis.5. Through the trial in the tank, the feasibility of SC-FDE for the underwater acoustic communication is demonstrated, and the performance of SC-FDE and OFDM system is compared.