Device Class
What is it?
A device class is a characteristic of the LoRaWAN® network’s devices that refers to their operating mode and capabilities. There are 3 device classes: Class A, Class B, and Class C. While Class A is implemented in all LoRaWAN® devices, Class B and Class C are extensions to it. Each of the device classes supports both uplink and downlink communication.
How does Class A work?
Class A devices can route an uplink message at any time. Upon the uplink transmission, a Class A device opens 2 short receive windows to get downlink messages from the network. If the server does not respond, the next downlink is scheduled after the subsequent uplink transmission.
Among other things, Class A devices feature low power consumption, the ability to operate with battery power, the predominance of sleep mode, and long intervals between uplinks. Some of the use cases for these devices include environmental monitoring, animal tracking, forest fire and water leakage detection, smart parking, asset tracking, and waste management.
How does Class B work?
In addition to Class A capabilities, Class B devices regularly open receive windows called ping slots to get downlinks. The network periodically broadcasts time-synchronized beacons over gateways to end devices. These beacons supply the devices with timing references to harmonize their internal clocks with the network. It lets the network server know when to route a downlink to the devices.
Although Class B devices are often battery-powered, their battery life is shorter than that of Class A devices. They can also operate in a Class A mode. Common uses for Class B devices embrace utility meters (electrical meters, water meters, etc.) and streetlights.
How does Class C work?
Class C devices keep receive windows open unless transferring an uplink, so they can get downlinks at almost any time. These downlink messages may serve to activate some functions of the devices.
There are 2 receive windows opened by Class C devices: RX1 and RX2. The latter is not closed until the next uplink transmission. When the device routes an uplink, a short RX2 receive window opens, preceding a short RX1 receive window. Afterward, a continuous RX2 receive window opens and does not close until the subsequent uplink is scheduled. Uplinks cannot overlap downlinks in time.
Since Class C devices consume the most power compared to previous device classes, they cannot operate with batteries for a long time. Like Class B devices, they can function in a Class A mode as well. Class C is applied for utility meters, streetlights, beacon lights, alarms, and the like.
