Design Of Underwater Acoustic Digital Voice Communication System Based On OFDM

With the maturation and widely use of the digital communication technique, the underwater acoustic voice communication technology is under developing. However, the communication technique used on the land may not be used in the underwater acoustic communication field completely. It was mainly due to the limited communication bandwidth and time-vary and space-vary nature of the underwater acoustic communication channel. OFDM was widely used in the land wireless communication field now. It had some advantages. Firstly, the using rate of the frequency spectrum was higher. Secondly, the capability of multi-route-interrupt resistance and the frequency choice decline were stronger. Thirdly, the capability of decline-poor through the united coding of sub-carrier waves was stronger too. Finally the implementation of DSP was easier because of the modulation and demodulation of OFDM through the using of IFFT and FFT. In the underwater acoustic communication field these advantage of OFDM were the same as which was used in the land wireless communication field.This thesis developed a half-duplex and low power consuming underwater acoustic digital voice communication system based on OFDM. The theory and key technology of OFDM were analyzed. A low power consuming operational amplifier and converter of A/D and D/A were used in the design of the hardware. Furthermore AMBE-2000 was used to compress the origin voice coding and TMS320VC5416 DSP was used to modulate and demodulate the digital voice signal. OFDM was used in the developed of software. FFT and IFFT were used to implement the modulation and demodulation of the data. At the same time, the working flow of the software and the frame structure in the communication were analyzed in this thesis.At last, the feasibility of the underwater acoustic digital voice communication system based of OFDM is proved through the test in the tank.