Study On Spectrum Sensing Algorithm In Cognitive Radio Based On Array Antenna And Covariance Matrix

With the rapid development of wireless communication technology, the spectrum resources become more and more scarce. It also seriously hinder the development of wireless communication. The spectrum utilization is authorized by management, and the use efficiency of authorized spectrum is very low. In order to solve this problem, cognitive radio has been proposed. Spectrum sensing is a key technology of cognitive radio. Spectrum sensing is used to sensing the existence of "Spectrum holes". Cognitive users can use spectrum dynamically on the premise that cognitive users can achieve successful spectrum detection.Energy detection, matched filter and cyclostationary feature detection are conventional spectrum sensing. We are bounded by many conditions if we want to use methods mentioned above to sensing "Spectrum holes". The spectrum sensing algorithm based on covariance matrix can achieve spectrum detection successfully without any information of primary users and noise. Compared with methods mentioned above, spectrum sensing algorithm based on covariance matrix is more practical.To derive the threshold, Conventional spectrum sensing algorithm based on covariance matrix requires approximation. In addition, the arrival direction of primary signal and the receiving antenna of cognitive users is not consistent, which result in reduction of SNR. A spectrum sensing algorithm based on covariance matrix and array antenna is reported in this article. The algorithm can achieve good performance even though the arrival direction of primary signal and the receiving antenna of cognitive users are not consistent. From the derivation of the threshold which is introduced later, we can get that the threshold is more accurate than the threshold of conventional spectrum sensing algorithm based on covariance matrix. The performance of the proposed spectrum sensing algorithm is superior to conventional spectrum sensing algorithm. Applying array antenna to spectrum sensing algorithm based on covariance matrix can increase SNR of signal received by cognitive users. So applying array antenna to the spectrum sensing can improve performance of spectrum sensing.Spectrum sensing algorithm based on covariance matrix and array antenna construct covariance matrix firstly. And then a new test statistics for spectrum sensing based on the covariance matrix is constructed and the decision threshold based on the test statistics is derived, thus allowing the comparison of the test statistics with the decision threshold to make a final decision. This article verifies the performance of spectrum sensing algorithm based on covariance matrix and array antenna by MATLAB. The simulation show that performance of the proposed spectrum sensing algorithm is superior to conventional spectrum sensing algorithm, and performance of spectrum sensing which employ array antenna is superior to spectrum sensing which employ single antenna. The results also show that the threshold derived by this article is more accurate than the threshold of conventional spectrum sensing algorithm based on covariance matrix.Finally summary of spectrum sensing algorithm and future research perspective are given.