Analysis of noise and load effects on broadband performance over residential power lines employing VDSL2

Broadband over power lines has received attention with a view to distribute it inside a residence. Power lines are different in topology and load impedances compared to universal twisted pair copper used in telephony. We examine the rates achieved over a typical home power line by reusing the Transmit Power spectral density (PSD) as in VDSL2. The power line has a thicker gauge and shorter straight lengths, apart from a large number of bridge taps (BT) with inductive load terminations. ABCD parameters of the individual sections are used to analyze the power line channel of upto 10 bridge taps over a 600 meter length. Tone loading profiles have been obtained using Discrete Multitone Transmission (DMT) as in VDSL2 over a bandwidth of 30 MHz. The noise profiles considered include impulse noise which is predominant over power line sections, apart from AWGN. This analysis points to the fact that lower Transmit PSD would suffice to match the rates achievable by traditional VDSL2 when bridge taps are open. However with inductive loads in the BTs as is typical in residences, we recommend a two step approach of equipping existing VDSL2 modem front end hybrids with settable impedances that would approach a conjugate match of the loaded line along with a capability to nominally increase the Transmit PSD to achieve the desired rates in a seamless manner as in VDSL2.