ADR (Adaptive Data Rate) is a LoRaWAN mechanism in which the Network Server analyses the link quality reported by the gateways (RSSI and SNR) and instructs each end device to switch to a lower spreading factor (faster, less battery-hungry, for example SF7 instead of SF12) whenever the signal margin allows it.

End devices typically start at a high spreading factor for safety on first uplink. The Network Server then averages the link margin over the last 20 frames or so, and if the margin is comfortable it sends a LinkADRReq MAC command telling the device to step down in SF, increase its data rate and possibly reduce its TX power. If conditions later deteriorate, the device autonomously climbs back to a higher SF after a configurable number of missed acknowledgements (the ADR back-off). The mechanism saves battery, reduces duty-cycle consumption and is central to LoRaWAN scalability.

Enable ADR only on stationary devices — for moving assets (asset trackers, vehicles) ADR oscillates and wastes energy, so the LoRa Alliance explicitly recommends disabling the ADR bit on mobile end devices.