IoT Device Implementation Guide

Disable connectivity when SIMs are deactivated

Last Updated: June 28th, 2024

When an IoT Device attempts to connect to a network using a SIM that has been suspended or terminated, the network will reject the connection accordingly.

Even though no connection is made, numerous signals are still exchanged with the network, which if repeated will increase the load on the entire network, similar to connecting and disconnecting excessively.

For this reason, IoT Devices should be implemented such that the device does not continuously repeat connection requests when the SIM is suspended or terminated, such as exponentially increasing the duration between reconnection attempts, or ceasing reconnection after a set number of attempts.

If a device fails to connect to a network, check the error cause code indicated by the communication module and ensure that the failure is not a result of a rejected network connection based on the status of the SIM.

Soracom provides the following SIM status options to address different scenarios:

  • Inactive status: When a Soracom SIM is set to this status, data sessions are blocked by sending a temporary reject cause to the communications module. Because of this, a compliant module will normally attempt to reconnect at regular intervals, potentially leading to excessive signaling with the network as well as additional power consumption. Therefore, you should use the Inactive status only when you need to temporarily stop the device from consuming traffic. Implementing an exponential duration, threshold, or other reconnection mechanism mentioned above is also recommended.
    • If you do not plan to use the SIM for a longer period of time, you should change the SIM to the following Suspended status instead.
  • Suspended status: When a Soracom SIM is set to this status, data sessions are blocked by sending a permanent reject cause to the communications module, and a compliant module will normally cease attempting to reconnect to this network by adding the network to a Forbidden PLMN (FPLMN) list stored in the SIM and ignoring these networks when attempting to reconnect. However, it is important to note the following:
    • (1) It is very easy for an IoT Device Application to unknowingly override the default behavior of the module and cause the device to repeatedly attempt to reconnect, despite the permanent reject cause sent by the network. Therefore, it is critical to test and confirm that the module correctly ceases reconnection attempts. Similarly, implementing an exponential duration, threshold, or other reconnection mechanism mentioned above is still also recommended.
    • (2) When a device correctly ceases attempting to reconnect to a network, changing the Soracom SIM status back to Active will simply tell the network to allow any subsequent connection attempt, but does not initiate the connection itself. In order to do so, the device must be manually rebooted or power-cycled in order to clear the FPLMN list and allow the communications module to resume network connections. Therefore, before utilizing the Suspended status, ensure that you will be able to access the device in order to restart it.

Soracom also provides a Terminated status, which will also result in the same permanent reject cause network behavior as the Suspended status. The functional difference between these statuses is that Terminated status SIMs cannot be reactivated. If you will no longer use a Soracom SIM, terminating the SIM will ensure that it cannot be accidentally reactivated later.

Learn more about SIM status in the Soracom User Console

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Gracefully Shutdown IoT Devices
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