Research On Key Technologies Of Underwater Acoustic Spread Spectrum Communication

The ocean is an important foundation for the survival and development of mankind.In recent years,underwater communication technology has become one of the hot topics in marine science and technology.However,the channel for underwater acoustic communication is extremely complicated.The attenuation of high-frequency components in seawater medium is serious,and there is a great noise interference in low frequency range.Therefore,the bandwidth of underwater acoustic communication is very limited.In addition,the underwater acoustic channel has strong reverberation,Doppler and multipath effects.And it has time-varying,space-varying and frequency-varying characteristics.Therefore,research on underwater acoustics will be much more difficult than wireless communication.Spread spectrum communication technology has strong anti-interference ability and good concealment,it can realize reliable transmission of information under a lower signal-to-noise ratio,and has stable and reliable performance in underwater acoustic channel.However,although the traditional spread spectrum communication mode has high reliability,the communication rate is slow and the number of users in the system is very limited.Therefore,base on the study of traditional direct sequence spread spectrum communication,this paper studies the underwater acoustic spread spectrum communication technology combining binary phase shift keying and cyclic shift keying,and the multi-user spread spectrum underwater acoustic communication technology.In this paper,the composition and principle of direct sequence spread spectrum communication were analyzed firstly,then discussed the properties of spread spectrum sequence and the anti-interference ability of direct sequence spread spectrum system,and verified the performance of underwater acoustic direct sequence spread spectrum system through simulation experiment.Then a new underwater acoustic spread spectrum communication technology combining binary phase shift keying and cyclic shift keying modulation method is proposed,which improves the communication rate of spread spectrum system through two-channel communication,and a time-frequency two-dimensional search method is designed to realize the synchronization of the system.The performance differences between this technology and the traditional spread spectrum technology are compared through simulation experiments.At the same time,the multi-carrier spread spectrum communication method combining code division multiple access and multi-carrier is studied.This method can resist inter-symbol interference and has high user capacity.The bit error rate of each multi-carrier spread spectrum mode is compared through algorithm simulation,and the influence of different sub-carrier frequency intervals of generalized multi-carrier spread spectrum system is analyzed.In order to further verify the ability of the above communication algorithms,in the last part of this paper,I made several pool experiments,and compared the differences between the simulation results of each communication scheme and the actual experiment.