Multi-carrier High-speed Underwater Acoustic Communication System And Channel Equalization Technology

The effect of multipath propagation commonly exists in the underwater acoustic channel and the fading which was caused by multipath propagation was the main influence factor of underwater acoustic communication system. In this thesis, a multicarrier modulation high bit-rate underwater acoustic communication system was designed and constructed after analyzing those effects. The system employs Multicarrier Modulation (MCM) technique as the modulation method, and Linear Frequency Modulation (LFM) signal as the synchronization signal and Digital Signal Processor (DSP) as the hardware's core chip. The system can transmit data one-way over a distance of up to 1 kilometer at a bit-rate of 10 kbps in shallow water, and the bit error rate was less than 5 percents.In this thesis, the characteristics of underwater acoustic channel were analyzed, the MCM technique and the LFM signal which were used in the multicarrier modulation high bit-rate underwater acoustic communication system was discussed in detail, the important parts in system designing were examined.The realization of the system was discussed, and was divided into hardware and software designing parts. For hardware designing, emphasis was placed on introduction of the hardware structure and the designing results of circuits. For software designing, emphasis was placed on many key points and solutions. A new bootloader method was proposed for the problem of bootloader, and by which the system can work independently.The system's experimental environments, results and analyses were given, and by these experiments, it was proved that the theory of system designing was reasonable.An adaptive equalization method suitable for multicarrier modulation system was examined and simulation research was carried out. Computer simulation results showed that the method has better effects on the underwater acoustic channel, and could be used in the practical system.