Research On Spectrum Sensing And Routing Algorithm For Cognitive Radio Networks

Spectrum sensing and routing protocols attract research attention because they are crucial technologies to promote the development of cognitive radio network. This dissertation is supported by the projects like National Natural Science Foundation of China etc, and attempts to make contribution on both theory and application of cognitive radio network.This dissertation mainly researches spectrum sensing and routing algorithm for cognitive radio network. The main contributions and innovative achievements of the dissertation include:Cooperative spectrum sensing for multiband under constrained control channel was proposed for the problem that energy detection is not robust to noise uncertainty on cognitive radio network. Every secondary user will sense all frequency bands utilizing two thresholds energy detection simultaneously under noise uncertainty. For the uncertain frequency bands, the multi-point cooperative spectrum sensing is performed. In this scheme, secondary users transfer sensing information utilizing the idle frequency bands rather than only depending on common control channel and it can decrease communication overhead of common control channel and obtain smaller miss alarm probability for the uncertain spectrum bands compared to traditional cooperative sensing schemes.A linear cooperative spectrum sensing scheme based on ant colony algorithm was proposed for cognitive radio network. In this scheme, the fusion center can adjust the proportion of every secondary user's detection result on cooperation spectrum sensing decision-making according to actual wireless environment. The sensing performance will be improved. Nonquiet primary user detection scheme was proposed because the traditional cyclostationary feature detection will incapable once the secondary user signal has same classification and cyclic frequency as primary user signal. At first, the linear prediction was utilized to predict the signal of secondary user in order to reduce its effect on spectrum sensing. The residual signal will be gained by means of the received signal subtracting the predict signal. By calculating the autocorrelation function of residual signal and comparing it with the threshold, the nonquiet primary user detection scheme will be realized. In this method, quiet period is not needed and the transmission performance can be improved without the interruption of on-going transmission and the utilizing efficiency of spectrum will be improved.In this paper, a routing protocol based on improved ant colony algorithm is proposed because the available channels of secondary users are dynamic and the secondary users can change their communication frequency actively in cognitive radio network. The best path can be found out according to compositive function in this scheme and it needn't the common control channel to transfer routing protocol information. This scheme can effectively reduce the routing overhead and the route discovery delay.Finally, the content of the whole dissertation is summarized and several valuable research directions of cognitive radio are also discussed.