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Openreach UK Project Targets Speed Boost for G.fast Broadband

Friday, May 31st, 2019 (10:27 am) - Score 9,602
gfast openreach sidepod install

Openreach (BT) is slowly progressing with a future upgrade of their hybrid-fibre G.fast broadband technology, which could enable the service to harness some of the existing radio spectrum frequency being used by VDSL2 based Fibre-to-the-Cabinet (FTTC) lines. Early tests show a possible boost to speed and coverage.

The last time we reported on the possibility of spectrum sharing (refarming) between G.fast and VDSL2 was back in 2017 (here and here), when it was still just a concept. Since then further work has been done and BT have also updated their Access Network Frequency Plan (ANFP) to support it, plus the future 212MHz G.fast profile. Further related guideline changes for Digital Subscriber Line (DSL) transmissions are expected around September 2019.

At present both VDSL2 (uses 17.664MHz of spectrum and delivers speeds of up to 80Mbps) and G.fast (uses 19-106MHz for speeds of up to 330Mbps) keep their spectrum separate so as to avoid interference and also because they use two different forms of half / full duplexing (i.e. the transmission of data in two directions, either asymmetrically or symmetrically): VDSL2 uses Frequency Division Duplex (FDD) and G.fast harnesses Time Division Duplex (TDD).

Getting both technologies to co-exist in overlapping spectrum frequencies down to 2.2MHz is extremely difficult, particularly due to the risk of worse performance on existing VDSL2 lines (highly undesirable). However, if it were possible, then G.fast technologies could benefit from a fair improvement to speed and coverage (note: vectoring may be needed on VDSL2 and for technical / regulatory / cost reasons that’s not widely deployed).

vdsl gfast overlapping spectrum

One recent report on the work appears to suggest that it might just be possible for Openreach to achieve an “ultrafast broadband” speed of 100Mbps at 450-500 metres (copper line length) from the PCP street cabinet (G.fast extension pod) or remote node, which in the current deployment is NOT possible (speeds tend to fall below 100Mbps after around 300 metres).

However the potential gain to G.fast would only be up to 10Mbps if all they chose to do was reduce the technology’s start point from 19MHz to nearly 17.7MHz (i.e. trying to avoid any overlap with VDSL), which means to get the best boost they’d still need to overlap and that’s what this work is all about.

The work has been led by BT’s Kevin Foster, DSL Task Group Chairman, and receives input from UK ISPs including BT, TalkTalk, Vodafone and Sky Broadband. Meanwhile Ofcom, ASSIA, ECI, Huawei, Intel, Nokia and Sckipio have also given feedback to the team during their research.

The NICC recently published a public summary of Kevin’s work so far (here) and a technical report on the concept (here), which found three options (3, 4 and 5 below) that “offered attractive G.fast performance increases with varying complexities” (some of which do hurt VDSL performance).

NOTE: Frequencies below 2.2MHz are out of scope for this proposal (G.fast doesn’t use it).

Options Considered
1. No change to existing ANFP.
2. Static overlapping (REJECTED).
3. Re-farming; static re-assignment of high frequencies from VDSL to G.fast.

Re-farming can scale from limited impact to large impact on VDSL with corresponding increases on G.fast speeds. The service coverage of existing un-vectored VDSL DSLAM may be maintained by vectoring the VDSL at the same time as enabling re-farming. It isn’t practical to define a single version of re-farming in the ANFP because the trade-offs will be heavily affected by DSL performance, product and services offerings and consensus between the DSLAM operator(s) and relevant Communications Providers (CPs).

Re-farming has the potential to provide significant improvements in G.fast rates and could be enabled within the ANFP subject to consensus between DSLAM operator(s) and relevant CPs. Re-farming could be combined with a Dynamic Spectrum Management (DSM) based control approach.

4. Variable split frequency (semi static); allow G.fast to use high frequencies on long loops unused by VDSL.

In co-located cases there is no gain for G.fast from the variable split frequency per DSLAM option, beyond that from reducing the start frequency to 17.7MHz. In non-co-located cases there is gain where Y is greater than about 700m, this gain is up to 113Mb/s. The option as presented requires knowledge of the loss between the G.fast and VDSL DSLAM, CGAL, and may require knowledge of whether the VDSL is vectored or not. A process would be required to manage recording and distribution of loss between DSLAMs and VDSL vectoring state.

5. Variable split frequency per line (dynamic).

DSM can offer improvements to downstream G.fast around 80 Mbps in co-located cases, and up to 164 Mbps in non-co-located cases relative to the current ANFP. DSM by its nature has considerable flexibility, but is not amenable to being defined by simple rules. A spectrum management centre would be required with interfaces to collect data from and configure DSLAMs.

