Of growing interest in the field of VDSL2 transmission is the evaluation of algorithms for improved performance using Far-end Crosstalk (FEXT) Cancellation Pre-coding. In order to perform fair evaluations of different algorithms, it is necessary to define a Multiple Input Multiple Output (MIMO) channel model that realistically represents the nature of the FEXT coupling dispersion that may be encountered in a multi-pair cable. This paper describes a general method for generating a MIMO channel model for a twisted wire pair cable that is extended from the currently defined 1% worst case FEXT coupling model. This extended model defines varying levels of FEXT cross-coupling values across the channel matrix and still preserves the 1% worst case crosstalk levels. Based on cable measurements, we determine a best fit probability density function to model the FEXT coupling dispersion; then for an example 25-pair 26-gauge (AWG) cable, we define four reference 25x25 channel matrices that contain varying degrees of channel dispersion: specifically, we define a 25x25 dispersion matrix for each of 'zero,' 'low,' 'medium,' and 'high' dispersion. Finally, we compute rate vs. reach performance of FEXT Cancellation Pre-coding with cancellation of 5 dominant disturbers for each channel matrix.

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This paper develops adaptive step-size blind LMS algorithms and adaptive forgetting factor blind RLS algorithms for code-aided suppression of multiple access interference (MAI) and narrowband interference (NBI) in DS/CDMA systems. These algorithms optimally adapt both the step size (forgetting factor) and the weight vector of the blind linear multiuser detector using the received measurements. Simulations are provided to compare the proposed algorithms with previously studied blind RLS and blind LMS algorithms. They show that the adaptive step-size blind LMS algorithm and adaptive forgetting factor blind RLS algorithm yield significant improvements over the standard blind LMS algorithm and blind RLS algorithm in dynamic environments where the number of interferers are time-varying.

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