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BT, Tier 1 providers' G.Fast installation mirrors traditional DSL, but success hinges on ability to scale

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As Tier 1 telcos move forward with their G.fast plans, the real test will be when these carriers roll out service on a broader scale beyond the lab and limited field trials being conducted today.

There's been no shortage of G.fast trials. BT (NYSE: BT), Deutsche Telekom and Cable & Wireless Panama have been touting their ability to deliver between 300 Mbps to 1 Gbps over short copper loops in lab and limited field trials.

In terms of network installation, test and measurement vendors like EXFO which recently released a new handheld G.fast CPE emulation solution, said that it does not expect the process to be any different than earlier generations of DSL, but the real test will come when operators roll out these services broadly across the markets they serve.

"From our perspective, we believe the installation process will be quite similar to the other DSL variants that we already support, which is why we basically evolved our capabilities," said Andrew Long, group manager for EXFO's access business unit, in an interview with FierceInstaller. "The question mark that's yet to be determined because there are not any volume field deployments is around quality of the copper and the performance of the copper in the ground."

Long added that noise impairments within the existing copper lines could be an issue service providers will have to grapple with as they roll out G.fast into single-family homes and multi-dwelling units (MDUs). This is all depends on the age of the copper and its condition at the local CO, RT and inside of a user's home.

"We suspect that everyone believes there's going to be a lot of challenges around things like noise in the field from external sources and noise from devices in the home," Long said. "A lot of the high bandwidth numbers we're seeing are typically in lab environments where they have one line that's brand new piece of wire with no external noise, but it's yet to be determined how that works."

What's interesting about the G.fast trials of the incumbent telcos is that all of them are leveraging different architectures.

BT, for one, has taken the approach of delivering testing G.fast by leveraging its existing fiber-to-the-cabinet (FTTC) infrastructure to deliver services over infrastructure platforms from Nokia's (NYSE:NOK) Alcatel-Lucent subsidiary and Adtran.

It is leveraging Adtran's 500G fiber-to-the-distribution-point (FTTdp) platform as part of its G.fast trial taking place in over 2,000 premises in Huntingdon, Cambridgeshire, UK. Similarly, BT is conducting trials in Huntingdon, Cambridgeshire, UK with Alcatel-Lucent as well as in Gosforth, located in northeast England, and Hethersett, Norfolk.

"The thing that BT is trying to do is run it over longer loops than was originally envisaged by a lot of the equipment vendors," Long said. "They're trying to put it into the cabinets, which are typically further away from the customers and the typical distribution point locations that could be much closer to customers."

The UK-based telco is likely taking this approach so it can contain costs by not having to pull fiber into every neighborhood they plan on serving.

"BT is trying to stretch it so they don't have to pull fiber closer to the residences, but they're still claiming they're getting respectable data rates," Long said. "It's all about ultimately the capital outlay if you have to run fiber to every single neighborhood and that gets very expensive so BT has been one that's extending the loops to make them longer than originally planned and from what we have seen with the longer loops the data rates drop significantly but are still impressive."

But G.fast is just one next-gen DSL technology service providers are looking to deploy to provide enhanced services over their copper pairs.

Other service providers like A1 Telekom Austria are using a dual approach of using G.fast and VPlus.

As the ITU-T standard VDSL2 profile 35b, VPlus is an extension to VDSL2 that allows operators to achieve aggregate speeds of 200 Mbps and more over copper at distances of up to 500 meters and 300 Mbps over distances shorter than 250 meters.

The technology has been championed as a way to satisfy wireline providers who need to deliver higher speeds economically on medium-length copper loops.

A1 Telekom Austria, an early proponent of VDSL2, has deployed Alcatel-Lucent's ISAM gear supporting a mix of G.fast and VPlus.

Meanwhile, Deutsche Telekom recently achieved 10 Gbps over existing copper wiring during a lab trial using XG-Fast technology at the end of 2015.

Additionally, a growing number of European providers like Belgium's Proximus, DT and Telecom Italia are looking at using VPlus as a complement to their G.fast and VDSL2 networks. Service providers are looking at VPlus as another way to potentially preserve fiber network installation costs and as a step towards G.fast.

"Some of the other providers are looking more towards this 35b, which is an extension of VDSL2 and it's more cost effective because you can run it from a remote DSLAM rather than having to run fiber out to a distribution point," Long said. "Over those longer loops, it does get respectable rates so people like Proximus in Belgium, TI in Italy and DT in Germany are looking at VPlus as potentially as an alternative to G.fast because the equipment costs are lower."

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BT says G.Fast trials are on track with eight competitive providers aboard
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