[opendtv] Ultrawideband under the gun

Would be nice to know the unvarnished details.

This scheme they're talking about is the one in which three low-power
and wide band COFDM channels are used, to mimic a UWB signal. Something
isn't meeting up with all the previous hype, but they don't tell us
what.

My quess is that the peak to average power ratio being what it is, the
power had to be turned down lower than they hoped, to keep this from
interfering.

Bert

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Ultrawideband under the gun

Rick Merritt
(10/25/2007 8:47 AM EDT)
URL: http://www.eetimes.com/showArticle.jhtml?articleID=202601507

SAN JOSE, Calif. - In the race to a gigabit-per-second wireless link for
the digital home, some ultrawideband backers are gasping for air while
Wi-Fi proponents are revving up for the next lap.

An IEEE 802.11 study group is gearing up to launch a standards effort
next year that could pave the way for Wi-Fi to step up to 3-5
Gbits/second data rates. Meanwhile an independent tester reports two UWB
products now shipping have average throughput of just 20 Mbits/second at
a range of 15 feet.

"We are finding throughput is quite disappointing," said Fanny
Mlinarsky, an industry expert in wireless test. "There is nothing above
50 Mbits/s maximum, and the average is 20 Mbits/s. Everyone thought this
was going to be the short-range Gbit network," she said.

Mlinarsky's lab, Octoscope, is conducting tests of shipping UWB systems
sponsored by UWB vendor Pulse~Link Technologies. So far, companies
shipping UWB silicon have declined to participate in the tests, many
citing the fact a competitor is sponsoring the program. Jack Shandle,
editor of sister Web site Wireless DesignLine, has publicly called on
UWB chip makers to participate in the tests, so far without effect.

Vendors said inefficiencies in today's media access controller chips and
software drivers are inhibiting throughput, something that should be
cleared up in future products. Mlinarsky plans to acquire a LeCroy
tester to check the physical layer performance of the systems.

"We are getting less than a tenth of the PHY data rate-that can't be all
MACs and drivers," she said.

Octoscope tested systems from Belkin and IO Gear using Alereon chips. It
plans to test Toshiba systems using other silicon this week. Pulse~Link
did not ship its test chips to Octoscope before fires swept through the
San Diego area this week, cutting off some communications.

Mlinarsky believes the orthogonal frequency-division multiplexing
technology used in the wireless USB version of UWB may be the culprit.

"Everyone joined Intel in the WiMedia Alliance before they did due
diligence on the technology," Mlinarsky said. "OFDM is not the optimal
choice at these low power levels, so the industry may have made a
mistake," she added.

Companies doing their own tests of UWB silicon agree that performance of
the parts is so far unacceptable.

"I haven't seen anything I want to build a product around. We can't
afford to design in a 1W radio to get less than 100 Mbits/s over a few
feet," said John Barr, a standards director at Motorola.

The UWB problems may be just a passing storm, said wireless analyst
Craig Mathias of Farpoint Group (Ashland, Mass.). But the problems need
to get addressed soon or other technologies such as advanced Wi-Fi or
emerging 60 GHz radios will steal UWB's thunder, he added.

"We think UWB can get to 200 to 300 Mbits/s at the application layer
without too much trouble," said Mathias. "We think this is just a matter
of early chips and drivers [but] UWB doesn't have this market all to
themselves," he added.

Indeed, last week IBM backed an emerging push to 60-GHz radios, an
approach pioneered by startup SiBeam for a variety of consumer uses. IBM
said it will make in its silicon germanium process radio that can be
paired with baseband chips from MediaTek and other companies.

Another startup, New LANs, also is pursuing 60-GHz radios. Meanwhile
other companies such as Amimon and Radiospire are rolling out their own
approaches to Gbit-class wireless links for a range of consumer
applications.

For its part, the IEEE 802.11 convened a Very High Throughput study
group to look at Gbit-class versions of Wi-Fi. To date, the group has
heard a range of presentations from AT&T, Intel, Motorola, Nokia and
startup Wilocity. It could be ready to launch a formal standards effort
as early as January.

One presentation mentioned the possibility of building 3 to 5 Gbit/s
products in the 5-GHz band that could serve a range of uses including
wireless links to monitors, projectors and video cameras. Those are some
of the same apps UWB is attacking.

A presentation from AT&T Labs called on the group to raise its voice
against spectrum allocation plans in Europe that could shut Wi-Fi out of
the 275 GHz to 1 THz bands.

"The best terahertz spectrum is being carved up among science, satellite
and amateur radio interests. The give-away of this precious spectrum is
unexpected, capricious and irreconcilable with the evolution of future
broadband wireless networks," David Britz of AT&T said in his
presentation.

Britz also noted that startups such as Phiar Corp. (Boulder, Colo.) are
already working on terahertz-class transceivers. "The 2.4 and 5 GHz
bands are getting crowded, and 60 GHz is looking like the promised land
for high performance LANs," added Mathias.

Meanwhile, the many startups pushing UWB could be running into trouble
keeping investors interested. Several sources report Tzero Technologies,
one of the early hot startups in UWB, may be taking a hard look at its
options. "We are in the midst of a funding round and its OK, but not
going as rapidly as we would like," said a company spokesman. "M&A is
one of the possibilities. We have talked to strategic investors for
awhile. It's anybody's guess how things will end up," he added.

Tzero has working UWB chips that can deliver more than 200 Mbits/s at
the applications layer, he said. But the company has no independent
testers who can verify that claim and has so far opted out of the
Octoscope tests.

All material on this site Copyright 2007 CMP Media LLC. All rights
reserved.
 
 
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