Research Of Key Techniques For Spectrum Sharing Based On 230MHz

The cognitive radio(CR)based spectrum sharing scheme is an effective method to improve the utilization ratio of the narrowband private network on 230 MHz frequency band and realize the broadband demand.CR usersaccess the idle spectrum by spectrum sensing.The OFDM-based spectrum pooling technology,also called NC-OFDM technology,does well in flexibly controlling the spectrum resources by the way of opening or closing the subcarriers,which is suitable for data transmission in CR system.However,due to the serious out of band radiation(OBR)of OFDM,it will cause interference to the authorized usernearby during the information transmission.Therefore,it is significant to research the interference suppression algorithm.Firstly,the spectrum sharing scheme based on CR of 230 MHz frequency band is studied.On the basis of the above analysis,the interference of broadband OFDM system and narrowband private network system is discussed.After the analysis and calculation,the paper gives the suggestion of the coexistence of the system,and then verifies the rationality of the system through the interference test.Secondly,the active interference cancellation(AIC)algorithm in cognitive OFDM system is studied.After introducing the NC-OFDM technology and the principle of OFDM sidelobe interference,the basic active interference cancellation(AIC)algorithm is derived and its performance is simulated.Considering the large amount of calculation,we introduced an AICalgorithmthat is based on power spectral density(PSD-AIC),which can reduce the computation cost based on part of online calculation replaced by offlinecalculation.Compared with the traditional AIC algorithm,the interference suppression ability is shown to beequivalent.Finally,the algorithm is optimized and verified by the semi-physical simulationplatform.For the sake of improving the performance of the algorithm,the dynamic PSD-AIC algorithm is proposed.It can select the location of the dynamic interference cancellation subcarrier by traversing search.As the simulationresults showed,the algorithm we proposed can achieve a better interference suppression effect under the same parameters.The semi-physical simulationplatformis set up by using signal generator,digital radio transceiver and other hardware equipmentfor the verification of the optimization algorithm,which can simulate the actual working environment of 230 MHzfrequency band.Comparedsemi-physical simulation results of optimization algorithm with the standard test,optimization algorithm achieved better performance.