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BT Prepare Phase 2 Vectoring Trials to Boost UK FTTC Broadband Speeds

Tuesday, May 6th, 2014 (2:08 am) - Score 7,620

BTOpenreach has decided to extend their on-going trials of VDSL Vectoring (ITU-T G.993.5) technology into a second phase, which could improve the speeds delivered via BT’s existing “up to” 80Mbps hybrid-fibre (FTTC) superfast broadband network by helping to eliminate interference (crosstalk). But it might also push any future roll-out back to late 2014 or 2015.

Regular readers will recall that Openreach began their first field trials of Vectoring technology in September last year, which works a bit like those noise cancelling headphones and employs the coordination of multiple copper line signals in order to create a reduction of interference (i.e. in order to work at its best all of a street cabinets FTTC lines must be upgraded but there is some flexibility).

The first trial began with three street cabinets [26, 41 and 42] in Barnet (London) and another three [12, 39 and 74] in Braintree (Essex). At the time Openreach said that its trials would be “monitoring the maximum speed trial lines could theoretically achieve” and indeed similar deployments by Eircom in Ireland have seen headline rates jump from “up to” 70Mbps to 100Mbps. Danish Vectoring trials, which are arguably more comparable to the UK’s infrastructure, have also recorded a similar capability jump to 100Mbps.

However BT’s Head of Access Platform Innovation, Kevin Foster, last year cautioned that Vectoring was being seen more as a “speed enabler rather than a speed booster” and the operator currently has no immediate plans to increase the advertised rate from its current maximum of 80Mbps (but we wouldn’t be at all surprised if they did.. eventually).

At the same time ISPreview.co.uk also revealed last year that Openreach had been conducting a separate “limited trial” of Physical Retransmission (G.INP) on a small number of FTTC/VDSL lines (here), which is a method designed to tackle spikes / burst of electromagnetic interference (impulse noise); this can make some problematic lines more stable and less prone to errors (we’ll touch on this again later). Sky Broadband also use G.INP.

But since last year we’ve heard very little about the progress of Openreach’s trial, which is not for lack of trying. The good news is that the sheet of thick ice that appears to have been covering the flow of Vectoring related information from BT appears to be thawing, which began in February 2014 after we heard that BT had begun evaluating the results from the first trial.

Trial Phase One.. Results?

The first good news surfaced in March 2014 when a communication to ISPs revealed that BT had seen what appears to be, as PlusNet put it, a “very positive” outcome to the Vectoring trials. Similarly ISPreview.co.uk has kept in contact with three customers on the relevant street cabinets, albeit only those with good lines that already ran at between 50-70Mbps, and all have reported improved download speeds with an increase of around 10-15Mbps+.

Upstream speeds will also benefit, although our group already had close to the headline rate and this made it difficult to know what to expect. Crucially we have no data for longer/slower lines, which are arguably of much more interest, although Eircom’s new line profiles for FTTC / VDSL Vectoring might offer some hints. Just remember that there are differences between the telecoms platforms but these do appear, at first glance, to be quite similar to the general expectations for vectored FTTC lines.

Eircom (Ireland) FTTC Vectored Line Profiles
Line Length (max) – Down (Mbps) – Up (Mbps)
300m – 100 – 20
450m – 90 – 20
525m – 80 – 20
600m – 60 – 20
750m – 50 – 20
850m – 40 – 10
1000m – 30 – 8
1200m – 25 – 8
1300m – 18 – 5
1500m – 15 – 3
1700m – 12 – 1
2000m – 7 – 1

It’s worth pointing out that some Vectored FTTC lines could go beyond 100Mbps (we’ve heard of 120-130Mbps being possible), although ISPs tend to like capping a bit below the peak (partly to avoid raising expectations when going mass-market). In any case if something similar to the above is confirmed for the UK then it might mean more people gaining access to “superfast” (30Mbps+) speeds, which would no doubt be a boost for the Government’s Broadband Delivery UK (BDUK) plan (the vast majority of FTTC lines are on a sub-1000m run of copper).

