Airport Monitoring System Combines RFID With Video

The designers of the system chose 5.8 MHz because the frequency isn't too crowded. "We like 5.8 because, at the moment, there isn't too much interference and the antennae size is small, so it makes the tag and reader more compact," says Brennan. "We could make it work on other frequencies [as well]. It's not critical." He added that consortium members are also developing their own readers with extra functionality to locate individuals based on triangulation.

Each tag will send out a pulse twice per second. The pulse will be received by at least two readers. Prototype readers include four antennas and a microprocessor, which will perform computations to determine the direction of the signal. With two or more bearings for the same tag, the computer system can be programmed to triangulate, calculating the position of one tag based on the angle of arrival of the signal. Personal information in an airline's system, such as the passenger's name, age, gender and flight number, can then be linked to the tag's unique ID number.

The consortium initially considered calculating the location of a person carrying a transponder by measuring the time difference between when the device transmits a signal and when the reader receives it. However, Brennan said such a technique would be more difficult to implement because it would require greater transmission bandwidth. The data rate currently planned is 1 megabit per second, which would take 1 MHz of bandwidth. If a time-difference analysis were to be conducted, 150 MHz of bandwidth would be needed because the range resolution (how accurately you can pinpoint the range of something) varies with signal bandwidth.

The final component of the system, the user interface, is also being developed in-house, with the help of UCL's Geomatic Engineering Department. Plans are in place to create a simple interface using the C++ programming language.

"With enough development time, we could make a sophisticated interface that could be used to archive location information to be reviewed later if there was some kind of safety or security incident," Brennan says. "This could be a project in itself."

The simple interface currently planned will allow video output to be panned and zoomed for easier use, says Phil Bacon, a project consultant for Europus, which puts together and manages multidisciplinary research-and-development projects in Europe. Bacon helped the consortium win funding for the project by bringing together partners and managing the grant-application process. He continues to work with the project within a limited scope as a project manager.