Research On FBMC Signal Modulation Recognition Method In Cognitive Radio System

The FBMC-OQAM(Filter Bank Multicarrier-Offset Quadrature Amplitude Modulation)signal is a multi-carrier modulation signal based on a filter bank because it uses a special signal processing at both ends of the transceiver to eliminate inter-symbol or inter-carrier interference.Therefore,this new modulation method can avoid the disadvantages of the OFDM(Orthogonal Frequency Division Multiplexing)modulation method,which uses the cyclic prefix to affect the data transmission rate and the inflexible spectrum usage,and becomes one of the alternatives for the 5G mobile communication.However,due to the method is newer,the research on the combination of FBMC-OQAM modulation technology and cognitive radio technology is rarely touched upon yet.Therefore,this paper proposes an algorithm based on spectral analysis,constellation clustering projection and log-likelihood function to solve the problem of FBMC-OQAM signal modulation recognition in cognitive radio.The main contents of this paper include:1.Introduce the similarities and differences between FBMC-OQAM modulation and OFDM modulation in system architecture,modulation principle and subcarrier modulation method.2.The characteristics of the FBMC-OQAM modulation signal are analyzed.The two main characteristics that the sidelobe attenuation of the power spectrum of the FBMC-OQAM modulated signal is fast and the virtual real interval modulation of the OQAM subcarrier signal are obtained..3.The classification and recognition of FBMC-OQAM signals and different subcarrier modulation methods in multi-carrier systems are studied.The power spectrum of the FBMC modulated signal is analyzed by the spectrum analysis method,and the log-likelihood function of the two carrier signals of OQAM and QAM is calculated.These two methods to realize modulation recognition of FBMC-OQAM modulation signal are combined.In addition,the classification of MPSK and MQAM subcarrier modulation signals is also performed using the constellation cluster projection method combined with the log-likelihood function method.The results show that this method can well classify FBMC-OQAM signal and OFDM-QAM signal.But also can effectively classify different sub-carrier signals in multi-carrier systems.