Martin Kuipers

Jointly optimizing the Virtual Noise mask and the SNR margin for improved service in xDSL systems

In Digital Subscriber Line (DSL) systems, the concept of Virtual Noise was introduced to improve the protection against fluctuating crosstalk and to increase link stability. This paper investigates the joint optimization of the Virtual Noise power spectral density and the initialization SNR margin. A new algorithm is developed for modems to estimate the optimum Virtual Noise power spectral density and the initialization SNR margin from crosstalk measurements. Using this algorithm leads to both a better stability in terms of outage probability and an improvement in the achieved data rates compared to the traditional SNR margin approach. Moreover, it makes the use of the Low Power mode in VDSL2 systems possible.

Optimization of the per tone noise protection in xDSL systems employing virtual noise

In Digital Subscriber Line (DSL) systems, the concept of Virtual Noise (VN) was introduced to improve the protection against fluctuating crosstalk and to increase link stability. In our previous work, we have presented an algorithm that estimates the VN mask and the initialization signal-to-noise-ratio (SNR) margin from noise measurements. In however, perfect bitswapping was assumed. In practical DSL systems bitswapping might be too slow which makes the link sensitive to sudden noise increases. Hence, the outage probability achieved in can only be realized in slowly changing channels. This paper investigates the optimization of the VN mask and the initialization SNR margin presented in in order to improve the robustness against sudden noise increases in terms of outage probability, especially for modems with slow bitswapping procedures.