DSL Soldiers On

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The world’s telecommunications networks increasingly are dominated by fiber, which controls the core of the network and in many cases extends to homes and businesses. For most of the life of the telephone industry, however, that last mile of wire was copper. Although it all started with copper—and lots of it—the migration to fiber and wireless is going to be a decades-long process.

That’s not the bad news that it seems on first glance. Technical advances have been made, and a bit of copper is not such a bad thing. Alcatel Lucent has announced that it has updated its digital subscriber line (DSL) technology to make it a true competitor to fiber. In a test, the XG-Fast, which is being standardized by the International Telecommunication Union, sent data at 1 Gigabit per second (Gbps) symmetrically (in both directions at once) for more than 70 meters.

The technology is a step up from previous efforts to speed DSL. In fact, G.fast technology reaches only 500 Megabits per second (Mbps). Both techniques have a major limitation, however:

Indeed, as with all copper broadband technologies, attenuation is a big issue. The speed of G.fast tails off at distances over 100 metres. However, the speed of XG-Fast drops after 70 metres.

The faster DSL will not arrive a moment too soon. In June, the Federal Communications Commission reported good news about ISPs in general: They generally are over-delivering on promised download speeds. The study found that last year these providers were 97 percent true to their advertising. This year, that number jumped to 101 percent. That compares even more favorably to an August 2011 study, which found that only 80 percent of promises were being met. The Broadband Breakfast story doesn’t say when those numbers actually were collected, though.

DSL did poorly in the study, however. Ars Technica reports that speeds were slower and the odds that providers told the truth about them lower:

DSL providers not only promise worse speeds than cable and fiber but are less likely to deliver the lower speeds they advertise. That can be seen in the numbers for Verizon’s DSL services and others like Frontier, Windstream, and CenturyLink.

Though engineers are finding ways to speed DSL, telecoms have a general desire to reduce reliance upon it. AT&T, for instance, is asking the FCC to allow it to transition some DSL users to wireless in its time-division-multiplexing-to-IP trials.

DSL is in a unique position. It was widely deployed as the telephone industry’s first response to the competitive threat posed by the cable industry’s foray into data delivery. Decades later, it is the third best last-mile option, after fiber and wireless. The telephone industry has a two-prong strategy that makes sense: Work hard to improve its capacity while looking for efficient ways to retire it.