Cooperative Spectrum Sensing Technology In Cognitive Radio

As radio resource is becoming increasingly scarce, more and more people realize the contradiction between the allocation and the usage of the spectrum. The appearance of Cognitive Radio will provide effective solution to the problem of spectrum shortage. Cognitive Radio as a revolutionary intelligence technology is becoming a hot research topic in wireless communication field.The thesis analyzes the concept of Cognitive Radio technology, the study status quo at home and abroad, and the spectrum sensing technologies which are usually used, and focus on the principles and performance of energy detection, laying a theoretical foundation for research. Spectrum sensing is one of the most critical technologies in cognitive radio. During the spectrum sensing, performance of single-node detection will degrade due to the fading channel, the shadowing effect environment and the noise uncertainties, but collaboration between multiple nodes can improve the performance under the above-mentioned conditions. So we introduce cooperating detection to the detection process.Collaborative spectrum sensing is usually achieved in two ways. One way is distributed or centered data fusion, fuse local detection according to some fusion rules and make the decision. Another way is the space diversity, combine signals from different users or rely between users in order to achieve reliable detection. The simulation results show that multi-node collaboration can improve detection performance, shorten the testing time and obtain the agility gain by sharing information.The thesis studies deeply the optimization of collaborative spectrum sensing technology. The received signal to noise ratio reflect the channel status of users, users with higher SNR make decisions more reliable. Therefore, the optimization scheme chooses users with higher signal to noise ratio to participate the collaboration. Studies show that in AWGN channel, the system detection probability first increase and then decrease according with the increase of cooperation user number and there is a maximum; and false alarm probability experience an increase after the first drop and have a minimum; the optimal detection performance is always superior to the performance when all users cooperate. Take use of the optimization scheme in the fading channel and shadowing environment. Studies show that the system doesn't have the optimal detection probability and the optimal cooperation user number. But because of the role of the decline gain, the performance doesn't degrade in the larger user number area, at the other side, better than the performance under the AWGN channel.