BT and Alcatel-Lucent Hit 5600Mbps Broadband Using XG-FAST Tech

Forget BT’s plan to deploy “ultrafast” 300-500Mbps capable G.fast broadband technology to 10 million UK premises by 2020 (here). Today the operator has joined with Alcatel-Lucent to test future XG.FAST (G.fast2) technology, which under lab conditions has just pushed aggregate speeds of 5.6Gbps over 35 metres of copper cable.

The figure represents a “record for full-duplex data transmission over a standard single BT line at this distance” and the technology also performed quite well over longer distances, with aggregate speeds of 1.8Gbps being achieved over 100 metres (BT claims that most UK homes are within this distance of their local distribution point, be that a pole, street cabinet or footway box).

Mind you the technology itself, which is still some-way off becoming a commercialised solution like G.fast, is nothing new to ISPreview.co.uk regulars as we first reported on it over a year ago during the very early alpha testing and prototype stages (here).

Mike Galvin, MD of BT’s NGA Technology Service Division said:

“These are exciting results. We know that G.fast will transform the UK’s broadband landscape but these results also give us confidence the technology has significant headroom should we need it in the future.

The UK already boasts the biggest fibre footprint among major European nations, as well as the highest take up, but it is vital we continue to invest. That is why we have announced plans to get ultrafast broadband to ten million premises by the end of 2020 and to most of the UK by 2025. G.fast is the ideal technology as it can be deployed at scale and speed, allowing as many people to benefit a soon as possible.

Fibre to the premises technology has a role to play – and Openreach has the largest such network in the UK – but G.fast is the answer if the UK is to have widespread and affordable ultrafast broadband sooner rather than later. Those who argue otherwise aren’t being realistic and should look at Australia where the authorities have changed tack on their fibre deployment and followed our example.”

In order to understand XG.FAST you first need to be familiar with G.fast, as the two have a near identical deployment approach. G.fast functions in a roughly similar way to the current 80Mbps capable VDSL2 (FTTC) service that dominates today’s market (often dubiously marketed as “fibre broadband“), although it requires significantly more spectrum (G.fast 106MHz+ vs VDSL 17MHz) and thus operates best over a much shorter run of copper cable (ideally less than 350 metres).

G.fast can be installed inside existing street cabinets, just like VDSL2, although the technology may also be delivered from smaller nodes / distribution points (DP) that can be built either underground (manholes) or placed on top of nearby telegraph poles. Related nodes would be fed directly by fibre optic cable, although they still have to be supported by small nearby power supply units at ground level.

By comparison XG.FAST increases the frequency range up to 500MHz in order to achieve higher speeds, but this requires significantly shorter distances / copper lines in order to work. Higher frequencies attenuate more quickly than lower frequencies (interference grows over distance), meaning there are diminishing returns in speed as the frequency range increases. In essence BT would need to ensure that their fibre optic cables get even closer to homes.

The result of the latest BT test suggests that XG.FAST is performing more or less as last year’s prototype did, although how easily this might translate into the real-world UK market depends upon the operator’s approach to G.fast and how close they build their nodes to homes. In any case we won’t be seeing XG.FAST for a while and even G.fast won’t begin its commercial roll-out until 2017 (significant pilot in 2016).