Research On Cooperation Scheme And Node Selection Strategy In Wirless Cooperative Networks

To be considered as the two major important issues to deal with development of wireless communications technology in the future, cooperative communication technology and cognitive radio technology are the hotspots of research. Cooperative communication technology allows the user-nodes in system relaying each other’s information to the destination node to cooperate. Through this technology, nodes can effectively form a distributed antenna array to obtain diversity gain. By taking advantage of dynamic spectrum allocation, cognitive radio technology can dynamically adjust the transmit power, frequency, modulation and other parameters so that the cognitive nodes could use the idle spectrum for communication without affecting the authorized user.Under this background, this dissertation conducts systematic studies about cooperation scheme in cooperative communication combining with network coding and game theory. Then we study the node selection strategy in cooperative spectrum sensing.Firstly, the transmission processes of basic decode-and-forward scheme and amplify-and-forward scheme in cooperative communication were introduced, which are the foundation of the following studies. Based on the system model of three nodes, the work procedures of performance outage probability in different schemes with different combing methods are detailed elaborated and simulated.An amplify-and-forward scheme based on pseudo-physical-layer network coding is proposed in system model of three nodes. Detailed description of proposed scheme and expressions in signal procedure are are given. Through the analysis and the simulations of outage probability, it proof that the proposed scheme can enhance the outage probability performance in cooperative communication, effectively. Further more, the scheme is improved based on the research. A detailed analysis of relevance between diversity order and outage probability is provided. The improved scheme enhances the diversity order, and then improves the performance of outage probability by well designing pseudo-physical-layer network coding at relay nodes. The performance of this scheme is verified through numerical and computer simulation results.Problem of applying the bargaining problem in game theory into cooperative communication is studied, and propose a Nash-bargaining-solution based cooperation scheme for cooperative communication networks. By analyzing the utility of wireless communication systems, a utility function with clear physical meaning is defined. Exploit the utility function in a symmetric wireless cooperative communication network system model and formulate the problem as a 2-person bargaining problem. It could be solved by finding Nash-bargaining-solution. The results show that the scheme could obtain better performance compare with independent transmission. The proposed scheme answered the questions that when to cooperate and how to cooperate. This scheme is a study of cooperation scheme and also a study of nodes selection strategy. More over, problem of fairness is discussed by analyze the situation of nodes with different bargaining capacity.The nodes selection strategies in cooperative spectrum sensing are studied and a SNR based multiple thresholds cooperative spectrum sensing technology is proposed. The basic local spectrum sensing technologies in cognitive radio are introduced, and advantage of energy detection technology is analyzed. Based on the cooperative spectrum sensing system model, results of different fusion rules are analyzed. We illustrate the importance of nodes selection through simulations. A utility function is defined and method of finding optimal single threshold by maximum utility function is analyzed. Numerical and computer simulation results show that the proposed scheme can improve the performance of detection probability.