Partial Crosstalk Precompensation in Downstream VDSL

Very high bit-rate digital subscriber line (VDSL) is the latest generation in the ongoing evolution of DSL standards. VDSL aims at bringing truly broadband access, greater than 52 Mbps in the downstream, to the mass consumer market. This is achieved by transmitting in frequencies up to 12 MHz. Operating at such high frequencies gives rise to crosstalk between the DSL systems in a binder, limiting achievable data-rates. Crosstalk is typically 10-15 dB larger than other noise sources and is the primary limitation on performance in VDSL. In downstream transmission several crosstalk precompensation schemes have been proposed to address this issue. Whilst these schemes lead to large performance gains, they also have extremely high complexities, beyond the scope of current implementation. In this paper we develop the concept of partial crosstalk precompensation. The majority of the crosstalk experienced in a DSL system comes from only a few other lines within the binder. Furthermore its effects are limited to a small subset of tones. Partial precompensation exploits this by limiting precompensation to the tones and lines where it gives maximum benefit. As a result, these schemes achieve the majority of the gains of full crosstalk precompensation at a fraction of the run-time complexity. In this paper we develop several partial precompensation schemes. We show that with only 20% of the run-time complexity of full precompensation it is possible to achieve 80% of the performance gains

Waterfilled VDSL Echo Limitation for Rate-Reach Performance Improvement

Digital Subscriber Line (DSL) deployment is evolving to ever higher bit rates resulting in the use of broader spectra. The DSL flavor using the broadest spectrum today is known as VDSL. The reach performance of VDSL is upstream limited as the upstream bands use the highest frequencies. These high frequencies experience more channel attenuation, resulting in smaller SNR values. In this contribution, a way of increasing the upstream reach performance is described. After investigating the VDSL transceiver, the reach performance of a VDSL modem is identified to be dominated by the echo power. Therefore, limiting the downstream echo yields a better upstream receive signal. This results in trading off downstream bit rate for more upstream bit rate. The way to optimally limit the echo isderived and high performance gains can be achieved. Finally, the optimal solution is approximated with a near optimal solution with considerably less complexity. The near-optimal solution performs very well compared to the optimal solution

Method to provide cross-talk cancellation

A method to provide cross-talk cancellation in a multiple input, multiple output system that comprises a plurality of outputs is described. The method comprises a step determining during a first phase and according to a heuristic model, for a first signal to be transmitted to a first output of the plurality of outputs at least one dominant interfering tone of at least one second signal to be transmitted to a second output of the plurality of outputs. The at least one dominant interfering tone is in fact a tone of at least one second signal that would generate cross-talk upon the first signal when it would be transmitted to the first output. The method further comprises a step of executing a step of partial cross-talk cancellation for the first signal during a second phase for the one or more determined dominant interfering tones associated to one or another second signal

Method for cross-talk cancellation

A method to provide cross-talk cancellation in a multiple input, multiple output system that comprises a plurality of outputs is described. The method comprises a step determining during a first phase and according to a heuristic model, for a first signal to be transmitted to a first output of the plurality of outputs at least one dominant interfering tone of at least one second signal to be transmitted to a second output of the plurality of outputs. The at least one dominant interfering tone is in fact a tone of at least one second signal that would generate cross-talk upon the first signal when it would be transmitted to the first output. The method further comprises a step of executing a step of partial cross-talk cancellation for the first signal during a second phase for the one or more determined dominant interfering tones associated to one or another second signal

Power control method for remotely deployed communication service

The present invention relates to a power control method for transceiver units conveying data over discrete tones. The present invention has application inter alia for remotely deployed communication service, and achieves significant gains over existing methods

Method and apparatus for spectrum management for communication channels with crosstalk

The present invention relates to a method for determining at least one operation transmti power over a communication channel coupled to a disturbance causing transceiver, for at least one tone, said communication channel degrading one or more victim communication channels by crosstalk interferences