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

A spatial approach to identify priority areas for pesticide pollution mitigation

Identifying priority areas is an essential step in developing management strategies to reduce pesticide loads in surface water. A spatially explicit model-based approach was developed to detect priority areas for diffuse pesticide pollution at catchment scale. The method uses available datasets and considers different pesticide pathways in the environment post-application. The approach was applied in a catchment area in SE Flanders (Belgium) as a case study. Calculated risk areas were obtained using detailed landscape data and combining pesticide emissions and hydrological connectivity. The risk areas obtained were further compared with an alternative observation-based method, developed specifically for this study site that includes long-term field observations and local expert knowledge. Both methods equally classified 50% of the areas. The impact of crop rotation on the calculated risk was analysed. High-risk areas were identified and added to a cumulative map over all five years to evaluate temporal variations. The model-based approach was used for the initial identification of risk areas at the study site. The tool helps to prioritise zones and detect particular fields to target landscape mitigation measures to reduce diffuse pesticide pollution reaching surface water bodies

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

Reanimatie van de extreem preterme pasgeborene: medische en ethische aspecten

The decision to resuscitate a newborn infant born at less than 26 weeks’ gestation is controversial. Atlhough survival rates have increased significantly during last decades, the absolute risk of lifelong disability still remains very high. Defining ‘viability’ is essential in the decision-making process. Socio-cultural, institutional and personal values may explain international variability in the approach. Coming to an individualized decision based upon contemporary scientific evidence, personal experience and parental expectations seems to be an ethically acceptable attitude

Low complexity equalization for burstmode communication in upstream CATV networks

The recent interest in the use of CATV networks for advanced telecommunication purposes has spurred research in modems for upstream communication. Signal disturbances along the upstream path necessitate the use of advanced signal processing methods. One of these disturbances is group delay distortion. This paper describes two algorithmic alternatives to solve this particular problem. I. Introduction Recently, coaxial cable networks have received much attention in the context of interactive applications [1], [4]. In countries with a high penetration of CATV (e.g. Belgium ? 90%), the cable network forms a viable alternative to classical telephone networks. Envisaged applications include telephony, interactive television, home-shopping, video-on-demand and high-speed internet browsing. The interactive nature of these services requires two-way communication on a network that initially was only intended for a one-way broadcasting of television signals. What is aimed at now, is a low bit-r..

Partial crosstalk cancellation for upstream VDSL

VDSL is the next step in an on-going evolution of DSL systems. In VDSL downstream data rates of up to 52 Mbps are supported by operating over short loop lengths and using frequencies up to 12 MHz. Unfortunately, such high frequencies result in crosstalk between pairs within a binder-group. Many crosstalk cancellation techniques have been proposed to address this. Whilst these schemes lead to impressive performance gains, their complexity grows with the square of the number of lines within a binder. In binder groups which can carry up to hundreds of lines, this complexity is outside the scope of current implementation. In this paper we investigate partial crosstalk cancellation for VDSL. The majority of the detrimental effects of crosstalk are typically limited to a small sub-set of lines and tones. Furthermore, significant crosstalk is often only seen from neighbouring pairs within the binder configuration. We present a number of schemes which exploit these properties to reduce the complexity of crosstalk cancellation. These schemes are shown to achieve the majority of the performance gains of full crosstalk cancellation with significantly reduced run-time complexity. We present both the optimal scheme for partial crosstalk cancellation which has a high initialisation complexity and a number of low-complexity schemes which achieve near-optimal performance in a wide range of scenarios