Queue Mode

When configuring a energy saving endpoint that uses LTE-M or NB-IoT, queue mode must be enabled in Zephyr so the device will sleep between data transmissions. The Zephyr documentation explains the LwM2M Client in Zephyr in detail.

Enable Queue Mode in Zephyr with a registration update interval of 10 minutes

 CONFIG_LWM2M_QUEUE_MODE_ENABLED=y
 CONFIG_LWM2M_QUEUE_MODE_UPTIME=20
 CONFIG_LWM2M_RD_CLIENT_STOP_POLLING_AT_IDLE=y

 # Default lifetime is 10 minutes
 CONFIG_LWM2M_ENGINE_DEFAULT_LIFETIME=600

See chapter Data Flow: Backend -> Endpoint to know know more about how queue mode is implemented in flownexus.

eDRX Settings

eDRX (Extended Discontinuous Reception) is a feature that allows the device to sleep for longer periods of time. The device will wake up periodically to check downlink paging messages. If new messages are available, the device will stay awake to receive them. Otherwise, the device will go back to sleep. - Nordic Devzone Article

Setting the eDRX interval to a value significantly smaller than the timeout value of the LwM2M server would theoretically allow flownexus to reach endpoints at any time.

Warning

This approach has not yet been tested! The typical way is to configure endpoints to connect to the server within specific intervals. Inbetween those intervalls, the endpoint will sleep and can’t be reached from the server.