Optimization Design And Realization Of Underwater Emergency Speech Communication System Based On LDPC-OFDM Code Modulation

Traditional underwater voice communication system uses analog modulation,transmission distance close,the effect is seriously affected by the environment.Digital communication equipment has gradually become the development direction of wireless underwater voice communication equipment.The digital communication system based on LDPC-OFDM coding and modulation technology can solve the above problems and is the research focus of underwater communication technology.In this paper,aiming at the demand of speech communication between rescuing ships and submarines in rescue aid,this paper designs an underwater emergency speech communication system based on LDPC-OFDM coding and modulation to realize real-time wireless underwater speech communication.First of all,based on the system requirements,the hardware system platform is designed,including the internal signal transmission structure of the subsystem.Then the system parameters were designed,selecting the core processor and other devices.After introduced the software-driven design,including voice compression,underwater acoustic signal transmission,underwater acoustic signal reception system.According to the speech compression and the underwater acoustic OFDM algorithm,a software driver with parallel PING-PONG acquisition function is designed to realize the underwater acoustic signal acquisition and data communication functions.Then,the software simulation and hardware algorithm implementation of LDPC coding are carried out,the coding method is optimized,the most suitable decoding method is selected,then the design of LDPC encoder and decoder is introduced,and the LDPC coding is added to the OFDM system In contrast with the convolutional code to achieve the purpose of optimizing performance.Finally,the codec was added into the underwater speech system.The performance of the underwater acoustic speech communication system is verified through laboratory alignment,pool test and outside of field experiment.The whole system was verified by the code and the performance of the underwater voice communication system was verified.