Specifications

Watson Ethernet
Operating Manual
Watson-Ethernet-Manual.doc
Version 3.3-01
3-4
Revision: 2010-01-20
3.1.4 Power Backoff
The transmit power of the modems can be decreased by activating the power
back-off mode. This reduces interference to other transmission systems operat-
ing on adjacent pairs bundled in the same cable.
With enabled power back-off the transmit power will be reduced adaptively in
function of the estimated cable attenuation:
Estimated Power
Loss(*)
Power Backoff
< 1 dB
6 dB
< 2 dB
5 dB
< 3 dB
4 dB
< 4 dB
3 dB
< 5 dB
2 dB
< 6 dB
1 dB
6 dB
no backoff
(*) Calculated as Tx Power –
Estimated Rx Power
Table 3-2: Power Backoff
Note:
Power backoff can be configured individually for plug-in and tabletop.
3.1.5 Symmetric and Asymmetric PSDs
The Watson Ethernet tabletop modems support asymmetric PSDs for linerates
of 2'056 kbit/s and 2'312 kbit/s.
Activating asymmetrical PSD masks will increase upstream transmit power (STU-
R  STU-C). This improves near-end crosstalk (NEXT) at the STU-C side and
will increase the possible loop length in cases where many DSL spans have to
share the same cable e.g. coming out of a central office.
Note:
The Watson Ethernet plug-in and the Watson SHDSL Router do not support
asymmetric PSDs.
3.1.6 DSL Performance Parameters
The Watson Ethernet modems provide information about the current Signal
Quality and Attenuation of a DSL span.
Signal Quality
The Signal Quality is the noise margin calculated by the modem:
SQ = SNR1 - SNR0
Where
SQ is the calculated noise margin
SNR1 is the signal to noise ratio calculated by the transceiver by analyzing
the error correction bits (Trellis bits) in the line code.