Back in the UK and some ISPs have suggested that the number of subscribers achieving the headline rate of 80Mbps has noticeably increased since Vectoring was enabled in related areas, which makes sense given the 10-15Mbps+ speed gains being reported by some.

However Openreach has since clarified to ISPreview.co.uk that vectoring will have the “most impact” on lines between 50m and 500m (note: most of these might already be getting “superfast”). But beyond 500m vectoring impact reduces and “very little gain” was seen past 1.5km, although Openreach did note some limited speed improvements for a few longer lines impacted by cross-talk. It’s important to remember that not even Vectoring can overcome the laws of physics.

As previously expected, Openreach also had to remotely update the firmware for some of their VDSL Modem’s and a few others needed to be replaced in order to work with Vectoring but the “majority” were not a problem. However we can see this being more of an issue if people have adopted third-party VDSL routers because some of the early kit doesn’t seem to support Vectoring (note: this won’t stop vectoring from working for everybody on the cabinet).

Trial Phase Two

So far, so good and Openreach believes that it can push even more performance out of Vectoring. But in order to test that they need to conduct a second trial in the same areas, which we’re informed will take place during the summer 2014 period and last for around 3 months (possibly longer or shorter) much like the first trial. Note: decisions are yet to be taken on the inclusion of further street cabinets.

The new trial will also include both Physical Retransmission (G.INP) and Seamless-Rate-Adaptation (SRA) technologies, which Openreach said they’re “very interested in testing” and see as being useful to help augment the benefits provided by vectoring. Back in 2011 BT ruled out SRA for its older ADSL2+ lines (here) but it’s good to see they have plans for it alongside FTTC/VDSL; SRA does a much faster and more reliable job of varying your line speed depending on its quality.

Openreach also told ISPreview.co.uk that its new trial would evaluate an enhanced vectoring engine (ASIC), which is “capable of cancelling out significantly more cross-talk interferes per line“. But contrary to some suggestions BT claims that its plans have “always” been based around the use of an ASIC vector engine, although outside of the trial they’re currently said to be determining the potential use of vectoring through “normal governance processes“. An ASIC version of the hardware instead of FPGA could have implications for the cost of deployment.

Officially no decision has been taken on whether or not to deploy Vectoring across the United Kingdom, although the positive outcome from Openreach’s first trial suggests that the only real hurdle might end up being the issue of cost. But this could easily be outweighed by a desire to remain competitive with Virgin Media and rising expectations from the Government’s broadband scheme.

Admittedly there are some other problems too, such as the need to replace a small number of VDSL modems and compatibility issues with Sub Loop Unbundled (SLU) ISPs that use different kit. However SLU providers don’t cover that many people, especially since Digital Region’s collapse in South Yorkshire, and new solutions are being explored.

On top of all that, if BT are serious about adopting the next generation of FTTC style technologies (e.g. G.fast) then Vectoring will be essential. Put another way, we wouldn’t bet against Vectoring’s introduction but the additional trial means it might be 2015 before we see it, but that’s just our own speculation given the summer start period.

Leave a Comment
31 Responses
  1. Avatar Bob2002

    > But contrary to some suggestions BT claims that its plans have “always” been based around the use of an ASIC vector engine

    How does this “ASIC engine” integrate with the current ECI/Huawei equipment in the cabinets? Or doesn’t it?

    • Avatar MikeW

      Using an ASIC effectively means using custom-designed hardware… so requires some level of hardware replacement.

      Use of an FPGA makes for “re-programmable” hardware. If the FPGA has sufficient capability, then it could be re-programmed on the fly; if not then a hardware replacement would be necessary too.

  2. ‘But this could easily be outweighed by a desire to remain competitive with Virgin Media’

    Openreach/BT have absolute no interest whatsoever in being competitive with Virgin Media on speeds, never have. It’s also probably a bit generous to say they have a desire to ‘remain competitive’.

    They have a nice captive audience in a part of the country and rely on CPs selling the products, including their own Retail operation at potentially squeezy margins, to handle the rest where there is actually competition.

    Vectoring is progress, it’ll help, it’ll be interesting to see how they choose to use the technology.

