Cooperative Relay-based Spectrum Sensing Technology

With the development of wireless communication technology, the number of wireless subscribers has increesed dramatically,the wireless spectrum resources are becoming more and more limited , hampers the development of the wireless communication. At this stage the most practical method is changing the right of spectrum useing, to improve spectrum utilization efficiency and make full use of idle spectrum. While spectrum opening means can cause interference to licensed users. Cognitive radio(CR)is an intelligent spectrum sharing technology,can sensing wireless environment, real-time adaptive to changing operating parameters, utilize the spectrum dynamically and utilize the idle spectrum effectively.can solve the question of the harmful interference to licensed users and the low spectrum utilization. As one important technique in CR,spectrum sensing plays a vital part in CR realization.In this paper,we introduce the dvelopment background, research significance, orresponding notions, pivotal techonlogy and function module firstly. Then, exhibits various categories of existing techniques on spectrum sensing in CR,including matched filter detection,energy detection,cyclostationary feature detection .When users experiences shadowing or fading effects ,we adopt cooperative spectrum sensing to improve the system's spectrum sensing performance. In this paper, we adope the cooperative schemes which has been recently proposed by G.Ganesan, we derive a novel numerical model for the scheme of cooperative sensing based on cooperative relay, and study the impacts of different parameters on the improvement of spectrum sensing performance under urban environments, while there is power constrain for relay user. The numerical simulation results show that under the urban environment the improvement on sensing performance of U1 is very sensitive to environment factorλ2 ,and The smallerλ2λ1 is, the bigger the cooperation gain is;whenλ2λ1 is fixed, the larger the value ofλ2 is, the better the cooperative spectrum sensing scheme works. The cooperation gain of U1 is decreased with the increase of the angleφ.Finally, compared with the improvement of sensing performance under suburb environments,we find that the improvement of sensing performance under urban environments is much better than uburb environments'. We get this conclusion: cooperative relay spectrum sensing scheme is more suit to urban environments.