In Betaflight OSD, Modern RC systems like ExpressLRS, Crossfire, and Tracer support RSSI dBm reporting, but older systems like Frsky and Spektrum only support RSSI in percentage. RSSI dBm is the recommended option as it provides a true measurement of signal strength. In Betaflight OSD, you have two different RSSI options RSSI Value (in percentage) and RSSI dBm Value. As you can see in this conversion table between dBm and mW, it perfectly demonstrates the benefits of using dB over mW. It’s just so much easier to use dB when there are so many zero’s in mW. Using dBm is preferred over mW because receivers can detect incredibly weak signals that are difficult to express in mW. 130dBm is the hard limit, however in reality the lowest RSSI is usually not that low as it depends on the update rate and signal frequency. RSSI starts from 0 as the highest value, and goes down as signal decreases. While there is no simple precise solution that is used universally, we will try to explain the approximate correlation between signal ( RSSI) and quality (percentage).RSSI (Raw Signal Strength Indicator) measures the strength of a received signal and is crucial in determining how much range is left during a flight. RSSI is measured in dBm (decibel milliwatts), a logarithmic scale, as opposed to mW (milli-watt) which is a linear scale. RSSI level less than -80db may not be usable, depending on noise. RSSI is usually expressed in decibels from 0 (zero) to -120db and the closer it is to zero, the stronger the signal is. How does RSSI (dBm) relate to signal quality (percent)?ĭepending on your OS and application, WiFi signal strength is represented either as quality in percentage, or an RSSI value in dBm, i.e. In 802.11 networks, re-transmissions adversely affect throughput and latency. Data corruption and therefore re-transmissions will occur if the received signal is too close to the noise floor. For example, if a radio (client device) receives a signal of -75 dBm and the noise floor is measured at -90 dBm, the SNR is 15 dB. SNR is not actually a ratio but the difference in decibels between the received signal and the background noise level (noise floor). Any functionality is highly unlikely.Īnd what about SNR (Signal to Noise Ratio) Packet delivery may be unreliable.Īpproaching or drowning in the noise floor. Minimum signal strength for basic connectivity. Minimum signal strength for reliable packet delivery. Minimum signal strength for applications that require very reliable, timely packet delivery. Not typical or desirable in the real world. The client can only be a few feet from the AP to achieve this.
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