RSSI and Kalman Filter

RSSI

(reference: https://www.wouterbulten.nl/blog/tech/kalman-filters-explained-removing-noise-from-rssi-signals/)

RSSI (Received Signal Strength Indicator) is a kind of a power of received radio signal, which is measured in dBm. As you might expect, the higher the RSSI value, the higher the signal strength. 

Since we can describe RSSI with distance using a model, the Log-Distance pathloss model, we can get the measurements to distance in meters with RSSI.

RSSI=−10nlog10(dd0)+ A0A

In this equation, d is the distance between the transceiver and recipient, n is the signal propagation exponent, and A0 is a referenced RSSI value at d0.

Kalman Filter

Even if we translated the distance from RSSI, in the real world, RSSI value is more influenced by the environment with the high level of noise. In order to filter out the noise from the raw RSSI signal, we use the Kalman Filter. 

RSSI=−10nlog10(dd0)+A0(1)