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

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).

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.