Research Of Space-time Coding In Underwater Acoustic Channel

MIMO technology of underwater acoustic communication is one of the scientific areas of concern.The transmission medium-underwater acoustic channel is a complex channel.Due to the influences of the natural environment,geography and random factors,its physical characteristics are the complexity and instability.Its ocean noise,acoustic energy loss,multipath,Doppler frequency shifts and other factors seriously affect the propagation of sound waves.Therefore,reliable and effective communications solutions in underwater acoustic communication are the key.The problem we face is how to improve underwater acoustic communication channel capacity and data transfer rates as well as lower bit error rate of underwater acoustic communication system.So the space-time coding technology based on MIMO system(STC)is used in underwater acoustic communication in this article.The performances of underwater acoustic communication system can be improved.In wireless communication system,the space-time coding technology based on MIMO system is used to improve system capacity,increase the bandwidth efficiency,data rates and against the fading.So the focus of this paper is the space-time coding technology based on MIMO system in underwater acoustic channel.The space-time block coding technology based on MIMO system(STBC)is able to overcome fading caused by underwater acoustic channel and improve the reliability of underwater acoustic communication.Effects of multipath underwater acoustic channel decrease the anti-fading performance of space-time block coding.The space-time block coding and orthogonal frequency division multiplexing(OFDM)are combined to avoid inter-symbol interference caused by multipath effects and build the STBC-OFDM communication system.In this system,OFDM is used to overcome inter-symbol interference caused by multipath effects and improve anti-fading performance of space-time block coding.Then,for the case where the underwater channel multipath time delay spread is larger,on the premise without sacrificing the effectiveness of communication,we use time reversal precoding(TRM)to construct a TRM-STBC-OFDM communication system.The system has a higher communication speed than STBC-OFDM system.The reliability and validity of STBC-OFDM system and TRM-STBC-OFDM system are validated by computer simulation.