The reaserch about spectral correlation of subcarrier of OFDM and blind recoginition about modulation type

OFDM is an important technology for 4G and being used of the wireless data communication, but it is very difficult to have a blind recognition method about subcarrier modulation type of OFDM. The characteristics of cyclostationarity modulation spectrum which will be not affected by noise, This paper gives out a blind recognition method about modulation types of OFDM subcarrier based on coefficient of cyclic spectrum correlation through analysis and simulation about spectral cyclostationary of the OFDM subcarrier in the nonperiodic of nonhomogeneous Markov chain. First, the signal of OFDM which is received by adaptive receiver is divided into single subcarrier and transform it to spectrum, the coefficient about main part of the OFDM subcarrier´s spectrum can be calculated and compared with parameter which has gained through experience, Then the modulation type can be recognized through the emulational calculation with computer. The step of this calculation is fewer than that of other method which is used as usual, it is very useful to detect the modulation type about subcarrier of OFDM. It is nearly 100% right rate of detecting modulation type if the SNR is more than 10dB.