Taking a Cue from GPS
November 05, 2003
Location-based networks are hardly the norm these days, but one startup company says that's because the technology needs improvements like Time Difference of Arrival positioning techniques, which it's trialing now.
There is no lack of companies doing location-based networking, trying to make wireless LANs aware of not just who is logged on, but also where they might be. The uses of positioning go well beyond that however; companies like Newbury Networks got their start using WLAN positioning to deliver content to handhelds that could, for example, display information about exhibits in a museum as you wander around.
Existing location-based technology has been, for the most part, based on the Receive Signal Strength Indicator (RSSI), which is used to try to determine the whereabouts of a client by the energy levels of signals from laptops and access points. However, the main location-based system -- the global positioning system (GPS) -- as well as some radar systems and even some wireless 911 emergency systems, use what's called Time Difference of Arrival (TDOA) positioning.
One startup location-technology maker, Cognio of Waltham, Mass., says it can provide TDOA to WLANs today.
Kurt Hoff, company CEO, says "an understanding of the complete RF environment can make [positioning] work better."
"Tools that use signal strength to find location have to be properly calibrated," says Hoff. "A change of moving a single filing cabinet can mess it up. Things fall apart. Because we base our calculations on the speed of light, fundamentally, there's no need for calibration or recalibration. You're accurate and reliable at install, the next day, and the next month."The TDOA technology is part of Cognio's overall Intelligent Spectrum Management (ISM) solution, which it says manages the unlicensed radio frequency (RF) spectrums used by 802.11a (5GHz band) and 802.11b/g (2.4GHz). Cognio plans to provide ISM in licenses to original equipment manufacturers (OEMs). Chip companies can build the ISM system into silicon, hardware vendors can incorporate it into access points.
"Primarily the difference between a product with our technology and others is that it can detect and identify any emitter in the unlicensed band," says Hoff. "An access point [with ISM] can see not only the 802.11 devices, but any device emitting energy in the unlicensed 2.4 or 5GHz bands, so it would see Bluetooth, or a cordless phone, or a microwave, or radar -- anything using the spectrum at the same time."
Cognio's first product is Astra, a hardware and software reference design using ISM. The company is providing prototypes now and expects products using its technology to be available by the second quarter of 2004. The company's other big news was that they are currently doing an "overlay" trial of the ISM with TDOA technology. Hoff would not identify the company, but said that it is in the Pacific Northwest and has the largest enterprise deployment of 802.11 access points in the world. (He stopped short of saying it rhymes with Nicrosoft.) Cognio has augmented off-the-shelf access points with ISM, which will report back to a white-box server running Cognio's software at the company NOC.
Ultimately, the overlay solution they're trialing is not the way Cognio wants to go. Instead, Hoff would like to see ISM embedded in units from enterprise WLAN product vendors. The licensing of Cognio's technology to others is, he believes, the beginnings of putting location-awareness into everyday WLAN products.
In discussions with potential customers about whether they'd be willing to deploy extra hardware as an overlay to get monitoring or location-awareness, Hoff says customers said those features should be just that -- features of products, not products in and of themselves.
"The analogy we like to use is that the tools and infrastructure available to WLANs today are analogous to airline collision detection programs that only identify jets from Delta," says Hoff. "While necessary, that's woefully insufficient. You need to see other jets, weather balloons, and anything else that's up there."