3 - Receiving Messages
Messages sent from a network server to an end device are referred to as downlinks. These are sent to the end device via a single gateway. If there are multiple gateways near a device, the network server will select the most suitable gateway to broadcast from. This means the end device does not need to consider de-duping.
Devices operating in Class A mode only receive downlinks during the receive windows opened following an uplink, as described in the section Opening Receive Windows of the Sending Messages Book.
Devices that support Class B mode as well as Class A can receive additional downlinks in receive windows opened at fixed time slots. Read more about Class B mode in the Class B Book.
Devices that support Class C mode as well as Class A can receive additional downlinks at any time. Read more in the Class C: Continuously Listening for Downlinks book.
Todo
Fix link
In this book, you learn how to receive and handle downlink packets using the LoRaWAN® 1.0.4 specification.
Handling MAC Commands
End Device Time Answer (DeviceTimeAns)
The network server sends the DeviceTimeAns in response to the DeviceTimeReq command which is initiated by the end device to sync the device time with the network time. The DeviceTimeReq command can be used to accelerate beacon discovery when enabling Class B mode. The DeviceTimeAns response contains the seconds and subsequent fractional seconds that have passed since the GPS epoch (January 6th, 1980, at 00:00:00 UTC).
Read how to process the DeviceTimeAns response in section Request the Network Server Time of the Class B Book.