On a Novel Pre-FFT OFDM Adaptive Antenna Array for Delayed Signal Suppression

Montree BUDSABATHON  Shuichi HANE  Yoshitaka HARA  Shinsuke HARA  

IEICE TRANSACTIONS on Communications   Vol.E86-B    No.6    pp.1936-1945
Publication Date: 2003/06/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technology
pre-FFT OFDM,  adaptive antenna array,  delayed signal,  maximum SNIR criterion,  MMSE criterion,  

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It is well known that Orthogonal Frequency Division Multiplexing (OFDM) scheme is robust to frequency selective fading in wireless channels. However, once delayed signals beyond a guard interval of an OFDM symbol are introduced in a channel with large delay spread, inter-symbol interference causes a severe degradation in the transmission performance. In this paper, we propose a novel pre-Fast Fourier Transform (FFT) OFDM adaptive antenna array, which requires only one FFT processor at a receiver, for suppressing such delayed signals. We analytically derive the optimum weights for the beamformer based on the Maximum Signal-to-Noise-and-Interference power Ratio (SNIR) and the Minimum Mean Square Error (MMSE) criteria, respectively. Computer simulation results show its good performance even in a channel where Directions of Arrival (DoAs) of arriving waves are randomly determined.