ADSL2+ Frequency Spectrum
5.7.5 VDSL2
Frequency configuration options of 8.5 MHz, 12 MHz, 17.7 MHz, and 30 MHz are set automatically depending on DSLAM
settings.
Note: Impulse Noise Protection (INP)
Electrical appliances and installations at customer premises often generate short bursts of noise of relatively
high amplitude. These bursts, called impulse noise, are electromagnetically coupled into the digital subscriber
line, degrading performance and in some cases disrupting service. The ADSL2/+ standard introduced a
parameter called Impulse Noise Protection (INP), that allows operators to select the maximum impulse length
that the DSL system can correct.
VDSL2 uses the same parameter and when implemented, an INP value between 2 and 16 can correct errors
from noise impulses ranging from 250µs to 3.75ms in length.
INP is a key feature in most IPTV video deployments and enables better Video QOS by minimizing the effects
of Impulse Noise.
The INP value for the interleaved channel can be set by the user and is expressed in symbols. For example,
an INP value of 1 means that 1 symbol can be corrected i.e. a burst of noise for 1 symbol duration can be
corrected without errors. One symbol equals 250µs, therefore an INP of 1 correlates to a correction time of
250µs.
The Impulse Noise Protection (INP) or interleave depth is defined by the S and D parameters where:
S is the Interleave DMT symbols per FEC code word (1, 2, 4, 8, 16)
D is the Interleave depth (1, 2, 4, 8, 16, 32, 64)
Interleave delay can vary from 4.25 to 263.75 msec
MTTplus-_Test_Module
Page 28 of 44