Sensitivity of the mean-square DDFSD to a noisy estimate of the noise variance

In signal equalization, a suboptimal technique for reducing the number of states of the Viterbi detector is the delayed decision feedback sequence detector (DDFSD). In order to achieve good performance a mean-square (MS) prefilter is employed before the DDFSD. This paper is devoted to investigate the sensitivity of the MS-DDFSD to a noisy estimate of the variance of the noise. Analytical performance evaluation is addressed. A truncated version of the union bound is used to approximate the bit error rate. The analysis includes a method for determining the terms that dominate the bound.