G.fast is a telecommunications protocol standard for DSL (Digital Subscriber Line) local loops that are shorter than 500 meters (the local loop being the ‘final’ part of the infrastructure, also known as the last mile; it is the physical link that connects the customers premises to the service providers network) and can be gained from original copper infrastructure that was initially used for voice calls.
What sets G.fast apart from conventional broadband is that typically your modem connects to the Digital Subscriber Line Access Multiplexer (DSLAM) in the network providers exchange (which is often located several hundred kilometres away from the user), whereas with G.fast it utilises FTTC (Fiber to the Cabinet), which is a street cabinet located near the customers premises that houses the DSLAM equipment.
This reduction in distance is essential to gaining faster broadband speeds because signals that have much less distance to travel do not degrade over space and time. The increase in speed is huge when you consider that the same copper wiring achieved a speed of just 64Kbps when originally used for voice and now reaches over 330Mbps using G.fast technologies.
The distance has such an effect on the speed that it is possible to know exactly what can be achieved just by measuring the distance to the cabinet:
In tests performed in July 2013 by Alcatel-Lucent and Telekom Austria using prototype equipment, aggregate (sum of uplink and downlink) data rates of 1.1 Gbit/s were achieved at a distance of 70 m and 800 Mbit/s at a distance of 100 m, in laboratory conditions with a single line. On older, unshielded cable, aggregate data rates of 500 Mbit/s were achieved at 100m.
Service rate performance targets over 0.5 mm straight loops
|<100 m, FTTB||500–1000 Mbit/s|
|100 m||500 Mbit/s|
|200 m||200 Mbit/s|
|250 m||150 Mbit/s|
|500 m||100 Mbit/s|
This isn’t only a huge benefit for the customers either. Some locations are extremely difficult to reach with fiber, so this technology allows providers to use the existing copper lines without needing to overhaul existing infrastructure. This cuts time and saves a huge amount of money. Not only that, but it allows operators to increase their portfolio and offer more services to their customers without needing to enter and rewire homes and buildings.
Many network operators have been working on the development and research of G.fast in order to offer it to their customers first.
BT began to switch on the pilot locations for their G.fast service in May of this year, which includes deployment to around 138,000 properties in the United Kingdom, but with the rollout of their ‘Ultrafast’ broadband service still underway, it is likely that the transition will be staggered to G.fast, and without any confirmed dates for public availability the chances are it won’t be fully implemented for a few years yet.