    Mark, FYI vectoring on FTTC / VDSL 2 is nothing at all to do with vectoring on G.Fast. G.Fast will avoid crosstalk with VDSL 2 simply by not using the frequency band that VDSL 2 lives in.

    • I don’t agree with the “no interest whatsoever in being competitive with Virgin Media on speeds” PoV. I do agree that there’s clearly less actionable interest, largely due to the constraints of their existing budget / copper platform choice, but it’s not like all urban populations pick only Virgin Media; service speed is always a factor otherwise we’d still be on ADSL1 lines.

      PS – I was speaking generally with regards to G.fast vectoring, which are still fundamentally similar approaches and so what you learn from one can still benefit the other in ways that may only show themselves during a trial.

    • Avatar Matthew Williams

      Not everyone at moment needs 150MB from Virgin sure most residential people in the world at moment would be perfectly happy with an 100/20 connection. A lot of people live within 300 metres of there local cabinets. Obviously some rural areas don’t maybe the solution for them is a combination of vectoring and fibre to remote node pretty sure nearly everyone lives within in a KM of that.

    • Avatar Phil

      @ Matthew Williams – I agree with you over 152Meg from Virgin Media. As I used to be with VM with 152/12 as I do find it pointless as the world of internet, streaming online and downloading is fine with 80/20 FTTC which I have now with Plusnet. As for 80/20 into 100/20 by BT would be welcome. But, I think many peoples will be happy to settle with 100/20 for now. Why need 152Meg or 200Meg or even 1Gigabit.

    • Avatar Matthew Williams

      @Phil I’ve just recently switched to BT 80/20 from Virgin was on 30/2 before. When I was rang up to cancel they were like why are you leaving we can offer you higher speeds than BT and I asked then what could I do different on 80 download compared to 152 and they couldn’t answer says it all. Actually biggest part I’ve noticed that has been useful for me is the increased upload speed if I remember right Virgin still traffic manage that. Obviously as I’m in a cable area I could always switch back in the future.

    • Meh BT are doing the bare minimum. They deployed ADSL2+ in response to LLU operators doing so.

      The VDSL is not to compete with Virgin Media so much as the UK average on ADSL doesn’t cut it anymore. They’re not going to make any attempts to upgrade VDSL to compete with Virgin Media.

      If they were genuinely interested in competition with Virgin Media they’d be trialing pair bonding and phantom pairs. Relatively low expenditure.

    • Avatar DTMark

      BT *are* interested in “headline” or “up to” speeds.

      Ironically, I suspect this is one of the issues with the uptake of VDSL. Why have “4x faster” when you have up to 20 Meg anyway, who needs 80 Meg, and so on. 20 Meg is fine.

      “So why does You Tube keep on buffering when I have 20 Meg”


    • Avatar No clue

      Looking at the new ASA story it seems even their UPTO speeds are a lie.

  3. Avatar gerarda

    The Eircom profiles indicate that vectoring is not a solution for rural areas as its impact fades out beyond 1KM

    • Avatar Matthew Williams

      True but under BDUK guidelines 1.2KM would be able to get super fast speeds still. Guessing for places that are further than a KM away fibre to the remote node and vectoring together could be a potential solution,

    • Avatar MikeW

      I would have thought that bonding would be a useful addition to the armoury for properties out beyond 1km too.

    • Useful but historically not terribly popular due to the high cost of having to pay for both a second phone line and broadband service. On top of that there’s always an element of diminishing returns in terms of the actual bonding performance.

    • Avatar gerarda

      @MikeW The problem with bonding is that twice or even several times sod all is still sod all. It might work for some lines say 1- 1.5km from the cabinet, but will also presumably take up more cabinet and landline capacity, which has already been an issue round here. Enabling a cabinet in what was a not spot is likely to produce an 80% take up of some sort of DSL, not just 20% VDSL

    • Avatar DTMark

      At which point, unless you’re a very heavy user, the option of simply hanging a 3G or 4G modem out of the window starts to look rather cheaper and more attractive.

      And makes “superfast fibre optic broadband” over BT’s network look rather silly.

  4. Avatar Chris

    and still no comments on ECI cabinets from them.

