U.K. Researchers Study Distributed Antenna System for Airports

By Rhea Wessel

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.

Airports and other large, complex infrastructures have diverse communications needs that include complex and often varying service requirements, traffic profiles and user expectations. A project known as TINA (The INtelligent Airport) aims to develop a self-organizing, next-generation advanced wired and wireless network that will meet the expectations for future airport environments.

The TINA system is designed to handle a wide range of fixed and mobile equipment, including RFID readers, security cameras, biometric sensors, and explosive and chemical detectors. It is also built to provide logistical support for passenger information and entertainment services, airport retailers, transport services and runway operations. With such a capability, the system is expected to meet other application requirements as well.

Sithamparanathan Sabesan

This three-year research project is being conducted by the University of Cambridge, the University College London (UCL) and the University of Leeds, with funding provided by the Engineering and Physical Sciences Research Council (EPSRC). The project is managed by Ian White, a professor of engineering and head of Cambridge University's School of Technology. At Cambridge, White works alongside Michael Crisp, Richard Penty and Sithamparanathan Sabesan, a researcher at the university's Centre for Photonic Systems. The team collaborates closely with Bill Krug of Boeing.

According to the group, airports will require extremely advanced adaptive computing and communication systems to provide users with mobile, secure and automatic means of conducting business. One prime application area is in international travel, which necessitates any solution being implemented on a global scale.

The main focus of the research carried out by Cambridge University's Engineering Department, under the TINA project, is to support passive RFID technology that is expected to be of particular interest in airport applications, on a radio-over-fiber distributed antenna system (DAS) that will also simultaneously carry other wireless services, both current and future. One of the many advantages of radio-over-fiber is the inherently wide bandwidth, enabling all common communications standards to be supported simultaneously on a unified infrastructure. Since the system allows radio frequency identification to be supported alongside these services on the common infrastructure, ubiquitous RFID coverage can be provided with little additional cost.

It is anticipated that passive RFID tags in airports will be used to track a wide range of objects, including luggage and commercial goods, as well as on intelligent boarding passes and access-control tags, and for goods-location support in airport shopping areas. The use of these RFID tags can also aid the detection and identification of possible threats by intruders, and will improve efficiency and security through the active tracking of passengers and employees. The RFID system must be in a form that can be readily integrated with other systems, such as CCTV-based vision systems, in order to ensure maximum robustness and security. Other applications include the location of checked-in passengers who are either missing or late, which should help reduce passenger-induced delays, and thus speed-up aircraft turn-around times.

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.