Applications of device-free localization in the real world
What's the big deal about using RF sensor nodes to detect people? Can't you use video cameras, infrared, or simple "magic eye" light beams in doorways? Or heck, just get a dog that barks when someone's around.
Yes, all that is fine. But cameras and infrared can't see through walls very well, doorway detectors can only tell if someone trips the detector going one way or the other, and who's going to feed the dog? An array of RF sensor nodes and some clever data processing can reveal where someone is in a building or a room, which is why it's such an interesting area of research.
Here are a few of the applications this kind of device-free localization can be used for.
In this application, you don't need to know exactly where someone is, only that someone has entered a restricted area. This requires fewer nodes, and some security companies now employ this technology to protect their clients' properties.
Try out the interactive demo to get an idea of how this works.
Imagine being able to quickly set up a system of nodes around a building that has collapsed in an earthquake. It's too dangerous to enter the building or send dogs in, and the robots that have been deployed can only crawl so fast — and may hit obstacles. An array of RF nodes can be set up relatively quickly, and can be used to help find people.
For assisted living facilities, it would be useful to detect if one of their residents needs help. The concept of such facilities is that residents can live somewhat autonomously, without constant monitoring of a caregiver — even if we get to the point of having robotic assistants. Video cameras are intrusive, and there's no guarantee that someone will be looking at the video monitor when an accident happens.
If the environment itself could have knowledge of the people in it, it may be possible to monitor an assisted living facility for unusual behavior such as falls. Then there's no need for residents to wear any kind of device, such as those things you put around your neck, where you press a button if you've fallen — assuming you're wearing it when you fall and are conscious when it happens. More than once, when I told people about my senior thesis, they told me about an elderly relative who had one of those devices, but wasn't wearing it when they needed help.
Some of the above scenarios are not yet reality, or have only been done experimentally, but these are the applications we have in mind when performing research on device-free localization.