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More speed in 2017 from Openreach VDSL2
Tuesday 15 November 2016 11:13:41 by Andrew Ferguson

Tweaks to the way the Dynamic Line Management (DLM) works for VDSL2 (Fibre to the Cabinet - FTTC) are on the way in 2017. It appears that those people with stable VDSL2 lines may be see an increase in speeds as lower target noise margins of 3dB, 4dB and 5dB will be made available.

The current minimum target noise margin is 6dB, thus allowing lower margins will potential give people a couple of extra Meg, and for those on the 1 to 1.5km type line lengths any extra speed will be welcome and it may bring some up from 22 Mbps to the 25 Mbps region. This is not a setting that you will be able to request but the DLM system will determine if a line appears stable enough and then try a lower margin and if the error rates don't increase the new setting will stick.

The information comes from a suppliers information note (SIN 498) which describes the Openreach VDSL2 service and March 2017 is the current date for when the DLM will change. For those who feel the need for speed, it should be pointed out that the lower margins are only going to be applied to those who see a stable connection at the existing 6dB margin, so if you are running on a 9dB margin currently the change will not impact you.

Myths around the Openreach DLM still persist, but the general rule is that the line starts off life at its fastest and the DLM will do most of its major changes in the first 48 hours of a VDSL2 line going live, but thereafter the DLM continues to run and will react to changes in conditions and while reactions to increase stability are generally fast, things like giving back speed after a period of instability can take a few weeks.

Comments

Posted by 961a 21 days ago
This is welcome news, but the sting is in the tail. "..giving back speed after a period of instability can take a few weeks."
Can Openreach not address this problem, as many find loss of speed after a power cut or a need to shut down the router can persist for months.Resolving this problem would be more welcome than what is happening here
Posted by andrew (Favicon staff member) 21 days ago
A single power cut should not trigger DLM, unless this was the one event on top of an already big pile of recent high error rates.

Part of the reason some may feel DLM does not relent, is that modems do not automatically resync to higher speeds once a period of noise is over.

So in short a PPPoE disconnect and a single reboot of modem a couple of days after the slow speed event when it is showing spare noise margin above the expected target dB will often improve things.

Without this a modem will happily sit with 15dB actual noise margin and 31 Mbps sync for weeks, even if the target is 9dB.
Posted by 961a 21 days ago
Accept what you say, but you will agree that week after week we see complaints on this site from folk who do wait mega periods of time and continue to be told "nothing can be done you'll just have to wait"
Posted by andrew (Favicon staff member) 21 days ago
I see moans and some are fixed by a reboot once stats have shown that this may bring about an improvement.

The question is whether the number we see are the tip of the iceberg and millions have the issue.

The big unknown and hard to quantify issue is crosstalk which is a bigger issue on VDSL2 to ADSL2+ and possibly why DLM has some lag to it.

Posted by markybaby76 21 days ago
Why can't they just use the full spectrum for vdsl? 17c instead of b.
Posted by andrew (Favicon staff member) 21 days ago
Thought Openreach was on profile 17a (band plan 998ADE17 B8-11)

Not aware of a 17b, 17c profile, but they have looked at 35b but backed on in favour of G.fast. Might have missed it of course.

Perhaps you mean Long Reach VDSL band plan 998 (B8-4)
Posted by andrew (Favicon staff member) 21 days ago
The are power restrictions on 17a to ensure it does not play nasty with ADSL2+, and part of the long reach trials has been showing what can be gained running VDSL2 in areas with no ADSL2+ present. The investment in LLU in UK does make no ADSL2+ scenario difficult en-masse.
Posted by markybaby76 20 days ago
The simple answer is to just connect everyone to a cab and just sell speed based products. Of course open reach don't want that as it is making money out of fttc in areas where adsl2 is not viable. I would be happy to drop back to up to 24mbps it would save me £25 a month
Posted by WWWombat 20 days ago
So what you want to do is take advantage of the extra infrastructure - that required money investing to deploy it closer to you - but then you dont really want to pay anything for it.

To connect everyone to the cab would require even more hardware deployed nearby. Plausible, until you factor in the people that don't want to pay anything for it.

In the end, it costs Openreach the same to deploy a cabinet close to you, regardless of what protocol/speed you choose to use. Expect that a cabinet-based ADSL service would perhaps cost 50p less, not £25.
Posted by rtho782 20 days ago
Another case where enforced false competition, this time via LLU, has made the situation worse. I honestly feel we'd be better if Ofcom went away and we went back to a BT monopoly.
Posted by 961a 20 days ago
rtho782

Ofcom certainly hasn't helped in rural long line areas. Don't think it's made stuff cheaper either
Posted by Pendlemac 20 days ago
Thought this article was going to be about a speed-lift for Infinity 2 similar to the recent one for Infinity 1 as I have a max attainable rate of 99999 showing. Need to sort out the iffy house wiring to see if that is the actual speed or all the HH6 can display.
Posted by connormill 1 day ago
Will be interesting to see if this actually makes an improvement to those of us just below the current maximum 80mbps

I'm with SSE and get a downstream sync of 73.1mbps on a very steady 6.1db SNR, if I could get that SNR down by a few db how much would I gain?
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