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BT’s Trevor Linney Reveals G.fast Broadband UK Trial Results and Speed

Tuesday, July 5th, 2016 (8:45 am) - Score 5,420

The Head of Access Network Research at BT, Trevor Linney, has revealed some results from the recent trials of its 300-500Mbps capable G.fast broadband technology in Huntingdon, Swansea and Gosforth. Overall 75% of lines were able to deliver more than 300Mbps download (30-50Mbps upload).

All of the three trials took place over a period of around 6-9 months between 2015 and 2016, which included two larger scale trials (around 2,000 premises covered) in England’s Huntingdon (Cambridgeshire) and Gosforth (Newcastle) areas. The third trial in Swansea (Wales) represented a technical trial that only covered a small number of premises around Multiple Dwelling Units (e.g. blocks of flats) and business centres.

Broadly speaking G.fast technology, under BT’s current cabinet dominated approach, works in a roughly similar way to the current ‘up to’ 80Mbps Fibre-to-the-Cabinet (FTTC / VDSL2) service. This means that a fibre optic cable is run to your local Street Cabinet and then the remaining copper run to your home uses G.fast to deliver the service.

However the trials also made use of a more expensive Fibre-to-the-distribution-point (FTTdp) style deployment, where the fibre optic cable is instead run to a smaller node that could be installed inside a big building, underground or on top of a pole. The remaining line would often then go over a much shorter run of existing copper cable to reach your home, which could produce faster speeds.

Most of the PR pictures from the trial showed the FTTdp based deployment, although improvements to the technology mean that BT can now achieve much the same performance by rolling out from Street Cabinets instead (cheaper) and this is the approach that will now dominate.

Sadly Trevor Linney, who was speaking at the recent G.fast Summit 2016 in Paris, doesn’t provide a detailed breakdown of the data so that we can see how each approach fairs. Never the less we do get some useful stats, courtesy of Dave Burstein (G.FAST NEWS) who attended the event.

Copper Line Length Distribution (Trials)
Lines Shorter than 100 Metres = 38.4%
Lines of 100-150 Metres = 35.3%
Lines of 150-200 Metres = 13.7%
Lines of 200-250 Metres = 8%
Lines Longer than 250 Metres = 5%

As anybody with a basic understanding of the technology will already know, longer copper lines mean slower speeds due to signal degradation over distance (interference etc.). G.fast tries to push extra data down the line by using more spectrum (G.fast 106MHz+ vs VDSL 17MHz) and power etc., but this in turn only works best over much shorter distances.

Last year BT showed that it was theoretically able to deliver 300Mbps over a 350 metre copper line using G.fast (here), although the trials indicated that Openreach’s current systems are not yet able to achieve this goal.

Recorded Download Speeds (Trials)
Speeds Greater than 300Mbps = 75%
Speeds of 200-300Mbps = 12%
Speeds of 100-200Mbps = 10%
Speeds Less than 100Mbps = 3%

At this point it becomes even easier to understand why the final G.fast product will initially come in two flavours: 1) ‘up to’ 330Mbps download (50Mbps upload) and, 2) ‘up to’ 160Mbps download (30Mbps upload). Aside from 160Mbps being double the 80Mbps FTTC / VDSL2 maximum of course.

The 160Mbps option should be achievable by the vast majority of people within the service’s initially expected coverage and more improvements are coming, which means that the original 300Mbps at 350Mbps expectation should still become viable. Linney notes the following expected enhancements.

Future G.fast Developments
* Enable higher bits per tone (12>14)
* Improve the receiver sensitivity (<-150dBm/Hz)
* Increase the transmit power (4>8dBm)
* Optimise the frequency usage with VDSL
* Increased vectoring group sizes (>96)

BT currently aims to make G.fast available to 10 million premises by 2020 (roughly 40% of the UK), with “most of the UK” likely to be done by 2025 (this probably equates to around 60% coverage).

The operator did originally suggest that its top download speed could also be upgraded to 500Mbps by 2025, but this aspiration was set when they envisaged a more FTTdp orientated roll-out and only time will tell if they are still able to achieve this (it’s viable on very short and stable runs of copper in the tens of metres, but that seriously limits its coverage).

Now we just need to know how much Openreach will charge ISPs and the new pilot should soon give us a good indication.

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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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19 Responses
  1. Adam says:

    Hope they run this alongside their planned noise cancelling tech, might make lines faster & more stable.

    1. Mark Jackson says:

      You mean Vectoring? That pretty much comes as standard for G.fast, although initially they’ll only be able to vector about half of the 96 maximum ports per cabinet until the technology is upgraded to vector all of them (expected soon).

  2. Steve Jones says:

    My suspicion is that the price premium for g.fast over vdsl2 will have to be very low to gain much market penetration. My reasoning is that there is no compelling need for the great majority of broadband users within g.fast range of an existing cabinet to upgrade as they will, almost by definition, get a reasonably good speed from VDSL2. Undoubtedly there will be some for whom that jump to ultrafast speed is attractive, but will that be anything like enough to justify the investment?

    The thing that I do note is that there is the potential for a lowering of GEA-FTTC wholesale charges as the penetration rate increases. Indeed, Ofcom might well be introducing price controls which force it. What this could do is turn GEA-FTTC into the majority BB technology on the OR network, thereby supplanting much of the ADSL network. This could be accelerated as SOGEA becomes available and some LLU operators seek to save costs by withdrawing MSANs from many local exchanges and provide BB (and voice) in those areas using the GEA-FTTC hosting nodes.

