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Author Topic: VDSL Extension cabs and impact on vectoring  (Read 780 times)

mr_mf

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VDSL Extension cabs and impact on vectoring
« on: August 26, 2020, 11:01:20 PM »

Hi guys,

For the past few years I have been happily connected to a BDUK funded cabinet (Huawei 384 HD) that luckily benefited from vectoring - with the net result that my attaintable rate was 116Mbps with a 12db margin.

Now that the main cabinet is full they have added an extension cabinet to the PCP.  Sadly my lovely high attaintable rate seems to be taking a noise dive - today it has dropped to 92Mbps with a 6db margin, which is quite a drop in a single day!

So my question is do these extension cabs offer vectoring ?  And if they do how do the two cabs coordinate the noise cancellation, as based on what I am observing it would appear they don't!

Mike

Max:   Upstream rate = 26438 Kbps, Downstream rate = 92020 Kbps
Bearer:   0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps
Bearer:   1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State:   L0
Mode:         VDSL2 Annex B
VDSL2 Profile:      Profile 17a
TPS-TC:         PTM Mode(0x0)
Trellis:      U:ON /D:ON
Line Status:      No Defect
Training Status:   Showtime
      Down      Up
SNR (dB):    6.1       9.9
Attn(dB):    15.6       0.0
Pwr(dBm):    12.6       6.9
« Last Edit: August 26, 2020, 11:05:08 PM by mr_mf »
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Alex Atkin UK

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Re: VDSL Extension cabs and impact on vectoring
« Reply #1 on: August 27, 2020, 05:16:12 PM »

Its not wise to draw any conclusions from attainable rate, its only an estimate and can be completely wrong.

Given that you have a 6.1dB SNR downstream, it seems rather optimistic to suggest you'd get 92Mbit uncapped.  I believe even at 3dB you'd never gain more than 10Mbit.

Ultimately its all moot as I don't see the 79.9Mbit cap going anywhere.
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j0hn

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Re: VDSL Extension cabs and impact on vectoring
« Reply #2 on: August 27, 2020, 08:19:41 PM »

It's likely technically possible for them to deploy Vectoring from the VDSL Sidepods.
I've never seen them do this though.

OpenReach only ever deploy Vectoring on the BDUK cabinets and I believe any additional cabinets/pods that are installed are done as part of their commercial rollout and not related to BDUK in anyway.
So it's no surprise they haven't coughed up for Vectoring.

Even if they installed a Vectoring module in this new DSLAM/pod it would only cancel crosstalk for lines that are connected to the pod.

They would need to link the 2 DSLAM's together and use Node level Vectoring so that every line on both cabinets is properly Vectored.

As it is at the moment any line on your fibre cabinet is Vectored but any line on the new pod will cause crosstalk.

I'm not sure if this is deliberate by OpenReach or if the planners didn't even know your cabinet had Vectoring.
It's a pretty inefficient way to deploy things though.

I've no idea what changes need made to the VDSL pods to add Vectoring. They contain a Huawei MA5818 DSLAM.
There might not even be enough space in the pod.
I don't know enough about how Node Level Vectoring works to be honest.

The whole point in BDUK funding being used for the Vectoring kit is that it increases the number of properties on the cabinet who can get SuperFast speeds (24Mb or 30Mb).

I think OpenReach are only paid by BDUK for properties that reach SuperFast speeds.
The addition of this pod may now decrease that number of properties.

It might be worth querying this with your local BDUK team or even firing an email off to someone at OpenReach.

It's certainly a grey area and not something I've come across.
It probably won't be the only Vectored cabinet to have an additional DSLAM installed though.
« Last Edit: August 27, 2020, 08:25:14 PM by j0hn »
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Alex Atkin UK

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Re: VDSL Extension cabs and impact on vectoring
« Reply #3 on: August 27, 2020, 09:08:29 PM »

I think OpenReach are only paid by BDUK for properties that reach SuperFast speeds.
The addition of this pod may now decrease that number of properties.

It might be worth querying this with your local BDUK team or even firing an email off to someone at OpenReach.

It's certainly a grey area and not something I've come across.
It probably won't be the only Vectored cabinet to have an additional DSLAM installed though.

It would certainly be interesting to hear if this could actually be in breach of the agreement should it cause a bunch of lines to drop below the requirement.
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mr_mf

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Re: VDSL Extension cabs and impact on vectoring
« Reply #4 on: August 28, 2020, 10:21:03 PM »

Thanks John and Alex - you've confirmed what I think is happening.  I will drop the BDUK folks and email, as you are correct this latest 'addition' is not going to do speeds any good.

Mike
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