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

Abstract

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.

Iterative Receiver Based on SAGE Algorithm for Crosstalk Cancellation in Upstream Vectored VDSL

“…For performing the simulations, we adopt the stochastic channel model [19] and consider the binder to consist of eight lines such that there are seven disturbers per line. We have simulated the proposed algorithm for various VDSL scenarios in the context of real VDSL deployments.…”

Performance analysis of a common-mode signal based low-complexity crosstalk cancelation scheme in vectored VDSL

“…The DM channel model is well established (verified through measurements) and widely adopted in literature (see [23][24][25], and references therein). In particular, a stochastic MIMO channel model based on Gaussian distribution is proposed in [23] that extends the conventional 99% worst case model [2].…”

“…In particular, a stochastic MIMO channel model based on Gaussian distribution is proposed in [23] that extends the conventional 99% worst case model [2]. Similarly, crosstalk models based on beta distribution [24] and sum-of-sinusoids [25] have been suggested to characterize the crosstalk accurately.…”

“…In this study, we use earth as a common reference and develop a MIMO CM channel model by incorporating the MIMO DM stochastic channel model of [23], and the single-pair model of CM channel proposed in [18]. As discussed in [23], the stochastic DM channel H (d) is given by…”

“…To assess performance of the existing crosstalk cancelers on the proposed system model, we study characteristics of the equivalent CM-DM channel at each tone. To do so, we model (due to non-availability of an analytical model for the CM channel) a CM vectored channel by extending the recently proposed single-TP CM channel [18], and modify it to include the statistical dispersion (using the approach for DM channels in [23]). In particular, we show that the CM-DM channel matrix is more column-wise diagonally dominant (CWDD) than the DM channel at high frequency and/or longer loop-length.…”