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U.K. Researchers Study Distributed Antenna System for Airports

The group is developing a network infrastructure that will provide ubiquitous wireless coverage for RFID, as well as for a broad range of other equipment.
By Rhea Wessel
Speaking at last month's RFID Journal LIVE! Europe 2010 conference, Sabesan explained that the DAS system is based on a new form of wireless signal distribution in which multi-service antenna units cooperate, not only to provide communication, identification and location services, but also to offer network resilience.

In addition to security applications and those that help reduce passenger-induced delays, the TINA network can also be employed to manage a wide range of fixed and mobile equipment, Sabesan says, such as wireless security cameras, mobile data terminals, biometric reading terminals, RFID-based boarding cards and information and entertainment displays.

In designing the system, the research team chose to utilize passive tags since they are cheap and widely available. A similar research project known as Optag, conducted in the United Kingdom and also involving UCL, focused on an alternative active tag technology (see Airport Monitoring System Combines RFID With Video). There is much interest in designing a system that can identify and locate passive RFID tags, however—though this involves significant technical changes if the antenna range is to be large enough for suitable applications. The researchers anticipate that such a system would need to track approximately one million moving tags per day, and the tags must be compact, cheap and reusable. To meet this challenge, the team needed to develop a new form of wireless signal distribution, by which multiple services (including communications and public safety radio, as well as passive RFID) could be supported.

In addition to supporting RFID on the same infrastructure as other wireless services, the RFID-enabled DAS is anticipated to have 100 percent coverage, comparable to a wireless local area network (WLAN), thus allowing the same wideband antennas to be used for all wireless services. This is beyond the capability of any current passive RFID system, the researchers note, but with direct support from Boeing, research has been carried out to overcome this challenge. In short, Sabesan says, the group wanted to use passive tags that would provide sufficient read ranges and could be read in bulk while providing enhanced location accuracy.

In their work, the researchers are employing a DAS solution from Zinwave to increase the read range of passive RFID tags, and are applying a number of techniques to enhance the passive RFID coverage. To date, the team has demonstrated RFID tag reading within a three-antenna DAS system, with 100 percent of the read test points reported as successful. According to the researchers, the detected signal strength from the tag has also been observed to increase by an average of 15dB, compared with a conventional RFID system for the same total antenna power.

The DAS system, used in conjunction with an off-the-shelf Motorola EPC Gen 2 RFID interrogator and Alien Technology ALN-9540 Squiggle EPC Gen 2 passive tags, was demonstrated to an industry advisory board of the TINA partners. "We demonstrated error-free tag reading using a commercial Gen 2 RFID reader at reduced output power over a 20-by-6-meter area," Sabesan says. A report about the demonstration was published for the IEEE RFID 2009 conference, an event colocated with RFID Journal LIVE! 2009.

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