Signal Detection And Recognition In Non-Cooperative OFDM System Based On The Cyclicstationary Of OFDM Signal

Orthogonal frequency division multiplexing (OFDM) has been regarded as a core technique for the fourth generation (4G) mobile communication system, due to its advantage of high data rates in multipath fading environments. But, the widely application of OFDM technology in wireless spectrum resources management and Electronic warfare has also brought great challenges. Recently, researching on OFDM cooperative communication has been a hotspot. However, researching on OFDM non-cooperative reception is on the scratch line. For national information security, it is important to study non-cooperative reception deeply.In this paper, the key technologies in OFDM non-cooperative reception are discussed. The primary works and innovations are as follows:Firstly, we propose OFDM non-cooperative reception mathematical model, and analyze the properties of OFDM signal in time domain, frequency domain and cyclostationary domain. Then, prove that the OFDM signal with CP is cyclicstationary and point out that there are three key problems should be solved in this paper, i.e., signal recognition, modulation recognition and parameters estimation.Secondly, we propose blind signal classification algorithm and parameters estimation algorithm for OFDM systems based on the second order cyclostationary of OFDM signal. Furthmore, the peak vaules of2-nd cycle cumulant of OFDM signal and Single carrier linear signal(SCLD) are at different position in time domain and cyclostationary domain, and the positions of peak values of OFDM signal are related to the modulation parameters. So, we use these features to conduct signal recognition and parameters estimation. High performances of the proposed algorithm are proved by simulations.Thirdly, we use high order cumulant of OFDM signal to distinguish modulation type. This is based on the statistical property of information symbols on each sub-carriers. Simulation results demonstrate the algorithm has strong ability in Multipath channel and at a low SNR.