Crosstalk Channel Estimation via Standardized Two-Port Measurements

Abstract

The emerging multiuser transmission techniques for enabling higher data rates in the copper-access network relies upon accurate knowledge of the twisted-pair cables. In particular, the square-magnitude of the crosstalk channels between the transmission lines are of interest for crosstalk-mitigation techniques. Acquiring such information normally requires dedicated apparatus since crosstalk-channel measurement is not included in the current digital subscriber line (DSL) standards. We address this problem by presenting a standard-compliant estimator for the square-magnitude of the frequency-dependent crosstalk channels that uses only functionality existing in today's standards. The proposed estimator is evaluated by laboratory experiments with standard-compliant DSL modems and real copper access network cables. The estimation results are compared with both reference measurements and with a widely used crosstalk model. The results indicate that the proposed estimator obtains an estimate of the square-magnitude of the crosstalk channels with a mean deviation from the reference measurement less than 3 dB for most frequencies.

Performance of linear and non‐linear precoders in G.fast ultra‐broadband DSL networks

“…To date, different crosstalk estimation solutions have been proposed in the literature . For example, the crosstalk channel estimator in proposed in is standard‐compliant and does not require hardware or software modifications or dedicated measurement apparatus. In order to examine the effects of channel estimation error on the performance of precoders on G.fast frequencies, we follow the approach used in by varying the values of the true channel matrix H k uniformly by ±3 dB, where the value of Δ = 3 is assumed to be typical for practical networks .…”

An hybrid evolutionary multiobjective algorithm for multiuser margin maximization in DSL

“…Apart from the wide range of low-complexity SB algorithms that could fit in the main loop of the proposed method, practical methods for estimating the crosstalk gains between the copper pairs are also available, for example, [41,42]. Apart from the wide range of low-complexity SB algorithms that could fit in the main loop of the proposed method, practical methods for estimating the crosstalk gains between the copper pairs are also available, for example, [41,42].…”

“…The application of the proposed method in today's working networks is realistic. Apart from the wide range of low-complexity SB algorithms that could fit in the main loop of the proposed method, practical methods for estimating the crosstalk gains between the copper pairs are also available, for example, [41,42]. In addition, line grouping techniques [43] can effectively reduce the number of dimensions of the problem (i.e., the search space) during the optimization process.…”

An Evolutionary Algorithm for Improved Diversity in DSL Spectrum Balancing Solutions

“…where N is the number of users, K is the number of subchannels (tones), and the element s k n represents the PSD value of user n at tone k. The channel gains (direct and crosstalk) are represented by a threedimensional array G of dimension N × N × K. For each tone k, the matrix {g k i, j } is the squared magnitude of the transfer function corresponding to the channel from user i to j. To determine G in practical scenarios, there are procedures to estimate the direct channel g k i,i , ∀k of the ith user [10,11] and the far-end crosstalk (FEXT) channels g k i, j , ∀k, i / = j [12]. It is assumed that in frequency-division duplex (FDD), the down-and upstream transmissions reside in nonoverlapping frequency bands.…”