Research Of Cooperative Wideband Spectrum Sensing Algorithms In Cognitive Radio

The spectrum,as a precious resource,has being congested day by day with the rapid development of wireless communication.And it is suffering a heavy profligacy due to its inefficiency utilization.Cognitive radio(CR)is viewed as a promising solution to the problem of spectrum shortage.It is a smart wireless communication system that can significantly increase the spectrum efficiency.The spectrum sensing plays a key role in the establishment of cognitive radio.In recent years,wideband spectrum sensing has become a research hotspot of CR because of the application of wideband wireless communication in various scenarios.This dissertation focuses on the wideband spectrum sensing algorithms.In order to fix the drawbacks of conventional algorithms,the dissertation proposes the cooperative wideband spectrum sensing based on double threshold energy detection.In the algorithm mentioned above,the whole licensed wideband spectrum is divided into several sub-channels,and some of them are sensed by the double threshold energy detection.The final decision of the primary user's absence is made by two-stage combination which is at second users and the data fusion center.The simulation results show that cooperative wideband spectrum sensing based on double threshold energy detection detects less sub-channels than traditional algorithm when they have the similar performance,so its energy consumption and communication overhead are less.The dissertation also investigates the application of radio environment map(REM)in wideband spectrum sensing and proposes the cooperative wideband spectrum sensing based on REM.This algorithm is an improvement of cooperative wideband spectrum sensing based on double threshold energy detection,it processes the hard and soft decisions made by the double threshold energy detection respectively.In the algorithm,hard decisions are combined by the voting rule and soft decisions are combined with weights which are based on the location information stored in the REM.The final decision is based on the results of both hard and soft combinations.The simulation results suggests that cooperative wideband spectrum sensing based on REM can achieve equal detection performance compared to the one based on double threshold energy detection,and it is more suitable for the for practice wireless communication due to its low computational and implementation complexities of second users.