A novel guard interval based ISI-free sampling region detection method for OFDM systems

A novel guard interval based method for detecting the ISI-free sampling region in OFDM systems is proposed. We employ a symbol-by-symbol correlator, a phase processor, and a modified edge detector to detect this region. The symbol-by-symbol correlator is based on the cyclic prefix structure of the guard interval and symbol-by-symbol average operation is adopted to reduce the noise effects on this region. The phase processor outputs a feature signal that can be utilized to detect this region with a modified edge detector which uses both the thresholding and the run-length filtering techniques. Estimations of symbol timing, fractional frequency offset and maximal multipath delay are also obtainable through this method. The present is unique in that it has low computation complexity because an optimal detection threshold can be chosen independently of average SNR and it can be determined before system operation. Computer simulation results verify that this method achieves similar performance as earlier methods. In general, the proposed method is feasible and can be applied to detect the ISI-free sampling region for OFDM systems in any mobile radio environment.