Supercharging copper lines using vectoring technology should boost broadband connection speeds up to 100 Mbit/s, but that's unlikely to be enough for the deluge of high-definition video and other advanced services that will soon be heading to a neighborhood near you. (See Vectoring: Some Va-Va-Voom for VDSL.)

For that, the long-held assumption was that operators would have to bite the investment bullet and roll their fiber networks out to customers' homes. Then another copper-fortifying technology called G.fast came along.

Still very much at the trial stage, G.fast works largely by extending the range of frequencies over which broadband signals travel. According to Chinese equipment maker Huawei Technologies Co. Ltd. , VDSL2 -- a very high-speed copper-based technology -- uses either 17MHz or 30MHz frequencies, but G.fast will work on 106MHz or even 212MHz. By fattening up the frequency pipe, operators can pump more bandwidth down the line. During tests carried out by Huawei as far back as 2011, G.fast reached speeds of 1 Gbit/s -- ten times as much as vectoring-enabled VDSL2 can offer in the choicest conditions -- though real-world speeds are likely to peak below that headline speed.

Yet even more so than vectoring (which is also used with G.fast to reduce interference), G.fast is at its most effective over very short distances. Huawei's trial was over a loop length of just 100 meters. As acknowledged by Huawei rival Alcatel-Lucent (NYSE: ALU), the high frequencies used with G.fast cause signal strength to deteriorate badly over distances of several hundred meters. Indeed, the French equipment maker insists that vectoring-enabled VDSL2 is preferable to G.fast for longer loops.

Due to this problem of attenuation, G.fast is intended for use in broadband deployments where fiber has been deployed as far as the local distribution point, meaning copper is retained only for the last 100 or so meters to the customer's premises. No doubt, this is far less costly than rolling out fiber-to-the-home (FTTH). According to Sckipio Corp., an Israeli semiconductor company focused on G.fast development, if the cost of deploying FTTH is currently about US$1,500 per home, that of building fiber to the distribution point and using G.fast over "the last 200 meters" is just $300.

But this still means dipping into the coffers, and others have expressed concern about the overall investments needed for G.fast. Point Topic, a market-research company, said "the extra cost will be significant" in a white paper published last year, while noting that it was "not yet clear how much contribution G.fast will be making by 2020."

Clearly, progress has been halting. The industry reached agreement on the G.fast standard in December 2013, and the International Telecommunications Union was expected to ratify it in April, but that now seems unlikely to happen until the end of the year. Alcatel-Lucent expects field trials to follow in 2015, with "volume deployment-ready G.fast products" appearing by 2016. No wonder Point Topic doubts the impact G.fast will have before 2020.

Nevertheless, some prominent operators have the technology in their sights. Swisscom AG (NYSE: SCM) is working with Huawei, its main fiber-to-the-street (FTTS) partner, on G.fast, while Telekom Austria AG (NYSE: TKA; Vienna: TKA) has been conducting trials with Alcatel-Lucent, and last year claimed to have recorded speeds of 800 Mbit/s over loop lengths of 100 meters. In addition, Germany's Deutsche Telekom AG (NYSE: DT) was reported in February to be planning its own G.fast trials later this year. (See Swisscom Boasts FTTX Milestone and Telekom Austria Tests G.fast.)

Regardless of standardization and equipment availability, the strategy that operators pursue will largely determine how soon commercial G.fast services appear. Presenting G.fast as a kind of stepping-stone to FTTH, Alcatel-Lucent unsurprisingly urges operators to push fiber out to local distribution points immediately, instead of waiting for G.fast equipment to materialize. Yet it's true that investments required for this move could support subsequent planning for an all-fiber future. With vectoring merely a stopgap, and the cable community planning its own move to the bandwidth-boosting DOCSIS 3.1 standard, the pressure to act is mounting. (See DOCSIS 3.1: What's Next?)

— Iain Morris, Site Editor, Ultra-Broadband