TY - JOUR
T1 - Analysis of inverse crosstalk channel estimation using SNR feedback
AU - Whiting, Philip A.
AU - Kramer, Gerhard
AU - Nuzman, Carl J.
AU - Ashikhmin, Alexei
AU - Van Wijngaarden, Adriaan J.
AU - Živković, Miroslav
PY - 2011/3
Y1 - 2011/3
N2 - Digital subscriber line (DSL) data rates for short loops are typically limited by crosstalk between adjacent lines rather than by background noise. Precoding can reduce crosstalk in the downstream from the access node to the customer premises equipment significantly if an accurate estimate of the inverse crosstalk channel is provided. Recently, a backward-compatible method has been proposed for estimating downstream crosstalk channels using standardized signal-to-noise ratio (SNR) reports. This paper develops a probabilistic model of the estimation process and, within this model, provides conditions under which successive updates of the precoder are guaranteed to converge to the ideal inverse precoder. Bounds on estimator variance and convergence times are obtained and optimized with respect to system parameters. The analysis can be applied to the situation in which a new line is being activated and added to a group of precoded lines seamlessly, that is, with controlled impact on the SNR of the active lines. Two phases are proposed to achieve seamless activation; the protection phase is used to let the active lines learn the crosstalk from the activating line and the acquisition phase is used to let the activating line learn the crosstalk from the active lines. Results of the analysis are illustrated by numerical simulations.
AB - Digital subscriber line (DSL) data rates for short loops are typically limited by crosstalk between adjacent lines rather than by background noise. Precoding can reduce crosstalk in the downstream from the access node to the customer premises equipment significantly if an accurate estimate of the inverse crosstalk channel is provided. Recently, a backward-compatible method has been proposed for estimating downstream crosstalk channels using standardized signal-to-noise ratio (SNR) reports. This paper develops a probabilistic model of the estimation process and, within this model, provides conditions under which successive updates of the precoder are guaranteed to converge to the ideal inverse precoder. Bounds on estimator variance and convergence times are obtained and optimized with respect to system parameters. The analysis can be applied to the situation in which a new line is being activated and added to a group of precoded lines seamlessly, that is, with controlled impact on the SNR of the active lines. Two phases are proposed to achieve seamless activation; the protection phase is used to let the active lines learn the crosstalk from the activating line and the acquisition phase is used to let the activating line learn the crosstalk from the active lines. Results of the analysis are illustrated by numerical simulations.
UR - http://www.scopus.com/inward/record.url?scp=79951604009&partnerID=8YFLogxK
U2 - 10.1109/TSP.2010.2094189
DO - 10.1109/TSP.2010.2094189
M3 - Article
AN - SCOPUS:79951604009
SN - 1053-587X
VL - 59
SP - 1102
EP - 1115
JO - IEEE Transactions on Signal Processing
JF - IEEE Transactions on Signal Processing
IS - 3
M1 - 5643185
ER -