Bluetooth LE RSSI for proximity detection iOS

Question

I\'ll start with the question.

Is the BTLE RSSI a good way to indicate two devices proximity to each other or not? does it only work with small devices like fobs et

Answer 1

The experience of Matthew Griffin matches mine. However - when we can measure for a fair period of time two things have helped us calibrate this better.

We did have to wrap a simple (kalman) filter on the antenna orientation and the IMU to get a rough running commentary though - and this is not very CPU or battery light.

• Using the IMU you get a fair idea of the distance/direction of travel - and if this is over a short period of time - we assume the other 'side' is stationary. This helps a lot to get a value for 'current' orientation and 'callibrate current environment noise.
• Likewise - do the same for rotations/position changes.

We've found that in general a re-orientation of the device is a better way to get direction; and that distance is only reliable some up to some 30 to 600 seconds after a 'move' calibration' and only if the device is not too much rotated. And in practice once needs some 4-5 'other' devices; ideally not too mobile, to keep oneself dynamically calibrated.

However the converse is quite reliable - i.e. we know when not to measure. And the net result is that one can fairly well ascertain things like 'at the keyboard' and 'relocated'/moved away through a specific door/openning or direction. Likewise measuring a field by randomly dancing through the room; changing orientation a lot - does work well once the receiver antenna lobes got somewhat worked out after a stationary period.