Combination of interference cancellation with channel estimation for OFDM transmission over mobile radio channels

Abstract

This paper proposes a new method, which combines interference cancellation with channel estimation for an orthogonal frequency division multiplexing (OFDM) system in the case of insufficient guard interval (GI) length. To avoid the problem of causing additional errors of conventional cancellers in the presence of strong additive noise, the proposed cancellation scheme uses the channel state information (CSI) and the so-called remodulation technique to reproduce the interference distortions. Then, these distortions in both the received pilot symbols and the data symbols are iteratively cancelled. Consequently, the channel estimation as well as the data equalisation performances are iteratively enhanced. In the range of high signal-to-noise ratio (SNR), the proposed scheme improves significantly the performance of the system. It does not cause any additional errors to the received signal, when the system suffers from very low SNR. In comparison to the case of sufficient GI length, the required SNR can be reduced by 0.5 dB to achieve the same symbol error rate (SER). Moreover, the spectral efficiency of the system can be increased, because the GI length is allowed to be insufficient. The proposed method is applicable to future OFDM-based wireless local area networks (WLANs). Copyright © 2007 John Wiley & Sons, Ltd.