The RSS (Received Signal Strength) sometimes referred as RSSI (Received signal strength indicator) is a measurement of the power present in a received radio signal. The BLE nodes used by Bluetooth Beacon Tracker are capable of measuring the RSS of nearby BLE beacons. The RSS values are measured in dBm and have typical negative values ranging between 0 dBm (excellent signal) and -110 dBm (extremely poor signal).

Please keep always in mind that the RSS does NOT decrease linearly as the distance increases and it is affected by many factors, including:

• the antenna of the device that is transmitting.
• the antenna of the node itself.
• the number of walls and other obstructions in proximity of the nodes.
• the presence of water in proximity of the nodes.
• the material of the objects inside the environment.
• the number of people.

Some empirical tests can be done to determine how the RSS varies with the distance from the nodes in a specific environment but it must be kept in mind that the problem of calculating the distance based on RSS is a noisy process by default. On top of that, the error tends to increase with the distance. So it can be relatively easy to determine when a device transmitting is very close to a node (<1m), but as distance increases the estimates become more and more erratic.

In this page it is explained how to proceed in order to find the correlation between the RSS and the distance.