Exploring field noise on G.fast frequencies

G.fast is the most recent standard in Digital Subscriber Line (DSL) technology. It aims to provide up to 1 Gbit/s on twisted copper pairs. At these data rates and frequency ranges, the noise environment in the copper infrastructure remains largely unexplored. Noise characterization allows performance optimization, a.o. by determining whether a single set of configuration parameters, common to all lines, will be sufficient to guarantee network stability, or if a per-line configuration optimization mechanism such as Dynamic Line Management (DLM) is desired. A homemade low-cost and portable equipment has been built that covers the G.fast 212 MHz band. An off-line post-processing of the acquired traces was performed to study stationary and impulse noise characteristics using different temporal and spectral analyses. As main results of this paper, a spectral kurtosis computation of stationary noise is proposed as a novel tool to derive tone notching requirements due to their probability to exceed the Signal-to-noise ratio margin. In addition, in the case of impulse noise, a strong impulsive PSD content was sporadically observed at higher frequencies, contrary to what is commonly admitted, namely that interferences from home appliances are bandwidth limited and tend to decrease with frequency.