Research on Base-Band OFDM Underwater Acoustic Communication System

It is tough to achieve higher transmit speed and lower bit error rate(BER) because of the complexity of the underwater acoustic channel. This paper proposes a method of orthogonal frequency division multiplexing (OFDM) modulation technique for improving the situation. It can reduce BER with the ability of resisting multi-path interference and can increase communication rate with the characteristic of parallel multi-carrier transmission. The system on underwater acoustic channel proposed in this paper is a base-band system. It can simplify the structure of receiver and reduce the requirement of carrier frequency synchronization. It can improve the system reliability by choosing the appropriate length of OFDM symbol and using frequency diversity method. We perform the experiments in the very shallow waters with depth of 6 meters and the distance between transmitter and receiver is 1km. The experiment results show that the BER is less than 10e-5 and the transmission rate is greater than 1kbps.