Author Topic: FTTC (VDSL2) and G Vector  (Read 284 times)

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Offline mervl

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FTTC (VDSL2) and G Vector
« on: Oct 11, 2019, 16:49:49 »
Old hat I know but we're always behind . . .

G Vector (Correction) has just  been enabled at the DSLAM and I have a modem (Fritz) able to take full advantage running on FTC/VDSL2, apparently. (Nothing faster available).

Since installation many moons ago I've been blessed, and stuck, with dropping throughputs, I suspect due to the ever growing local impact of crosstalk on the congested estate, reinforced by the fact they've now fully recovered to where I'm hitting the profile limit I'm paying for. I considered moving to the next 55/10 tier, which the modem now reports as attainable, for a couple of quid more but IDNet are insistent I'd hit the 43 limit they say my line is capable of rather than the 57 attainable now reported by the modem. So far my experience is that throughputs have tracked the modems reported attainable closely, but of course at a much lower (and ever declining) level.

Anyone experience of this with G Vector? I'm thinking that as the error correction is negotiated locally, I'm not sure what IDNet rely on,  presumably an OR formula? It is really just for devilment, rather than necessity I have to admit, to get my line doing the best it can, though I hope it'll now have less dropouts and major errors too, with or without a profile change.

Just out of interest the upload throughputs seem to have halved with G Vector, though I hope this is temporary whilst the DSLAM settles down again. Or they've not adjusted it right yet - the upload SNR is reported as 6, and the download 16, and the upload attenuation has also doubled. I'm  reported by the modem as 750m from the Cab, which seems about right walking it, so I suspect not doing too badly if the modem is right, with our decrepid suburban infrastructure.

I know the standard reply is that FTTP (and Boris) will sort out everything, but we've no demand for it (like most people, I suspect; except those who frequent the forums!)
« Last Edit: Oct 11, 2019, 17:05:59 by mervl »

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #1 on: Oct 12, 2019, 09:55:48 »
A further thought. To my (very simple) mind isn't the point of vectoring to eliminate virtually all noise on the line (by counter noise). If so, is there no remaining reason (apart from interference in the premises - only me here + dog, who doesn't generate the right, or wrong, sort of noise) for  the throughput to be less than the attainable - as long as  IDNet's backhaul is up to the job!

Why we've suddenly got vectoring - not a BDUK cab, I have no idea. I thought OR had other priorities and things to spend our money on these days! Perhaps desperation to  deal with the ever increasing drops in throughputs, which were threatening our superfast status, and their local performance stats?

Offline Simon

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Re: FTTC (VDSL2) and G Vector
« Reply #2 on: Oct 12, 2019, 21:57:37 »
Sorry, Merv, I've no idea on this, but hopefully someone else will. 
Simon.
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This post reflects my own views, opinions and experience, not those of IDNet.

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #3 on: Nov 13, 2019, 13:30:14 »
Ah well, after a few weeks and a DSLAM resync speeds have dropped as low as ever, so luckily I resisted the temptation to move to the higher price plan! Nothing untoward reported by the modem though to offer an explanation. Fortunately I can live with it. Not that us estate-people have any option despite all the PR hype!

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #4 on: Nov 17, 2019, 14:42:28 »
... and after last night's power cut it's resynched at the 40Mbps profile limit, and after it's brief rise the upload is back down where it was.

Bouncing around like a tennis ball all over the shop. Reality v hype!  :thumb: At least this year the broadband might not be dropping with the temperature (even if the electricity is). That's progress, after a decade. Patience pays, after all.

Offline andrue

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Re: FTTC (VDSL2) and G Vector
« Reply #5 on: Nov 18, 2019, 20:16:04 »
I think there's some confusion here. There's no such thing as 'G Vector'. What there is is:

* G.FAST - the next generation of DSL. This uses frequencies above those of VDSL so is only available to those whose lines can already connect at or near full speed for VDSL.
* Vectoring - crosstalk cancellation technology. This is available for VDSL on some - possibly only a few - cabinets (generally those with longer lines so mostly rural). G.FAST always uses vectoring.

@mervl - where/how did you learn about this? BT don't generally advertise when vectoring is enabled on a cabinet as it's a technical matter. It's more likely they'd have advertised G.FAST which from the sound of it your line wouldn't support anyway.

