The Study Of Adaptive Equalization Technology For Underwater Acoustic Communication Based On SC-FDE System

With the deepening of ocean utilization and development, the underwater acoustic communication technologies play an increasingly important role in the development of marine economy and national defense construction. Underwater acoustic channel is an extremely complex random channel, its time, frequency and space is variable. The signal frequency selective fading caused by Multipath effect seriously affect the performance of underwater acoustic communication system, so combating Multipath and reducing inter-symbol interference is the focus of underwater acoustic communication study. According to the variation of the channel transmission characteristic adaptive equalizer is able to automatically adjust parameters to realize the best channel equalization as far as possible. Besides, single-carrier frequency domain equalization technology (SC-FDE) can effectively combat the frequency selective fading and reduce inter-symbol interference, with the advantage of low peak-to-average power radio and low sensitivity to frequency offset. SC-FDE technology has been the hot research.Based on the characteristics of shallow sea underwater acoustic channel, the paper combines SC-FDE with adaptive equalizer. We design and realize the adaptive equalizer, which is based on SC-FDE underwater system, through the SEED-VPM642demoboard. The purpose is building a high data rate and strong reliability underwater acoustic communication system.The main contents are summarized as follows:1. The paper studies the channel estimation algorithm in the SC-FDE system. We combine the LS estimation algorithm and MP estimation algorithm. We can summarize the result through MATLAB simulation. When the SNR is less than10dB, the MP estimation algorithm is better than the LS algorithm, so the SC-FDE system adopting the MP channel estimation algorithm has the low date error rate. 2. The paper studies the adaptive equalizer in the SC-FDE system, which contains frequency domain linear equalizer, decision feedback equalizer and time-frequency hybrid decision feedback equalizer. We can summarize the result through MATLAB simulation. When the SNR is low, the time-frequency hybrid decision feedback equalizer is the best performance of the three equalizers, and the frequency domain linear equalizer has the worst performance in the SC-FDE system.3. The paper summarizes the pool-experiment about the adaptive equalizer in the SC-FDE system. It shows that the bit error rate of the frequency domain linear equalizer is10-1, while the bit error rate of the decision feedback equalizer and time-frequency decision feedback equalizer is10-3in the different channels conditions.4. The paper summarizes the ocean-experiment about the adaptive equalizer in the SC-FDE system. When the communication distance is10km and the data rate is4kbps, it shows that the bit error rate of the frequency domain linear equalizer is10-1while the bit error rate of the decision feedback equalizer is1%, and time-frequency decision feedback equalizer is0.6%.5. The paper finally designs and realizes the adaptive equalizer, which is based on SC-FDE underwater system, through the SEED-VPM642demoboard.