G.fast – the Next Generation

The following is a guest post from Les Brown, Chair of the Broadband Forum’s Metallic Transmission Working Group

Les BrownG.fast is the latest and greatest generation of DSL technology being specified by ITU-T, designed to support Fibre To The Distribution Point (FTTdp) deployments. FTTdp brings fibre very close to the end customer. This could be to a pole or an underground enclosure near a single family residence, or to a basement of an MDU. G.fast operates over the final copper drop wires between the fibre termination at the Distribution Point Unit (DPU) and the user. This is typically 50 to 100 metres, but G.fast is specified to operate up to at least 250 metres.

G.fast has been developed to help operators meet broadband targets (both their own and some government ones) by expanding the footprint of their fibre networks. It is attractive to operators because it is a low cost, low power, low complexity solution that combines the best aspects of Fibre-To-The-Home (FTTH) and legacy ADSL2. Specifically, FTTH like data rates (up to 1 Gbit/s) along with customer self-install (no need for truck rolls to bury fibre on customer property or for technician appointments to install equipment in customer premises).

G.fast also supports reverse power feed (being specified by ETSI) for the DPU from the customer premises since access to electricity is often unavailable at DPU locations. Unlike ADSL2 and VDSL2, G.fast uses Time Division Duplexing (TDD) which has two benefits, it allows the ratio of upstream to downstream data rates to be easily changed as application requirements evolve, and it provides power saving since many functions of the transceivers can be turned off when there is no data to send. G.fast also supports vectoring to remove far-end self-crosstalk, retransmission to improve robustness to impulse noise and forward error correction to improve robustness to Radio Frequency Interference (RFI).

Several vendors are developing G.fast chipsets, some of which should be ready for public demonstration in the Broadband Forum Interoperability Pavilion during the Broadband World Forum, 21-23 October in Amsterdam.

The Broadband Forum has scheduled G.fast interoperability plugfests starting in January 2015, and has initiated a certification program for G.fast, with a goal for completion by mid-2015.

For more information on operator requirements, key features of G.fast, and the status of G.fast standardization in ITU-T, you’re invited to attend the talks by Greg Jones and Frank Van der Putten during the “Going Turbo with G.fast” session at 10:00am, Wednesday 22 October in The-Next-Big-Thing hub in the exhibition hall. See the website for more details: http://broadbandworldforum.com/the-next-big-thing/

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