The aforementioned technical report includes a wealth of simulations on the potential performance benefits of all this and the work is now continuing to develop a technical solution, which could form part of a future trial. So far Openreach has only run a very brief and limited Proof of Concept (PoC) test with 300 lines in All Hallows (Kent) via two street cabinets, which helped to inform the aforementioned report.

As usual any report that uses simulated modelling should be taken with a pinch of salt, not least because the real-world environment often has additional complications to consider (e.g. poor home wiring), which means that performance for some lines may be worse than the models.

In any case we’re probably still some way off from seeing a viable solution in the wild, assuming they can make one that works and delivers a strong improvement without harming VDSL2 lines. Admittedly all of this is somewhat of a sideshow to the now dominant focus on rolling out FTTP across the UK, with G.fast taking a diminished back seat position.

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Mark Jackson
By Mark Jackson
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on Twitter, , Facebook and Linkedin.
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54 Responses
  1. Avatar adslmax

    G.fast got no chance for more than 300m! Mine is approx 250m away and estimate for G.fast in amber are Clean A 184/12 out of 330/50. Zen Internet say I am better off staying with VDSL 80/20 instead of G.fast as the line are too far away from the pcp cabinet could end up getting less upload speed than VDSL2.

  2. Avatar adslmax

    Future 212MHz G.fast profile would be pointless because again you have to live much closer to G.fast pcp cabinet. No good for anything more than 250m away.

    • The 212MHz profile is separate to this article, but obviously if you’re one of the few million premises that do live within around 100 metres of your local PCP cabinet then there’s a benefit (assuming Openreach ever adopt it). But as I say, that’s not at all relevant to this story.

  3. Avatar Mike

    I wonder what distance/speed graph would look like if all the spectrum was G.Fast only…

    • Avatar Joe

      The low freq used by adsl propagates best over distances so it would have a significant impact if you had just G.Fast on a line and could use those.

    • Avatar adslmax

      Not much the difference as long you live within 150m for G.fast, anything more that – forget it.

    • Avatar JustLittleMeAndMy

      Max, do you have any personal experience with g.fast? I only ask as you always seem to post very negative comments in relation to g.fast and wondered if you have had the service or just that you want to troll every single article regarding the technology.

  4. Avatar bob

    wouldnt it be better to halt g.fast rollout and instead enable 30 or 35 vdsl2 profile and give everyone a speed boost?

    • The cost and technical challenges of upgrading the network and then downgrading G.fast to compensate wouldn’t be worth it now that FTTP is the focus. Not going to happen.

    • Avatar Joe

      You’d get more gain from turning off everything but g.fast (when it exists) and maxing that out with increased distance and let fttp or 4/5g catch anything that fails on that.

    • Avatar A_Builder

      I am not sure I agree with @MJ that the technical side of a 17 -> 35 upgrade is that hard.

      Firstly 35 is backward compatible with 17.

      Secondly the upgrade is linecards in the main so very cheap and very quick to do.

      Thirdly there are distinct usefulness profiles for 35 or GFast. The usefulness profiles essentially are generated by the distribution of the line lengths.

      -35 can be used on estate where the lines are longer: some are about 350m and others are very short. In this kind of case 35 will give the best throughput for most people.
      – Gfast has a usefulness case where the distribution profile is skewed to a lot of lines that are around 150m in length: such PCP’s do exist.

      I agree with @MJ that where the GFast pod is in place then it is highly unlikely that 35 profile VDSL will ever appear it is too much bother.

      However, where there is no Gfast and the lines fit the distribution for 35 to shine then it should a good interim and v cheap solution until FTTP comes along.

    • Avatar CarlT

      35 requires vectoring doesn’t it, guys?

      That’s going to be a problem for ECI.

    • Avatar A_Builder

      @CarlT

      Sure 35 and ECI are not happy together.

      But that is a small subset.

      All the HUAWEI cabs can be modded – they are the vast majority.

    • Avatar A_Builder

      But more the point is that BT/OR have to do something fast as VM are on the 350->500->1G path and they cover 50% of UK addresses so 80/20 doesn’t look too clever.

      Granted very few domestic users need 1G IRL but over 80Mb/s is a growing usage class with 4K everywhere.

      I suppose my point on 35 is that it is less resource intensive, people & money than Gfast as you don’t need new physical infrastructure pods etc. And it can be rolled out by either subbies (as I think DSLAM maintenance already is?) or by quite a small team working their way through locations.

  5. Avatar Gary

    I’m All for Joes suggestion, Get all us sad sacks off adsl and onto FTTP and you can do what you want with the copper 🙂

    • Avatar Joe

      Were they to do what I say many would have to go to fttp via some time on 4/5G but in the end copper is dead so its a just a useful way of speeding/pushing deeper deployments.