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #6 on: Nov 19, 2019, 10:34:24 »
Andrue, thanks that corresponds with my understanding; but I was using the modem's terminology, which reports:

Negotiated Connection Properties
      Receive Direction    Send Direction
Max. DSLAM throughput   kbit/s   40000   10000
Min. DSLAM throughput   kbit/s   128   128
Attainable throughput   kbit/s   60948   3622
Current throughput   kbit/s   39998   3622
Seamless rate adaptation      off   off
          
Latency      fast   fast
Impulse Noise Protection (INP)      58   0
G.INP      on   off
          
Signal-to-noise ratio   dB   14   6
Bitswap      on   on
Line attenuation   dB   24   39
approximate line length   m   727   
          
Profile   17a      
G.Vector      full   full
          
Carrier record      A43   A43

Error Counter
   Seconds With    Not Remediable Errors (CRC)
   Errors (ES)    Many
Errors (SES)    per
Minute    Last
15 Minutes
FRITZ!Box    0    0    0    0
Central exchange    33    0   0    0
(Sorry the columns are out of sync).
Elsewhere the modem reports:

DSL active since:
2 days, 8 hours, 16 minutes
VDSL2 17a G.Vector (ITU G.993.5)
Huawei        Broadcom: 177.45

I'm on the 40/10 package, the maximum my line could support would be 42Mbps according to IDNet, presumably advised by local OR data. It is, by the way, a residential estate cabinet, serving no rural premises.

Regards, Mervyn.
« Last Edit: Nov 19, 2019, 10:59:43 by mervl »

Offline andrue

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Re: FTTC (VDSL2) and G Vector
« Reply #7 on: Nov 19, 2019, 18:25:37 »
Thanks for that @mervl. Very interesting. Was your cabinet installed as part of BDUK? Because what I've heard is that openreach are doing this in order to meet BDUK obligations. They are more interested in extending cabinet reach than increasing average speeds. One reason given for them not rolling it out nationally is that ECI cabinets don't support it which could lead to awkward demands from those on ECI cabinets.

And you learn something new every day as it appears that 'G.Vector' is a thing which I hadn't realised. My apologies for doubting you.

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #8 on: Nov 19, 2019, 23:07:57 »
No BDUK in the village. It was all a commercial rollout, in 2011. So Why? is, as so often with OR/BT, one of life's great mysteries.

Hence why I speculated that maximum throughputs having dropped since then from above 40Mbps, down to the mid 30s, and in the last couple of years to 30, and this autumn the low 20s, it might be a desperate measure to keep us in the superfast category, for their local performance stats? A bit cynical I know, but if the new residents who seem to be moving in as us older ones move on have been complaining?

Certainly BT are a bit coy about it all, and (no criticism, but they have to face the BT brick wall, too) IDNet have been as much use as the proverbial tub of lard. I even got a phone call from Simon when I provisionally considered moving to A&A to tell me I had to "live with it" and nobody else could do any better, either! As there's no information, I don't know whether it needs a special modem, like the Fritz, to take full advantage? Or whether it's just that OR's database hasn't caught up yet. (The latest Fritz! OS might be something to do with it too - AVM can be a bit coy, too). Certainly I can understand why BT wouldn't want to give disgruntled customers something else to campaign about, that doesn't fit the usual narrative.
« Last Edit: Nov 19, 2019, 23:17:41 by mervl »

Offline andrue

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Re: FTTC (VDSL2) and G Vector
« Reply #9 on: Nov 20, 2019, 11:26:49 »
I think originally openreach required all modems attached to its network to support vectoring. It may still do. As long as your modem supports it (and it seems to) then things should just work. However how well they work is another matter. If your problem is cross-talk from other users and if those users all have vectoring capable modems it should improve your connection.

Otherwise..I dunno.

https://www.increasebroadbandspeed.co.uk/vdsl-vectoring-arrives-on-a-rural-fibre-broadband-cabinet
https://www.ispreview.co.uk/index.php/2019/06/openreach-uk-could-replace-eci-fttc-broadband-cabinets.html
https://forums.thinkbroadband.com/fibre/4581044-vdsl-vectoring-enabled-then-unconfigured.html?fpart=all

Now you probably know as much or more than I do :)

Offline mervl

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Re: FTTC (VDSL2) and G Vector
« Reply #10 on: Nov 20, 2019, 14:48:28 »
Thanks Andrue. I had got snippets of that but not the whole picture.

The tone graph on the Fritz is consistent.There is a noticeably greater range, and depth (except on upload) of tones across the spectrum, I suspect it's wouldn't be enough to justify moving to a more expensive package; and the decline in upload speeds is a bit irritating but let's hope it's sorted out as things settle down (or may be it's activated on the upload, but not yet active?) For the time being having a more reliable connection and less buffering are a welcome improvement anyway. I've also noticed a new feature that (within a small margin) the reported attainable on downloads is now constantly changing which would presumably seem to indicate that some software is busy doing its job.
Regards, Mervyn.
« Last Edit: Nov 20, 2019, 15:03:51 by mervl »


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