Research On The Detection Of Spectrum Holes In Cognitive Radio

The thesis is funded by the National High-tech Research and Development Program (863 Program): the research of cognitive radio technique. With the rapid development of wireless communication, the finite spectral resource becomes more lacking in the fixed assignation mode, in which the percent of utilized spectral resource is low. Cognitive radio is defined as an intelligent wireless communication system that is aware of its surrounding environment and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states by making corresponding changes in certain operating parameters in real time, in order to promote the efficient of the spectrum usage and revive the lack of spectral resource.As one part of the 863 Program, the thesis mainly researches the techniques of spectrum estimation and spectrum holes detection in cognitive radio. Multi-taper method is a kind of nonparametric spectrum estimation, in which multiple orthonormal windows are first applied to the received data and then periodogram method is used to estimate the spectrum. The discussion and comparison of the statistical performances of MTM and WOSA are given in quantity under the circumstance that the dynamic range of the true spectrum is large. And some individual views are presented. Two linear algorithms of MTM and their statistical performances are also analyzed. They are the best linear combinations of the eigenspectra which are obtained using BLUE and MMSE individually. And their statistical performances are also discussed. A method of spectrum holes detection based on single node is presented. For a given frequency band, a reasonable threshold of the interference is set according to the communication service requirements of cognitive radio. It is decided whether the threshold is exceeded by the interferences from the sensed signals and the spectrum holes are detected through the decision. At the last part, the detection and analysis of spectrum holes in GSM frequency bands is measured. It is shown that many spectrum holes are still available to unserviced users some times even in the bands which are frequently used. The result sets a stable base for the cognitive radio research.