uncertified modem and different carriers


What happens if I have a modem that is end device certified on AT&T, but not on Verizon (say it is a LTE-M modem), even though it will work on carrier Verizon. Will Hologram still try to connect to Verizon?

Is there any way to know what carrier it is connected to?

Is there any way to control or limit what carriers are used?


Depends on the module. I use u-blox M1 modules so I’ll speak to that experience:

The hologram simcard will allow the modem to connect to any network they have agreements with (so in your example both AT&T and Verizon). There is no way for Hologram, or the simcard to know the certification status of the device it is on. The modem will decide which network of the set of networks it authorized on it will connect to (usually highest signal strength). Many modems will allow you to further limit the networks it connects to, this can be done on U-blox (and possibly other modems) by:

  • Writing your firmware to scan and report all available networks (COPS=?), and manually select the network to connect to (COPS=1,2,“123456”). This gives you the most control but requires more effort on firmware and handling of corner cases
  • Restricting the LTE bands the device connects on (AT+UBANDMASK=0,123456). For example you can restrict to only channel 2,4,5,12 for AT&T. This wont work well if the carriers overlap (I think Verizon also uses 4 but mostly 13).
  • Set the network operator profile (AT+UMNOPROF=2). Check the documentation but this sets up the modem for a specific carrier and should effectively restrict access to that carrier.

You should be able to identify which network the modem is connected to on the device (AT+COPS?) or the hologram API / Dashboard. Click “Inspect” under “Usage This Period” in the dashboard:

{"success":true,"limit":100,"size":85,"data":[{"linkid":457xxx,"record_id":35307xxxx,"session_begin":"2018-07-30 10:21:48","timestamp":"2018-07-30 16:47:35","bytes":7836,"imei":"3527530xxxxxxxxx","cellid":48xx,"lac":345xx,"network_name":"AT&T Mobility"}]

What happens if you connect to a network where you aren’t end-device certified? In reality, for low volumes, probably nothing. Essentially ALL hobbyists / all “shields” etc. are not end-device certified and they work. Worst case is the given carrier will block your simcard(s) and if its a real problem they will probably yell at Hologram who will turn around and yell at you. I don’t have experience with this but I am guessing you would need 1,000’s of devices misbehaving (like registering and de-registering constantly) to get hit with this.

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Thanks! I appreciate the detailed information.

Just wanted to chime in here. @AndrewGifft thanks for the great answer! Pretty much what came across my mind when I first read the question. However, its best for both your device and the network to use the networks you are certified to use. That will reduce any issues you might run into and will avoid any yelling on Verizon or our side :smiley: Using the COPS command you can manually select the AT&T network to make sure your device uses that and if you are using a U-blox modem the other two commands will also help.

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