Real-time ISI free window tracking scheme for OFDM systems

A novel real-time intersymbol interference (ISI) free window tracking scheme for OFDM systems is proposed by exploiting the inherent correlation between the cyclic prefix and the port of the received OFDM signal. This real-time measured size of ISI free window can be utilized to estimate the maximum delay spread of the channel, then a transform domain channel estimator is adopted to reduce the noise variance further and thus improve the accuracy of the channel estimator. Because the ISI free window can be estimated before the application of FFT to the received signal, it is a parallel processing, and very suitable for practical systems. Simulation results demonstrate that the proposed method can track the variation of delay spread of the wireless channel, and improve the MSE of channel estimation significantly, thus give an improvement of at least 1 dB in an ITU PA3 channel and 0.5 dB in an ITU PB3 channel.