Research On Spectrum Sensing In Cognitive Radio Network

Because of many spectrum segments have been allocated to the licensed spectrum users and the spectrum utilization of the existing systems is little, cognitive radio technology is proposed as a solution to this question. A lot of research shows that the technology can effectively relieve the scarcity of spectrum and improve the utilization of frequency resource. Spectrum sensing is a key technology in cognitive radio systems, and also the first step of the whole cognition process.This paper first introduces normal algorithms of individual user's sensing. The advantages and disadvantages of these algorithms are analyzed and compared. Because of a single user's spectrum sensing is affected by shadowing, fading and time-varying natures of wireless channels, cooperative spectrum sensing schemes have been researched to combat negative factors. During process of cooperative spectrum sensing, information from different CR users is combined to make a decision on the presence or absence of the primary user, so choice of fusion algorithm is important to collaborative spectrum sensing. This paper studies the collaborative spectrum sensing and divides the collaborative spectrum sensing algorithms into decision fusion and data fusion. Later it discusses and analyzes the performance of these algorithms.The above-mentioned algorithms are based on fixed sample detection. However, transmission channel resources can be saved if we employ mutative sample detection. In addition, some sensing users for cooperative sensing may be hostile users in actual communication systems which will deteriorate the performance of spectrum detection. In this case, an improved sequential test scheme based on reputation for spectrum sensing is proposed. It's a non-fixed sample detection method which can not only use the incorrect sensing reports of hostile users, but also update the list of the hostile users.The simulation results show that the method can effectively reduce the number of samples required by fusion center and improve the performance of detection.