Performance Improvement of Decision-Directed OFDM Channel Estimation in a Fast Fading Environment(Signal Processing for Communications)(<Special Section>Digital Signal Processing)

概要

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Decision-directed, pilot-symbol-aided channel estimation (PSACE) for coded orthogonal frequency division multiplexing (COFDM) systems has structurally unavoidable processing delay owing to the generation of new reference data. In a fast fading environment, the channel condition which varies during the delay induces channel estimation error. This paper proposes a method of reducing this estimation error. In this method, channel equalization is performed for the received signal twice. One is done as pre-equalization with the delayed estimates of channel frequency response in order to update them periodically. At the same moment, the other is done as post-equalization for the received signal that is delayed by the processing delay time, with the same estimates as the pre-equalization. By the proposed method, more accurate channel estimation can be realized without significant output delay. Computer simulations are performed by utilizing the IEEE 802.11a packet structure of 24Mbit/s. The result shows that the proposed OFDM transmission scheme having the delay time of 20μs offers 2.5 dB improvement in the required E_b/N_0 at PER=10^<-2> in the ESTI-BRAN model C Rayleigh fading channel with f_d=500Hz.
社団法人電子情報通信学会の論文
2004-08-01