Active Badge, the predecessor to Active Bat, worked on much the same principle. However, it used an infrared signal and could pinpoint the device only to within a few feet. Ward and his colleagues at the Cambridge labs, formerly known as the Olivetti Research Labs, are looking for a way to allow doctors, for example, to be able to immediately access patient information from the network as they move through a hospital. Each Active Bat transmitter uses 48-bit encryption for the user's identification and would be more secure than a password. Of course, the transmitters could be easily lost or stolen, Ward noted, and might be used in conjunction with a fingerprint or other biometric scanner installed in the wearable device.
Cost is a factor in the development of ultrasound tracking technology, according to the researchers.
The Active Bat system would require a smaller, but still significant, infrastructure investment. Currently, Active Bat receivers must be placed every 1.2 meters or so to work, which is roughly every third or fourth ceiling tile. Ward said he's working on reducing the number of receivers needed, which would lower costs. But it's probably going to be several years before this is commonplace. Ward said the ultrasound emissions are within guidelines set by international health bodies, and those standards have been tested for 20 years with no evidence of ill effects on humans.