Is G.lite G.oing, G.oing, G.one?

G.lite made its debut as the savior of DSL access. It was quickly embraced as the digital darling for provisioning high-speed services worldwide. But as G.dmt evolves, some question whether G.lite is the splitterless salvation of copper — or just a PC put-on.

by Jim Thompson
[November 20, 2000]

When it comes to high-speed data transmission, G.lite seemed to have everything — low cost, streamlined provisioning and ready for high-speed transport over the existing copper-based infrastructure.

But after more than a year of hype, G.lite remains in the starting blocks — leading many to question whether or not it has a future as the universal ADSL standard for the industry.

Still has a pulse
Throughout much of the country, G.lite is losing its appeal, taking a backseat to the superior speeds offered by G.dmt. According to Cahner's In-Stat Group, more than 654,000 G.lite lines will be active in North America by the end of the year. In Europe, more than 115,000 G.lite lines will be deployed before the year is through.

TeleChoice reports that more than 1.8-million DSL lines are currently transporting voice and data in the U.S. and Canada right now. TeleChoice analysts predict that there will be more than 2.1-million revved up copper lines in use in North America by 2001. So G.lite has only captured about 36 percent of the current DSL market.

Similar, yet different
Both G.lite and G.dmt are standards for asymmetrical, or ADSL connectivity. Both standards are approved by the International Telecommunications Union.

G.dmt is also known as full-rate ADSL [G.992.1] and supports speeds of up to 8-Mbps downstream and 1-Mbps upstream.

Sure, G.lite is about seven times faster than regular phone even at its lowest downstream rate of 384 Kbps. But G.lite continues to fall out of favor because its [G.922.2] upstream speed limit is equivalent to a 128k ISDN line.

Certainly, G.lite has been "turbo-charged" with faster chip sets and the development of dual-mode customer premises equipment that can take the standard to transporting 3-Mbps on the downstream and 1-Mbps on the upstream. But when it comes to speed, G.dmt outperforms G.lite.

Same old line
Keith Higgins, Copper Mountain Networks, Inc. vice president of product marketing points out that both standards are still copper-based, so as the length of the loop increases, actual transport speed decreases.

"G.dmt's speed advantage only holds for short loops. Once the copper loop exceeds about 8,000 feet, the speed difference disappears," Higgins said. "While full-rate may be faster for some subscribers, G.lite is known as a 'pragmatic' variant of ADSL, because it overcomes many of the provisioning problems in getting DSL installed, and provides sufficient bandwidth for the average residential consumer." Tradeoff on consumption
One big advantage for G.lite is that it requires far less power than G.dmt. In most cases, G.lite provides about a 40 percent power savings. Higgins said that alone "can make a difference in the number of lines that can be deployed in the central office cage or the remote terminal pedestal."

When G.lite first hit the scene its greatest claim to fame was that it made DSL access splitterless — need to dispatch a technician to provision the line. Enhancements in the basic G.dmt technology have, to a large extent, dispelled this issue by making it equally easy to provision.

According to Higgins, "the splitter issue has been largely resolved with self-installed micro filters. These are simple 'dongles' that an end-user just plugs into the phone."

Same rendition
The two technologies also share a number of other features. For example, both G.lite and G.dmt support simultaneous voice and data services. This opens to door to providing value-added services like Voice over DSL and streaming audio or video.

The two G-dot standards are also compatible, so they can fully interoperate with another. A number of manufacturers currently offer equipment that support both systems, several others have made announcements for upcoming releases of compatible products.

For example, Copper Mountain has a multi-mode ADSL line card that supports all versions of asymmetric DSL, including G.dmt, G.lite, ANSI T1.413, Issue 2 and CAP/RADSL.

According to Higgins, outside the U.S., "many of the PTTs have mandated that the only flavor of DSL that can be deployed by the competitive carriers is full-rate. In many cases, this is G.dmt. So, there's really a need for both G.dmt and G.lite. It all depends on whether the service provider is a CLEC or an ILEC and whether the market is international or domestic."

But wait, there's more
As if the accepted DSL provisioning standards aren't confusing enough, new technologies are under development.

"We're working on the next round of interfaces like G.shdsl, which will offer some performance and distance boosts," Higgins said. "G.shdsl will also be a symmetrical multi-rate variant, which solves one of the problems with HDSL-2. It was only one speed. And G.shdsl will be an international standard, which will greatly assist in its acceptance."

End of the line
The bottom line is that there is a place for both standards. Higgins advises that which DSL flavor' you choose depends on a number of factors, including the "application, whether you require packet or lifeline voice services or just Internet access, and your distance from the central office."

The ultimate choice comes down to your application, your power requirements and your budget. But with all the options already on the table and new ones being added to the mix every day, what is a poor ISP and, or CLEC to do?

Higgins said the consensus seems to be that interfaces won't differentiate too much in the near future with most providers offering multi-mode ADSL, G.shdsl and VDSL.

"What I think the service providers will have to focus on is what services they can offer and how can they differentiate themselves from the competition," Higgins said. "Also, they have to ask what DSL platforms can they put in that enable them to offer these new services efficiently."

— End

Related resources:
  Copper Mountain's Fast Start DSL Program

     

Related articles:
	[June 23, 2000]	G.lite: Hot Alternative to Cable
	[May 9, 2000]	G.lite Consumer Rollout Underway