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UPD BT Openreach Extends UK Reach of 20Mbps ADSL2 Broadband Services

Sunday, October 5th, 2014 (5:28 pm) by Mark Jackson (Score 2,955)
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A recently updated specification document for BT’s ‘up to’ 80Mbps capable Fibre-to-the-Cabinet (FTTC) service (SIN 498) has included mention of a new Street Cabinet based ADSL2+ broadband service, which would be “used to provide extended reach beyond what is possible with VDSL2“.

The standard copper line ADSL2+ service, which continues to dominate most of the current home broadband market, typically offers maximum download speeds of up to 20-24Mbps. In a normal setup this product will effectively be delivered from your local telephone exchange (usually over distances of up to around 6.5km), while the new Street Cabinet based ADSL2+ would obviously imply delivery direct from the cabinet instead of an exchange.

SIN 498 Statement

GEA over ADSL2plus employs Ethernet over ATM mode (XoEoA, where β€˜X’ is PPP or IP) over cabinet based ADSL2plus. Cabinet based ADSL2plus is used to provide extended reach beyond what is possible with VDSL2. The Ethernet layer functionality and requirements do not differ from what is offered and supported on standard GEA-FTTC.

Cabinets are closer to the home and, in an FTTC setup, benefit from being supplied via a fibre optic link back to the primary telephone exchange. But as ever there appears to be some trade off with performance andΒ Thinkbroadband predict that the service would offer a maximum download speed of 12Mbps (1.4 Mbps upload). Given the limits of FTTC we’d expect that it would be best placed to benefit those who live more than 2km from their cabinet (i.e. roughly where FTTC lines hit the point of no return for viable performance).

Hopefully Openreach wouldn’t want to confuse existing market prices too much and will work to make the costs for this service as closely matched with a normal ADSL2+ line as possible, which would also allow ISPs to offer it in the same way as they do for a standard ADSL2+ product and without meddling with FTTC. Never the less it’s likely that the market for this service will be fairly small, focusing on the extreme outlying areas of a cabinets coverage.

We hope to have more info. soon and will update when Openreach responds.

UPDATE 9th Dec 2014:

We have repeatedly tried to get more information out of Openreach about this technology, yet so far they have nothing further to say beyond what has already been reported above.

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25 Responses
  1. MikeW

    Certainly be interesting to see where this fits into the market.

    • gerarda

      Even without a market case BT have to provide a USC solution for the some of the BDUK contracts within the next few months and this will cut down on the number for which they will have to seek more innovative solutions

  2. X66yh

    They will want to limit it to 12Mbps download as otherwise people might well choose cheaper ADSL2+ from the cab instead of paying a lot more for something they don’t yet need – FTTC.
    So by doing this rate limiting they don’t screw over the market for FTTC

    • Steve Jones

      I just love conspiracy theorists. The technical reason why the download will be limited is simply to co-exist with exchange-based ADSL. That means applying a restrictive power mask to the lower frequencies, which will be the only ones usable by the time you get to more distant cabinets (as the higher frequencies will have been severely attenuated so as to be useless for ADSL so can be effectively “re-used”). I probably means that this will not be usable on cabinets close to exchanges, which that long lines connected to such cabinets will not gain.

      Of course, what would make this technically much better is for all lines running via an enabled cabinet to be serviced from that cabinet using a suitable “long-reach” VDSL frequency plan (and some capped services to match ADSL pricing). However, that would mean disabling full LLU on such lines, so that’s never going to happen, even though it’s a much better way of using the network.

  3. DanielM

    From taking a look those DSLAMS they use for FTTC can already serve ADSL2+ (just not enabled)

  4. Patrick Cosgrove

    Is this how the 2Mb guarantee will be met for most users? If so, as a rural user, I’ll be quite happy with 12 Mb download and 1. 4Mb upload. How many really need Superfast? The majority of rural users (maybe the majority of all users) just need faster than what they’ve got now and more reliable. That will obviously change in the future, but right now people trying to run farms and other businesses on 0.25 Mb would be extremely happy with this.

  5. Tim

    I can see how that will work for lines on cabinets that are 3km+ from the exchange then another 2~3km d-side to the customer. However if the cabinet is near the exchange, say only 500 meters from it and then the customer is 2~3km from the cabinet is this going to work? Wouldn’t ADSL2+ from the cabinet be dialled back so much that it wouldn’t be better than from the exchange?

    Well that scenario is where my mums line sits. What makes it worse is there is a nearer cabinet which is 800 meters away and next door is connected to it. Will BT ever consider rewiring which cabinet her house (and 59 neighbours) connect to? Or perhaps she should hope for FTTP or FTTPdp (which would be better in the long term).

    • MikeW

      Yes, it almost certainly requires cabinets to be at least 2km from the exchange – otherwise the power cutback will get in the way.

      Unless, of course, they can get rid of the power reduction … but that will require all DSL connections to be made at the cabinet instead of the exchange. The ANFP would need updating, which wouldn’t be hard, and the right to LLU would need to be rescinded in favour of VULA, which might be less palatable. However, for small rural exchanges with little prospect of full LLU, it might be a reasonable choice – a matter for the regulator, I guess.

      For your mum, & neighbours, the likes of FTTrn might be a solution. BT have mentioned the possibility of doing copper re-alignment, but I’ve only heard of it properly mentioned in the Warwickshire BDUK project.

