Systems methods and computer program products for controlling undesirable bias in an equalizer

TL;DR: In this article, the error signal is used to update the equalizer filter coefficients instead of using the error signals to correct the RBS effect in the output signal, which can be seen as an indication that the reference signals or reference levels are accurate.

Abstract: Bias control systems, methods, and computer program products generate an error signal that corresponds to a difference between a reference signal and an equalizer output signal. The error signal is then filtered using a first filter circuit to generate an error signal average. If the absolute value of the error signal does not exceed a suitable threshold that is proportional to the error signal average, then the error signal is coupled to the equalizer for use in updating the filter coefficients. Furthermore, a second filter circuit may be used to generate an average of selected equalizer output signal samples. If the absolute value of the error signal is greater than the threshold that is proportional to the error signal average, then the reference signal is updated to correspond to the average of selected equalizer output signal samples. Large errors are interpreted as resulting from inaccurate reference signals or reference levels. The reference signals or reference levels may be inaccurate due to the effects of digital impairments in the network, such as RBS, exhibited in the equalizer output signal. Rather than using the error signal to update the equalizer filter coefficients, the reference signal or reference level is updated to correspond to the average of selected equalizer output signal samples. Conversely, small errors are interpreted as an indication that the reference signals or reference levels are accurate and do not require additional refinement. In this case, the error signal is used to update the equalizer filter coefficients.