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BT uses G.fast to deliver mobile backhaul over copper

One of BT’s ongoing trials successfully delivers a cloud radio access network cell service over copper lines

BT has successfully used G.fast – a developing technology that allows telcos to extract speeds of well over 100Mbps across short copper loops by boosting the available frequency range – to deliver a cloud radio access network (C-RAN) mobile service over a copper-based network.

C-RAN, a type of network architecture used to link mobile base stations to core networks, has traditionally needed a dedicated fibre link to connect transmitters on a mobile mast to signal-processing equipment deeper in the network.

The research at BT’s R&D site in Suffolk – which was conducted with support from US semiconductor supplier Cavium – found it is possible to deliver mobile data packets over copper at speeds of 150-200Mbps.

This is significant for BT, because it gives it the ability to squeeze more capacity out of its existing copper links, and removes the need for often complex and costly engineering work to install fibre to support C-RAN.

For mobile network operator (MNO) customers, it should have a similar effect, eliminating the need to invest in high-capacity backhaul over dedicated fibre connections.

BT said that by deploying a more economic fronthaul connection between base stations and core mobile networks, a G.fast-enabled C-RAN service would “significantly lower the cost” of deployment.

Tim Whitley, BT managing director of research and innovation, said: “These technologies will play a key role in 4G networks and will be fundamental to 5G architectures. The trials are another step towards a fixed and mobile network that will support customers’ increasing demands for data.”

Raj Singh, general manager of Cavium’s Wireless Broadband Group, added: “We are very excited to collaborate with BT, using Cavium Octeon Fusion-M base station and ThunderX® server processor technology to validate this new class of radio access application with G.fast technology.

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“Our successful testing has laid the groundwork for enabling LTE deployments today and 5G deployments in the future using G.fast.”

Up to now, G.fast has been seen as a key enabler for ultrafast fixed broadband networks – and has been criticised as such because it allows operators to sweat copper assets for longer than many feel is tenable, and the possibility of using it as a mobile backhaul technology may elicit a similar reaction.

Nevertheless, BT is conducting a number of tests of the technology around the UK, with Openreach projects currently under way in Huntingdon, Gosforth and Swansea.

BT hopes G.fast will allow it to deliver ultrafast speeds, generally held to be higher than 100Mbps, much more quickly than if it was to roll out full fibre-to-the-premises (FTTP) access networks.

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