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Profile capping mechanism on 21CN, ADSL2+

Community Veteran
Posts: 2,329
Thanks: 237
Fixes: 2
Registered: 04-08-2009

Profile capping mechanism on 21CN, ADSL2+

After my phone line went down last week (also causing mayhem on the DLM), BT have provided a replacement line pair to the local JB. On first sight, the line performance, as shown on DMT, has lots of gaps in bit loading at higher frequency tones, and as an aside the line is displaying a worrying amount of errored seconds although sync is steady. For example, I had about a 60% errored second rate in the last four hours, which has completely disappeared in the last 45 mins!
I've been told by a CSC that it looks as though my line is now capped at 9mbps. and a request is in to have it removed. Question - is the speed capping actually achieved by deliberately restricting the number of higher frequency tones available? If so, this would explain why the d/s and u/s frequency profiles look so ragged and would also give me hope that I can regain the excellent sync speed I once had before the line failure. If not, how can I get a "clean" line, or is that impossible?