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Watson TDM

Operating Manual

Watson-TDM-Manual-W.doc

Version 2.0-01

3-28

Revision: 2008-02-07

3.7 Performance Monitoring

3.7.1 DSL Parameters

The Watson TDM modems provide information about the current Signal Quality

and Attenuation of a DSL link:

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.

SNR0 is the signal to noise ratio that gives a bit error rate of 10

-7

in presence

of average white Gassian noise. For TC-PAM16 the theoretical value

for SNR0 is 27.7 dB.

The Attenuation is the link attenuation calculated by the modem, assuming

0.4mm PE cable without bridged taps and measured at 150 kHz (for linerates of

200 kbit/s up to 1'992 kbit/s) or 200 kHz (for linerates of 2'056 kbit/s and above).

Note that the calculated attenuation may differ from the attenuation measured by

other equipment for other cable configurations (other cable diameter, splices,

bridged taps).

Both Signal Quality and Attenuation are effective maintenance tools for determin-

ing inadequate or bad cable pairs.

3.7.2 G.826 Performance Monitoring

The G.826 error performance parameters provide quantitative performance in-

formation of a specific link. They are intended to be used for long-term evaluation

of operating DSL links.

The evaluation of the G.826 error performance parameters is based on CRC

(Cyclic Redundancy Check) error detection.

DSL Interface

On the DSL side, six CRC6 check bits are generated per DSL frame for each

channel and direction. The software counts block errors and evaluates the error

performance according to ITU-T G.826 using these CRC6 bits.

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Schmid Watson Specifications Page 50