Tag Archives: g.fast

G.fast isn’t so gee whiz compared to fiber, Verizon exec says

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G.fast technology, which in theory allows telcos to push gigabit speeds over existing copper wire, isn’t a good substitute for fiber upgrades, according to Verizon’s director of network planning. Vincent O’Byrne, quoted in an article by Sean Buckley in FierceTelecom, said that even in multi-tenant office buildings or apartments, it’s more cost effective to install fiber all the way to the customer, than it is to bring fiber in or near a building and then use G.fast to close the gap…

“It’s a bit more expensive to put the single family unit fiber connections out there, but we have the same kind of service as the rest of the network,” O’Byrne said. “We also found that the trouble report rate is less on the fiber all the way to the living unit.”

“At Verizon we were finding the trouble reports on the copper were two to three times more than when we had fiber to the living unit,” O’Byrne said. “For a long time, the copper plant in the Verizon network was not as good as it was in some locations so if we went to G.fast it would be low volume and we would have the same issues five years down the road.”

Of course, if Verizon maintained its copper plant, instead of letting it rot on the poles and then selling it off, as it did in California, some of these issues might not have come up. But it’s true that copper circuits carrying G.fast traffic need to be relatively pristine in order to work over any real distance. If a lot of work is needed, there’s not much of a cost difference between refurbishing copper and replacing it with fiber.

Rapid and constant changes in technology are also a problem. O’Byrne said that as equipment hits end-of-life, it can’t always be replaced with compatible gear, and the mix of different generations of technology can be costly to maintain and difficult to support.

G.fast field trial shows both speed and limits

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Strictly for short tracks.

British Telecom – aka BT – is offering real world verification of the speed claims made regarding the G.fast standard, which is technology that’s designed to get fast, fiber-like broadband speeds out of copper wires. The results are encouraging and live up to reasonable expectations, if not all the marketing hype surrounding G.fast.

According to a story by Sean Buckley in FierceTelecom, BT has found that G.fast’s field test results reasonably match laboratory predictions…

The provider is seeing great interest from customers and favorable technical results from its G.fast technology pilot deployment.

BT has been conducting G.fast trials with Nokia’s Alcatel-Lucent subsidiary, Adtran, as well as Huawei.

During its trials, BT found it can deliver about 330 Mbps to a home within 300 meters of a remote terminal (RT) cabinet.

“[Among] the first pilot customers the indications are that the performance of the product over the new equipment is pretty much spot on what we had predicted from the labs in the earlier few trials and I am very pleased with that,” Selley said. “I’m very pleased with where we stand right now on G.fast.”

The G.fast standard has gotten a lot of attention because it’s designed to fit as comfortably as possible into legacy copper networks and standard telco provisioning practices. In other words, it offers a degree of hope to both telephone companies and their customers who currently rely on lagging DSL platforms.

It’s not a substitute for fiber, which supports speeds a thousand times faster over distances a hundred times greater, but it’s better than what telcos have now and keeps them in the same ballpark as cable companies. If they adopt G.fast and make the necessary upgrades to their copper systems. Simply slapping the gear onto existing networks would be like dropping a V-8 engine into a go-kart: amusing but any improvement in performance would be short lived indeed.

Bell Labs test shows faster speeds on shorter copper

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Next generation cable technology – DOCSIS 3.1 – can support symmetrical 10 Gbps speeds over hybrid fiber coax plant, according to a press release from Bell Labs, now known as Nokia Bell Labs. Nokia completed its purchase of Alcatel Lucent earlier this year and Bell Labs was part of the bargain.

Bell Labs is pitching its XG-Cable technology for integration into CableLabs’ DOCSIS 3.1 standard, which is undergoing field trials in a few U.S. markets. It’s essentially the same pitch that companies with G.fast gear are making to telcos: our stuff will dramatically boost broadband speeds on existing copper wire networks.

From everything I’ve seen, that’s true. At least as far as it goes. And that’s the catch. Both XG-Cable and G.fast are relatively short range technologies. Bell Labs’ says it simultaneously pushed 10 Gbps in both directions over 100 meters of coaxial cable on 1.2 GHz of bandwidth under laboratory conditions. The speed dropped to 7.5 Gbps symmetrical when a point-to-multipoint architecture was used. Ultimately, Bell Labs expects to get that level of performance at up to 200 meters.

