BT researchers claim gigabit broadband speeds using G.fast over copper wires

BT researchers claim they can deliver ultrafast broadband at up to a gigabit per second using G.fast technology that is now undergoing field trials at the company's Adastral Park research centre in Ipswich. Fibre optic cables deliver broadband connections to roadside cabinets (FTTC), as with the current BT Infinity service. With G.fast, the fibre is extended to what BT calls "fibre to the distribution point (FTTdp)". This might be, for example, a telephone pole or another junction box.

Broadband speed falls off rapidly with distance. The idea of the FTTdp is to extend fibre close to homes and businesses, cutting out another stretch of copper wire. Ultimately, of course, it would be better to have fibre to the premises (FTTP), but that involves expensive and time-consuming engineering works, digging up roads and pavements.

BT's announcement said: "During the G.fast trials, downstream speeds of around 800Mbps were achieved over a 19m length of copper, combined with upstream speeds of more than 200Mbps. Impressive speeds of around 700/200Mbps were also achieved over longer lines of 66m, a distance that encompasses around 80 percent of typical connections."

These speeds go beyond Infinity, which typically delivers 40Mbps to 80Mbps to users close to fibre-enabled cabinets. Companies who buy dedicated lines can get speeds up to 10Gbps.

BT Infinity uses VDSL routers to deliver broadband from the roadside cabinet to the premises, and a growing number of routers now support both ADSL2 and VDSL/VDSL2. It's not clear how G.fast would be introduced, but it will need a supply of G.fast routers (aka modems) to get started.

G.fast is still under development as an ITU standard (drafts ITU-T G.9700 and G.9701), and is seen as a development of VDSL2, rather than a replacement for it. G.fast only works up to about 250m, so VDSL2 will still be required for longer distances.

BT thinks G.fast equipment could be commercially available by the end of 2015. Even if BT decides to go ahead with its implementation, it could be some years before you get the chance to subscribe.