For a project, I read the Received Signal Strength Indicator (RSSI) out of the Advertising Data. My question is, in which relationship stands this value to the absolute value of the Received Signal Strength?
The value depends on the environment conditions and distance between central and peripheral.
RSSI value depends on the environment. It can either increase or decrease the value (as the interference can be constructive or destructive). If your environment has many wireless devices, then there could be more variation in the RSSI value.