DSL reaches speeds of 170 Mbps

If you’re stuck with slow DSL, speed increases via G.fast may be on the horizon.

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While those of us interested in obtaining the fastest download speeds possible closely watch, and then seize on, fiber and upgraded cable rollouts, salivating over speeds of 100 Mbps and up, it's easy to forget the many people still can't get cable and rely on lowly, twisted-pair DSL. DSL download speeds at common ISPs range from 14 to 43 Mbps, according to Ookla's Speedtest.net. Crosstalk between lines has restricted bandwidth, for one thing.

However, things might be about to change, particularly in Europe.

G.fast technology

G.fast is a fiber-to-the node (FTTN) DSL technology that has obtained accelerated speeds of 170 Mbps over a quarter mile in the lab, and 1 Gbps over a less-usable 100 yards in the same setting. It works best over short distances.

FTTN is fiber that terminates in a street cabinet, in the neighborhood somewhere, with the final, possibly long, stretch to the premises over copper.

The G.fast tests were run across 16 active pairs and are aimed at finding ways to speed up service for those on existing DSL, and for mobile backhaul.

Copper here to stay

Why invest in DSL, you might ask? Fiber is surely better.

Some telco operators haven't given up on copper and are trying to beef up speeds on their existing infrastructure. G.fast works, and could provide an acceptable alternative when it makes it out of the lab.

Piloting G.fast

One member of the consortium, UK-operator BT, has "publicly committed" to upgrading its DSL network to G.fast. It intends to start pilot programs in two UK cities this summer, according to Brian Santo, who has been writing about G.fast in Wireless Week.

Santo explains that multiple companies are involved in the overall development of the technology, including BT, AT&T, and France Telecom, now Orange. Huawei is developing G.fast system products.


Amusingly, it's worth noting that the non-system vendors involved in the project all used to be government-run Postal, Telegraph, and Telephone service (PTT) monopolies—disowned during Thatcherism and Reaganomics.

Those old enough will remember that state monopolies have historically had a musty whiff of under-investment around them. Perhaps that's a reason that we're seeing, in this case, the revisiting of now-aging DSL technology rather than a gung-ho charge with the obviously superior, but more expensive, fiber-to-the-home (FTTH) or fiber-to-the-desktop (FTTD)?

Clearly, things don't change in some places.

The technology

Speed gains in G.fast are obtained through Distribution Point Units (DPUs) which forward the signal to the end user. Santo says that the commercial version will work over one TCP wire, instead of the 16 pairs as used in the tests. Two TCP wires could be bonded, too, according to Santo.

Interestingly, G.fast is "reverse-powered," which means the customer supplies the power, not the network. Copper-based phone networks have traditionally been powered by the telco at the switch. FTTH, such as Verizon's FIOS in the U.S., needs power at the home to work.

The more cynical will say that's in order to save money too.


And why bother with copper, you might ask? As a telco, why not just run cable or fiber to the home, or desk?

Well, the answer is that it's cheaper. The way telcos look at it, they've already made the investment in the copper, albeit some years ago, but aren't about to rip it up and start again with fiber. In particular, the complicated last mile through the expensive and slow-to-build-out NIMBY-ism minefields.

And who are we to argue? Many telcos were setup as altruistic, socialist-leaning organizations. They were started by governments to provide a public service many years ago in the days of the telegraph. Being told what to do by the customer, historically, was never in their culture. And if you've ever had any dealings with telco and cable customer service, even today, you'll know what I mean.

That's why we should be excited about the prospect of a DSL speed up. We may be eagerly anticipating fiber-to-the-desktop, but there's a good chance DSL will be on your block for the foreseeable future in some places.

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