Spectrum Sensing Algorithm Based On Frame Structure Design And Secondary User History Decision Information

In recent years,with the development of society and the progress of science and technology,the wireless communication business has increased rapidly,and the existing radio spectrum resources can not meet the needs of users.In the global scope,the radio spectrum resources are in short supply,and more and more serious.Cognitive radio technology is one of the important methods to solve this problem and its core is spectrum sensing technology.First,the secondary user(SU)finds out the spectrum hole in the cognitive environment through the sensing technology,and then,the SU attempts to access the frequency band to data transmission,provided that the SU does not interfere with the primary user(PU).There are many problems of the traditional spectrum sensing technology,including the low throughput and the poor detection performance.The thesis studies and improves it from the following two aspects.Firstly,in the thesis,the traditional frame structure is improved on the basis of cooperative spectrum prediction technology,cooperative sensing technology and continuous spectrum sensing technology.By dividing the primary user's frequency bands into two sub bands,one is used by the SU for data transmission,the other is used by the SU for continuous spectrum sensing.Therefore,the SU can use the whole frame time slot for data transmission and the continuous sensing technology can effectively alleviate the problem of sensing interruption,so the throughput of the SU has been improved to a certain extent.In addition,the spectrum prediction phase is added to the frame structure,which provides the correct direction for the subsequent sensing phase.The user cooperation after the prediction stage can effectively improve the prediction accuracy,and the user cooperation after the sensing stage can also effectively improve the detection performance.The simulation results show that the frame structure designed in the thesis improves the throughput of SUs compared with the traditional method.Secondly,the thesis studies and improves the multi-user cooperative sensing algorithm based on the historical decision information about SUs.The traditional energy detection(ED)algorithm based on single threshold has a general detection performance,and the traditional energy detection algorithm based on double threshold often adopts the strategy of re-sensing when the energy statistics obtained by SUs are between the upper and lower thresholds.The thesis considers the number of historical uncertain decisions for the SU.When the number of uncertain decisions reaches a certain threshold,we increase the number of sampling points of the SU to improve the detection performance of the system and reduce the average uncertainty decision probability in a certain range of Signal-tonoise ratio(SNR).In addition,the thesis proposes a weighted cooperative sensing algorithm based on the combination of secondary user history decision and SNR.The core idea is that the fusion center(FC)makes real-time statistics on the historical decision information of each SU,then calculates the current decision credibility of each SU according to the historical decision information,and finally allocates the real-time weight based on the decision credibility and SNR of each user.The simulation results show that the improved double threshold cooperative detection scheme has a higher detection probability than the traditional scheme while the SNR is the same.The thesis also combines the improved double threshold cooperative detection scheme with the proposed weighted cooperative scheme,and compares it with the traditional scheme in the simulation.The results show that proposed scheme has better detection performance.