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Wibree turns handsets into sensor gateways

Posted: 01 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Wibree? Bluetooth? Nokia? mobile? handset?

Wibree, which aims to develop a low-power extension to Bluetooth for a short-range wireless sensor link, was unveiled at Nokia Research's 20th anniversary press event in Helsinki last October, as part of the Finnish company's overarching theme of making technology as human and personal as possible. Doing so means engineering a handset that is more aware of its surroundingsone that has ambient intelligence, such that it can configure itself to take advantage of available resources like displays, memory and processing power; select applications; and implement location-based services.

"The mobile device becomes the gateway to both the global networked world and the physical world," said Tapani Ryhanen, head of strategic research at Nokia Research Center.

In the near term, the company envisions a simpler model that provides a link for short-range connections to devices such as heart monitors and pressure sensors, pedometers and dive watches, and mice and keyboards.

"The ultimate potential here is huge," said Jan Rabaey, co-director of the Berkeley Wireless Research Center in California. "What's happening today is that you have more and more little devices or gadgets, and one way or another, they'll all have a wireless interfaceand that's where you open the door to new types of applications." Such a link, he said, could one day enable the ad hoc self-configuration of local devices using ambient intelligence.

Although "manufacturers would like to make the cellphone the center of the universe," Rabaey said he is wary of making the handset too feature-rich, given the power constraints: "You're tied to under 3W." Also, cellphone operators will be competing for this central role with last-mile-access providers of all sorts, from fiber to DSL to cable. So their ownership of the subscriber isn't a slam dunk.

Wibree: Low-power extension to Bluetooth for short-range wireless sensor links.

Technical issues also abound, from device discovery and control to lowering power consumption to the point where the device can run for months in the field on nothing but a coin battery. Peak, average and idle power consumption are a concern, as are cost, size and ubiquity, said Bob Iannucci, senior VP and head of Nokia Research Center.

Meeting these interface needs is the goal of Wibree. Developed within Nokia, the extension to Bluetooth allows for data rates of up to 1Mbps over distances of 5-10m in the 2.45GHz band at very low power. Though Wibree is similar to Bluetooth and can leverage the same chips and antennas, it diverges in important ways. Wibree does not use frequency hopping for interference avoidance, as Bluetooth does. It has a variable-length packet structure vs. Bluetooth's fixed length. And it uses a different-unspecified-modulation scheme. All told, the innovations can reduce power by up to 10x, said Iannucci.

In addition, Wibree "uses AES security from the start," whereas AES is "only just now being adopted in Bluetooth," said Jani Tierala, manager of business development for Nokia Research. Though the modulation scheme is unspecified and Tierala said functions such as profiles and device discovery are still being defined, he expects the specification to be completed by Q2 2007, with chips following in the second half. The specification will provide for both standalone Wibree and dual-mode Bluetooth/Wibree implementations.

Nokia hopes to push Wibree through established standards bodiesthe Bluetooth Special Interest Group (SIG) is the obvious oneand will license the technology to any interested party. The initiative was launched with chipmakers CSR, Broadcom and Nordic Semiconductor on board as partners and licensees.

Why Bluetooth?
By leveraging Bluetooth instead of developing a standard from scratch, Nokia aims to give designers an embedded base and an established infrastructure and brand to tap into. "The big question over the years has been, 'What do I connect to once I'm wirelessly enabled?'" said Eric Janson, senior VP of worldwide sales for chipmaker CSR. "Bluetooth has shipped about a billion units500 million this year alone, and it'll be up on that next year."

Those volumes also lower the cost. According to Janson, Nokia's target is to add no more than 15 cents to chip costs, with a total cost target of 65 cents. That there are theoretically no hardware changes required to the basic Bluetooth chip design goes a long way toward ensuring those price goals can be met. "There will be a change in the coefficient for the Gaussian shift keying, but most of the rest of the changes will be in the MAC," said Janson. Those MAC changes include setting up for longer periods of deep sleep to save on power.

While the arguments in favor of leveraging Bluetooth are strong, so too are the arguments against it, in terms of both performance and established market competition. "Bluetooth was never designed with power in mind," said Berkeley's Rabaey. Although he said he has yet to see the figures for anticipated Wibree power levels, Rabaey noted that "they're taking something that's not very good to begin with. They need to think more orthogonally."

Wibree faces tough competition in low-power sensor applications. The spec's success rides on installed Bluetooth base and infrastructure.

In terms of competition, Wibree will go up against both proprietary solutions from the likes of Analog Devices and standards-based offerings like Zigbee. "It's very clearly entering the Zigbee space, but you don't see Zigbee in watches," said CSR's Janson, who sees Wibree as also applicable in home automationa key target market for both Zigbee and competing technologies like Zensys' Z-Wave.

Wibree may even face competition from Bluetooth itself, as the Bluetooth SIG has been continually tweaking the specification to optimize for power. Version 2.1+EDR, due out in the December to January time frame, will include features such as sniff subrating. "This would allow a device to extend its sleep mode without losing its priority in the network," said Mike Foley, executive director of the Bluetooth SIG, who added that the group keeps chipping away at the protocol to address wristwatches and the like. Long sleep times with sporadic communication are an inherent requirement for sensor devices.

While Foley has yet to see the Wibree specification, much less start the evaluation process for getting it incorporated into the Bluetooth SIG's spec, he's open to the possibility. "I don't know if Wibree is the way to do it, but I would like to learn more about it," he said. "If it's the best solution, we will incorporate it."

Depending on how complex the scheme is, Foley said, ratification could take anywhere from six to 18 months.

- Patrick Mannion
EE Times

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