Blind on-line testing for equalization errors in digital communication systems

We present an on-line test for blind detection of equalization errors in digital communication systems. The test is based on the observation that for linear time-invariant channels the relationship between the transmitted symbol estimates generated by the equalizer and the noisy channel output can be represented by an underlying linear time-invariant model if and only if the equalizer output sequence is not in error. The presence of equalization errors renders this relationship time-varying, whose occurrence is detected by the proposed on-line test. The test is obtained from a previously proposed off-line least squares test by essentially replacing the least squares algorithm with its recursive version.