The Research On Underwater Acoustic Communication Technology Of Hexagonal Multicarrier Modulation

In recent years, due to the demand for the development of military science and technology and ocean resources, people pay more and more attention to the development and research of underwater communication system. Therefore, the underwater acoustic communication become a new research field. OFDM technology has been widely applied to underwater acoustic communication with its advantages of high speed data transmission. Due to the underwater acoustic channel with severe time varying and frequency selective fading, OFDM technology applied in the underwater acoustic communication also has several serious flaws:(1) the spectral attenuation is slow and high side-lobe; (2) sensitive to the frequency offset and phase noise; (3) OFDM only solve the inter-symbol interference caused by multipath. Compared with OFDM, hexagonal multicarrier modulation technology (Hexagonal Multicarrier Transmission, HMCT) has a high anti-intersymbol interference and anti-intercarrier interference capability. Therefore, the research of its performance in underwater acoustic channel has important significance.In this paper, the performance of HMCT in underwater acoustic channel is studied. By comparing with OFDM, it is proved that HMCT is suitable for transmission in underwater acoustic channel. First, in view of the high complexity of the direct summation algorithm implemented to HMCT, based on filter bank multicarrier transmission system principle, we derive the filter representation of HMCT and by the introduction of IFFT transform, fast algorithm is adopted to implement the system. At the same time, it is proved that the fast algorithm is equivalent to the direct accumulation algorithm. Secondly, this paper introduces the characteristics of underwater acoustic channel, including the propagation loss, multipath effect and Doppler frequency shift. And a kind of underwater acoustic channel model in the ocean environment is used, Then we simulate the tine varying acoustic channel. Finally we do channel estimation in the OFDM, HMCT system, because the underwater acoustic channel is a typical sparse channel, and compressed sensing technology is a kind of method which makes full use of the sparsity of signal on the data sampling and coding, and by using less measurement value it can reconstruct the original signal with a great probability. Therefore, by orthogonal matching pursuit compressed sensing algorithm we can achieve accurate estimation of the sparse channel, then compare with the traditional LS algorithm to verify the validity and accuracy of the orthogonal matching pursuit algorithm for underwater acoustic channel estimation.