Construction of a DSL-MIMO channel model for evaluation of FEXT cancellation systems in VDSL2

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 25×25 channel matrices that contain varying degrees of channel dispersion: specifically, we define a 25×25 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.