The Implement Of Least-Symbol-Error-Rate Criterion For Underwater Communication

Underwater communication technology plays an important role in the construction of national marine military strength and marine resources exploration.In the world,underwater communication technology is a hot research field.The difficulty of underwater communication is comparable to deep space communication.The difficulty of communication is mainly caused by the bad conditions of the channel,such as the rapid time-varying of underwater channels,strong noise interference,strong multipath effects,and limited bandwidth.To achieve high rates of underwater communication must overcome the difficulties caused by these harsh factors.In communication receiver algorithms,the Minimum-Mean-Square-Error?MMSE?criterion is widely accepted as a simple,easy-to-use criterion in the field of wireless communications.In fact,the symbol-error-rate?SER?is a more direct measurment for communication systems.Designing a receiver algorithm based on symbol-error-rate can make more efficient use of spectrum resources.For bandwidth-constrained underwater acoustic communication systems,using the least-SER?LSER?criterion can undoubtedly improve receiver performance.In this paper,the application of the least-symbols-error-rate criterion in underwater acoustic communication is deeply studied.The thesis first summarizes the development of equalization technology in underwater acoustic communication?UAC?and receivers,and analyzes the characteristics of underwater acoustic channels,and gives time-varying and non-time-varying channel models.Based on the deep research of the traditional equalization algorithm,this paper gives the derivation of adaptive least-symbol-error-rate equalization,including the LSER equalization algorithm of linear structure and decision feedback structure.At the same time,this paper also deeply studied the Turbo equalization technology and combined it with the criterion to obtain the least SER Turbo receiver.Based on this,for the characteristics of strong noise interference,severe multipath effect,rapid time-varying and other characteristics of underwater acoustic channels,the paper introduces the space diversity technology,time reversal technology and digital phase locked loop technology combined with the least SER Turbo receiver.The receiver algorithm that can be truly used under the real underwater acoustic channel is finally obtained.This paper also carries out a comprehensive simulation and experimental analysis of the proposed algorithm.The simulation and experimental results show that the LSER Turbo algorithm can still achieves the bit error rate?BER?of less than10^-4 under severe channel conditions,and relative to the minimum mean square error algorithm,it has a performance gain of about 3dB at low SNR and 10dB of performance gain at high SNR,which verifies the effectiveness of the least SER Turbo receiver algorithm in the multipath time-varying underwater acoustic channel,and has better communication performance than the MMSE criterion.This paper also carries out a comprehensive simulation and experimental analysis of the proposed algorithm,which verifies the effectiveness of the least SER Turbo receiver algorithm in the multipath time-varying underwater acoustic channel,and has better communication performance than the MMSE criterion.