Research Of Underwater Acoustic Communication System On Multicarrier Modulation

Acoustic communication system based on multicarrier modulationsystem is studied with the purpose of solving the problems of low bandwidthefficiency, severe multipath interference and serious frequency selectivefading in acoustic communication system. The main achievements of thispaper are as follows:Firstly, design a frame synchronization algorithm upon double chirpsignals in the aim of accurate synchronization between sended signal andreceived signal. The characteristics of chirp signal’s good autocorrelation,low PAPR, and wide bandwidth are used in this algorithm, thus making thechirp signal be the guide symbol. When received, the signal is autocorrelatedwith the local chirp signal stored. Signal synchronization technology isachieved by the process of autocorrelation peak searching.Secondly, design the automatic gain control algorithm for power, whichcan adjust the power’s gain of receiver end flexibly according to the receivedsignal value, thus overcoming the problem caused by severe near-far effect inacoustic communication system. The first step of the algorithm is to speculatechannel fading gain through the second chirp signal’s power, which isfollowed by the step of estimating the power’s gain of receiver end throughthe channel fading gain.Thirdly, four typical time-frequency estimation algorithm in the OFDMcommunication system are analyzed, including the ML algorithm, the C&Salgorithm, the S&S algorithm and the Byungjoon Park algorithm. Time-frequency error is estimated by the peak searching, which is derivate from themathematic formula considering the influence of frequency accum ulation inthe use of the correlation of OFDM symbol itself and the cyclic prefix.Forth, communication system indexes and bit error rate characteristic arecompared to analyze the advantages and disadvantages between the MC-MFSK and OFDM multicarrier modulation communication systems. The fourtime-frequency estimation algorithms, including ML,S&C,S&S, ByungjoonPark, are also simulated, analyzed and compared in the OFDM multicarrier modulation communication system.In the end, the author make the conclusion and put forward theimprovement direction of the multicarrier modulation acoustic communicationsystem.