Research On Blind Spectrum Sensing Algorithms In Cognitive Radio

In recent years,the number of wireless users is increasing continuously with the rapid development of 5G and other communication technologies,which makes the spectrum resources become more and more tense.Because the existing spectrum allocation method is static,it is possible for the primary user to occupy the authorized frequency band for a considerable period of time without communicating,which makes the utilization of spectrum resources very low.In order to improve the availability of spectrum resources,cognitive radio has been proposed.Accurate spectrum sensing of the authorized frequency bands concerned is the premise of cognitive radio technology.By spectrum sensing of the surrounding environment,it ensures that cognitive users can access the band quickly and safely when it is not used by the primary users,so the spectrum resources are fully utilized.First,taking the covariance matrix spectrum sensing algorithm of classical algorithm in multi-user system as an example,we make the performance improved.In a multi-user system,if the number of collaborative users is small,the detection performance can be greatly affected.Therefore,the method of "matrix splitting and reorganization" is applied on this kind of algorithm.The performance changes of CAV(Convariance Absolute Value)and MME(Maximum Minimum Eigenvalue)after this method are analyzed,and the performance simulation is given.We study the disadvantage of splitting and reorganization,and then put forward a method of "matrix sliding window reorganization" applied on CAV and MME.Combining theory with simulation,it further improves the detection performance when the number of collaborative users is small.We then improve the WMUSIC(Weighted Multiple Signal Classification)algorithm based on angle.the spectrum sensing algorithm of spatial angle dimension enables cognitive users to communicate when primary users occupy spectrum resources by adjusting the antenna angle.With different angles,it realizes the resource utilization of the same frequency at the same time.In the signal detection stage,multi-level detection statistics are constructed by spatial spectrum,and the corresponding threshold value of each level detection statistics is given.Combined with simulation,we verify the improvement of detection performance.At the angle estimation stage,by analyzing the relationship between element space and angular resolution,and combing practical engineering application,the maximum element space without false spectral peaks is given,which breaks through the limitation of half-wavelength element spacing.The improvement of angular resolution is verified by simulation.WMUSIC blind spectrum sensing algorithm can not process related signals,so we do some improvement on it.Combined with Matlab simulation,the improved algorithm can distinguish related primary user signals.Besides,considering Doppler frequency shift,the analysis of WMUSIC blind spectrum sensing algorithm under Doppler frequency shift is given.Finally,the existing TCT(Two-sided Correlation Transform)algorithm is improved.Neither angle estimation nor source number estimation is needed.A blind spectrum sensing algorithm from the spatial dimension for wideband signals based on TCT algorithm is proposed.In the phase of wideband signal detection,detection statistics are constructed from spatial spectrum,and the method of deciding threshold values corresponding to detection statistics is given.The existence of wideband signals is perceived by comparing detection statistics with threshold values.Through Matlab simulation,the different effects of the parameters of the spectrum sensing algorithm on the detection performance are given.At the wideband signal angle estimation stage,we construct a new variable instead of focusing matrix to improve the accuracy of angle estimation to a certain extent.After estimating the angle of the wideband signal of the primary user,the LCMV(Linear Constrained Minimum Variance)criterion is selected by analyzing the adaptive beam technology,so that the primary user and the sensing user can communicate separately without affecting each other.