Research And Measurements Of Spatial Spectrum Sensing Based On Cognitive Arrays

The wireless spectrum is not a kind of renewable resource. It almost has beenallocated in most countries. As the wireless business is growing, the wireless spectrumbecomes more and more strained. But the utilization efficiency of spectrum in somefrequency bands now is very slow. Cognitive radio suggests cognitive user using thespectrum hole to communicate without disturbing the primary users. With cognitiveradio, the utilization efficiency of wireless spectrum can be improved.Based on differentdimensions, spectrum hole can be divided to three kinds: time domain, space domain,and frequency domain.The sensing method for different kind of spectrum is different.This paper emphasizes on the spatial spectrum hole sensing.In Chapter1, the background and research status of cognitive radio are introduced.And the main work of this thesis is outlined.In Chapter2, the difinition of cognitive radio, spectrum sensing and spectrummanagement which are the key technology of cognitive radio, and algorithm for spatialspectrum sensing are introduced.In Chapter3,The character of cognitive array is introduced. A kind of widebandmicrostrip antenna is designed to form a6-element array used for spatial spectrum holesensing. The receiving element patterns in the time domain are measured in arrayenvironment. With these receiving element patterns, a time reversal based arraysynthesis method for wideband arrays is testified through experiments. By using thetime reversal based array synthesis method, the scanning range of the array can beeasily calculated.In Chapter4, experiments and analysis for spatial spectrum sensing aredemonstrated. We did some DOA experiments with the6-element array. A peak appearsat the angle of source. But it appears pseudo peaks in some undesired angles. Thereason of pseudo peak is analyzed. At last, it is suggested that using the the receivingelement patterns to construct new steering vector to do DOA estimation. Theexperimental results show that the pseudo peak is not only migrated, but the resolutionis also improved remarkably. In Chapter5, the summary about the work of the project and the expectation aboutnext work are presented.