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[Bowdon]

https://www.ispreview.co.uk/index.php/2018/06/margot-james-mp-hints-isps-should-pass-fttc-price-cut-on-to-homes.html

The UK Minister of State for Digital, Margot James MP, yesterday reaffirmed the government’s commitment to a Gigabit “full fibre” (FTTP) future and also called on ISPs to “pass on [the] benefit” from Ofcom’s recent wholesale market reviews in order to improve the take-up of “superfast broadband.”

The remarks were made during Margot’s speech to the Digital Britain event in London, in which she confirmed that some 2,000 vouchers under the new £67m Gigabit Broadband Voucher Scheme (GBVS) had so far been issued to businesses. On top of that she also spoke of the need for ISPs to pass on the benefit from Ofcom’s recent wholesale market review.

The review itself requires Openreach (BT) to adopt stiffer Quality of Service standards for installations and repairs, as well as to open up their cable ducts to rival ISPs and to introduce a big price cut on 40Mbps (10Mbps upload) Fibre-to-the-Cabinet (FTTC / VDSL2) based broadband lines.

    Margot James MP said:

    “I am also very keen to increase the take-up of superfast broadband. We want providers to be confident that demand will follow where they build: through increased take-up providing more returns to the market and realising greater benefits.

    The more affordable it is compared to standard broadband, the higher the take-up will be. I would call on ISPs to pass on benefits from the WLA review, and look at how to promote further take-up.

    This will not only realise the benefits of superfast, but continue to stimulate consumer demand for the next step to full-fibre and 5G.”

[Weaver]

I do not see why there should be a price cut enforced on 40 Mbps FTTC because if a lot of people do not know about speed and do not care then they can choose ADSL2+ instead.

Who cares what the take-up of FTTC is anyway? You can’t force people to take an interest.

However, if the government would force BT to dump ADSL2+ completely where it interferes with FTTC and give everyone rate-limited cheap FTTC instead then that would be brilliant because it would stop the crosstalk caused by ADSL2+ and presumably would mean that they could get rid of the stupid power-cutback PSD V-shaped notch for VDSL2 users. Is that correct? I got this idea because at the test site for long range VDSL2 at Tolastadh bho Thuath in the Island of Lewis it had to be a cab with no ADSL2 as I recall.

I think it would be excellent if the operators were all forced to draw up an early phase-out date for ADSL2/2/2+. The replacement would either have to be FTTP or FTTC.

[Chrysalis]

ADSL2+ been dumped in FTTC areas is a no brainer but it hasnt been done because of ofcom hand holding the LLU isp's wanting to sell cheap ADSL in those areas.  Yes that V shaped power cutback is to protect ADSL2+ services.  If it wasnt there then ADSL signals would be weakened severely or even wiped out from VDSL crosstalk.

[Weaver]

They really do need to get rid of ADSL as quick as you like to stop it mucking up VLDSL2. It could get so ridiculous: there could be one old granny still on ADSL2+ in an area and that one account would be stopping everyone else from having rather better VDSL2. I have not added up the cost of the V-shaped notch but I presume counting the bits in the V is not that hard with a little care taken.

Question: is the notch something published by the DSLAM or is it in some standards doc?

Never having really looked at the standards for VDSL2, not wanting to torment myself. I assume, based on thinking about the LR-VDSL trial, that the notch can just be made to go away by changing the tables in the DSLAM. If the notch were built into one of the standards then it could not just be made to go away just like that and so LR-VDSL would not happen without customised modems that were rather more ‘non-standard’. But basically I have no idea what I am on about. Someone will I am sure have the answer.

[Chrysalis]

On my line I have calculated it to be worth about 16-18mbit sync speed, I would comfortably be at 80/20 without the notch and a healthy noise margin to boot.

The graph is missing on my public stats, I will try to update to newer graph pages soon, but basically on my bitswap per tone data, most of my bitswaps are in the D3 tones, and also in the V notch tones, so it has a negative affect on error rates as well.

[burakkucat]

Each cabinet has a CAL (cabinet assigned loss) which has been assigned by measuring the attenuation of an exchange based G.992.{1|3|5} at that location. The notch is then profiled so that the power of the G.993.2 signal v frequency is identical to that of the G.992.{1|3|5} signal v frequency.

[Weaver]

Actually Burakkucat set me thinking. They could do anything, they could in fact make the notch worse, cutting out everything in that frequency range so as not to be a disturber at all for G.992.* users and give those suffering most a bit of extra help from further reduced crosstalk.

[kitz]

they could in fact make the notch worse, cutting out everything in that frequency range so as not to be a disturber at all for G.992.* users and give those suffering most a bit of extra help from further reduced crosstalk.

Which would be disastrous for lines with a long D-side.   There's quite a lot of lines which don't get that much more from VDSL than ADSL because of that notch.   There's even been a few cases on here whereby VDSL offers slower speeds than ADSL because of PCB over those tones.

As far as anyone still on ADSL, then its better for them if their neighbours are on VDSL, because VDSL causes less x-talk to an ADSL line than an ADSL neighbour would.  Also a fair amount of FeXT is supposedly generated at the DSLAM.

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As an aside, whilst on the subject of ADSL/VDSL crosstalk, this happened to me the other day.   My neighbour who has only ever had adsl (18Mbps was sufficient for her use) moved out.    This was what happened to my line when she turned off her router.   I know it was her because she knocked on my door for a final bye hug before she dropped the keys off at just gone 11am.  She'd already said a few days previously that she was keeping her broadband until the last min.    Of course I took advantage to reboot and its given me a few extra Mbps.    New neighbour hasn't yet fully moved in so no doubt that will vanish again when they get xDSL.   But this is a good example of how just one ADSL2+ line causes me slightly over 2Mbps of crosstalk.

[Weaver]

And this just shows how badly vectoring is needed.