Abstract Semi-blind equalization at the symbol rate with application to OFDM

Blind equalization algorithms for non-minimum-phase channels are generally based on oversampling the output of the system. In this paper, we consider a symbol-rate sampled scheme that requires the periodic transmission of a few zeros within the data sequence. Sampling at the symbol rate relaxes some of the identi4ability conditions, and ensures that the additive noise is uncorrelated. We develop a least-squares approach for the blind equalization of such a system, that works well with very short observation windows. The price paid for eliminating the oversampling is the reduced throughput. We derive the necessary and su7cient conditions for the identi4ability of the system. Our simulations show that channels with near-common zeros can be equalized better using the proposed scheme, as compared to existing schemes. Also, the proposed method is seen to perform much better than the recently proposed methods (IEEE Trans. Signal Process. 47 (1999) 2007) in terms of bit error rate, for short observation windows, and requires much less stringent identi4ability conditions. However, the computational complexity of the method is high. The method can be applied directly to the blind equalization of orthogonal frequency division multiplexing systems that use a zero pre4x instead of a cyclic pre4x