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

Abstract

This paper considers a VDSL downstream system where crosstalk is compensated by linear precoding. Starting from a recently introduced mathematical model for FEXT channels, simple analytical methods are derived for evaluating the average bit rates achievable, taking into account three of the most important nonidealities. First, absolute and relative estimation errors in the crosstalk coefficients are discussed, and explicit formulas are obtained to express their impact. A simple approach is presented for computing the maximum line length where linear precoding overcomes the noncoordinate system. Then, the effect of out-ofdomain crosstalk is analyzed. Finally, quantization errors in precoding coefficients are considered. We show that by the assumption of a midtread quantization law with different thresholds, a relatively small number of quantization bits is sufficient, thus reducing the implementation complexity. The presented formulas allow to quantify the impact of practical impairments and give a useful tool to design engineers and service providers to have a first estimation of the performance achievable in a specified scenario.

Optimizing power normalization for G.fast linear precoder by linear programming

“…It shows that the even bits QAM have much lower energy increase than the odd bits. (4) 0.280 32 (5) 0.79 64 (6) 0.0684 128 (7) 0.68 256 (8) 0.0170 512 (9) 0.66 1024 (10) 0.0042 2048 (11) 0.65 4096 (12) 0.0011 After normalization, the SNR of the received signal for user i becomes:…”

“…In practice, it gets very close to single-line performance when the RWDD assumption holds, as the case in VDSL2. The RWDD assumption is adopted in [2], [9]- [11] and assessed by:…”

Multi-Pair Cable Measurements for 5G Indoor Service Provisioning

“…For the simulation purpose, the empirical multi-pair channel models based on American and European test loop configurations were developed and standardized [10], [11], [12]. The general consensus exists for the adoption of an empirical model of the direct channel, however, the empirical models for crosstalk channels are not accurate to predict the measured crosstalk channels [13], [14], [15]. Further, this channel model was only valid for frequencies up to 30 MHz [11], [12].…”