RSSI (Received Signal Strength Indicator) is a measurement of how well a device (phone, laptop, IoT device) can hear a signal from an access point or router. It measures the power level received in decibel-milliwatts (dBm), usually as a negative number between 0 and -100, where numbers closer to 0 indicate a stronger, better signal.

Interpretation: Because it is measured in decibel-milliwatts (dBm) the values are negative. A higher value (closer to zero, like -50) is better than a lower value (farther from zero, like -90).

Limitations: RSSI does not always reflect signal "quality" because it can include interference and noise in its total measurement.