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正交多载波M元循环移位键控扩频水声通信
Orthogonal multicarrier M-ary cycle shift keying spread spectrum underwater acoustic communication
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摘要: 针对水声扩频通信中频带利用率低的问题，提出了一种M元扩频技术和循环移位键控(CSK)技术相结合的多载波调制方式，将M元扩频后选择的扩频码同时采用CSK调制，并调制在多个正交的载波上，显著提高了频带利用率。在水声多途信道下，采用相同的通信速率和带宽， m序列、Kasami小集合序列和Gold序列为扩频码时，比较了系统的误码性能。仿真结果和实验结果均表明， m序列为扩频码时性能最优， Gold序列性能最差。由于m序列数量有限，为了进一步提高通信速率，并使其他序列的性能接近m序列性能，提出了一种复合序列抑制载波间干扰的算法，该算法能够很好抑制多途干扰，使复合序列性能接近m序列的性能。Abstract: To solve the problem of low bandwidth efficiency of underwater acoustic spread spectrum communication, a multicarrier modula-tion scheme combined with M-ary spread spectrum and cycle shift keying (CSK) is proposed in this paper. The code sequences chosen by M-ary modulation are then modulated by CSK, simultaneously, they are modulated by the orthogonal multicarrier. The approach enhances the bandwidth efficiency greatly. The performances of the system with m-sequence, Kasami-sequence, and Gold sequence as the code sequence are compared over the underwater acoustic multipath channel with the same data rate and the same bandwidth. The simulations and the results of pool experiment show that m-sequence as the code sequence performs best and Gold sequence performs worst. The number of the m-sequence is limited. In order to increase the data rate further and make the performances of other sequences close to the m-sequence, a new approach to suppressing the inter-carrier interference (ICI), named multiple sequences, is proposed. The approach can greatly suppress the ICI caused by multipath and make the performance close to the performance of the m-sequence.
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