Line stability has a huge impact on user quality of experience (QoE). A digital subscriber line (DSL) made unstable by crosstalk, for example, can cause service degradation and even service interruption. In a typical DSL network, up to 25 percent of lines may be unstable, leading to higher operational costs, lower average revenue per user (ARPU) and higher churn. Increasing the noise margin is the traditional approach to stabilizing lines — but it typically comes at too high a cost in today’s triple play world (i.e., a significant loss of bandwidth).
Artificial Noise (AN) for asymmetric DSL (ADSL) and Virtual Noise (VN) for very high-speed DSL 2 (VDSL2) allow service providers to stabilize DSL lines with minimal bandwidth loss — typically at bitrates up to 30 percent higher than with the traditional approach of increasing noise margin. VN is part of the VDSL standard and works with any standards-compliant customer premises equipment (CPE) that supports VN. AN, on the other hand, requires no specific CPE support and works with any ADSL modem in the field.