OFDM Signal And Subcarrier Modulation Recognition

In wireless communications, civilian mobile communication technology has developed rapidly. Currently, the fourth generation mobile (4G-LTE) technology has been fully promoted. In order to achieve ultra-fast data transfer rates,4G-LTE standard adopts OFDM (Orthogonal Frequency Division Multiplexing) technology. In a wireless electromagnetic environment, various types of signal modulation mode exists, and one modulation signal can have different modulation parameters. From a number of different modulation mode or different modulation parameter signaljudging desired signal and estimating the modulation parameters are a prerequisite for a subsequent signal demodulation.This paper focuses on the OFDM signal under the system of 4G-LTE background, the existence of the OFDM signal and the identification of the sub carrier modulation mode were studied. Firstly, this paper introduces the basic theory of OFDM system,OFDM modulation signal expression is given and discusses the principle of selecting the basic parameters of OFDM signal; secondly, on the basis of the theory of higher-order statistics, making use of the principle of moment and high-order cumulants, extraction and characteristic parameters of different modulated signals, and through the analysis of modulation signal difference, realize the existence of OFDM signal discrimination; then, in the identification of sub carrier modulation, using the decision tree to classify the modulation, and analyses the effects of carrier frequency offset in OFDM system. At the same time, in the Matlab platform, OFDM signal characteristic parameters, the correct recognition rate signal, the carrier frequency deviation MSE respectively simulation results show that the algorithm in this paper is feasible and effective.