Adaptive interference cancellation using common-mode information

Exploiting the common-mode (CM) receive signal in wireline com-munication can yield significant improvements in terms of channel capacity compared to using only the differential-mode (DM) sig-nal. Recently published, independent, scientific work proposed the employment of an adaptive CM-reference based interference can-celler and reported performance improvements based on simulation results. Adaptive processing of correlated receive signals, however, bears the potential danger of cancelling the useful component—an undesired effect we will address. We present an analysis of the linear adaptive cancellation ap-proach in this application. For a large class of practically rele-vant cases, it can be shown that a canceller, whose coefficients are adapted while the far-end transmitter is silent, yields a signal-to-noise-and-interference power ratio (SNIR) which is higher than the SNIR of the DM-only channel output. Moreover, the performance of a canceller with this tap-setting is close to the performance of the front-end that is optimum in the sense of maximising the SNIR at its output. Adaptation while the useful far-end signal is present yields a front-end whose output SNIR is considerably lower compared to the SNIR of the DM channel output. The results and their practical impact are demonstrated by an example. 1