At Wireless Technology Park 2011, NICT demonstrated an intruder detection system using radio signals.

This security system uses a single transmitter and several antennas to detect changes in the indoor situation from changes in the signal’s angle of incidence. Compared with conventional infrared systems, this radio system isn’t prone to blind spots, which enables it to detect changes in the state of rooms accurately and consistently.

“In the case of home security, if you press a button while you’re out of the house or in bed, the interior situation is recorded, and if there’s a change, the change is detected. For example, if a person comes in, a window is opened, a door is opened, or furniture is moved, the system detects that. So the idea is, you only need to press a button once to record the situation.”

This demo uses four antennas to determine changes from the signal’s amplitude and phase. Ordinarily, the percentage change is zero. If the situation in a room changes in some way, the percentage change increases. By setting a threshold value, you can adjust the level of change at which the alarm sounds.

“The example presented here is home security, but sensing people with radio signals is also useful for detecting, for example, if someone’s fallen down in the bathroom. In cases like that, infrared sensors can’t be used, and cameras can’t be used either, for privacy reasons. But this sensing system can be used to detect, firstly, whether there’s anyone in the bathroom, and secondly, whether they’ve stopped moving. So it could be used to monitor people’s movement in the bathroom or toilet, and it could also be used in nursing care.”

“One problem is deciding how the system will be used. For example, the frequency has to be specified to some extent, depending on the size of the room. So standardization and regulation are issues to be tackled from now on.”

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