Application Of Time Reversal Mirror In Spread Spectrum Underwater Acoustic Communication

The complexity of underwater acoustic channel seriously affects the quality of underwater acoustic communication system, which makes high-quality underwater acoustic communication become very difficult. Time reversal mirror technology can lead to spatial focusing and time compression using the physical properties of underwater acoustic channel.The application of the time reversal mirror technique in underwater acoustic communication system will effectively improve the performance of the system, achieving high quality communication.This paper focuses on time reversal mirror technology applied in the spread spectrum underwater acoustic communication system. The theoretical analysis on the time reversal mirror technology principle is first made and then single sensor time reversal mirror technology is proposed in order to meet the requirements of simple node structure and low power consumption in underwater acoustic communication. Combining time reversal mirror with decision feedback equalizer, the time reversal mirror decision feedback equalization algorithm is proposed in this paper, which can realize stable and efficient channel equalization.Spread spectrum communication technology has good anti-interference ability,anti-multipath ability, networking capability and is able to work under low SNR. In this paper,differential spread spectrum communication, cyclic shift spread spectrum communication and combinatory spread spectrum communication based on direct sequence spread spectrum system is proposed. Single sensor time reversal mirror applied on the point to point spread spectrum communication system can ensure that each system can efficiently and reliably spread decoding.The system impulse response function in underwater acoustic channel is very sensitive to spatial variation, which makes function of different spatial positions have weak correlation.Time reversal mirror can be applied on multi-user underwater acoustic communication using the physical characteristics of underwater acoustic channel, focusing on the desired users and shielding the undesired users to realize Space Division Multiple Access (SDMA). In addition,a single vector active average intensity method is proposed in this paper, which can measure the azimuths of same frequency band multi-users simultaneously. Using the estimated azimuth to achieve electronic spin vector hydrophone can realize the directional communication. Combining the single vector active average intensity with time reversal mirror, SDMA with underwater acoustic characteristics is proposed, which achieve high-quality multi-user underwater acoustic communication.In this paper, the algorithm was carried on computer simulation experiment and lake test validation. The results showed that: the combination of time reversal mirror technology with underwater acoustic spread spectrum communication improves the performance of underwater acoustic spread spectrum systems, and provides reliable guarantee and high-quality for point-to-point underwater acoustic communication and multi-user underwater acoustic communication.