Research On The Modulation And Identification Of OFDM Signals

With the development of communication technology,wireless communication technology is diversity and the using of communication protocols is not unified.Therefore,if the modulation information and parameters are unknown,how to identify the modulation signal is a key technology to demodulate signal correctly and get the useful information.In recent years,Orthogonal Frequency Division Multiplexing(OFDM)has been widely used in the communication systems,which has higher spectrum efficiency and better anti-multipath-fading ability.This paper studies recognition method of OFDM signal over the Gaussian white noise channel,narrowband Rayleigh fading channel and multipath fading.This paper introduces the theory of higher-order cumulants,then calculates the second and fourth-order cumulants of the received signal,and based on this signal characteristic parameters to obtaine signal recognition and achieve OFDM signal and digital single-carrier signal {MASK,MPSK,MFSK,MQAM} modulation type identification.Through theoretical analysis and simulation verification,the application of these methods to identify OFDM signal has good recognition feature.This paper furtherly researches signal recognition method based on wavelet decomposition,with the extracted minutiae as the received signal characteristic parameters of signal to modulation type identification for OFDM signal and digital single-carrier{MASK,MPSK,MFSK,MQAM} signal.Simulation results show that over Gaussian white noise channel,narrowband Rayleigh fading channels and multipath channel,there is a higher rate of correct identification signal.This paper also using wavelet decomposition algorithm modulation type identification for OFDM signal and DS-CDMA signals.Simulation results show that under the Gaussian white noise channel and Rayleigh channel,the proposed algorithm can effectively identify the OFDM signal with DS-CDMA signals,but it does not apply to identify DS-CDMA signal over multi-path channel.