  6. Avatar Graham Brooks

    I’am gamer and occasional Streamer, when my Internet let’s me,, I run average 53 Download and 18.24 UpLoad, which is poor, to say this is Superfast? according to my provider. My question is will your SuperFast up Grade becoming to the North Devon Area anytime soon, has we are classed as a Rual Area, I noticed Cornwall is being Up Grade . Thank You.

    • Avatar Joe

      FTTC speeds. Unless you are close to the cab (<300m) you prob won't see much else until fttp arrives hard to know that. Wheres the nearest fttp in your area

  7. Avatar Sarah

    This is great that it’s being upgraded – and someone said this was thanks to Virgin – but we have Virgin and can get up to 500 – but BT don’t seem to have bothered to put g.fast in our cab – so they probably won’t?

    • Avatar Joe

      That they haven’t done G.fast is no guide to future plans. G.fast is often a guide they aren’t doing fttp soon.

  8. Avatar Oache4u

    Many countries invested in fibre ..uk still invest in upgrading copper lines and bumping the prices every year ..only we the users complain but BT keep saying we dont need faster speeds as is enough to have 80/20

    • Avatar HarmzN

      I don’t understand how you can browse this website and read the articles here, and yet think this.

      Openreach are investing billions into fibre, cityfibre also investing billions, and their are many other altnets in the country that are investing heavily too.

      Openreach being the major infrastructure provider, are investing the most, but where do you think all that moneys going to come from? Price increases exist for pretty much every utility, it’s a fact of life, and it’s going to help pay for FTTP. Yes, you may have paid less for the internet 10years ago, but you got less speed too. If you look at you cost/Mbps over time, your internet is definitely getting cheaper.

      This article clearly states, that this is some background research into improving speeds for copper, and it’s obviously taking a back seat compared to FTTP. I don’t know why people are complaining about this. I know everyone wants FTTP, and not gfast or faster VDSL, but the rollout can only go so far, there’s only so many engineers and civil workers. This guy is doing research to improve copper lines so that MAYBE you can at least get a speed boost while you wait for FTTP to get to you. I’m sure you would be greatful for a speed boost in a couple of years if your FTTP deployment date was still 10 years away. It’s not something to complain about, if this researcher wasn’t doing it, he wasn’t going to be digging up pavements instead, the research isn’t slowing down FTTP deployment, so why hate? It’s a good thing!

    • @ HarmzN. +1 for logical pragmatic reply.

  9. Avatar useless

    My FTTC runs at about 70Mb. The cabinet for that along with the older cabinet and the new G.Fast pod is all about 300-350M actual distance from my house, yet i can not have G.Fast 🙁

    Using BTs (openreach and retail) various checkers and entering my and others details (with their permission) via Zens checker (my current ISP) it appears in my street of 128 properties only about 5 of them at about the mid point in that numbering range can actually have G.Fast. For every other house it does not even give you an estimate for it.

    G.Fast is an utter waste of time, luckily my road has Virgin media so thats where i will be getting my 100Mb+ fix later this summer, a shame as Zen are a superb ISP. Too bad they are dependant on the penny pincher BT Group for products though.

    • Avatar Fastman

      suggest you ask you CP to invest millions to build you a network for you

      or could as ZEN for a bespoke FTTP for you

      love to see their reply on that one

    • Avatar JmJohnson

      I used to think Zen were superb… then I read there SLA for leased lines.
      Standard traffic is contended 1:5 so your bandwidth has to drop below 20% before they consider it an issue.
      BT and Daisy on the other hand… superb SLAs… guaranteeing latency to the pop as well as bandwidth… hell, BT even guarantee latency to the US.

    • Avatar useless

      “suggest you ask you CP to invest millions to build you a network for you”

      BT have already done that and failed in delivering any consistent product. They were late delivering FTTC to this area and now the G.Fast cab only serves a couple of properties in the road, they are truly pathetic. NO idea what the other shill is on about with his lease line sales spiel. I just feel lucky i have another provider that i can go to for actual ultrafast services and do not have to rely on BT and the poor ISPs whos hands are shackled selling their rubbish.

    • Avatar JmJohnson

      If you read it in context of your responses… you were blaming Openreach for the service ISPs like Zen can supply.
      My response was that Zen’s SLA is below what other ISPs provide… ergo the blame isn’t all Openreachs and that’s why my opinion of Zen has decreased.
      It’s general practice that if one states that they disagree that they then provide a reason as to why.

    • Avatar useless

      Quite what “leased line” SLA has to do with anything apart from you plugging the horrid BT is anyones guess.

