What is it?
Over-the-air activation (OTAA) is one of the methods for connecting a LoRa sensor to a LoRaWAN® network.
The sensor’s participation in the network depends on the DevAddr (a unique address within the network) as well as the Network Session Key (NwkSKey) and Application Session Key (AppSKey), both used for the encryption of messages. These pieces of data must be known to both the network and the sensor. They are generated and exchanged between the network and the sensor during the join procedure as part of OTAA.
How does it work?
Within the join procedure, the NwkSKey and AppSKey are determined. Additionally, the DevAddr is distributed to the sensor by the network. When the sensor opens a new session, a new NwkSKey and AppSKey are generated.
For the process to take place, the DevEUI (the end-device identifier), AppEUI (the application identifier), and AppKey (the key unique to the end device) are configured on the sensor and network side. This makes it possible to run the join procedure and calculate DevAddr, NwkSKey, and AppSKey. These are generated dynamically, so the sensor can switch networks.
OTAA is the opposite of activation by personalization (ABP), which skips the join procedure. In this case, the DevAddr, NwkSKey, and AppSKey for a pre-selected network are hardcoded into the end device. They do not change throughout the device’s lifespan.