Frequency domain scalable and adaptive cancellation of baseband to multitone crosstalk

Coexistence of baseband (e.g., HDSL, T1) and discrete multitone (e.g., ADSL, VDSL) services in the multipair cable results in a significant amount of baseband to multitone crosstalk. Redundancy in an oversampled crosstalk spectrum allows for partial crosstalk estimation and cancellation without the prerequisite of collocation and synchronization. The canceller proposed in this letter is blind to transmitted information and coupling transfer function and is adaptive to channel, coupling, and clock rate variations. It is also scalable by allowing for the tradeoff of complexity (number of weights) for achievable gain. Adaptation of canceller weights is implemented as LMS training and decision directed LMS update. Simultaneously, a digital PLL compensates for clock rate deviation. The simulation examples of an ADSL system with HDSL crosstalk confirm the ability to significantly reduce crosstalk with a low-complexity canceller