    • Avatar Fastman

      useless

      I did not mention SLA’s

      I mentioned you could ask you service provide for a bespoke FTTP service

      as an aside you can buy a leased line from any number of provider

      the only person who mentioned BT was you

    • Avatar JmJohnson

      If you care to read my initial comment then you’ll see I mentioned BT and Daisy.
      The reason why I mentioned BT and Daisy ? Because the 3 ISPs I have experience of in a business environment are BT, Daisy and Zen.
      You claimed BT were penny pinchers… whereas when you have 3 ISP’s offering the same service except Zen apply contention to theirs (costing the same as BTs) then it’s fairly obvious that the reverse is true.
      Anyways… I’m done with this debate… it’s apparent that you’re one of “those” people.

    • Avatar useless

      @Fastman
      I never did say you mentioned anything about SLAs. It was JmJohnson that brought them up. I’ve also not mentioned anywhere about FTTP or wanting that instead. The “CP” which is what you originally replied with of Zens products is BT Group. As if it were not clear already i have no interest in a lease line from anyone. As mentioned ill be getting my 100+Mb speeds from VM for a small fraction of what a lease line would cost.

      @JmJohnson
      According to BTs Business pages their lines are contended also although they no longer quote the figure. But they do clearly say it is not a ‘1:1 contention’. Not that it matters i have no interest in spending hundreds or thousands on some silly BT line when i can get faster than what i currently have from elsewhere for less as mentioned already. Though im sure you will be appreciated somewhere for your attempt to drum up business for BT.

  10. Avatar Phil

    The article doesn’t say anything about the upload speeds improving, so you might get 100Mbps a little further out in the downward direction but what’s the upload speed achieving?

    It also sounds like those very close to the cabinet get a small speed increase at the edges of what is acceptable for G.Fast and everyone else on VDSL starts going slower from extra interference.

    Presumably any G.Fast pod with an ECI as an older brother is ruled out due as per usual.

    Stop the G.Farse and just concentrate on FTTP rollout please BT.

  11. Avatar Opti

    So fany, spent money on 90th technology… Someone, who put normal optic cable, smash all old fashion communications mammoths in this country. Just annoying to read about DSL in 2019.

  12. Avatar Andrew Harrold

    Not much use in improving my meagre 0.5mbps download on copper wire. Still waiting on Openreach to advise on cost of privately installing a fibre connection, or other new tech that will benefit me ☹️

    • Avatar Gary

      DO you have an idea where your closest aggregation node is ? And are you on aa sparsely housed route or multiple properties clustered. It’ll have a big impact on the price for fttpod or any self assist type scheme.

    • Avatar Joe

      Just wait for USO. Unless you want to get fttpod and pay through the nose

    • Avatar Fastman

      who says that UO will get you FTTP — It says you can request a 10 mbps it does not says how that is delivered (or what the cost will be if its over a set figure — because there will be one)

      just out of interest what cost are you waiting for and where

    • Avatar Joe

      @fast: read the comment he said “or other new tech that will benefit me”. USO will clearly up his speed and will be more than covered by ‘other new tech’! Maybe fttp maybe 4/5g or something else.

    • Avatar Fastman

      don’t make any assumption that USO will be FTTP

  13. Avatar Sean

    My dad and my mum no longer unwanted to BT anymore another Virgin Media SuperHub 3 WI-FI Broadband Internet connection is better just fine.

  14. Avatar Peterson Bertalinon

    Give upload speed same as download if you charge so much for shitty internet connection. BT. It’s like having incomplete package.

    • Avatar GNewton

      You’d have to go with an Altnet provider then, BT won’t do symmetric fibre broadband.

    • Avatar Phil

      Getting a symmetrical (same speed up and down) connection doesn’t happen due to the technologies involved. ADSL/VDSL are shackled largely by physics of the line and so upstream is slower. G.Fast can be symmetrical, but speeding up the upload speed on G.Fast decreases the download speed.

      Virgin (DOCSIS) and GPON FTTP as used by BT also have slower upload speeds due to how they work. In some cases upload speeds on these technologies are slower than they need to be but I think this just to keep an even ratio on all their products and not compete with their own business offerings.

    • Avatar craski

      “ADSL/VDSL are shackled largely by physics of the line and so upstream is slower”

      @Phil
      This isnt correct. The ITU standards define the frequency bands used for upstream/downstream so it isnt “physics of the line”. There are symmetric DSL ITU standards.

  15. Avatar Peterson Bertalinon

    DIAL UP BOOSTED COPPER$ CABLES comes with the price nowadays :D.

  16. Avatar Adam

    Meanwhile in my town where they installed G.fast pods almost 2 years ago, they still haven’t put a single on live. At least they finally seem to have put the ones in the neighbouring village up. (According to https://labs.thinkbroadband.com/local/broadband-map#/gfast/)

  17. Avatar George

    In terms of internet we are a 3rd level country charging the prices of the top speed ones

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