Meaning of Android Bluetooth RSSI Value

Question

I'm wodering what the RSSI Value, delivered from the Android BluetoothDevice object, exactly means. Is it a value in dBm unit or only a measured signal stregth?

Thank you in advance.

Jopa

BTW, RSSI stands for Received Signal Strength Indicator – Experiential

Answer 1

The RSSI Value refers to the signal strength, and the dBm is the unit. dBm (sometimes dBmW) is an abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW).

Algesia

Answer 2

I asked a similar question (Bluetooth RSSI values are always in dBm in all Android devices?) and there was no answer at all. My app uses Bluetooth to receive data from a small load cell amplifier. While in some devices (Samsung ones) the RSSI vary as dBm (from around -20, at short distance, to around -80, at 10m), in some others (one LG model, at least) the RSSI are quite weird, as around 200 (positive value!) at short distance. I'm supposing that LG phone is not giving RSSI values in dBm. So, the meaning of RSSI value depends of each implementation in Android devices.

Franglais

Answer 3

In this blogpost on bluetooth.org it says that every manufacturer can have it's own RSSI unit or scale.

Unlike RX, RSSI is a relative measurement that is mostly defined by each chip manufacturer. There is no standardized relationship of any particular physical parameter to the RSSI reading. For example, Manufacturer A could have an RSSI max value of 100 while Manufacturer B will return RSSI values anywhere from 0 to 127. However, on one specific chip, we could have a mapping of an RSSI value to a particular physical RX value. For some platforms, only RSSI data is available from the high level API.

Stepper