Beyond 18,000: an ADSL odyssey, DSC, Westell develop high-speed transport through Litespan-2000

DSC Communications and Westell Technologies are partnering to develop an asymmetrical digital subscriber line platform that skirts the usual DSL access multiplexing method and the costs and constraints it involves.

The companies have developed a new card designed to be inserted into existing DSC Litespan-2000 digital loop carrier platforms. The new card takes ADSL traffic from the end user and converts it to ATM before moving it onto the network and vice versa, according to David Ehreth, DSC access products division vice president.

"The bank controller unit [in the DLC] was responsible for TDM traffic only," Ehreth said. "Now what we've added is a parallel path for ATM traffic.

The Litespan platform, which DSC began to develop in 1988, was designed from the start to accommodate some sort of high-speed transport capability, Ehreth said. Now that ADSL is emerging as one of the frontrunners among telcos for such applications, DSC is moving to take advantage of that capacity.

The partnership with Westell emerged as the result of a request by Bell Atlantic, a common customer for the companies. Bell Atlantic has Litespan DLCs embedded in its networks and is conducting ADSL testing with Westell's SuperVision CPE modems and DSLAM platform. Bell Atlantic announced last week that it will install the new DSC/Westell solution in its network but isn't taking delivery on the new cards until September (see story on page 14).

The primary challenge in developing the ADSL-over-DLC solution was developing specs that would allow Westell's CAP-based ADSL technology to function within the Litespan platform, said Westell President J. Nelson. But it didn't pose too much of a problem.

"What made it really easy was DSC having enough bandwidth on the backplane," Nelson said.

The main effect of ADSL over DLC is that it gives service providers the opportunity to extend ADSL service to customers that are more than 18,000 feet from a central office. With a DSLAM configuration, users must be within that distance. And unlike ISDN, repeaters that maintain signal strength along a network have not been developed for ADSL.

"That's a real problem, given that the people most likely to foot the bill for DSL are usually the farthest away from a central office," said Kieran Taylor, broadband analyst for TeleChoice, Verona, N.J.

According to Nelson, that's what prompted Bell Atlantic to ask DSC and Westell to develop a DLC solution.

"Bell Atlantic has a large customer base, with a large amount of DSC Litespan in its network," Nelson said. "It would be very valuable to them to be able to deploy ADSL through Litespan.

Although other companies are working on similar solutions, including a Pulsecom/3Com alliance, Taylor said DSC and Westell are the first to declare their solution ready for market.

But expect competition for remote ADSL deployment solutions to increase rapidly, said Brett Azuma, vice president and principal analyst for DataQuest, San Jose. In fact, Westell has been working with Northern Telecom, and DSC is working with Aware Inc. on a DMT design.