SNR Margin is the maximum increase in dB of the noise power
received at the xTU (xTU-R for a band in the downstream direction
and xTU-C for a band in the upstream direction), such that the
BER requirements are met for all bearer channels received at the
xTU. Values range from -640 to 630 in units of 0.1 dB (Physical
values are -64 to 63 dB).
A special value of 0x7FFFFFFF (2147483647) indicates the SNR
Margin is out of range to be represented.
A special value of 0x7FFFFFFE (2147483646) indicates the SNR
Margin measurement is currently unavailable.
This object reflects the value of the parameter following the
most recent DELT performed on the associated line. Once the DELT
process is over, the parameter no longer changes until the row is
deleted or a new DELT process is initiated.