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New Active RFID System Strives to Eliminate the 'Overhead'

InPoint says its system—consisting of "dumb tags" that transmit only an ID number, and low-cost reader modules that plug into computers—can read and locate more than 1,000 tags per second in highly metallic environments.
By Claire Swedberg
Jun 18, 2010Two health-care companies and two U.S. Department of Defense (DOD) agencies are testing a prototype of a new active RFID system known as Roll-Call. The new system promises tags that are smaller and less expensive than active tags currently on the market, and that are designed to operate in hostile environments, such as those with densely packed, tagged products or a high quantity of metal. Developed by InPoint Systems, a start-up company based in Los Altos, Calif., the Roll-Call system can not only determine a tag's location, but also provide information regarding the tag's movement and any activity around it, says Eitan Fenson, one of the company's four founders.

Unlike most RFID transponders, whether passive or active, a Roll-Call tag transmits only its license plate (the payload) at a preprogrammed rate—every five seconds, for example—while it has no other built-in intelligence or "overhead," such as instructions allowing the tag to store information or receive transmission from readers. The tag, which Fenson describes as "brain dead," simply transmits a ultrahigh-frequency (UHF) 900 MHz signal encoded with an ID number, using a proprietary air-interface protocol. Because that is all the data being sent, it can operate in environments in which passive or other active tags may struggle, such as around large amounts of metal.

Eitan Fenson, InPoint's president and CEO

The intelligence, Fenson says, is built into the reader side of the system. A simple reader module, used merely to receive the tags' signals, plugs into a USB port of what InPoint calls a hub—a small, off-the-shelf Linux computer with Power over Ethernet (or any other generic computer running on a Linux operating system)—which is loaded with software that records and analyzes the tag signals. Two or more reader modules connected to a single hub via USB cables could cover a 400-square-foot space, such as a typical jewelry store. With multiple hubs, the data is then forwarded to a central server, where the Roll-Call software calculates a specific tag's location in 2-D using the Generalized Real-time Adaptable Indoor Localization (GRAIL) algorithms developed by Kordinate, a real-time locating system (RTLS) research-and-development firm based in Metuchen, N.J. During the past two years, Kordinate assisted InPoint in the research and development of the Roll-Call system, says Richard Martin, Kordinate's chief scientist and an associate professor at Rutgers University's computer science department. Some staff members and top executives of both companies serve on Rutgers' faculty.

With GRAIL, Martin explains, the system can not only determine a tag's approximate location within about 10 feet, but also determine when its RF signature changes, which would occur if the tag moved at all, or if something passed in front of it. This detection of movement, Fenson says, is of greater importance to many end users (including jewelry retailers) than location data more precise than 10 feet.

A server using data from an array of computers (hubs) fitted with Roll-Call RFID reader modules is able to discern whether a tag has moved, or if an untagged person or object has moved around it, based on a change in the RF signature. The readers can also capture the ID numbers of more than 1,000 tags per second, Fenson says, and they can successfully do this with tags from a distance of 20 feet to hundreds of feet, in densely packed, highly metallic environments with a great deal of background RF noise. A hub with a single reader module, he adds, can process beacons from several thousand tags continuously. "Our simulations yield results in excess of 10,000 tags in benign circumstances," he says, estimating a more challenging environment to be approximately 3,000. A single computer can serve as a hub for as many as four reader modules, thereby providing a measure of redundancy and resulting in even higher read rates.

Fenson and his colleagues initially developed the technology to track jewelry, and two of the founding members come from the jewelry retail industry. The challenge at that time, about two years ago, was to develop a system that would provide jewelry retailers with real-time data regarding the location of a large number of items from a tag small enough to be attached to each ring, necklace, bracelet or watch. As the jewelry industry has been in recession, Fenson says, the company is now targeting several other markets.

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