Research On Cooperative Spectrum Sensing Technology Based On Relay Selection

Along with the tireless efforts of academic experts who have done further research over the years, wireless communication technology makes it more efficient and convenient for human beings to communicate and exchange information with each other. However, the contradiction between the scarcity of wireless spectrum resource and the increasing demand for higher resource utilization becomes much sharper, faster signal processing speed and better system reliability. Low spectrum efficiency has become a bottleneck limiting the further development of wireless communication technology. Therefore, cognitive radio technology is proposed to improve the spectrum efficiency, by which the cognitive user can sense spectrum by itself and use licensed spectrum for communication without harmful interference to the primary user. As a result, it is considered to be one of the important techniques to explore spectrum characteristics and efficiency for next generation wireless communication.Sensing spectrum quickly and accurately is an important prerequisite and foundation for the cognitive user to use licensed spectrum in cognitive radio system effectively. So spectrum sensing technology plays a key role in cognitive radio research. Furthermore, cooperative communication technology can increase the capacity and improve the performance of cooperative system by space diversity between multiple nodes. Therefore, cooperative spectrum sensing system, which combines cooperative communication with spectrum sensing, can improve the performance of spectrum sensing obviously.Cooperative spectrum sensing technology based on relay selection is studied in this paper. Firstly, the paper introduces cognitive radio technology and spectrum sensing technology briefly. Secondly, basic theory on cooperative spectrum sensing technology is elaborated including foundation theory, spectrum sensing detectors and standards of information fusion. Thirdly, considering cognitive system with multiple relays, the sensing performance of cooperative spectrum sensing schemes based on different relay selection strategies are thoroughly studied. The cooperative spectrum sensing scheme based on global AF relay selection is presented. On the basis of a sufficient study of variable-gain based relay selection, the fixed-gain counterpart is investigated to simplify the complexity of the system. The sensing performance with energy detector is analyzed, and especially a closed-form lower bound of the average missed-detection probability is proposed to evaluate the sensing performance in a convenient way. Theoretical results are corroborated through simulations. Then, the cooperative spectrum sensing scheme based on partial AF relaying is discussed. Relay selection with fixed gain is investigated following the analysis of the scheme with variable gain. The similar detection performance analysis and simulation are also offered for the fixed-gain scheme. Particularly, numerical results show that a partial relay system with only two relays can achieve good detection performance, indicating that complexity can be further reduced when detection performance is guaranteed.