Research On Detection Algorithms Of Underwater Acoustic Communications Signal Based On M-Sequence

With the development of China's strategy of buil ding a "smart ocean" and "marine potestatem",underwater acoustic communications are of great significance in the development and protection of marine resources.In underwater acoustic communications,the multipath of the channel and various types of underwater interference pose challenges to the detection of communication signals.In addition,underwater acoustic communication s are often used in military systems,and security concealment in communication also needs to be considered.Because of its good autocorrelation,the m-sequence is suitable for signal detection in complex environments.At the same time,it can work at low SNR and has confidentiality,which is conducive to confidential transmission.The purpose of this dissertation is to investigate the potential of m-sequences in underwater acoustic communications.This dissertation first studies the preamble signal based on m-sequence.An important module of the underwater acoustic communication s system is the detection of the preamble signal,which is a series of signals transmitted b efore the transmission of the useful signal to alert the detector to receive effective signals.HFM and matched filtering based detection algorithms are commonly used.In this dissertation,by comparing the detection performance of HFM and m-sequence under different underwater acoustic noise and interference background under several classical detection algorithms based on matched filters,it is concluded that in partial-duration-partial-band interference and narrowband interference environment,the detection performance of m-sequence is better,and analyzes the setting of the optimal parameters.This dissertation also analyzes the LPD communication based on m-sequence.LPD communication uses low SNR signals for communication to achieve a covert transmission effect.In this dissertation,DSSS underwater acoustic communications system is used,and the m-sequence is used as a spread spectrum sequence.The influence of multipath channel and complex Doppler in underwater acoustic communications on the system is mainly investigated.An iterative error compensation algorithm for reducing the timing error is proposed.Combined with the energy transition detection algorithm,the error compensation accuracy of the original communication system is improved,and the communication performance of the m-sequence under LPD is improved.The simulation results show the performance of the iterative error compensation algorithm for fixed and mobile sources at 10m/s and 13m/s.The results show that the new algorithm can effectively reduce the bit error rate of the system,improve system performance and achieve reliable communication.The above research proves that m-sequence has good applicability in underwater acoustic communications system.In the complex underwater acoustic channel environment with multipath and interference,it has good detection performance and covert communication performance.It provides a fundamental basis for the further application of m-sequence in underwater acoustic communications.