Spectrum Sensing Implementation Based On AD9361

Cognitive radio is an effective way to improve the utilization of wireless spectrum,and spectrum sensing is one of its key technologies.The research on this thesis is focused on the spectrum sensing algorithm and its implementation.Firstly,on the basis of analyzing and comparing the advantages and disadvantages of the classical spectrum sensing algorithms,spectrum sensing algorithm based on quadratic covariance matrix is proposed to avoid noise power fluctuation and the difficulty of signal prior information acquisition.Based on the covariance matrix,the algorithm further expands the covariance matrix difference between the primary user signal and secondary user signal.The detection performance of the algorithm is improved effectively.Because the algorithm requires multiple antennas to receive signal and engineering implementation is complex.Spectrum sensing algorithm based on extreme value and geometric average of power spectral is proposed(PSEGAR).The algorithm eliminates noise as much as possible and retains the main user signal,which reduces the influence of unknown carrier offset and noise uncertainty to the performance of spectrum sensing algorithms.Secondly,spectrum sensing system is designed based on AD9361 RF chip.The system consists of an AD9361 RF chip,a ZYNQ baseband processing unit and a computer(PC),The main functions of the AD9361 are RF signal transmission and reception,frequency conversion,A/D,D/A and other functions.The main function of the baseband unit is real-time processing of signal data.The system software designed by Simulink is implemented on the PC.According to the system software architecture,the numerical control module,the transmitting module,the receiving module and the main control interface module are designed.The software system implements the interaction of control parameters and signal data with the hardware platform.At the same time,the number of main user signals,power,frequency band position and symbol rate can be set.The PSEGAR spectrum sensing algorithm proposed in this thesis is implemented on the system.Finally,the spectrum sensing system is tested for real-time signal.The method of multi-modulation signal generation is proposed.Signal test results indicate that the EVM value of multi-modulation signal generated by the hardware platform is less than 2.1%.The performance test results of the designed spectrum sensing system indicate that the system can receive signals accurately in the actual environment.The PSEGAR algorithm can sense the received signal transmitted in the actual environment in real time.This algorithm does not require prior information of the primary user signal and is robust to noise uncertainty and carrier frequency offset.The spectrum sensing system has important application value for researching the spectrum sensing algorithm in real environment.