Blind on-line detection of equalisation errors in digital communications

Equalisation errors result from discrepancies between transmitted symbols and their estimates at the channel equaliser output in a digital communication system. This paper presents an on-line test to detect the occurrence of equalisation errors without direct access to the channel input. The test draws on the observation that for linear time-invariant (LTI) channels the relationship between transmitted symbol estimates generated by the equaliser and the noisy channel output can be represented by an underlying linear time-invariant model if and only if no equalisation errors are present in the sequence of transmitted symbol estimates. The presence of equalisation errors renders this relationship time-varying, of which the occurrence is detected by the proposed on-line test using the recursive least squares (RLS) algorithm. Simulation studies corroborate the good detection performance of the test