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Speed drop after second FTTC cabinet installed

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Speed drop after second FTTC cabinet installed

I've been a happy FTTC 80/20 customer for a number of years, running at 46/7 with multiple months between resyncs (typically router software update, etc.).  

That changed last week.  Openreach commissioned a second VDSL2 cabinet alongside the existing Huawei 288, and on the final days of the works my line dropped and came back with the following changes:

  • SNR margin dropped from 10 to 6
  • Downstream attainable dropped from 49 to 36Mbps
  • Upstream dropped from 6.8 to 2.8Mbps
  • Bitswap enabled on downstream (also on upstream, later removed)
  • Increased CRC errors
  • G.Inp still enabled on downstream (now at depth 44, no record of previous)
  • Attenuation unchanged

I've raised a fault, but yet to hear anything back.  Not sure what options exist if BT has reorganised the physical layer and left me on a suboptimal path.  Has anyone experienced anything similar?

 

I'd really like them to move my line from the duct to be via  the pole behind my property--it's very close to the cabinet--but realise that's a pipe dream! 

 

Doug

9 REPLIES
flanzm
Rising Star
Posts: 74
Thanks: 33
Fixes: 4
Registered: ‎20-04-2016

Re: Speed drop after second FTTC cabinet installed

Very similar thing happened to me when they activated more line cards in my cabinet and added additional tie pairs. Soon as they turned it on SNR dropped like a stone, errors increased etc.  My suspicion is that your line has been adversely impacted by crosstalk.  

They keep really quiet about crosstalk - but it's pot luck how it impacts you depending on how close your pair is to others.  When I was first activated at 300 meters from the cabinet my attainable rate was 102Mbps downstream - now I can only get 67Mbps.  I know it's crosstalk as I have a UPS and when we get powercuts (and everyone elses modem goes offline) I go straight back to ~100Mbps.

 

The key thing is to compare what you are getting with the availability checker.  If it's as expected you won't get any joy with raising a fault.

Not sure what you mean about being close to the cabinet.  A rate of 46/7 suggests you are quite a way from the cabinet.

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed

The cabinet is behind my house with a pole adjacent, but my line runs a different route. Hence the comment that a new line from the pole would make a huge difference.
flanzm
Rising Star
Posts: 74
Thanks: 33
Fixes: 4
Registered: ‎20-04-2016

Re: Speed drop after second FTTC cabinet installed

Maybe order a second line then and get it fitted to enter at the back of the house - you never know you might be lucky and OR will route it differently.

I would suggest raising it on this forum - quite a few very knowledgeable types Wink hang out there and will be able to advise on whether that would work for you based on procedures that have to be followed.

 

Edit: Actually just done my own research - apparently they are most likely to use spare pairs in your existing drop cable so unlikely to change route.

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed

Another resync, another speed drop (down to 34Mbps).

My upstream is about 1/3 of the lowest predicted by dslchecker.bt.com. Downstream is right at the bottom of the impacted figure.

Virgin Media is installing FTTP here sometime over the next 12 months. Unless I can get back to 6Mbps upstream then I may be forced to abandon BT's infrastructure; despite really not wanting to use Virgin.

Fingers crossed that Plusnet can restore me back to last week's service levels!
Moderator
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Re: Speed drop after second FTTC cabinet installed

Moderator's note by Mike (Mav)

Two duplicate posts removed after being released from Spam Filter

Forum Moderator and Customer
Courage is resistance to fear, mastery of fear, not absence of fear - Mark Twain
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DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed (ticket: 142489991)

My upstream is now 394Kbps!!!!!  Upstream attenuation has changed from 24dB to 42dB, downstream from 23dB to 37.

 

Still no word on the fault I raised: ticket 142489991.

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed (ticket: 142489991)

My neighbour has the same problem, a very similar drop in speed that started at the same time. He also lost dial tone for a day last week, on the first day of the problem.

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed (ticket: 142489991)

The engineer visited today and was unable to find a fault.  His advice is to wait until after the cabinet work is completed before troubleshooting further.

DougMa
Grafter
Posts: 115
Thanks: 3
Registered: ‎09-09-2011

Re: Speed drop after second FTTC cabinet installed (ticket: 142489991)

Openreach was back at the cabinet today.  My line resynchronized twice and my stats have improved significantly.  I'm back to 7.2Mbps upstream, but DLM has now limited my downstream to 30Mbps.

 

My understanding is that the engineer should have requested a DLM reset when they fixed the fault, but it looks like it got missed.  I updated my ticket 142489991 asking for a DLM reset.  

 

Can anyone here help get that triggered for me?

 

Many thanks.