Recovery of speed/target SNR margin after resoluti...

Question

I have had a line fault on my phone line (noise due to a damaged pair near the exchange) for the last couple of months until I finally got around to getting this fixed. This had resulted in many many frequent disconnections of the ADSL rounter and as a result the target SNR margin for the service currently seems to be somewhere around 12. Since the line has been fixed (perfectly clear phone line now) I was hoping that either a) BT could manually reset the target SNR margin or b) failing that the recovery would not take too long. I raised a fault and was informed that "something has been done" but there was no evidence of this. Having been away on business for the last week I thought I would see what happened over this time but it seems that after a week of no disconnections on the router the synchronisation speed still has not improved. Here is the current status of the ADSL connection
--------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
Running Mode : ADSL2+(G.992.5) State : SHOWTIME
DS Actual Rate : 6656000 bps US Actual Rate : 828000 bps
DS Attainable Rate : 14328000 bps US Attainable Rate : 1479492 bps
DS Path Mode : Interleave US Path Mode : Interleave
DS Interleave Depth : 0 US Interleave Depth : 0 NE
Current Attenuation : 38 dB Cur SNR Margin : 14 dB
DS actual PSD : 18. 3 dB US actual PSD : 12. 6 dB
ADSL Firmware Version : 232201_A
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 19 dB Far SNR Margin : 10 dB
CO ITU Version[0] : 00005453 CO ITU Version[1] : 00005443
DSLAM CHIPSET VENDOR : < TI >
and the results of a BT speedtest
Download speedachieved during the test was - 2101 Kbps
For your connection, the acceptable range of speedsis 2000-7150 Kbps.
Your DSL Connection Rate :6656 Kbps(DOWN-STREAM), 828 Kbps(UP-STREAM)
IP Profile for your line is - 5500 Kbps
Upload speed achieved during the test was - 652 Kbps
Upstream Rate IP profile on your line is - 828 Kbps
Up until the line fault I was synchronising at around 10Mb and achieving 8-9.5Mb download speeds. Has anyone got any suggestions on
a) Whether BT can/will reset the settings for my connection (target SNR margin etc)
b) Failing this how long would it expect to take for the algorithms to automatically recover from this type of event c) Would there be another issue causing this
Solved!
Go to Solution.

Answer 1

21CN adsl2+ connections can suffer profoundly from banded profiling.
If the line has seen frequent problems, as is the case, it may take from 3-5 days to see an improvement.
The dynamic line management of 21CN pays a lot of credence to connection history, and coming out of banded profiles can often be lengthy. Your connection even though now fixed has to recover, unfortunately your throughput for the BRAS profile, something totally different ... is not good.
You can either wait and look for improvement over the next few days .... or drop an email in to the moderators.
They can get the banded profiling lifted ... and see how you go.
I'm a little surprised it wasn't requested after the line repair, sometimes it is .... sometimes not.
The noise margin at 12db is not too bad, but should get better with time, if BTw don't reset it.
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