Collaborative Communication System Relay Node Selection Strategy Research

With the rapid development of modern science and technology, people’s demand for wireless communications are more imperative because they are constantly seeking high-quality transmission speed and quality of wireless service. However, there is a big problem that multipath fading in signal transmission has affected the development of wireless communication. Multiple antenna technology in MIMO fully can utilized airspace resources and improve wireless communication capacity, but multi-antenna terminals can’t be implemented in mobile terminals well because of the size and power of mobile terminals. The proposed cooperative diversity for the multiple antennas in MIMO provides another alternative, that is, multiple users share a single antenna. Each antenna forms a virtual multi-antenna to get the diversity gain. How to choose the best cooperative partner in the relay nodes and when to cooperate in the network is the first problem to solve.In this paper, we discuss the protocol of cooperative communication and analysis the method which the cooperative communication system chooses.First, the MIMO technology for wireless communication and the protocol of cooperative diversity are described in this paper. The outage probability of cooperative diversity protocol and some other performance parameters are analyzed and compared.Then several common solutions of selecting relay are analyzed and summarized. The paper emphatically introduces the principle of the opportunity relay and analyses collisions in the opportunity relay that may lead to the failure of relay selection. An improved solution that adding the threshold limit in the number of relay competition and control channel may shorten the time of collision is proposed to avoid this problem. Finally, we propose a new cooperative communications solution, FDSC (First Direct transmission Second Cooperative transmission),which combines direct transmission(DT) and decoded forward(DF) IF the direct transmission is successful, the second relay node is no longer forwarding messages and in next time slot the source node sends the next data directly. Therefore, the average outage probability and spectrum efficiency, etc has significantly improved compared to the opportunity relay solution. From another perspective, in order to save power, based on the total outage probability minimization of power solution is proposed, and then algorithms and simulation are analyzed.