Researches Of Spectrum Sensing Technology In Cognitive Radio

With the rapid development of technologies in wireless communications, wireless service is focusing on those applications which require more bandwidth and higher rates, such as multimedia communication. But the lack of radio spectrum is becoming more and more serious. Cognitive radio is a new intelligent wireless communication technology, it can change its transmitter parameters immediately based on interaction with the environment where it operates. The core idea of cognitive radio is to exploit the licensed but underutilized spectrum, in order to improve the spectrum efficiency. In cognitive radio systems, avoiding interference to primary users is the most important character. And spectrum sensing is the key technique to achieve this goal.Firstly the dissertation summarizes fundamental notions of cognitive radios, including its definition, concept model, main functions and important technologies and so on.Secondly introduce various categories of existing techniques on spectrum sensing in cognitive radio. Fully it summarized the principles, characteristics in cognitive radio spectrum sensing. It compared strengths and weaknesses through of analyzing the various sensing methods. This part systematically investigates three digital signal processing techniques: matched filtering, energy detection, and, cycle stationary feature detection. It makes modeling and simulation for various techniques. Also it analysis of the energy detecting method in sensing authorized users in both AWGN and Relay channel. Single node faced the"hidden terminal"and the low of detection probability problem, but the collaborative spectrum sensing algorithm can effectively over come this trouble. Then, analysis the collaborative sensing ignored the different channel, and not fit the actual communication environment.Thirdly, this dissertation analysis the character of current weighted cooperative spectrum sensing: through this algorithm consider the different nodes are in different wireless environment, resulting in different credibility in their sensing, have different weighted, the weighted is difficult to achieve. To solve this trouble. An improved algorithm is proposed, utilizing multiple sensing nodes and taking their sensing credibility as the weighted. Chapter 4 elaborates this algorithm in detail, and simulations are undertaken, based on energy detection, these simulations verify that this improved algorithm outperforms existing ones significantly and the weighted is easy to be calculated.