Triple-Play Service Deployment

Chapter 7: Troubleshooting Video Service in the Field
Step 2
Video pixelizations
– Physical layer problems? = yes
– Check VDSL stats for errors
• FEC errors: Un-correctable FEC errors
• If yes, impulse noise most likely cause, if noise margin at least 6 dB.
• Review Bits/Tone graphs for notches
– Notches = Noise problems
– Check Packet stats
• RTP Stats
• RFC 3357
• Check physical stats
– Video MOS
• Summarize video picture quality with video MOS score
These numbers are very low as
they should be for such a poor picture.
V-MOS should be about 3.5.
With more than one channel being affected, the issue is identifying the
source of the packet problems. Evaluating physical layer metrics over an
access link such as VDSL will help sectionalize the problem.
This shows an example of how this correlation can be easily made. If there
was a packet loss count over the ADSL interface under test, and no counts
for ATM and ADSL layer items, then the packet loss would be upstream of
the DSLAM or remote IP device terminating the ADSL link. The same
analysis can be accomplished at the Ethernet interface.
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