Relay Selection And Cooperative Transmission Protocols In Cooperative Communication Systems

In recent years, the rapid development of Internet of Things has lead wireless sensor networks become a major research focus. Similar to other wireless communication networks, wireless sensor networks transmit information through wireless channels, which affected by the surrounding environment. So the information transmission process in wireless channels will experience a variety of decline. Therefore there has been a wide variety of anti-decline research. Cooperative communication technology, for wireless sensor networks with their particularity, is a very effective anti-decline means.The subjects of this thesis are relay selection schemes and cooperative transmission protocols, which are two hot research of cooperative communication technology in recent years. First, the thesis describes and summarizes the related concept and the basic structure of wireless sensor networks. Then, a simple description of cooperative communication technology in aspects of principle and development is given. Finally, the thesis makes related presentations about research hot spots of cooperative communic’ation technology and expounds the research contents of the thesis:relay selection schemes and cooperative transmission protocols.First, the thesis focuses on cooperative transmission protocols in single-relay cooperative system. Through analysis and comparison of the classical cooperative transmission protocols, referred to the advantages and disadvantages of current cooperative communication protocols, Double Selective Decode and Forward (DSDF) cooperative transmission protocol has been proposed. By simulation experiment from aspect of outage probability, DSDF cooperative transmission protocol has better performance over the current classic cooperative transmission protocols.Secondly, the thesis studies relay selection schemes in multi-relay cooperative transmission system, in another words, how to select the optimal relay nodes in multiple relay nodes. The selection of the optimal relay node aims to improving the bandwidth efficiency of the system and while ensure the full diversity gain exists in traditional multi-relay cooperative transmission systems. Through analysis the several classic relay selection schemes and according to both the characteristics of radio channel and the characteristics of relay nodes, we propose C-P (Channel state information and Power ratio of node) optimal relay selection scheme. From the simulation experiments, it is clearly verified that C-P relay node selection scheme can largely improve the bandwidth efficiency of the system.Finally, the thesis derives the expressions of bandwidth efficiency and symbol error rate of the multi-node system which are based on C-P relay selection scheme and DSDF cooperative transmission protocol. Also, the expression of symbol error rate verifies the system can achieve full diversity gain as traditional multi-relay system. According to the rule of optimization based on the bandwidth efficiency and symbol error rate of the system, we got the optimal power allocation of C-P relay selection scheme and the transmission threshold of DSDF cooperative transmission protocol.