if you have seen ( it is a bit old) please ignore.
i don't recall seeing it here:
February 09, 1998, Issue: 992
Section: Business
New schemes bury a universal ADSL
Loring Wirbel
Fremont, Calif. - Any hopes that the fledgling Universal ADSL Working Group will standardize the world of digital subscriber lines look to be dashed this month by a flurry of alternative DSL proposals from startups and old hands alike.
Offerings from Amati Communications Inc. (Sunnyvale, Calif.) and PairGain Technologies Inc. (Tustin, Calif.) will support both full-rate ADSL and UAWG's new "splitter-less" proposal. Alternative DSL concepts in the works from other companies are based on quadrature amplitude modulation (QAM), the so-called 2B1Q coding that's used in ISDN and full-rate splitter-based asymmetric DSL.
Even the UAWG's "universal" moniker could be challenged. Centillium Technology Inc., a Fremont company founded by startup veteran Kamran Elahian, is calling its new QAM-based mid-speed entry Universal DSL, or UDSL. Since Elahian previously has backed such companies as NeoMagic, Cirrus Logic and CAE Systems, Centillium's line-code advocacy is bound to carry some weight.
Meanwhile, integration efforts by some of the pioneers in xDSL indicate that full-rate ADSL has an important user community to serve. Amati, acquired by Texas Instruments Inc. in the fall, introduced a subscriber-access system two weeks ago, based on a TMS320C6x derivative that TI will be able to bring to market as the TNETD2000 chip set.
PairGain, an HDSL-access OEM that has developed some component-based sales with its "Sparow" HDSL chip set, has introduced a CMOS ADSL transceiver called Falcon, with a power dissipation of 0.55 W. Chief scientist George Zimmerman calls the design so revolutionary in terms of power budget that PairGain is discussing licensing it to multiple OEMs and semiconductor manufacturers.
Even Globespan Semiconductor Inc. (Red Bank, N.J.), the originator of the carrierless amplitude/phase (CAP) modulation scheme for ADSL, is broadening its options by offering a mid-speed DSL chip based on the 2B1Q codes from ISDN.
"We agree with the UAWG's goal of making sure DSL service will work with POTS [plain old telephone service]," said Faraj Aalaei, Centillium's vice president of planning and business development. "A consumer service similar to analog modems must be very much like POTS and be capable of supporting POTS."
Aalaei said Centillium parts ways with UAWG in terms of modulation. UAWG is backing discrete multitone (DMT) for consumer ADSL services. The consortium, announced in late January at the ComNet trade show in Washington, is backed by computer giants Intel, Compaq and Microsoft, along with virtually all the Baby Bells.
Centillium founder Elahian said he has had little trouble raising $20 million for the company from a combination of venture and corporate partners, including several Asian banking firms and modem OEM giants. Funding by Mitsubishi Electric is particularly important in getting Centillium access to advanced fabs for the proprietary DSP solutions it aims to bring to market this fall. Elahian said he has heard many potential customers grouse about the "arrogance" of Intel, Microsoft and Compaq in claiming to speak for the telco equipment and semiconductor industries.
Founded by Cirrus Logic and Fujitsu Network Systems veterans in early 1997, Centillium quickly rejected DMT-based ADSL due to the high power consumption required in line drivers for each line. The development team used QAM methods similar to CAP to support a single-carrier modulation capable of both symmetric and asymmetric operation to speeds of 1 Mbit/second. Since the full DSP and analog solution could be developed as inexpensively as analog modems, Aalaei said, the top speed was plenty of bandwidth for a traditional consumer customer base.
"We think any multicarrier solution implies compromises," said Aalaei. "It's too bad more companies aren't out there fighting the single-carrier battle."
In addition, the company designed its full-custom DSP solution to support both splitter-based and splitterless solutions. Since Centillium planned to provide a full chip set, the company hired National Semiconductor Corp.'s analog VLSI group manager, Hessam Mohajeri, to form an analog design team.
Although the company's backers drive the design toward optimization for the consumer subscriber modem, Aalaei and Elahian hinted that Centillium's ace in the hole will come in efficient implementations for multiport central-office carrier access. This summer, Centillium will bring a full suite of semiconductor products to market for both consumer-oriented OEMs and system manufacturers serving telco carriers.
Falcon to fly
Even companies that would disagree with Centillium's position on ADSL might find some areas of solidarity in necessary ingredients for an effective DSL design. At PairGain, development of the single-chip Falcon has been under way for nearly three years. Zimmerman said that PairGain carefully analyzed where DSP-based semiconductor players were in their DMT programs and concluded that an internal custom ASIC would be a better bet, both for cost-reduction road maps and to ensure a reliable supply of chips. The company diverted slightly with a CAP-based ADSL system based on chips from Globespan, in order to fulfill a customer request. But in the meantime, PairGain developed a prototype version of Falcon based on multiple standard DSPs, an early sample version called Falcon 1 and a final version that used a process shrink to 0.35 micron, reducing supply voltages to 3 V and power dissipation to nearly half a watt.
"The move to generator-based synthesizable cores lets us easily port this design to new processes and new foundries," Zimmerman said. "Our decision to develop our own design ended up being a fortuitous one, since there are very few DMT-based semiconductor designs on the market now. Consequently, we're now in discussions to license this design to others."
One 160-pin chip integrates all digital functions specified in ANSI T1.413, including modulation, framing, error correction, interleaving and a dedicated interleave RAM block. The chip already has been demonstrated in a prototype version of PairGain's next-generation Megabit Modem, and will be offered in production PairGain systems later this year.
Zimmerman said support for splitterless ADSL will require only a change in software. He added that the UAWG's work appears to be the central direction for consumer DSL.
"We're aware of the Centillium proposals but don't see a lot of support out there for them," Zimmerman said.
Meanwhile, Globespan, originator of the CAP encoding method for ADSL, has made good on chief executive Armando Geday's promise of last December that the company would be "absolutely line-code agnostic." Last week, Globespan introduced its first chip set based on the 2B1Q line code. Globespan used the basic partitioning of its CAP ADSL chip set, a programmable DSP engine and associated analog front end to produce a midspeed DSL chip set capable of meeting T1 (1.5-Mbit/s) and E1 (2.048-Mbit/s) speeds. Globespan is keeping a common 100-pin pinout strategy for its CAP and 2B1Q chip sets, under the assumption that OEMs will want to provide common platforms for different DSL services.
This strategy also is being pursued by vendors such as Rockwell Semiconductor Systems Inc. (Newport Beach, Calif.) and Level One Communications Inc. (Sacramento, Calif.). Rockwell was one of the first proponents of midspeed 2B1Q DSL in its ZipWire chips, and is keeping that family alive even as it promotes a turn to the splitterless ADSL favored by the International Telecommunications Union's G.lite working group.
Level One, meanwhile, is promoting G.lite for consumer applications, but favors a combination of 2B1Q and single-pair HDSL-2 solutions for business and telecommuter applications, where symmetric access patterns are needed.
Copyright (c) 1998 CMP Media Inc.
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