Impact of Crosstalk Channel Estimation on the DSM Performance for DSL Networks

Abstract

The development and assessment of spectrum management methods for the copper access network are usually conducted under the assumption of accurate channel information. Acquiring such information implies, in practice, estimation of the crosstalk coupling functions between the twisted-pair lines in the access network. This type of estimation is not supported or required by current digital subscriber line (DSL) standards. In this work, we investigate the impact of the inaccuracies in crosstalk estimation on the performance of dynamic spectrum management (DSM) algorithms. A recently proposed crosstalk channel estimator is considered and a statistical sensitivity analysis is conducted to investigate the effects of the crosstalk estimation error on the bitloading and on the achievable data rate for a transmission line. The DSM performance is then evaluated based on the achievable data rates obtained through experiments with DSL setups and computer simulations. Since these experiments assume network scenarios consisting of real twisted-pair cables, both crosstalk channel estimates and measurements (for a reference comparison) are considered. The results indicate that the error introduced by the adopted estimation procedure does not compromise the performance of the DSM techniques, that is, the considered crosstalk channel estimator provides enough means for a practical implementation of DSM.

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

“…In practice, the acquisition of such information requires coordination and training among multiple transceivers and is subject to inaccuracies. Following the work in , the direct channel insertion losses are assumed known a priori without error, because the procedures to obtain them are well established in the DSL community. Our interest is to examine the robustness and performance of precoders because of the impact of imperfect FEXT channel estimation.…”

“…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 . Figures and show the percentage DS data rate degradation of precoders because of FEXT channel estimation error in the 10‐user equal‐length (for both G.fast profiles) and 16‐user mixed‐length (only the 212 MHz profile) scenarios, respectively.…”

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.…”

Simple Statistical Analysis of the Impact of Some Nonidealities in Downstream VDSL with Linear Precoding

“…Among the most significant papers in the field, a statistical analysis has been outlined in [13], where the authors, however, do not refer to any practical model and do not elaborate on the analytical problem. Very recently, in [14], random variable theory has been applied in the context of dynamic spectrum management algorithms at level 2 (i.e., without distortion compensation). A two-port FEXT estimator proposed by the same authors was considered, and a statistical sensitivity analysis was conducted to investigate the effects on the system capacity of measurement errors due to uniform quantization.…”