Toppling DSL's Distance Barrier
By Sue Marek
from the April 16, 2001 issue of Broadband Week
DENVER--Fixed wireless providers banking on building a broadband business around the current limitations of DSL and cable-modem service may be in for a bitter surprise. According to DSL industry executives attending the DSLcon 2001 Spring convention here last week, the elusive 18,000-feet from the central office distance barrier that has caused many potential broadband customers to look to fixed wireless and options other than DSL, soon will be a thing of the past.
Remote terminal installations dominated many discussions at the conference. According to Dennis Klein, director of DSL product management at Lucent Technologies Inc., approximately 40 percent of the 180 million lines in the United States are served by digital loop carriers, which house the remote terminals. And many carriers are planning to install gear in these remote terminals to extend their footprint beyond 18,000 feet.
Incumbent carrier SBC Communications has been the most vocal about its plans to work around DSL's distance limitations by using fiber to connect central offices to neighborhood broadband gateways, which are similar to remote terminals. By year-end 2002, the company plans to have 18,000 gateways equipped for DSL delivery.
For competitive providers, remote terminal installations provide a bigger challenge because these terminals are small and leave little room for competitive carriers to install their gear. According to Jason Oxman, senior government affairs council for Covad Communications, competitive providers must make the FCC "understand how important access to remote terminals is to the competitive industry." Oxman added that Covad is negotiating with SBC and government regulators to secure space in the incumbent's remote terminals, which he says should be open to colocation just as COs are required to be by the 1996 Telecommunications Act.
But remote terminals are not the only option for extending DSL's footprint. Several companies are promoting various forms of loop extension technologies.
New York-based independent carrier Berkshire Telephone Corp. is testing DSL newcomer Symmetricom Inc.'s GoLong ADSL loop extender as a way to double its DSL footprint. According to Donald Skipwith, vice president of business development for Symmetricom, the GoLong loop extender can provide Berkshire customers 25,000 feet from the central office with speeds of at least 1.5 megabits per second downstream and 382 kilobits per second upstream. Skipwith says that DSL providers can deploy GoLong for less than $700 per circuit, which means the GoLong loop extender makes sense for small clusters of subscribers beyond the current distance limitations, rather than large groups of subscribers, which would be better suited for remote terminal deployments.
Adtran Inc. also has developed a loop extension product for ADSL networks. However, instead of using repeater technology, Adtran's Total Reach ADSL loop extender uses trellis-coded pulse amplitude modulation techniques to extend DSL capability and reduce the number of failed ADSL deployments. Targeted at the 5 percent or so of ADSL installations that qualify for DSL service but are unable to get it because of bridge taps, noise or other obstacles, Total Reach ADSL is being tested by a "large ILEC in the Southeastern U.S.," says Keith Atwell, Adtran's director of business development. Atwell says most of the large ILECs are considering Total Reach ADSL and the company is involved in 50 U.S. field trials, with multiple trials per carrier.
And for DSL operators catering to the business user by offering symmetric DSL service, single-line high bit rate DSL, also known as G.SHDSL, is moving closer to reality. This new standard, which is expected to add 25 percent to 35 percent to the reach of a twisted pair loop with bit rates varying from 192 kilobits per second up to 2.3 megabits per second, is being deployed in Europe. According to Atwell, it's only a matter of time before G.SHDSL makes its way into the United States. He expects trials of the technology by year-end, with some deployments by small, independent carriers sometime early next year.
Of course, that sentiment isn't universal. Yankee Group analyst Matt Davis told a DSLcon panel that although G.SHDSL was compelling technology, it was unclear whether the ILECs that dominate DSL will be investing much capital in it over the near term.
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