An LDPC-coded OFDM receiver with pre-FFT iterative equalizer for ISI channels

This paper describes a low-latency LDPC- (low-density parity-check) based iterative equalizer, using pre-FFT (time-domain) signal processing, for OFDM (orthogonal frequency division multiplexing) inter-symbol interference (ISI) channels. Combined with a novel channel estimator, the proposed receiver can estimate both channel-state information (CSI) and ISI accurately even under a fast-fading environment. At a data rate of 100 Mbps, and vehicle speed of 100 km/h (at a carrier frequency of f_c=5 GHz), where almost 40% of the OFDM symbols face ISI, the receiver provides a block-error-rate (BLER) of 10² at 0.8-dB degradation from that of an ISI-free environment with perfect CSL. By introducing an adaptive iteration control (AIC) technique, our receiver maintains good performance with a maximum latency of 8 OFDM symbol durations. Computer simulations showed that the proposed scheme is robust and has potential applications in broadband, high-quality communication systems.