Over The Air Activation (OTAA) is a method by which a LoRa sensor is linked to a LoRaWAN network. Another method by which a LoRa sensor can be linked to a network is Activation By Personalization (ABP).
Before a sensor can participate in a LoRaWAN network, the following data must be known to both the sensor and the network: the DevAddr, NwkSKey and the AppSKey. The DevAddr is a unique address within the LoRaWAN network, which identifies the sensor. The NwkSKey and AppSKey are required for the encryption of the messages. In OTAA, these three data are generated and exchanged between the network and the sensor by means of a join procedure.
OTAA and the join procedure
During the join procedure, the security keys (NwkSKey and AppSKey) are determined dynamically and the network distributes a free DevAddr to the sensor. This means that every time the sensor opens a new session, new encryption keys are also generated. For security reasons, it can be decided to open a new session every once in a while, so that the security keys are refreshed.
To perform the join procedure with the OTAA method, three data are required (this is different data than the above data), this concerns the DevEUI, AppEUI and AppKey. When this data is configured on both the sensor side and the network side, it is possible to run the join procedure and dynamically calculate the aforementioned DevAddr, NwkSKey and AppSKey. Because this data is generated dynamically, it is possible to have the sensor switch networks. This is in contrast to the ABP method.