A Study Of The Implementation Of OFDM Underwater Communication System

Underwater Acoustic (UWA) communication is becoming more and more importantwith the exploration and utilization of Ocean. UWA Channel is very complexity. It hasvery strong time-varying and limit available bandwidth. So it is impossible to obtaingood performance for the communication system which using common modulationtechnology. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carriertechnology. This year it becomes one of the focuses in high-speed UWA communicationas it has good ability to anti multipath and pulse interference and high spectrumefficiency. Howe ever, due to some reason as hardware limit, most of the research still intheoretical and simulation stage. In this paper, we build an UWA environment and anOFDM UWA communication system under this environment.Firstly，after deeply research on realization method and key technology of OFDMsystem, Zero padding method in frequency domain is adopt in our system. In this method,the data can be directly modulated to pass band by inserting proper number zeros beforeand after the data before IFFT, and only real part of the result are needed.Secondly, set up the system using proper hardware and software. Properly set thesystem parameter using the data form channel test.Finally, do the underwater communication experiment using the synchronizemethod based on LFM and CAZAC sequence. The results of CAZAC sequencesynchronize experiment show that, the bit rate can reach5.22kbps in4kHz bandwidth,subcarrier using DQPSK modulation.