Cellular based devices need a working SIM card and a working APN to connect to the network.

Typically when using 4G technologies such as Cat-M1 and NB-IoT the network automatically sets the correct APN and no user input is required. However, this is not the case for all networks and APNs. An autoAPN list is used by the device for the networks that need specific APNs, however this list isn't exhaustive and occasionally you may be required to set the APN manually.

On 2G and 3G networks it was possible to send an SMS to set the APN, however 4G networks do not allow for this method. A device cannot receive an SMS without having the APN already configured.

Alternate methods are required for the 4G devices. One method for setting the APN is using a different network to get the device online and setting the APN in the admin parameters or sending it the APN SMS. The device can then be powered off and the sim swapped.

An alternate method involves storing an SMS containing the APN on a sim card, then inserting that sim card into the device that needs configuring. The device will then read the settings off the sim card and use those to get online. This feature is not available on older firmware versions. Devices with older firmware versions will need to use another network to get online before the APN can be set. 

In Summary:

  • 4G CAT M1 and NB-IoT devices may need an APN setup before they can get on air.
  • To set an APN on a 4G device:
    1. A "Config Sim" can be created by storing a special SMS on the SIM. 
    2. The special SMS format is shown below
    3. Then the config Sim can be inserted into devices that need configuring.

1. Creating a Config Sim - getting the SMS onto the Sim

There are multiple methods for storing the SMS onto a sim card, including:

  • Requesting a sim with your required APN from your Digital Matter representative.
  • Using a mobile phone that is capable of saving SMS's to its sim card.
  • Using a dedicated sim programmer
  • Sending the 4GINIT SMS to a device that is online via a different carrier and has firmware that supports the 4GINIT SMS. This saves the SMS to the sim card which can then be used to set the APN on other devices.

2. APN SMS Format

The format for the SMS is:

    #*,4GINIT,<apn name>,<RAT number>

Where RAT stands for Radio Access Technology.  The RAT is set using the following key:

0 - Automatic (use Cat-M1 and NB-IoT). This is the default setting, but doesn't work in some cases.

1 - Cat-M1 only

2 - NB-IoT only

If the APN details are omitted then the default APN and RAT will be saved to the sim card. The default APN is a blank APN. And the default RAT is 0 (M1 and NB1)






3. Using a Config Sim to set the APN on a device

The method for setting the APN using the Config Sim card is as follows:

  1. Insert the Config Sim with the 4GINIT SMS stored on it, and power on the device.
  2. The LED on the device will flash at its normal rate
  3. Within 10 seconds the device will begin a long, slow flash signifying the APN has been read and saved.
  4. Power can now be removed from the device, and the Config Sim can be removed and replaced by the final Sim.
  5. The Config Sim can now be used in the next device.

Warning! The devices will delete all SMSs stored on the sim that are not in the APN SMS format.