    In this re-drawn market, exchange-based ADSL services will decline considerably and will remain only in the larger exchanges (as a rock-bottom price product) and in other exchanges as BT only product for the remnant of customers unable (or unwilling) to switch to VDSL. VDSL services would be reduced in cost, largely due to a cut in the wholesale costs to the point where the premium over ADSL is small.

    That then leaves g.fast to take over the “premium” segment occupied by the 52/20 service. My feeling is that with BT Retail now having a base level 56/10 service, there is insufficient product differentiation between that and the 76/10 service to justify the price premium, especially as the majority will see lower speeds. I believe that’s where g.fast is headed – at a price comparable to current 76/20 products, or at least for slower speed options (maybe in the region of 160mbps).

    So my prediction for the market

    1) rock-bottom (mostly LLU) ADSL only on the larger exchanges with some BTW ADSL at others for those unable to get VDSL.

    2) a “standard” VDSL2 product from OR/BTW ISPs & LLU ISPs with the latter moving to SOGEA and VOIP gateways. The current GEA-FTTC speed tiers will gradually disappear in the same way ADSL speed tiers did.

    3) a “premium” g.fast product priced more like the current “premium” rate VDSL2 services.

    nb. all this leaves out FttDP, which is difficult to cost-justify at the moment but might re-emerge if it can be done cheaply enough. Possibly in large buildings.

    1. Mark Jackson says:

      I take a roughly similar viewpoint to what you’ve described, although we’ll have to see what Ofcom’s review turns up and whether or not they decide to leave FTTC/VULA pricing alone again.

    2. New_Londoner says:

      All very sensible, although it would be even better to drop ADSL entirely in order to bring forward long reach VDSL (and ideally move VDSL to profile 30a). It would be a simple matter to offer a capped (20Mbps?) VDSL product as the budget offering in place of ADSL.

      Of course the LLU operators would object, however they weren’t exactly keen on VDSL in the first place, not that you know this from their subsequent posturing on such matters to politicians and others!

    3. MikeW says:

      We already have some price pointers from the Infinity 3 and 4 variants available to native FTTP users. I guess those are probably the highest prices that G.Fast will go. The underlying Openreach prices offer a few more combinations, but show the highest premium comes with the highest upstream speeds.

      Profile 30a is unlikely still, as the higher spectrum overlaps G.fast spectrum, and makes the latter less attractive. If BT ever envisaged using it, I’d have thought profile 35b was a better choice nowadays, keeping vectoring compatibility with 17a – necessary with a large pool of legacy modems that cannot support either of the higher spectrum choices.

    4. GNewton says:

      @SteveJones: “Undoubtedly there will be some for whom that jump to ultrafast speed is attractive, but will that be anything like enough to justify the investment? ”

      I have to agree with your concerns that a low take-up might not justify the investment into a widespread G.fast. In view of this, wouldn’t it make more sense to revive a (nearly) nationwide Fibre-on-Demand product, to make it available to those who need it, e.g. small businesses etc?

    5. Mark Jackson says:

      On up-take. The Cabinet based G.fast approach will be comparatively cheap to do and so they can perhaps afford a more casual level of organic growth, at least for now.

    6. karl says:

      “My suspicion is that the price premium for g.fast over vdsl2 will have to be very low to gain much market penetration. My reasoning is that there is no compelling need for the great majority of broadband users within g.fast range of an existing cabinet to upgrade as they will, almost by definition, get a reasonably good speed from VDSL2…”

      I agree with you steve, hopefully they can sell it at a price that is appealing.

  3. lyndon says:

    So, the future looks ‘Rosie’ for VDSL customers who are a few 100m from their Cab.
    The more distant VDSL customers may be receiving…… ‘as good as you’re going to get’ for some time to come apart from some Vectoring improvements…we hope!

    1. GNewton says:

      Basically, yes, it will widen the digital divide, kind of a postcode lottery again.

    2. craski says:

      I’ve never been against copper based broadband improvements but whilst the focus remains on deploying copper based distance dependent solutions there is always going to be a digital divide for those on long lines. They might only be a “last few percent” but that still means millions of people facing a never ending cycle of catch up.

  4. lyndon says:

    Moving from ADSL to VDSL did reduce the effects of that ‘long line’ but the wonders of G.fast may lengthen it again!

    1. craski says:

      Still plenty people round my way on VDSL lines >2km. Mine is about 5.5km from the cabinet.

  5. adslmax Real says:

    The people who already on maximum sync speed for over a year with 79999k/19999k are probably getting a better speed by g.fast service possible 299999k/29999k

    1. adslmax Real says:

      or maybe:



  6. Diane Cummins says:

    meanwhile i will just manage on my 0.15-3Mbs “superfast” line.

  7. Slumbers One says:

    Diane, well said! I have to pay full whack for full blown Infinity fibre to get a stable RURAL connection of 1Mbs. I’m horrified but not surprised that G.fast prioritised for rural users has not had a mention here. All comments cow tow to the usual assumptions…

  8. Rod says:

    If I reword this report from the POV of broadband users that are already suffering slow speeds due to long copper distance to cabinet, the G,fast is only more speed for the super fast and a very poor minimal uplift for those of us 250 meters from a green box.
    This sounds very bad to me. More cake for those choking on cake isn’t a great idea. We need to stop looking at BB in terms of simple profit or we are only re-enacting the folly of Dr Beeching. Radio, as a concept worked well in the mid 1900’s as it really did reach a lot of people, easily 97% with an even handed approach. While Fibre to the property may be expensive, all these little add-ons to fix a % of the problem, doesn’t really do the job. Soon enough Openreach will have spent more fiddling at the edges than just getting on a delivering fibre, starting with the slowest.

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