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Tunnel Construction Companies Use RFID Badges to Text Workers

Ekahau's Wi-Fi-based tags help management locate workers and communicate with them as they bore through mountains in northwest Spain.
By Claire Swedberg
Dec 15, 2009Spanish construction firms Fomento de Construcciones y Contratas (FCC) and ACCIONA are excavating a pair of railroad tunnels near the city of Vigo, in the community of Galicia, bordering Portugal. The tunnels will expand the North-Northwest Railway Corridor, which connects Madrid to Galicia for the state-owned ADIF rail lines.

Inside the tunnels are multiple hazards, including heavy equipment, dim lighting and periodic blasting to bore through the rock. To track the hundreds of workers located within these tunnels, 24 hours a day, the companies sought technology that would enable them to know the locations of workers as they bore their way through the Galaico-Leones mountains, in Northwest Spain. The firms also wanted employees to be able to send a distress message if they were in trouble.

Ekahau's T301BD Wi-Fi-enabled RFID badge has an LCD screen for displaying text messages
The two companies wanted to use the construction site's existing infrastructure, installed when the project began in 2007 (it is scheduled to be completed in 2013) with Wi-Fi nodes connected with fiber optic cabling for data and voice transmissions. In early 2009, FCC and ACCIONA began researching a real-time location system (RTLS) that would utilize that Wi-Fi network, and hired integration firm Bautel Comunicaciones to provide them with such a system.

In fall 2009, Bautel installed a system using existing Wi-Fi access points, and equipped each employee with an Ekahau T301BD Wi-Fi-enabled RFID badge, says Tuomo Rutanen, Ekahau's VP of business development. The badge transmits at the Wi-Fi 802.11 protocol in the 2.4 GHz frequency band, and also receives transmissions, thus enabling it to be used as a way to locate an individual wearing the badge, while also allowing that user and managers to communicate with each other. With a rechargeable battery, the badge beacons a unique ID number at predetermined rates, and can also send distress alerts and receive text messages.

Upon checking in for work at the Spanish construction site, each employee takes one Ekahau T301BD badge from a bank of storage slots on the wall, or on a desk. Each badge has a unique ID number that matches an ID printed on the front of the slot in which it is stored. A worker removes the badge, which is attached to a lanyard he wears around his neck, and places his own company ID tag—with picture and name printed on the front—in the slot assigned to that tag. The employee's identity and the badge ID number are not linked electronically. In that way, the individual will be tracked anonymously in the server, using Ekahau software. However, if the companies need to know which worker is connected to a specific badge, the office staff can simply go to the storage slots and find out whose ID tag has been placed in that particular T301BD badge's slot.

Once the worker enters the tunnels, the wireless access points begin capturing the unique ID number transmitted by his badge. At least one—and often multiple—access points capture the badge's unique ID number as it beacons. That data is sent from the access points to the construction company's back-end system, where Ekahau's Positioning Engine (EPE) software determines its location based on the RFID tag's signal strength as received from specific access points. Management can then view an icon on a computer display showing a map of the tunnels, Rutanen explains.

If an employee pulls on the badge while wearing it on the lanyard around his neck, it activates a security switch on the top of the badge, causing an alert to be transmitted to the Wi-Fi nodes. That alert is then received by Ekahau's Vision software, which can forward it to phones, pagers and other badges. The badges themselves can also receive messages, such as alerts from managers, or from other badges.

If, for example, managers needed to warn a worker that there would be a detonation in his vicinity of the tunnel, they would send a text message through the Vision software that would be received by that employee's badge. The worker could then view that message on a screen on the front of his badge. The badge not only beeps when a message has been received, it also flashes, in order to catch the attention of the worker in the tunnel (which can be dark and noisy). The employee can then send an acknowledgement by pressing a button on the badge, indicating he has read the message displayed on the badge's LCD screen. In the event of an emergency within the tunnel, Ekahau's Vision software can alert management with the last known location of each worker within the tunnel.

Managers at both FCC and ACCIONA can view a map of the tunnel on their computer displays, containing icons representing all staff members within who are wearing tags. The companies are currently using approximately 200 badges, Rutanen says, while other workers need not wear the badges since they do not work in highly hazardous areas.
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