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zag164
Beginner
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Message 1 of 8

BT FTTC slowing down - SNR increased

Hello Support,

Our FTTC connection has been getting slower and slower since it was installed back in 2012.  I took a photo of the engineer's meter on installation day (FTTC had an engineer visit back then).  During the training period, the sync speed increased from this to 45Mb/s down and 7Mb/s up and was stable for a couple of years.

 Engineers meter at installation.Engineers meter at installation.

Over the past 4 years, however, the speed has gradually degraded with the downstream sync speed falling by 25%.  This is what we currently get. 

Current speedCurrent speed

Here are the full router stats:

---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Running Mode            :      17A       State                : SHOWTIME
DS Actual Rate          : 32394000 bps   US Actual Rate       :  5677000 bps
DS Attainable Rate      : 36814824 bps   US Attainable Rate   :  5758614 bps
DS Path Mode            :        Fast    US Path Mode         :        Fast
DS Interleave Depth     :        1       US Interleave Depth  :        1
NE Current Attenuation  :       25 dB    Cur SNR Margin       :        8  dB
DS actual PSD           :     5. 2 dB    US actual PSD        :     5. 2  dB
NE CRC Count            :     3714       FE CRC Count         :      198
NE ES Count             :     3248       FE  ES Count         :      154
Xdsl Reset Times        :        0       Xdsl Link  Times     :        1
ITU Version[0]          : b5004946       ITU Version[1]       : 544e0000
VDSL Firmware Version   : 05-07-06-0D-01-07   [with Vectoring support]
Power Management Mode   : DSL_G997_PMS_L0
Test Mode               : DISABLE

-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation :       35 dB    Far SNR Margin       :        6  dB
CO ITU Version[0]       : b5004946       CO ITU Version[1]    : 544eb206
DSLAM CHIPSET VENDOR    : < IFTN >

What is notably different though is the target SNR which was originally 6 and is now 8.  The stats show the maximum attainable rate is 36.8Mbps.   We did go through a period a few years ago where we had a large number of power cuts due to a major underground electrical fault in our neighbourhood.  Is it possible that the DLM has never recovered from this?    Looking at this linked article, since 2016 the target SNR should now be 3 which I imagine would increase the line speed.

 

https://www.ispreview.co.uk/index.php/2016/11/speed-boost-bt-openreach-prep-3db-snr-fttc-broadband-l...

Would a Mod be able to request a  DLM reset to initiate another 10 day training period, please? 

Thanks in advance for your help.

 

 

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7 REPLIES 7
pippincp
Sage
771 Views
Message 2 of 8

Re: BT FTTC slowing down - SNR increased

Target SNR is still 6dB if connected to an ECI cab. Which exchange and cab number are you?

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zag164
Beginner
761 Views
Message 3 of 8

Re: BT FTTC slowing down - SNR increased

Thanks for the reply.  We are on Highwoods  Exchange, PCP 15.

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pippincp
Sage
753 Views
Message 4 of 8

Re: BT FTTC slowing down - SNR increased

ECI cab. 6dB target.

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zag164
Beginner
747 Views
Message 5 of 8

Re: BT FTTC slowing down - SNR increased

Thanks.  The target SNR *should* be 6 rather than 3.  I saw at the bottom of the article I linked that the ECI cabinets are excluded from the SNR 3 target rollout.  

I am still keen to understand why the SNR is currently 8 though as we have confirmed it should be 6.  

 

 

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pippincp
Sage
743 Views
Message 6 of 8

Re: BT FTTC slowing down - SNR increased

Have you checked for line noise? 17070 option 2 any noise should be reported as a line fault not broadband.

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zag164
Beginner
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Message 7 of 8

Re: BT FTTC slowing down - SNR increased

Thanks, I have just tried that but there is no noise on line, other than a faint hiss.  I also tried a line test online and that came back clear.

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pippincp
Sage
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Message 8 of 8

Re: BT FTTC slowing down - SNR increased

A faint hiss with a corded phone is a line fault. Silent means silent.

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