Research On Fast Spectrum Sensing Technology In Satellite PCMA System

In recent years,satellite communication systems have made rapid progress due to its strong adaptability,low cost and wide range coverage and so on.With the novel technologies of paired carrier multiple access coming into being,satellite communications have achieved a tremendous breakthrough in spectrum utilization.At present,the traditional PCMA system uses the controller to distribute the spectrum right,which leads to discontinuity.In order to overcome this shortcoming,using spectrum sensing technology in PCMA system can understand the spectrum usage situation in real time.As a way to improve spectrum utilization rate,the fast spectrum sensing technology has become a hotspot in the research of satellite communication theory.In this paper,the quick spectrum sensing technology in paired carrier multiple access is studied.First of all,the performance of the classical CUSUM algorithm in baseband and frequency band is studied,such as detection probability,threshold,delay and so on.Then,based on this,the fast spectrum sensing algorithm under unknown Gaussian noise variance is studied.The signal model is two-channel baseband signal using QPSK modulation.For the unknown Gaussian noise variance,the maximum likelihood and the maximum a posteriori estimation method are used to obtain the variance estimate.Considering the fact that there is a phase offset between the signals,the existing theory cannot be used directly.In order to eliminate the effect of phase offset,the modified first order Bessel function is used to approximate processing.At the same time,the mathematical analytic formula of Gaussian noise variance is obtained by using polynomial fitting technique.Then,according to the combination of the noise variance estimation and the CUSUM algorithm theory,the recursive judgment formula is deduced and the simulation results and analysis are given,which play an important role in the performance of the satellite communication system under the Gaussian white noise.In order to compare the advantages and disadvantages of the two estimation algorithms,the simulation results are also given in this paper,that is,the spectrum sensing performance by the maximum a posteriori estimation is better than that by the maximum likelihood estimation.Finally,using the ISE design Suite 14.7 development platform of Xilinx company,the paper successfully realizes the hardware function simulation verification of the quick spectrum sensing.In this paper,the whole design scheme of the perception is given,in which the programming language chooses the hardware description language Verilog,and the Isim simulation software is used to simulate the function,which verifies the correctness and feasibility of the hardware module.