Research On The Identification Of OFDM Signal In Multi-path Rayleigh Channel

Various modulation techniques are widely used in wireless communication systems which occupy various frequencies and bandwidths. In order to acquire the information of a communication signal, it is necessary to know the modulation type and parameters. Receiving a communication signal, the modulation identification is to decide the modulation type and estimate the modulation parameters of the communication signal without any prior knowledge about the signal information, thus modulation identification is the first step for the correct demodulation algorithm, and ultimately acquire the useful information. At the same time, more and more complicated signals have been existed, which results in more than one signal being received by a receiver. Modulation identification has become more difficult because of the limited frequency resources and various modulation types.For the last several decades, many methods on the modulation identification have been studied, where the research focused on the single-carrier signal in Gaussian channel. There were few researches on multi-carrier signal in Rayleigh channel. By the combination of the 2nd and 4th order cumulants being used as the criteria function, it is realized to identify multi-carrier modulated signals (OFDM) from single carrier modulated signals (MPSK, MQAM and MFSK) in this thesis. The algorithm is simulated by Matlab with the performances analysis. It is shown by simulation that the algorithm is feasible with a 100% correct classification when the SNR is above 7dB in single-path Rayleigh channel. In the case of multi-path Rayleigh channel, the required SNR is above 8dB.