A LoRa network distinguishes Class A, Class B, Class C capable devices.
Bi-directional end-devices (Class A)
End-devices of Class A allow for bi-directional communications.
Each end-device’s uplink transmission is followed by two short downlink receive windows. The transmission slot scheduled is left to the end-device with a small variation based on a random time basis (ALOHA-type of protocol).
This Class A operation is the lowest power end-device system and is indicated for applications that only require downlink communication from the server shortly after the end-device has sent an uplink transmission. Downlink communications from the server at any other time will have to wait until the next scheduled uplink.
Bi-directional end-devices with scheduled receive slots (Class B)
End-devices of Class B allow for periodic receive slots. In addition to the Class A random receive windows, Class B devices open extra receive windows at scheduled times.
In order for the End-device to open it receive window at the scheduled time it receives a time synchronized Beacon from the gateway. This allows the server to know when the end-device is listening.
Bi-directional end-devices with maximal receive slots (Class C)
Class C devices have almost-continuous open receive windows (closed when transmitting). Class C end-device use more power to operate than Class A or Class B but they offer the lowest latency for server to end-device communication.