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Clash in the PAN as formats multiply

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

Keywords:personal-area networks? PAN? ultrawideband? UWB? Internet Protocol?

Too many personal-area networks (PANs) are trying to crowd into the digital home. At the recent Windows Hardware Engineering Conference, Microsoft Corp. disclosed its efforts to help build at least two of them.

WiNet, based on Internet Protocol over ultrawideband (UWB), and a new ad hoc, peer-to-peer capability in the works for 802.11 will join existing efforts to run Bluetooth and USB over UWB. Still other options are being considered, including running Bluetooth over Wi-Fi, creating a Wi-Fi mesh with 802.11s and running any of the above on top of an emerging IEEE standard for 60GHz radios.

The problem is that everyone has their favorite protocol. Developers differ on what they consider to be the best ideas for making it easy to associate nodes on an ad hoc wireless net. But systems have limited space for all the wide-, local- and personal-area radios and antennas that the new efforts are generating. "At this point, nothing's clear. We will be six to eight months working through this," said Alec Gefrides, a wireless strategist for Intel Corp. "People are still putting up flags for new camps."

"Right now, it's a mess," said Liam Quinn, CTO for communications and peripherals at Dell Inc. "We are collectively doing a poor job articulating what is Bluetooth, UWB and so on. If we can't do this as savvy technology people, how can users do it?"

Quinn said the industry should back UWB as a backward-compatible follow-on to Bluetooth. The resulting gigabit-class interface could enable wireless docking as well as streaming and backup between systems, he said.

But cellphone makers in the Bluetooth Special Interest Group (SIG) don't want to see Bluetooth running in the 3.1-4.8GHz UWB bands that may be used for 4G cellular. "They are taking a play-it-safe option," said David McCall, a group VP at Cambridge Silicon Radio (CSR), a Bluetooth chipmaker.

McCall said UWB could adopt cognitive-radio techniques to avoid interference with wide-area nets, although that would create extra design complexity and system costs. "There are other things you can do in radio design" to avoid the interference, he said, suggesting CSR has some proprietary techniques in its labs.

He and others said all the new PANs will have their niches. For instance, wireless USB (WUSB) is ideal for linking cameras to PCs, but is not suitable for PC-to-PC file transfers, where Bluetooth is a better choice.

"We are fully engaged in Bluetooth, WUSB, WiNet and Wi-Fi," said Vatsal Bhardwaj, Bluetooth program manager for Microsoft. "We are supporting a common user experience across buses."

But even Microsoft's top brass sees the drawbacks of being agnostic. "Whole-home computing is still too complex," Will Poole, VP of client systems at Microsoft, said in a WinHEC keynote.

Why WiNet?
One of the newest alternatives is WiNet, which encapsulates Ethernet on top of UWB. It uses separate 16bit source and destination device addresses to avoid the overhead of full Ethernet frames, said P.G. Madhavan, Microsoft's WiNet architect.

WiNet adapts security and QoS features of Wi-Fi, and has been built with low power in mind for devices that run off a battery.

Madhavan, working with a handful of unidentified partners, is also helping to define an ad hoc standard for a WUSB host controller interface based on PCI and Cardbus. The vendor-extensible interface could be made public in a few months, he said. Defining a similar interface for WiNet may also require a multicompany effort, Madhavan added.

Microsoft's position is that Wi-Fi and WiNet "complement each other," he said. "WiNet is the in-room high-bandwidth technology you can use so that you don't have to task Wi-Fi," which bridges traffic between rooms. But Quinn of Dell, which currently ships systems using Bluetooth, said he finds WiNet "very confusing," adding, "We have to push back, clarify and then move forward. It's a mess out there, and there's a chance some new technologies like UWB won't succeed."

A separate Microsoft team is working on a method of building ad hoc, peer-to-peer networking into Wi-Fi, leveraging application programming interfaces in Vista. The group hopes to enable scenarios such as letting a PC automatically discover a nearby printer, load a driver and print a pending job.

The new specs are in development as the first chips for WUSB begin to sample. Wisair is shipping hundreds of its two-chip WUSB solution. The company claims the chipset offers 480Mbps over distances of up to 10m and 53Mbps over 35m, while consuming 600mW peak. Production volumes will arrive later this year at prices north of $20.

NEC, for its part, is rolling out WUSB chipsets for hosts and hubs, touting specs that are somewhat less aggressive. Both companies said they will offer WiNet chips, perhaps before the end of the year, based on revisions of their firmware.

Pushbutton pairing
The holy grail for all PANs is a user-friendly way to let devices automatically discover one another. Sun Microsystems Inc. pioneered such an approach several years ago with its Java-based Jini software.

At WinHEC, Microsoft demonstrated a way of associating a Wi-Fi camera and a PC by briefly plugging the two together with a wired USB cable, then firing off pictures that were automatically sent to the computer wirelessly.

Separately, the Wi-Fi Alliance recently adopted a joint proposal from Intel and Microsoft for a simple wireless configuration method. It marked the first time the group had established a technical standarda fact that reflects how contentious the area has become, with separate incompatible configuration methods now being shipped by Atheros, Broadcom, Buffalo and several others.

Meanwhile, the Bluetooth SIG is working on its own scheme for so-called simplified pairing. "It's going to be as simple as having two devices with a button on each, and you push them simultaneously and they are paired," said Bhardwaj of Microsoft.

Microsoft's WiNet and Wi-Fi teams are collaborating on their own approach. It inserts Web services standards, such as WS-Discovery, into the beacon information of a wireless signal to avert the software "profile explosion we have seen in Bluetooth," said Thomas Kuehnel, a program manager in Microsoft's wireless networking group. "The features are similar to Bluetooth, but we want to do it in Wi-Fi."

At WinHEC, Microsoft rolled out a standard called Rally for easing the setup of wireless networks. Rally handles QoS, network mapping, wireless discovery and setup. It uses Microsoft's existing ConnectNow Wi-Fi setup technique, along with extensions to Universal Plug and Play, and Web services for devices.

- Rick Merritt
EE Times

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