| Underwater Acoustic channel is very complex with severe multipath effort, largeDoppler frequency shift and narrow available bandwidth. So it is impossible to get goodperformance using common modulation method. Orthogonal Frequency DivisionMultiplexing (OFDM) communication system has good ability to anti mulipath effort.What’s more, it has high spectrum efficiency because of the overlapped of subcarrierspectrum. These decide that it is very fit to use OFDM in underwater acousticenvironment. OFDM communication system demands strict synchronization. If we don’tsettle the synchronize problem very well, Coherent OFDM system may not accomplishcommunication task. Using differential modulation may reduce the demands ofsynchronization, but synchronize error can still increase bit error rate.Firstly, this paper discusses the synchronization problem of OFDM system in detailand analyzes the influence of synchronization error. Considering the characteristic ofexperiment system and environment, this article mainly discusses frame synchronization.Because of the complexity of the underwater acoustic channel, blind synchronizedalgorithm can’t obtain very well performance. So this paper mainly discusses the dataassistance algorithm. From the simulation result, we know that Ren-Chang algorithm andChoi algorithm resist the multipath better than other algorithms. According to the channelenvironment and OFDM system used in the experiment, this paper designs a type ofsynchronized algorithm and makes the simulation, at last, does the underwatercommunication experiment and analyzes the result. |
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