Snr Margin (Dsl Interfaces - Paradyne BitStorm 4800 User Manual

A. CLI Command Descriptions

SNR Margin (DSL Interfaces)

SNR (Signal-to-Noise Ratio) is the amplitude of the desired signal compared to the
amplitude of noise on the line. Margin is the amount of noise that can be tolerated
before a communication error or link establishment failure occurs. There are three
settings in the BitStorm 4800 related to SNR margin:
T
T
T
If behavior is set to adaptive, the target-downstream-margin and
target-upstream-margin settings determine the highest rates the modems can train
to. These rates may be less than the maximum configured rates.
For example, if target-downstream-margin is set to 6, the modems will train
(establish communication) at the highest rate downstream at which there is at
least 6 dB of margin, or, if it is lower, the maximum configured rate
(max-downstream-speed, in this case).
If behavior is set to fixed, the target margins determine the acceptability of the
signal at the selected fixed rate. If the margin is lower than the target margin at
that rate, the modems train again.
The min-snr-margin setting is for the upstream direction only. It causes the modem
to retrain if the margin falls and remains below the setting for 60 seconds.
A-22
min-snr-margin
target-downstream-margin
target-upstream-margin
July 2002 4800-A2-GB20-10