[ More Monday ]
It's getting better than the last one.
Now ... It's "auspicious"
Ray
June 23, 1997, Issue: 669
Section: SUPERCOMM Today
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Service providers eye xDSL opportunity -- Technology lets carriers provision high-speed services without major upgrades
By Terry Sweeney
Carriers and service providers are hoping to work a little alchemy and turn their copper lines into silver, if not gold.
The agent for this transformation? Digital subscriber line (xDSL) technologies, which promise to shove megabits down copper conduits at speeds that only fiber was thought capable of delivering.
The first half of 1997 has been filled with trial activities and a few commercial launches of xDSL services. Viewed as viable, high-speed pipes to the Internet, xDSL technologies give carriers a way to carve that Internet-bound traffic off of their voice switches to avoid congested network conditions, like at the end of the school day in a metropolitan area, when dialing out can be difficult.
Nynex Corp., along with Lotus Development Corp. and Westell Inc., Oswego, Ill., ran an xDSL test that began last year with 60 homes scattered among four central office switches, according to Bill Buck, member of technical staff for Nynex. Buck spoke on an International Engineering Consortium (IEC) panel, "ADSL: Paving the Road to the Information Superhighway," two weeks ago at SUPERCOMM '97.
"We proved ADSL is absolutely viable, and what we used was 1.5 megabits per second downstream and 64 kilobits per second upstream," Buck said in an interview with Telepath/CommWeek's SUPERCOMM Today. "It was really easy installing the remote modem in the home and watching the modem and the CO synchronize," he said. "We didn't need to set options or do switch translations," he said.
That's in striking contrast to ISDN, where manual intervention is required to set numerous parameters at both the customer site and the CO.
Nynex isn't the only one in xDSL testing mode. Ameritech, Bell Atlantic, GTE, MCI, Pacific Bell and US West are among the many carriers testing xDSL or who intend to roll out commercial services before the end of the year.
SUPERCOMM also played host to a number of vendors demonstrating xDSL technology in various forms and flavors. AG Communication Systems, Alcatel Network Systems, Amati Communications Corp., Cisco, Ericsson Inc., GlobeSpan Technologies Inc., Lucent Technologies Inc., Motorola Inc., Northern Telecom Inc., Orckit Communications, PairGain Technologies Inc., Performance Telecom Corp., Telesend and Westell are among the vendors which showed xDSL-based modems, routers, chip sets and access multiplexers.
[Snip]
CAP vs. DMT
Thankfully, the nascent xDSL industry also has moved on from a technical debate over two line-signaling methods, Carrierless Amplitude and Phase (CAP) modulation and Discrete Multi-Tone (DMT). CAP and DMT package information for transmission to the access multiplexer and are not interoperable.
Despite the attempts of some chip vendors building CAP or DMT ASICs to polarize the issue and make carriers and end users choose one or the other, it turns out this was more of a vendor battle to regain the development dollars they had spent.
Unlike ISDN, xDSL is not a switched, end-to-end service, so interoperable line codes are completely moot. Carriers have expressed no strong preference, but pushing toward a single or interoperable standard means volume purchasing will be easier and cheaper.
Buck acknowledged that the issue is vendor-driven. But as carriers like Nynex start unbundling their copper loops for resale, state and federal regulations need to be clear about what is expected of the carrier offering loops for resale.
"What we care about is special compatibility, since with unbundling we don't have control over what another service provider may do," Buck said.
What if an overzealous ISP or one of its customers blasts a 52-Mbps, very high-speed DSL signal across one set of copper pairs? How do you manage or eliminate the potential interference?
'Some guarantee'
"We need some guarantee that there's some level of performance for both [service providers'] systems," Buck added. "So much of the network requirements are dependent on the service applications and those need to be defined. We're making good headway with that."
This year will likely prove an auspicious one for ADSL in particular, according to Kim Maxwell, chairman of the ADSL Forum. He said it's clear that carriers can deploy ADSL networks easily and profitably.
As an overlay network, ADSL won't require any massive switch upgrades or signaling integration with the existing network. And all the requisite ADSL products are available today for building services, he said.
How far xDSL goes after this year invites one of the industry's more riveting contests-ATM or IP as the transport-but it will mainly enable telephone companies to launch a service with very low-risk capital and viable per-subscriber costs, he said.
If xDSL can match or beat the thresholds for ISDN-whether for equipment, installation or service-network service providers and their customers may share in the alchemy benefits.
Copyright r 1997 CMP Media Inc.
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