Adaptive Pre-FFT Equalizer with High-Precision Channel Estimator for ISI Channels

We present an attractive approach for OFDM transmission using an adaptive pre-FFT equalizer, which can select ICI reduction mode according to channel condition, and a degenerated-inverse-matrix-based channel estimator (DIME), which uses a cyclic sinc-function matrix uniquely determined by transmitted subcarriers. In addition to simulation results, the proposed system with an adaptive pre-FFT equalizer and DIME has been laboratory tested by using a software defined radio (SDR)-based test bed. The simulation and experimental results demonstrated that the system at a rate of more than 100 Mbps can provide a bit error rate of less than 10(-3) for a fast multi-path fading channel that has a moving velocity of more than 200 km/h with a delay spread of 1.9 mu s (a maximum delay path of 7.3 mu s) in the 5-GHz hand.