| Signal in the the underwater acoustic is affected significant by the multipath interference. Acoustic channel parameters, transmission loss and Doppler frequency shift are the several factors influencing. Especially in the shallow water area, the complex signal is formed by the direct sound and reflections and the intersymbol interference is formed. The OFDM technology having the characteristics of Anti-Multipath Interference is suitable for high speed rate of data transmission in the multipath and fading channel. From the mid-to-late 1990s, the OFDM technology is gradually used in acoustic communications.The OFDM technology is launched research in this paper. Discrete Fourier transform and its inverter change are used in the OFDM technology, in order to solve the multiple problem of sub-carrier orthogonal each other and the original signal recovered from sub-carrier. The many sub-carrier complexity of the system is reduced by the fast Fourier transformation. Therefore OFDM technology for the underwater acoustic communication system has strong practicability. Timing synchronization is the OFDM technology focus. This paper adopted the timing synchronization of matched filter ways. The specific algorithm is the method of overlapping reserved signal related. But application OFDM technology system will still lots of multifarious digital signal processing process. This will need digital processing powerful components. The OMAP L137 chip having ARM core and DSP core can complete things labor-intensive and compute-intensive tasks. And its interior having audio accelerated hardware, so it is perfectly for underwater acoustic communication system hardware platform. The OMAPL137 processor can fuse the two processor core of DSP+ARM. This paper completes the business management function of ARM processor core and the data communication function DSP core in a Linux operating system. Using the driver way to data exchange data, it realizes the management function of ARM and the coding and decoding function of DSP, complete and sufficient playing hardware efficiencyFinally, the method based on OMAP-L137 processor as the core module construction hardware and operating system with Linux for design software is discussed. The communications data encoding and decoding and are completed in DSP with the experimental conditions. Experimental results show that in the hardware platform with Linux operating system on the software, it can accurately completed acoustic communications tasks. |
