Design Of Portable Underwater Acoustic Digital Voice Communication System

With the improvement of utilizing and developing the resource of the sea, the research on underwater voice communication is getting more and more important. However, the communication technique used on the land may not be used in the underwater acoustic communication field completely. It is mainly due to the limited bandwidth and time-vary and space-vary nature of the underwater acoustic channel, so a communication mode like OFDM which has characteristics of resisting multi-routed interference and frequency selective fading well and makes best use of the frequency spectrum would be a better choice.Besides, in the underwater voice communication transmission of quantized speech samples at a high bit-rate is restricted due to the bandwidth-limited channel, so speech signals must be compressed. In this paper, digital voice compression algorithms are introduced, and an integrated chip is chosen to implement the compression function. In the mean time QDPSK mapping and OFDM modulation are also adopted in the system to make sure that a lower BER can be achieved.This thesis mainly dealt with the hardware and software design of the whole system, and designed a half duplex, low power and portable underwater acoustic voice communication system based on OFDM. The hardware design mainly contained the analog part and the digital processing platform based on TMS320VC5509A. According to the hardware design scheme, this thesis mainly discussed the circuits and interfaces between DSP and the periphery devices. In software design, OFDM modulation which fits the underwater acoustic channel was implemented in the digital processing platform based on DSP, and the software flow charts were primarily discussed. After the simulation in Matlab/Simulink, the experiments farther proved the feasibility of the system.