    Did ispreview feedback in regards to ECI and if yes why havent BT addressed it?

    BT dont seem in any rush to roll this out either, they seem more content to leisurly testing of every single possible configuration and non vectoring technologies before improving the live service. I fear we see some major uopdates in a few years on H cabinets only rolling out a bunch of changes at once instead of staged one change at a time every 6 months or so.

    • We’ll come back to touch on the ECI issues once all of BT’s trials have concluded in the late autumn or winter. Until then it’s better to wait and see what approaches are developed.

  5. Avatar Trevor Harris

    What we all realy need is FTTP. The Government should change the funding to only provide for FTTP. As far as I can see the cost of adding vectoring does not justify the small increase in speed.

    • Avatar FibreFred

      “What we all realy need is FTTP. The Government should change the funding to only provide for FTTP”

      Well that’s one idea, sadly that idea will leave the majority of people high and dry as you’ll burn through the very small pot of money very quickly leaving others with nothing.

  6. Avatar MikeW

    Good to hear that they are including SRA this time, as well as G.INP.

  7. Avatar cyclope

    All this obsesion with headline speeds and technical measures to improve them, what if any of these ie vectoring etc will be of any benefit to your online gamers, in other words are any of the talked about technologies work without adding/increasing latency ? I know SRA can be configured without interleave ,but are BT cabable of doing or willing to provide this ?

    • Avatar Chris

      Vectoring will make interleaving less likely as it will reduce errors on the line, increase snrm etc.

    • Avatar MikeW

      As Chris says, Vectoring removes the noise caused by crosstalk, so reducing errors on the line and making intervention less likely. However, other forms of noise exist, and stay on the line.

      SRA is one tool to avoid errors: it is a slow-reacting response to additional noise on the line, dropping the speed, allowing the SNRM to increase back to 6dB, or vice-versa. Restoring the margin helps reduce errors.

      There also appears to be an SOS/emergency variant of SRA that will help keep a link even in the sudden presence of a large amount of noise.

      G.INP is the alternative to FEC/interleaving for dealing with errors that remain; it works by re-transmitting blocks with errors, where FEC/interleaving uses some of your bandwidth to make errors correctable, and adds latency so the error correction is effective.

      G.INP, as I understand it, has two modes: one that adds a fixed but small amount of latency, and one that adds jitter (presumably when faulty packets get re-transmitted)

      It appears that combining SRA, G.INP and Vectoring is considered to be the best practice. There are more techniques though.

    • Avatar MikeW

      SRA; Seamless Rate Adaption

      SRA is one tool to avoid errors: it is a slow-reacting response to additional noise on the line, dropping the speed, allowing the SNRM to increase back to 6dB, or vice-versa. Restoring the margin helps reduce errors.

      There also appears to be an SOS/emergency variant of SRA that will help keep a link even in the sudden presence of a large amount of noise.


  8. Avatar Darren

    Seems like good news so far, can we replace the if question with when and how? I suppose we could but still wouldn’t get any answers yet. The wait continues.

    Higher upload would be good. 19Mbps is nice but more is needed to open up the usage possibilities.

    • Technically VDSL2 can do symmetric speeds up to 100Mbps and I believe HGC in Hong Kong did try a short line with 100Mbps in this style, although it was very unstable. Many VDSL2 based ISPs have tended to offer slower upstream speeds than we have in the UK, although a few have managed speeds of 30-50Mbps up.

      I suspect an upgrade from 20Mbps to 30Mbps on the upstream might be viable for the UK but only BT will have any idea about this. Most of the trial users we’ve chatted with still appear to be capped at 80/20.

    • Avatar No Clue

      “Most of the trial users we’ve chatted with still appear to be capped at 80/20.”

      That is probably because BT have said multiple times vectoring will only be used as a speed enabler rather than a speed booster have they not?

    • Yes but they also said the first trial would look at the maximum capabilities of Vectored lines (i.e. beyond 80Mbps), although so far we’ve not seen any evidence of this from end-users. On the other hand you can work out from the results what might be possible but still it’s always best to test rather than guess.

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