Sampling and prefiltering effects on blind equalizer design

In the development of equalization algorithms for unknown channels, the eff ects of the sampling rate and the analog receive prefilter prior to discret ization of the received signal are often overlooked. In this paper, these e ffects are investigated. The relationship between the fractionally spaced o utput samples of a noise-limiting prefilter and the symbol spaced output sa mples of a matched filter is studied for both the time-invariant and the ti me-varying channels. It is shown that the prefilter and the sampling rate c an have significant effects on blind equalization algorithms. Thus, this pa per provides a common framework for comparing different blind algorithms th at are studied in the literature with different sampling rates. A case stud y of the well-known subspace method for blind channel identification is pre sented. The effects of the noise color due to the prefilter on equalizers i s investigated, and the sensitivity of the truncation of the overall channe l impulse response in terms of the mean squared error (MSE) performance cri terion is investigated through numerical examples.