Research On Key Technologies For Cognitive Radio

Along with the development and widely usage of wireless communication technology, the scarcity of spectrum resources has become a major bottleneck to restrict the development of wireless communication technology. How to improve the usage efficiency of radio spectrum resources is an urgent problem for wireless communication technology now. Cognitive radio is an intelligent wireless communications technology, which can change its operating parameters with the surrounding environment interaction, and has adaptive spectrum access ability. It has wide application prospect in the future wireless communication and smart grid communication. This dissertation makes a deep research on the key technology of cognitive radio, such as spectrum sensing, spectrum allocation and routing protocol. The main contents and results are as follows:A novel cognitive user detection model is proposed for the primary user in cooperative network environment. The detection probability and the false alarm probability about the new model are derived in theory. The spectrum detection performance of the new model and the traditional model are checked and compared in different channel conditions. At the same time, with the cooperative relay environment, an optimum detection time optimization model is proposed about the spectrum sensing time, and its performance is compared by the simulation analysis under different channel conditions on cognitive users spectrum detection time. The simulation results show that the detection performance of the new model is better than the traditional model. The experimental results agree with the theoretical analysis. The correctness of the theoretical analysis is verified. This part of research will set a theoretical foundation for the combined application of cooperative communication and cognitive radio technology in the future.With the increasing number of cognitive users and available spectrum resources, the overhead time of the Color-Sensitive Graph Coloring (CSGC) spectrum allocation algorithm is also growing rapidly. To solve this problem, an improved algorithm is proposed based on the MMR criterion of the CSGC. The improved algorithm is made by bringing the benefit level parameter and designing a new label rules which concerned both the bottleneck user's gains and fairness of spectrum allocation. It is combined with the idea of the parallel algorithm. The simulation results show that the improved algorithm can heavily reduce the overhead time relative to the traditional CSGC spectrum allocation algorithm. At the same time, the performance of the improved algorithm is better than the CMIN criterion of the traditional CSGC algorithm in terms of average income of the cognitive users and the fairness of spectrum allocation.The SEARCH routing algorithm causes the end-to-end longer time delay, frequent switching channel and routing instability when routing nodes are located in forward avoidance region. A novel cognitive routing algorithm is proposed based on the forward feedback and the geographical location in order to solve the problem. It improved the performance of the SEARCH routing algorithm. The simulation results show that the improved routing algorithm has better performance than the SEARCH routing algorithm when routing nodes are located in forward avoidance region. At the same time, the performance evaluation model about end-to-end time delay is proposed for routing protocol in cognitive radio networks. The end-to-end time delay and cognitive nodes energy consumption are analyzed and compared between the improved routing algorithm and the traditional SEARCH routing protocol. The simulation results show that the performance of the improved algorithm is better than the SEARCH routing algorithm in terms of the end-to-end time delay and cognitive nodes energy consumption.