Triple-Play Service Deployment

Chapter 4: Troubleshooting the Copper Plant for IP Services
Wideband noise can be the result of radio frequency interference
from disparate digital services in the same cable, AM or shortwave
radio stations, and other sources. If excessive wideband noise is
detected, use of a test set with a wideband spectral analysis
capability is recommended as the next logical troubleshooting
step. This provides more in-depth analysis of the noise on the line
to determine the detailed characteristics of the interference and
aid in identification of the potential noise source. Intermittent
bursts or spikes of noise, commonly referred to as impulse noise
may also be present as discussed in detail in the next section. Due
to its intermittent nature, impulse noise may or may not be
detected using the wideband noise measurement. If impulse noise
is suspected, the impulse noise measurement is recommended for
further isolation and analysis of the problem.
While it is critical to make the determination whether or not the
level of noise present is sufficient to impair the service and to
attempt to ascertain the noise profile and potential source as
described above, it is also important to consider potential root
causes. Though a noise interference source can be strong enough
to impair xDSL service by itself, in many cases pair imbalance
and/or poor bonding and grounding of the cable are significant
contributing factors. Specifically, unbalanced pairs and cable
bonding and grounding issues reduce the noise immunity of the
pair making it far more susceptible to interferers.
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