G.fast, which is touted as an upgrade path for DSL networks, is limited to something like 250 meters to 500 meters of copper wire, with speeds ranging from 100 Mbps to 1 Gbps, again depending on how far it has to go (and who’s press release you’re reading). To get to the high end of the range, the distance needs to be less than 100 meters.

For either G.fast or XG-Cable to deliver promised speeds, the outside plant needs to be in good condition. Deteriorating lines will mean sharp drops in performance, to the point that older technologies will outperform it. With all due regard to the danger of taking an analogy too far, it’s not unlike trying to drive a Lamborghini on a dirt road.

But if you’re on a short, pristine track, a Lamborghini will fly.

It’s easy jump to the conclusion that technological advances such as these will render fiber unnecessary. That’s not true. The way you get short, final copper runs is to push more and more fiber, deeper and deeper into the network. At some point, it might not be necessary to go all the way to a home or business to get fiber-class broadband speeds, but you’ll have to extend the fiber portion of last mile networks much closer. And you’ll have to add fiber capacity – either more strands or better electronics – to handle the increased demand for bandwidth.

It’s still early days for this technology, but it’s good news that it might not be too far over the horizon.

G.fast means fiber speeds over copper, up to a point

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The point where the infrastructure collapses.

A short range, high speed technology standard for broadband over copper phone lines has been approved by the International Telecommunications Union. The G.fast standard is intended to make fiber-class speeds possible over legacy lines, with a maximum distance of 400 meters between the customer and the nearest fiber node.

Practical distances, though, are much shorter. “Service rate performance targets” – total bandwidth which can be split between up and down loads – are…

500-1000 Mb/s for FTTB deployments at less than 100m, straight loops
500 Mb/s at 100m
200 Mb/s at 200m
150 Mb/s at 250m

Bell Labs has succeeded in pushing a gigabit over 70 meters of pristine plant and 500 Mbps over 100 meters of lousy copper, using its implementation of an earlier version of the G.fast standard.

But it’s not just a transportation protocol. The G.fast standard is intended to fit typical telco provisioning processes, enabling consumer installation with shrink wrapped kit, just like DSL. It makes it easy for telcos to upgrade service levels.

With one big if.

Telcos have to be willing to extend fiber further into neighborhoods and install more nodes. In urban business districts and affluent suburbs – high potential areas, as AT&T puts it – that’s not such a big deal. Either the fiber is already built or the revenue is there for the taking, or both. With the typical AT&T node feeding 600 to 900 meters of copper, doubling fiber distances and quadrupling the number of nodes requires a very sweet business case, if AT&T is to make the investment.

Mass market deployment of G.fast technology is still a few years out. It’ll eventually be a boon to those on the high potential side of the digital divide: places where incumbents have already decided to invest. For people living where telcos let copper rot on the poles, it’s not much help.

Bell Labs bridges a gigabit over a copper gap

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The case for copper. Source: Alcatel-Lucent.

AT&T and Verizon should think twice about running away from older copper networks. Bell Labs has prototype technology that can already move half a gigabit through legacy wiring. Testing by parent company Alcatel-Lucent and Telekom Austria succeeded in pushing more half a gigabit over multiple legacy copper POTS pairs, using elements of the emerging G.fast standard and mixing in advanced vectoring technology – dubbed Vectoring 2.0 – developed by Bell Labs.

G.fast is an International Telecommunications Union standards initiative that’s intended to eventually develop technology that will allow 1 Gbps data speeds over copper telephone wiring at distances up to 250 meters.

There’s no free lunch. Although Bell Labs managed to hit 1.1 Gbps over 70 meters of a single, good quality copper pair and 800 Mbps at 100 meters with current G.fast gear, speeds dropped dramatically when older plant was tested. By itself, a legacy unshielded pair was able to carry 500 Mbps for 100 meters, but the crosstalk generated by lighting up a second pair in the bundle dropped throughput to 60 Mbps, putting it back into current VDSL2 territory.

Adding the Vectoring 2.0 technique cured the crosstalk problem. It expands the bandwidth of vectoring technology by more than a factor of ten, and brought throughput back up to 500 Mbps.

The objective is to create “the fixed networks equivalent of wireless small cells”. G.fast performance drops quickly as copper distances stretch out toward 200 meters or more. But if the promise holds and fiber is installed far enough into the network – think fiber to the curb or basement – homes might soon see gigabit speeds at significantly lower costs.