Image captured from Semtech SX-9 Datasheet. The minimum SNR required for demodulation at different spreading factors is shown in the table below: However, LoRa can demodulate signals that are below the noise floor. If the RSSI is below the noise floor, it is impossible to demodulate the signal. the receiver will be able to demodulate the signal. The positive SNR means that the signal power is greater than the noise power, i.e. By using these values you can calculate the SNR as follows: The x-axis represents the power level in dBm and the y-axis represents the time.īy looking at the above graph you can see that the RSSI is about -65 dBm and the noise floor is about -90 dBm. Image captured from the YouTube video by Richard Wenner. Here is a good example of a positive SNR: If the RSSI is above the noise floor the receiver can easily demodulate the signal. SNR (dB) = P received_signal (dBm) - P noise (dBm) SNR can be calculated using the following formula and is often expressed in decibels (dB): SNR is commonly used to determine the quality of the received signal. SNR (Signal-to-Noise Ratio), often written as S/N, is the ratio of the received signal power to the noise floor. The closer the RSSI value is to zero, the received signal is stronger.Īpart from the output power of the transmitter, the following factors mainly influence the RSSI: RSSI is measured in dBm and its value is a negative form. Since LoRaWAN supports bi-directional communication, RSSI is an important measurement for both gateways and end devices.

RSSI (Received Signal Strength Indicator) is a relative measurement that helps you determine if the received signal is strong enough to get a good wireless connection from the transmitter. This section contains information about two most commonly used signal strength indicators - RSSI and SNR. In wireless communication, a receiver needs a good signal strength and a signal-to-noise ratio to separate the original signal from the modulated carrier.

Rssi level ring