8 Introduction to Class B

This section describes the LoRaWAN Class B layer which is optimized for battery-powered
end-devices that may be either mobile or mounted at a fixed location.
End-devices should implement Class B operation when there is a requirement to open
receive windows at fixed time intervals for the purpose of enabling server initiated downlink
messages.
LoRaWAN Class B option adds a synchronized reception window on the end-device.
One of the limitations of LoRaWAN Class A is the Aloha method of sending data from the
end-device; it does not allow for a known reaction time when the customer application or the
server wants to address the end-device. The purpose of Class B is to have an end-device
available for reception on a predictable time, in addition to the reception windows that
follows the random uplink transmission from the end-device of Class A. Class B is achieved
by having the gateway sending a beacon on a regular basis to synchronize the all the end-
devices in the network so that the end-device can opening a short extra reception window
(called ―ping slot‖) at a predictable time during a periodic time slot.

16	Note: The decision to switch from Class A to Class B comes from the
17	application layer of the end-device. If this class A to Class B switch
18	needs to be controlled from the network side, the customer application
19	must use one of the end-device‘s Class A uplinks to send back a
20	downlink to the application layer, and it needs the application layer on
21	the end-device to recognize this request – this process is not managed
22	at the LoRaWAN level.

The authors reserve the right to change specifications without notice.

LoRaWAN Specification

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