Since accelerometric sensors require high amounts of power, active tags are often used. Instead of utilizing active tags, however, we would like to use two or three passive tags to track when patients have fallen. Is this feasible?
Technically, this might be feasible, but I don't think it would be very reliable or practical. First, let me explain how I think it might be done, and then I'll discuss why that approach would not be very practical.
You could place RFID readers every 5 to 10 feet along each hallway in which you to track patients. This would require putting antennas on both sides of every hallway. You could then situate one set of antennas about 5 feet off the floor, and another at a height of approximately 1 foot.
The antennas would be linear-polarized, so they would create beams of energy at the 1- and 5-foot levels. Patients would be tagged on both shoulders. If a patient were to fall, the tags would no longer be read by the antennas 5 feet off the floor, but they would be picked up by those near the floor, thereby indicating that the patient had fallen.
This system might not be reliable, however, because the tags might not be read for a variety of reasons when a person hit the floor, or while he or she was walking around. I would suggest using two tags, in order to make sure at least one tag was read, but there still might be issues ensuring that the system would be accurate.
The bigger problem, of course, would be that it would cost a lot of money to provide ubiquitous coverage within a hospital, or within a hospital wing, using a passive solution in which antennas are placed a few feet apart and at both the 1- and 5-foot levels. This would likely be more expensive than employing active tags that broadcast their signal hundreds of feet, allowing you to cover an entire hallway with only one or two interrogators.
—Mark Roberti, Founder and Editor, RFID Journal
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