The measured power value represents the received signal strength indication of the beacon when measured from 1 meter away. This value is expressed in Decibel-milliWatts (dBm) and typically ranges from -40dBm to -80dBm. This value is included in the beacon advertisement and is used by receiving mobile devices to compute the approximate distance of the mobile device from the beacon. This calculation involves computing the approximate distance as a factor of measured power and the currently received signal strength indication value.
The measured power value is established by a calibration process that requires a minimum of 20 samples from 1 meter away from the beacon, ideally using an iPhone 5S as the reference calibration device. The Calibration feature of the RadBeacon for iOS app automates this process for Radius Networks customers.