RSSI Fluctuation

I was trying to keep an iBeacon at a fixed place and receiver iPhone also at a constant location.
I was displaying the received RSSI on the plain mobile phone screen.
It seems that RSSI at a location is not consistent with 600mS or above as advertising interval.

Is this the expected behaviour ?

Hi Coimsat,

The stability of the Beacon’s signal is based on two main factors - advertising interval and signal strenght.

Advertising interval - the Beacon is not broadcasting continuously - it’s ‘blinking’ instead. The interval describes the amount of time between each blink, so in layman’s terms, you could just refer to it as frequency. The more frequent the blinks, the more reliable the signal.

Signal strenght - imagine that Beacon is your Hi-Fi set, and the broadcasting power is the volume setting. If you turn it up, you could hear it playing from far away, and as you’re getting closer, the sound becomes really crisp and clear. But if it’s really low, you might have problems with figuring out what track is playing even with your ear stuck to the speaker.

Now, it gets more complex. Imagine that the Hi-Fi set was put in some crowded place. You can clearly hear it playing, but it's really loud in there, so locating it becomes much harder.

It's pretty similar with the Beacons. But instead of city noise, you encounter factors like wave diffraction, multipath propagation, absorption or interference.

We use a value called RSSI (received signal strength indicator), which allows to estimate the proximity based on signal power. However, even calibrated, it might fluctuate heavily, due to the factors mentioned before.