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Get used to it: Multiple radios will be a fact of life

Posted: 24 Jan 2005 ?? ?Print Version ?Bookmark and Share

Keywords:ultrawideband? uwb? networking? network? ieee?

Ultrawideband (UWB) technology is hardly a panacea for wireless personal-area networking. Indeed, no single technology meets all of the needs of a mobile market soon to deliver handsets crammed with multiple radios on multiple chips.

"There are too many unsolved problems with UWB. It's interesting technology, but there are still questions whether anyone can get it to work," said Bob Heile, who, ironically, chairs the IEEE committee struggling to draft a UWB standard. When asked, the chairman rattles off a laundry list of UWB's problems.

Currently, UWB is licensed for operation only in the U.S. Japan and Europe are investigating separate spectrum bands for UWB-1 to 6GHz for Japan, vs. 6Hz to 10GHz for Europepotentially forcing specially tuned products for those regions. Meanwhile, the Multiband OFDM Alliance's version of UWB-one of two proposals vying for standardization-still lacks a media-access controller spec. Early chip sets are expected to cost as much as $20. And there's a little problem of interference.

At the 2004 Consumer Electronics Show, Heile made a point of standing between the UWB TV transmitter and receiver systems that Samsung and Motorola displayed at their booths. At both sites, the screens went blank.

"I was politely asked to move," said Heile. "Backers in both of today's competing UWB camps say that there are multipath tools that prevent this. So why does it stop working when I stand in front of it?"

About the time UWB arrives on the market, it will face competition from a 100Mbps to 5,000Mbps 802.11n specification. This next generation of Wi-Fi is expected to see use in distributing music and video around the home-one of the market beachheads for UWB.

"If you can get a good 100Mb from .11n, that could take away a major application from UWB," said Glenn Collinson, a co-founder of U.K. chip maker Cambridge Silicon Radio (CSR). CSR is already putting some .11n-like features, such as multiple receivers, in its Wi-Fi chips.

One-chip wonders

Rather than rely on UWB to solve all problems, engineers ought to consider multimodal chips that integrate Bluetooth, Wi-Fi and Zigbee, said Heile, who also chairs the Zigbee Alliance. "It would be very cost-effective for chip makers and systems OEMs, too."

But chip makers greet that idea coldly. "Most of the radios we are talking about are not too complex to implement in CMOS, so it's not a question of technology. It's a question of when market volumes are adequate to drive silicon integration," said Avner Goren, director of marketing for the cellular chip group at Texas Instruments Inc.

Collinson of CSR agreed that it makes no sense to integrate radio chips "until the attach rates justify it. Bluetooth attach rates [in cellphones] are at about 15 percent going to 20 percent," he said, "while Wi-Fi attach rates are at about zero. It's almost the reverse in PCs. In five to 10 years, the attach rates may be very high, and [then] it could make more sense."

In the short term, it appears the various radios all will have different uses. "What the uses cases imply is that we will have multiple radios," said Rick Wiefeldt, deputy chief technologist in the TI cellular group. "At some point in time, we may have software-defined radio or cognitive radio, but currently that does not look as interesting as we thought a few years ago."

In Wiefeldt's view, the handset operating systems will act as bridges between the software stacks of the various radios. Standards efforts from groups such as Unlicensed Mobile Access are already smoothing the road to multiple interoperable radios in mobile systems, he pointed out.

In late September, UMA released a spec for handing off wireless voice and data connections between cellular and Internet Protocol networks. That technology will be widely adopted, said execs from CSR and TI. Future standards efforts under UMA or other groups could pave the way for harmony between personal- and wide-area nets to, Wiefeldt said.

- Rick Merritt

EE Times

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