  6. Tim

    Thinking about this a little more… It would make sense if this new product became a new up-to 20/5Mbps VDSL service; VDSL for 12-20Mbps and dropping down to ADSL2+ for <12Mbps on long lines. This would kill two issues with one product, so long as it is cheaper than the 40Mbps FTTC product.

    I think for my mum's line it would be simple to pull some copper back from the other/nearer cabinet as they have already done the work unblocking the ducts to get the fibre past. I guess the problem will be those still wanting ADSL will not want moving to the cabinet which is a lot further away from the exchange. I expect BT don't like to mix wires from different cabinets. So FTTrn may be BT's preferred approach, which I suspect is very unlikely to happen. The exchange is down for FTTC AND FTTP, so she could actually see FTTP installed. However I suspect FTTP will be used for exchange-only lines, which 1/3 of the village appears to be.

  7. adslmax

    ADSL2+ on FTTC 12Meg with 1.4Meg is limit by BT is conned. Should let it full 24/2.5 instead. BT doesn’t want to do it because BT expect peoples to sign up FTTC 40/10 or 80/20 instead!

    I used to be with ADSL2+ before. getting 15Meg down and 1Meg up. Unbelieved that BT limit 12/1.5 now.

    • In this case there appear to be some very real technical restrictions. Separately you can’t do 2.4Mbps upload on ADSL2+ without using Annex M and sacrificing some download performance.

    • MikeW

      Hmmm. Annex M works by re-deploying some of the downstream bandwidth into upstream for that one particular line, doesn’t it?

      In which case that line is likely to suffer from NEXT crosstalk over that portion of the bandplan, quite possibly making it worthless.

      Even without the technical restrictions, the fact that it is aimed at lines over 2km means you wouldn’t get much faster than the 12Mbps anyway.

    • Steve Jones

      Whilst this may be aimed at lines more than 2km from the cabinet, there’s no reason why it wouldn’t work on shorter lines so (in theory) could support higher speeds. However, I suspect that the necessary power masking (to protect the lower frequencies used by exchange-based DSL services) will limit the reach of cabinet-based ADSL. Unless there was a radical review (like sacrificing exchange-based ADSL for lines going via an enabled cabinet), the full potential of this technology will not be exploited. Thus a line 4km from a cabinet will not get anything like the same speed as one 4km from an exchange.

    • @steve Jones For long lines in rural or in town centres the need to switch all customers on to a common means of delivery to optimise performance for all ought to feature in BDUK sponsored activity.

      The decision making and survey work all paid for by the public purse should be made transparent. Most of elo and very rural exchanges have no LLU so it should be possible to plan this in the BDUK activity.

    • Steve Jones

      It should certainly be feasible for market 1 exchanges, but it will be up to Ofcom as to do so would essentially rule out LLU and ISPs are still adding exchanges, albeit at an ever slower rate.

  8. robert scriven

    id be tempted to go for this if it meant i could get the damn interleaving turned off πŸ™‚

    • adslmax

      U won’t get it turned off or tweak SNR because FTTC cabinet is blocked it on the DSLAM. DLM will be hardest hit for all FTTC and ADSL2+ on the FTTC cabinet where all isp’s have no control over it, only the Openreach engineer.

  9. david

    if you can get upto 24megs then what the hell would people want fftc if you can only get 24mbps as what im getting with All Talk VDSL Rubbbish

  10. robert scriven

    i get 15mb on fttc and 760k upload, if i got 1.4 upload on adsl2 and this was cheaper, im all for it, cant see them putting it in every green cab though, or is it going in every cab?

    • Steve Jones

      It’s quite likely that the line-cards installed will be able to support VDSL & ADSL. They are, after all, closely related technologies and all the modulation/demodulation is performed by DSP (digital signal processing), which is driven by configuration data.

  11. Michael

    The original ITU work on defining VDSL2 roll-out architectures many years ago had ADSL2+ Cabinet delivery in the definitions. The idea was that you could cause a VDSL2 line card in the cabinet to behave in ADSL2+ mode, rather than have to embed discrete ADSL2+ cards into the cabinet. It will depend on how Huawei and ECI have engineered their solutions as to whether it is embedded in every cabinet already as a software defined option, or requires new hardware. Similar to the decision about vectoring capability in a cabinet.

  12. adslmax

    Pointless to have ADSL2+ on the FTTC cabinet. As you cannot ask the isp to turn off interleaving. U cannot tweak SNR. DLM will be hardest hit and isp’s have no control over it. It’s best to leave ADSL2+ at the PCP cabinet not FTTC cabinet. Biggest mistake move by BT.

    PCP cabinet ADSL2+ up to 24/1.4/2.5 can turn off interleaving, can tweak snr.

    FTTC cabinet ADSL2+ up to 12/1.4 cannot turn off interleaving, cannot tweak snr.

  13. adslmax

    FTTC cabinet ADSL2+ up to 12/1.4 cannot turn off interleaving, cannot tweak snr and crosstalk will be involved!

  14. dave

    I wish they would just launch a 20Mbps download 3Mbps upload FTTC broadband for slightly more than the cost of adsl2+ that way we could all get good speed at a low price.

  15. Michael.

    Update .
    As of February 24 my isp can not find any info about this product πŸ™
    I have a long 4.5kl rural line and this would do for me if I could get the product at a good price.

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