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Device classes

Class-A

ChirpStack supports LoRaWAN® Class-A devices. In Class-A a device is always in sleep mode, unless it has something to transmit. Only after an uplink transmission by the device, ChirpStack is able to schedule a downlink transmission.

Received frames are de-duplicated (in case it has been received by multiple gateways), after which the mac-layer is handled by ChirpStack and the decrypted application-payload is forwarded to the configured integrations.

ChirpStack persists downlink queue-items in its database. One a receive window occurs (triggered by an uplink), ChirpStack will transmit the items in the downlink queue FIFO to the device. Please note that mac-commands will get priority over application-payloads.

Confirmed data

ChirpStack sends an ack event with ack: true to the configured integration as soon the device has acknowledged the confirmed uplink. If the next uplink does not contain an acknowledgement, an ack event with ack: false is sent to the configured integrations.

Note: Always check the value of the ack field in the ack event! For some integrations default values are omitted, which is equal to ack: false!

Class-B

ChirpStack supports Class-B devices. A Class-B device synchronizes its internal clock using Class-B beacons emitted by the gateway, this process is also called a "beacon lock". Once in the state of a beacon lock, the device negotiates its ping-interval. ChirpStack is then able to schedule downlink transmissions on each occurring ping-interval.

The ack event works the same as for Class-A devices, with the only exception that an ack: false is triggered after the configured Class-B timeout. This timeout defines the maximum time that the device has to acknowledge a confirmed downlink. This timeout can be configured in the device-profile.

Requirements

Device

The device must be able to operate in Class-B mode.

Gateway

The gateway must have a GNSS based time-source, as Class-B beacon and ping-slot scheduling must be very precise. The packet-forwarder must be configured to send Class-B beacons such that the device is able to synchronize its internal clock.

Class-C

ChirpStack supports Class-C devices and uses the same Class-A downlink device-queue for Class-C downlink transmissions.

Confirmed data

The ack event works the same as for Class-A devices, with the only exception that an ack: false is triggered after the configured Class-C timeout. This timeout defines the maximum time that the device has to acknowledge a confirmed downlink. This timeout can be configured in the device-profile.