A device can use the Power Control Request procedure to check whether its peer can accept such a reduction in power and, if so, adjust its transmit power based on the response. Nevertheless, it may still be able to receive the signal at a level that is equal to or above a minimum acceptable RSSI (RSSImin) that is lower than the current RSSI. A device with such a receiver can use the Power Control Request procedure to bring the current RSSI (RSSIcurr) of the incoming signal to a preferred value within its golden range. Here is the description from the 5.2 specification for your reading pleasure:Ī radio receiver may have a "golden range" of RSSI that it prefers the incoming signal to remain within. That is, a device may have what the specification calls a golden range of power levels that is best to receive a signal. We must understand how the wireless system in use defines RSSI.īluetooth simply links the RSSI to dBm with +/- 6 dB accuracy in some cases however, it also allows for a remapping of RSSI based on a golden range for receiver signal strength. For this reason, we cannot just define RSSI as the received power in dBm. Therefore, an RSSI of -16 is not referencing -16 dBm, but rather it is referencing -80 dBm. For example, a reported RSSI value of -16 corresponds to a received signal strength of -80 dBm. RSSI reports shall be biased by +64 dBm to give an effective range of -192ĭBm to +63 dBm. RSSI shall be reported as a signed 8-bit integer, reflecting an estimate of received signal strength in dBm. For example, the ISA100.11a standard states: The reason? It is so non-specific as to leave it open for all of the varied definitions used by different standards and technical documentation. Oddly, this Wikipedia definition is among the best.
Wikipedia defines RSSI as: a measurement of the power present in a received radio signal. In the Bluetooth specification (5.2) RSSI is variously referenced as Receiver Signal Strength Indicator, Received Signal Strength Indication, and Received Signal Strength Indicator. Ok, those two are close enough, but sometimes things get a little odd. For example, sometimes you will be informed that RSSI stands for Received Signal Strength Indication, but more often you will see it referenced as Received Signal Strength Indicator. In this post, I will attempt to reveal the source of confusion and then do my best to clear it all up.įirst, one might ask if there is an authority on definitions of terms or acronyms like RSSI. The first several pages are filled with results defining and using RSSI in different ways. If you search for RSSI (Received Signal Strength Indicator) on the Internet, you will find 3.5 million results.
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