Research On Spectrum Sensing And Channel Switching In Cognitive Radio Networks

With the development of society and technology, the demands of telecommunications services, especially wireless telecommunications, are getting more and more. However, it is difficult for developing the wireless telecommunications due to the limited spectrum resources. In order to improve the efficiency of spectrum application and solve the spectrum shortage, the research and application of cognitive radio will be used to provide solutions.This article focuses on the important point of cognitive radio, for example how to sense spectrum and how to switch channel and so on. Some algorithm and solutions about performance optimization, channel prediction and detecting overhead have been proposed in this article. In summary, the main contributions are as follows:Decreasing the detecting overhead is the effective method to solve the spectrum shortage. An improved optimization strategy based on energy feature is discussed. We analyzed detection and false alarm probabilities by using binary hypothesis testing theory, energy detecting method and data fusion technology. The constrained condition of minimum detecting overhead is suggested. We theoretically deduced corresponding conditions of the number of sensing users and the length of sensing. Simulation results show that there is a particular set of parameters, i. e. the number of sensing users and the length of sensing, that correspond to the minimum detecting overhead when all cognitive radio users receive the same average and maximum value of SNR. Simulation experiments verified the rationality and effectiveness of the algorithm.Making an accurate channel switch plays an important role when it comes to the problem involved crash between primary user and secondary user. Compare to traditional method to avoid interference, the improved way based on predicting channel has good stability and robustness. By analyzing the current channel data and formers, we calculate the probability of primary user appearing. Moreover, the sensing overhead can be taken in account. Finally, an improved spectrum switching algorithm was proposed. The simulation results further illustrate the validity of the proposed method and show that the amounts of switching channel drops by 22% compared to traditional method.According to the feature of sensing spectrum in cognitive radio, we present the measurements and solutions based on IEEE 802.22 model system. First of all, this method can be used to analyze the several costs during working. After that, the system throughout model is employed to describe the energy performance. In addition, the normalized function of throughout is introduced to simplify evaluation of cognitive radio system effectiveness. An optimization algorithm related to maximum system utility was proposed under the condition of comprehensive evaluation of performance and effectiveness about cognitive radio. The simulation results show that there exit an appropriate amount of user and length of sensing spectrum which can make system get maximum effectiveness when the detecting probability is determined.Based on systematic performance optimization algorithm, we take further studies on this method. The expression of optimum users’ number is deduced by selecting partial users. Moreover, the algorithm of optimal performance is presented. The simulation shows that application of optimum users’ amount can guarantee the maximum value of system throughput, the new algorithm has obvious advantages by comparing with AND algorithm and OR algorithm. In addition, the simulation result also shows that even though the algorithm of partial participating users cannot produce the maximum value of throughput, its performance is still better than those of total participating users.