Badges can be used to identify people and things. If the badge is made active in some way then it can tell sensing equipment about its presence and respond to commands. There are many ways to do this including RF fields (RFID tags), Barcodes and scanners, and Infra Red (IR) tranceivers are a few examples. Many of these techniques are starting to appear in freight forwarding systems and RFID tags have made an appearance in supermarket shopping systems to replace Bar Code scanners.
We have chosen the IR approach as it provides high directionality with easily obtainable parts. In particular, our system is badeg on standard IrDA components and framing. The result is that a badge can communicate with a sensor through a subset of the IrDA IrLAP protocol and we don't have to re-invent the wheel again.
IrDA has an additional benefit of being quiet short range. It is specified to operate at up to 1M with a half-angele of 15 degreese. While this may appear to be a severe limitation, it means that a badge will only register with a sensor that is close and which the badge is pointing directly at it. In an open-plan office or a sityation with lots of controllable equipment this is a godsend. The short range of IrDA also makes it harder for somone to intercept the transmission leading to greater levels of privacy and security.
A three level hierarchy of location badge functionality can be easily described.
Our Dumb Badge design is available for download. It is copyright and can be used for educational purposes only.
H. W. Peter Beadle (Email: beadle@elec.uow.edu.au)
March 10, 1997
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