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UPD Alcatel-Lucent on G.Fast and Vectoring 2 for Future 1Gbps FTTC Broadband

Posted Tuesday, July 9th, 2013 (10:20 am) by Mark Jackson (Score 3,599)
bt openreach fibre optic cable install

Alcatel-Lucent has posted some tantalising details from its recent trial of future G.Fast and prototype Vectoring 2.0 technology at Telekom Austria, which could one day push today’s up to 80Mbps capable FTTC (VDSL2) broadband ISP lines to deliver speeds of up to 1100Mbps (1.1Gbps).

As most people already know, BT’s dominant Fibre-to-the-Cabinet (FTTC) product offers internet download speeds of up to 80Mbps (Megabits per second) by using a mix of fibre optic cable from the telephone exchange to your local street cabinet, followed by a “last mile” run over existing copper lines and into homes (aka – Hybrid-Fibre).

Unfortunately that “last mile” copper often acts as a bottleneck to performance because it is more susceptible to interference and the signal gradually degrades the further you are away from your nearest street cabinet (especially with a lot of users on the line). One way to tackle this and thus deliver better speeds to more people is by cancelling out the crosstalk interference via Vectoring technology (this works a bit like the noise cancellation technology in some headphones).

BT will later this month begin early UK trials of Vectoring technology (full details) but to really deliver better speeds we need to be looking towards the next generation of FTTC technology called G.Fast, which in theory could one day deliver 1Gbps uplink and downlink speeds but only within 100-250 meters of your street cabinet. This will also require an updated version of Vectoring (i.e. 2.0).

Now Alcatel-Lucent has written about some of their on-going trials of G.Fast and the latest so-called Vectoring 2.0 technology in Austria, which has produced some interesting data about the technology’s expected costs and real-world performance. The tests of G.fast on a “good quality [copper] cable” achieved aggregate speeds of 1.1Gbps over a single pair of 70 metre lines and 800Mbps over a single pair of 100m lines.

Hans Pichler, CTO of Telekom Austria, said:

Telekom Austria Group´s A1 was an early adopter of Alcatel-Lucent’s VDSL2 vectoring because we understand the value of upgrading our existing copper infrastructure to give our customers the best possible broadband service. We are pleased to be working with Alcatel-Lucent at the cutting-edge of fixed broadband technology to look at the possibilities of G.fast vectoring.”

Alcatel-Lucent G.Fast and Vectoring 2.0 Trial Summary

* On older unshielded cables, typical of most in-building cabling in Austria, the trial achieved speeds of 500Mbps over 100 meters on a single line. However, when a second line was introduced, creating crosstalk between the two, the G.fast speed fell to only 60Mbps.

* Vectoring was then enabled, removing the crosstalk and bringing the speed back up to 500Mbps over 100m. This is a huge improvement over widely deployed DSL networks, which typically offer speeds of 5-30Mbps, or VDSL2 vectoring networks supporting up to 100Mbps. Fibre-to-the-Home services typically range from 100Mbps to 1Gbps.

The BLUE LINE below indicates the performance when a single line is active in the cable. Once additional G.fast lines are activated in the cable, performance drops significantly (RED LINE). The blue and red lines are benchmarks by which all vectoring performance is measured. Activating G.fast vectoring causes a significant increase in performance (GREEN LINE).

gfast and vectoring 2.0 fttc vdsl2 speeds

It should be said that G.fast is not yet standardised and won’t be commercially available for “several years“. At BT G.Fast is currently confined to their labs for extensive testing and some fear that upgrading the United Kingdom’s national telecoms infrastructure to support it would be a tricky and a potentially quite costly effort.

But at the same time BT and other telecoms providers will likely view it as still being significantly cheaper and faster to deploy than the huge cost incurred by civil works (e.g. digging up roads), which would be needed to roll-out a true fibre optic (FTTH/P) service to every home and business in the country.

On the other hand even G.Fast and Vectoring 2.0 will still struggle to help those whom live furthest away from their local street cabinet. But this could be where Fibre-to-the-Distribution-Point (FTTDP) comes in, which brings the fibre closer to homes but still uses the existing copper wire for the “final few meters“. This solution is viewed as being “more cost effective than deploying fibre all the way to the premise” (Ofcom) and could be used with G.Fast.

Ofcom are currently encouraging BT to trial FTTDP within the on-going period of their market reviews (these are all due to be published next spring 2014). It will be interesting to see if that gives BT enough time to do it.

UPDATE 10th June 2013

Added a little snipped about FTTDP technology above.

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8 Responses
  1. DTMark

    Forget the lab tests over 100m of good quality copper.

    Let’s have some real-world tests from say ten randomly selected ancient GPO circuits each of 400m, 800m and 1200m and see how the results look.

    I suspect they would be nowhere near as eye-catching, that the performance would be all over the place and firm conclusions would be hard to draw.

    But then the data wouldn’t look like an advert for Alcatel-Lucent.

    • Kevin

      Already covered, read from:
      Alcatel-Lucent G.Fast and Vectoring 2.0 Trial Summary

    • DTMark

      If I’m reading that graph right, it appears that this technology has no benefits at all when the line length is circa 350m or longer.

      So if this is touted as a real alternative to fibre, lets see the maths: what’s the cost of putting one of those fibre cabinets within say 200m of every single property in this country (c. 350m line length)?

    • MikeW

      Exactly. G.fast is definitely technology for around 200-300 metres, with active electronics pushed deeper into the network. Swiss Telecom call this FTTS (S=Street), but the usual label seen alongside G.Fast is FTTdp.

      The whole architecture depends on being able to build the FTTdp nodes cheaply, with low install cost features such as the reverse power (ie no mains power supply needed; power is fed from the individual end-user modems).

    • Added a little snippet about FTTdp above as it’s well designed to tie in alongside G.Fast. Bit early to know what the future holds but I expect to see both.

  2. telecom engineer

    Well bt have said fttc is a 20year investment, by that time they should have the tech for 1gig at 600m. If not there really is no point in 100m runs aside from mdu. With bt now deploying fibre overhead a dp mounted dslam is pointless on a large scale as dp to eu drops overhead would cost only 60quid labour max with no civils ontop of what a dslam would be, infact less as no power required. So thats 60% of the network covered, take the hit for new duct on fttp for the rest isnt such a poor return ic you scrap the copper with a gradual rollout.
    I love working on copper etc but unless the tech is deployed from the cab anything on a large scale starts to look less attractive than gpon. Dont forget even buried sites are constantly being patched as lengths box to box buried get replaced with duct. One thing for sure there will be a lot more duct in the ground when current dslams are due for retirement, even more attractive and economical if bt decide to erect poles on buried sites to avoid the high cost and disturbance of digging drives up to each eu.

    • MikeW

      I’ve seen it said that 80% of the cost of rolling out fibre is in the last 200 metres. If that is true, FTTdp and G.fast have potential… especially if the “reverse power” option proves workable.

      On the other hand, a couple of decades to gradually duct everywhere, and make a viable transition from today’s (FTTC+Expensive-FoD) into (FTTC+cheap-FTTP), and it might turn out to be unnecessary.

      Hard to say which way it will go, as it will depends so much on the numbers.

  3. Clive

    Pointless for anyone 350m from the cabinet.

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