June 28, 1999, Issue: 1067
Section: News
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Wi-LAN's multimegabit demo shows orthogonal coding can handle voice, Internet and HDTV -- Wireless nets a new broadband alternative
Loring Wirbel
Calgary, Alberta - Widening its gaze from local to metro networks, Wi-LAN Inc. demonstrated here last week a 2.4-GHz wireless LAN system that achieves data rates close to 30 Mbits/second and spans entire neighborhoods. By bringing orthogonal frequency-division multiplexing (OFDM) technology into the commercial realm, the company is creating a fresh option for carrying voice, data and even HDTV signals, pushing wireless local-loop technology into the broadband era.
Partners on hand for the launch included carriers promising major rollouts of OFDM-based wireless local-loop (WLL) systems in Great Britain and Sweden, along with chip makers whose silicon will drive the underlying hardware. Wi-LAN chip partner Philips Semiconductors (Sunnyvale, Calif.) pledged to integrate OFDM wireless access in an upcoming set-top box, while Texas Instruments Inc. (Dallas) touted the Canadian company's I.WiLL system as spotlighting the parallelism possible in the TMS320C6x digital signal processing architecture.
OFDM modulation has been long on promise but slow to win respect. That appears to be changing. Just two weeks ago in Vancouver, B.C., sessions of the International Conference on Communications on OFDM coding were jammed to capacity. At last week's demo, Wi-LAN chief executive Hatim Zaghloul wryly told partners and guests that "we were into OFDM before OFDM was cool."
By implementing multimegabit Internet access in 2.4- and 3.6-GHz bands, the demo raises the issue of whether a WLL infrastructure can replace licensed broadband wireless schemes such as Metropolitan or Local Multipoint Distribution Services (MMDS and LMDS). That possibility arises just as LMDS providers step onto the acquisition and partnership merry-go-round (see related story).
Wi-LAN executives played down the competitive angle. In most cases, they said, broadband WLL will serve as a campus or multiblock access service for a system such as LMDS. Indeed, Wi-LAN has completed some I.WiLL demos in conjunction with an LMDS system. But, Zaghloul added, "it can also be used with fiber or coaxial as a backbone, and right now we're asking ourselves whether LMDS is interesting or not."
Wi-LAN's belief that orthogonal coding could be used cost-effectively in parallel DSP architectures led the IEEE's 802.11 working group on wireless local-area networks to add a special adjunct, 802.11A, just for OFDM. But last week's rollout takes the modulation concept far beyond LAN distances.
Wi-LAN specializes in a patented wideband form of OFDM, like that used by European digital video broadcasting networks. The European Telecommunications Standards Institute's BRAN (Broadband Radio Networks) project has elected to use OFDM in its wireless broadband systems, and Zaghloul is hoping it will find favor in the emerging work to merge BRAN and IEEE 802.16 broadband radio standards (see Jan. 18, page 1).
Steven Knudsen, Wi-LAN's vice president of engineering, said that wide-area services had been part of the company's business plan since its 1991 founding, but the cost of early DSP-board implementations was astronomical. The company diverted into wireless LANs, always keeping an eye on what was possible in processing power. Zaghloul pointed out that Wi-LAN went from Analog Devices Inc. 21xx boards, with 16 Mips of processing power, to multiple DSP arrays based on TI chips with an aggregate throughput of 6.4 Gflops.
"Our naivete helped us, in that we could show the algorithms and radio worked," Zaghloul said. "Semiconductors were on our side in the long term-we just had to sit and wait for processing power to catch up with where we needed to be."
Earlier last week, in discussing TI's acquisition of Libit Signal Processing Ltd., Leon Adams, TI director of worldwide strategic marketing, called orthogonal coding a key element of applying parallel DSPs in communications.
WI-LAN has implemented a central access system based on a quad-DSP architecture. There are four boards in the system: the DSP processor board, a system interface, a radio-frequency interface and an RF deck. Access points for I.WiLL will be on the market by August, carrying a list price of $15,000.
A year and a half ago, Wi-LAN launched an ASIC development program to shrink the system to a single board for customer premises equipment. Customer premises systems based on ASIC implementations will be offered later in the year at what Zaghloul promised would be a significantly lower price.
In theory, the OFDM system can provide data rates of up to 50 Mbits/s in ideal conditions, though normal rates hover around 30 Mbits/s. A forward error correction system uses about 7 Mbits/s, with another few megabits consumed by a spread-spectrum preamble appended to data flows. In practice, the system can sustain 22 Mbits/s.
Not only is that several times the rate of other broadband access methods for the Internet, it is enough to carry multiple MPEG-2 video signals or a high-definition TV signal. These rates also could support channelized 1394 services for interfacing consumer gizmos in a wireless environment.
M. Kursat Kimyacioglu, manager of wireless connectivity products at Philips Semiconductors, said it was precisely these factors that led Philips to consider OFDM wireless ports for cable set-top architectures. The technology could turn the set-top into a residential gateway capable of handling video, Internet access and phone service, he said. Kimyacioglu said he could not give specific details of licensing deals with Wi-LAN, but that "our first demonstrations will be soon, a few months away."
Zaghloul said Wi-LAN's next task will be to show the advantages of adding OFDM modulation boards to digital cellular and PCS/3G basestations.
OFDM involves creating several channels in a frequency band as independent modulation channels. Quadrature-amplitude and discrete-multitone modulation are both special cases of orthogonal codes.
Zaghloul said he expects to see OFDM systems emerge from Lucent Technologies Inc. or large Japanese and South Korean vendors, but there are few startups attempting to take OFDM work out of academia. One startup with an OFDM receiver, Clarity Systems, has been acquired by networking giant Cisco Systems Inc. Power-line specialist Intelon Corp. is using OFDM for ac power systems only, and not in a wireless environment.
One location where WLL already is being put through its paces is in the communities of Reading and Bracknell, England, where Tele2 UK Ltd. is building a wireless access network out of systems from BreezeCom Inc. (Carlsbad, Calif.) and Wi-LAN. BreezeCom does not see its Canadian neighbor as a competitor and is looking for more opportunities to partner with Wi-LAN, said BreezeCom's U.S. president, Bruce Sanguinetti. Indeed, Sanguinetti joined Tele2 chairman Peter Scrope to describe the Reading-Bracknell system at last week's Wi-LAN demonstration. Scrope said the license requirement for a 3.6-GHz band stipulated that Tele2 must take the network nationwide by 2003.
The next WLL network will come online from Telia Globalcast, which will implement I.WiLL in Stockholm, Malmo and Gotenburg, Sweden, this month, followed by extended systems in all Scandinavian countries by the end of 1999. Larger networks incorporating Baltic nations are on the drawing board for late 2000.
Copyright ® 1999 CMP Media Inc.
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