| Cognitive radio is an important technical means to alleviate the current uneven spectrum allocation and underutilization,mainly through sensing the spectrum usage in the wireless communication environment and accessing the idle spectrum for communication,so as to improve the spectrum utilization rate.In cognitive radio systems,reliable spectrum sensing is the prerequisite for spectrum management,and reasonable spectrum sharing technology can enable cognitive users to access the idle spectrum without affecting the communication of the primary user,and ensure the transmission quality of users.In view of the problem that single-node signal perception is susceptible to path loss,shadow effect and multipath fading,An improved spectrum sensing algorithm based on power spectrum is proposed.The algorithm makes use of the characteristic that the orthogonal basis of power spectral density is not easily changed by other interference,and solves the eigenvector cannot point to the direction of the primary user signal precisely because of the influence of noise.Firstly,the autocorrelation function of the signal after orthogonal expansion is obtained,and the power spectrum of the signal is further obtained by Fourier transform,and the ratio of the difference between the extreme value of the power spectrum and the geometric average of the power spectrum is used as a statistic.Then deduce the detection probability and false alarm probability of the algorithm,which proves that the performance of the algorithm is not affected by noise power.Experimental results show that the improved algorithm has higher detection probability under the same false alarm probability or signal-to-noise ratio,which verifies the effectiveness of the algorithm.Based on reliable spectrum sensing results,a partial-user cooperative spectrum sharing algorithm based on contract theory is proposed.The algorithm mainly solves the contract design problem of wireless communication system in different information scenarios and secondary user selection problem under limited budget.The algorithm takes the average of the power provided by multiple secondary users as the threshold,selects one or a group of secondary users as the relay node to forward the signal of the primary user,and the secondary users obtain the corresponding time excitation according to the provided forwarding power,and complete the signal transmission on the authorized spectrum according to the excitation.By comparing the system performance under different conditions,it shows that the algorithm has higher user benefit and better transmission rate. |
