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<<"Most of the mass-deployment decisions will be made within the next 30 days to nine months," he said, "and this coalition could shift the momentum.">>
Trio leads coalition to reshape ADSL landscape
By Loring Wirbel
WASHINGTON -- A generation of digital-subscriber-line chip sets and service trials could be scrapped if a coalition of PC companies and local telephone providers succeeds in a bid to deploy a DSL variant to be formally launched at ComNet next week. A push from an alliance with the clout to to roll out both modems and services could set a much-needed direction for the xDSL industry. But analysts and long-time DSL players are wondering at what cost.
The new Digital Subscriber Line Special Interest Group (DSL SIG) will leverage proposals made by a group led by Microsoft Corp. and Cisco Systems Inc. at last summer's Supercomm show. Though coali- tion principals Microsoft, Intel Corp. and Compaq Computer Corp. would not discuss the impending announcement, sources predicted it would involve consumer-oriented asymmetric DSLs using the Point-to-Point Protocol over asynchronous transfer mode. Sources said there is no guarantee whose technology the alliance may adopt.
The coalition-which includes four incumbent local-exchange carriers and GTE Corp.-wants to embed DSL subscriber modem technology within desktop PCs. It will therefore endorse emerging "splitterless" approaches, which sacrifice some downstream speed to allow analog voice phone service with no expensive filter outside the home, where digital service is carried from the local copper loop. A POTS splitter separates out a 4-kHz region of a copper-pair bandwidth at the dc end of the band.
In recent months, several proposals have emerged within a new G.Lite working group in the T1-E1 standards body for splitterless service. Rockwell Semiconductor Systems has proposed a consumer DSL, or CDSL, while Globespan Semiconductor Inc. has promoted a consumer-installable DSL, or CiDSL, that could be implemented immediately in CAP-based ADSL systems by external filter components.
Last week, Lucent Technologies' microelectronics group threw its hat in the ring with a proposal for "WildWire," a splitterless ADSL with 1.5-Mbit/second downstream capability, based on discrete multitone (DMT) coding. Lucent is already showing prototypes of a complete chip set with general-purpose DSP, data converters and line drivers.
Redesign needed?
In theory, the DSL SIG's backing of splitterless technology could require quick redesigns of first-generation chip sets. These include the long-awaited CopperGold transceiver from Motorola Inc.; the DMT ADSL chip set from Analog Devices Inc. and Aware Inc.; and a solution due this week from Amati Communications Inc. and new parent Texas Instruments Inc. Ironically, PairGain Technologies Inc. (Tustin, Calif.), one of the earliest HDSL OEMs, introduced its first single-chip ADSL transceiver device last week: the splitter-based Falcon.
"The amount of redesign for some of these chips would be based on the level of programmability and the filter partitioning," said an OEM customer of one such set, speaking anonymously. "In the best case, there'd be at least a few mask changes for the ADSL designs out there right now."
The number of G.Lite proposals on the table indicates how immature the technology still is. The G.Lite working group was to meet in Boulder, Colo., late last week to begin discussing initial concepts of noise margins and impedance changes. But it is still far from considering comprehensive draft proposals. One working-group member, who asked not to be identified, called the suggestion by a member of the DSL SIG that splitterless consumer products might be available by Christmas "nothing short of appalling-much worse than the pressure for 56-kbit analog modems."
Because the new coalition was formed without the leadership of a primary DSP player, analysts wonder how much clout it will have to drive standards. Will Strauss, principal analyst with Forward Concepts Inc. (Tempe, Ariz.), said there are too many installations of ADSL, mid-speed MDSL and symmetric HDSL services to assume the world will instantly turn in the direction suggested by the coalition.
"Any effort to drive standards should be seen as a good thing, particularly because it gives phone companies at least a chance against the cable-modem standards efforts," Strauss said. "But appearances would suggest this is a case of the folks on the sidelines jumping in front to lead the parade." In particular, Strauss said, Intel's on-again, off-again involvement in cable-TV modem markets and standards should make telephony OEMs and carriers view its DSL involvement with a grain of salt.
Standard interfaces
If the coalition were to propose its own standards, it might impinge on the work of groups like ADSL Forum or G.Lite. But ADSL Forum vice chairman William Rodey said that, based on what he knows of DSL SIG, it will bless standards set by official American National Standards Institute and International Telecommunications Union bodies.
Its best role, he said, would be to standardize interfaces at higher layers in the protocol stack, particularly programming interfaces at the network layer and above. Rodey said that the ADSL Forum tries to avoid direct involvement in physical-layer issues, and has kept neutral on carrierless amplitude/ phase (CAP) modulation vs. DMT. As splitterless concepts emerge, he said, they should follow the T.114 standards, which in essence specify DMT. Rodey said Lucent's proposals apparently meet that requirement, while Rockwell's would need modification.
Ken Brizel, strategic marketing manager for DSL products at Lucent's microelectronics group, confirmed that WildWire is based on a DMT line code. "It is important that we made this completely DSP-based and programmable, which allows us to explore other line-code options should they prove important," he said.
Lucent will bring several proposals before G.Lite "at the appropriate time," Brizel said. He added that chip sets will sample in the third quarter, and that many system products may arrive before a standard exists.
Opinions on the implications of a consumer DSL effort varied widely last week. Kent Savage, vice president of sales and marketing at NetSpeed Inc. (Austin, Texas), said there is "no question" that a push for splitterless ADSL could dissolve the market for first-generation ADSL, as well as mid-speed and symmetric alternatives. "Most of the mass-deployment decisions will be made within the next 30 days to nine months," he said, "and this coalition could shift the momentum."
Efficient Networks Inc. (Dallas) just came out with CAP-based subscriber modems to augment its original DMT-based ADSL systems. Product marketing manager Peter Bourne said Efficient has begun work on splitterless ADSL, but anticipates it will be some time before any such products are ready for consumer markets.
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