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The Active Badge Location System
R. Want, A. Hopper, V. Falcao, and J. Gibbon
in ACM Trans. on Information Systems, Vol. 10, No. 1, Jan. 1992, pp. 91-102
-- presented by Yu-Chee Tseng --
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How Do We Locate People?
 Goal: efficient location and coordination of staff in a large
organization.
 Ex: location of doctors, staffs, and patients in a hospital.
 Existing Solutions:
 broadcasting
 a phone to call several possible numbers
 a beeper with audible signal or call-back number
 key card (刷卡驗證) for access control:
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Active Badge System
 each badge that can automatically emit a unique code
 a network of sensors placed around the building
 a master server, also connected to the network, makes the
location information available to outside world
Active Badge
wireless
IR
network
Badge Sensor
Server/Application
Active Badge
Badge Sensor
...
Active Badge
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Active Badge Design (cont.)
 Pulse-width modulated infrared (IR) signaling:
 transmission range: 6 meters
 can reflect by office partitions, but will not penetrate like
radio signals
 emits a unique code every 15 sec, for about 1/10 sec.
 Quite power-saving. Can last for > 1 year.
 Has a light detector. On dark (e.g., badge placed in a drawer),
increase emitting period. Can last for > 4 years.
 Good performance to wear on breast pocket; OK to wear
on belt or waist.
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Badge Sensor and Networking
 many sensors can be installed, as the unit cost is very low.
 can be placed on walls, entrances, exits, corridors, public
areas, etc.
 sensor ---(RS232)---> computer ---(Ethernet)--> server
 up to 128 sensors can be supported by a computer
 a FIFO buffer can store 20 badge data items (to avoid
network congestion)
 sensor networking:
 4 wires (2 for power supply, 1for control/poll, and 1 for data)
 conform to telephone cabling, thus easy for cabling and lowcost
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Badge Sensor and Networking (cont.)
fig. 2
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Application: Active Office
 a system integrating
 name
 location information
 phone network
 commands supported:
 FIND (name)
 WITH (name): who are the other badges nearby name now
 LOOK (location)
 NOTIFY (name)
 HISTORY (name)
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Active Office Display Screen
 Fig. 3
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Benefits of Active Office
 automatic re-direction of incoming calls
 relieve burden of receptionist
 you have less chance of missing some important calls you
are waiting for
 receptionist can easily tell whether a person is in or not
 easier when calling for a meeting
 easy to identify visitors to our organization
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Conclusions
 Future:
 extend to 2-way communication
 Future: combine with motion detector
 can provide high security
 if a person moves without active badge being detected, an
alarm can be alerted.
 Mobile 911 (emergency call)
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