Research On Two-way Relay Underwater Acoustic Cooperative Communication Based On Network Coding

By the increasing of the exploitation and utilization of the ocean, underwater acoustic communication (UAC) will play an increasingly important role. The development of UAC is seriously restricted by the characteristics of long propagation delay, multi-path fading and noise of UA channel. Cooperative communication is an effective way to combat multipath fading in UAC, and many scholars have conducted in-depth research on it. Two-way relay cooperative communication was widely applied in UAC, such as communication between the underwater sensor, submarines and underwater robots, but the research is relatively few, so it is very significant to study the two-way relay in UAC.The idea of network coding is used to improve the end-to-end throughput of packet network. The research demonstrated that it can improve the diversity gain and spectrum efficiency of cooperative communication, and also can be used to deal with the two-way access information in two-way relay communication.In view of the research on Two-way relay UAC is relatively small, this paper try to apply the idea of network coding into Two-way relay UAC to improve the performance of Two-way relay UAC system. The main contents of this dissertation can be summarized following:(1) Based on studying the characteristics of UA channel, we introduced the UA channel models which used for UAC simulation.(2) This part we described the cooperative diversity techniques, and analyzed the performance of three kinds of combine techniques (SC, MRC, EGC) by simulation. Then we compared the performance of some commonly used protocols of cooperative communication. At last, the idea of network coding and its applications are introduced.(3) By studying of Two-way relay system and denoising mapping network coding, we proposed a two-way relay cooperative mode used in UAC based on denoising mapping network coding, derived the BER performance of this system, and analyzed its performance by simulation. The experimental results show that the proposed forwarding strategy is more superior compared with the traditional underwater acoustic AF strategy, the proposed forwarding strategy can improve the spectral efficiency and reduce the bit error rate of system. (4) According to the BER of our two-way relay UAC system, we put forward an optimal relay selection strategy. First we determined the relay node set which meet the condition of denoising mapping network coding, then through allocating of the transmit energy of source node to select the optimal relay node. Experimental results show that, the complexity of network can be reduced by selecting the optimal relay node and also improve the performance of system.