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I have an LTE CPE which has been provided by an ISP. When I tried to put the SIM into another device, it connected to the network but instantly got disconnected from the network. There should be some way that the ISP identifies the device. I guess it's not just IMEI. My question is that is there any other new way on LTE networks to identify the device? (Network operates on TDD-LTE 2300Mhz band).

Edit on 08 Jun 2020 02:35 PM +0530:

I tried changing the IMEI of other device to be same as of the original device but still didn't work.

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Feb 21 '18 at 18:21
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    Why do you think it's not just IMEI? Your other device has a different IMEI. – auspicious99 Jun 6 '20 at 14:00
  • @auspicious99 Because I tried changing the IMEI of the other device to be same as of the original device. – Iresh Dissanayaka Jun 8 '20 at 8:59
  • Hmm, interesting. IMEI is the normal unique device identifer that is used. Perhaps your ISP is supplementing IMEI checks with some other device identifier as well. – auspicious99 Jun 8 '20 at 10:44
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Have you checked that the APN name is configured correctly (normally it's just "internet" but it can be defined arbitrarily (for examples most mobile providers offer a whole APN for enterprise customers, where the APN name is used to differentiate). Additionally, they can be using authentication, or additional paramters.

Here's a screenshot from a Smartflex LTE enabled router for reference.

APN Settings

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It could be three possible reasons.

The first reason is that the APN (Access Point Name) has not been set up. Usually for phones directly bought from a cellular provider shop, have the APN already built in and thus is not entered. Setting up an APN is usually what is done when BYOD/switching to another cellular provider. By putting a sim into another cellular device, you may need to enter in the APN.

If the APN is already setup, then it could either be the IMEI (International Mobile Equipment Identity), which is different for every phone (like how every network interface has a different MAC address). It could be that the ICCID (Integrated Circuit Card ID), which you can find printed on your SIM card, is locked by your cellular provider to the IMEI number of your phone. This is typically done by cellular providers to prevent the use of stolen SIM cards.

The last reason I can think of is that your new device is not on the list of devices that are supported by the cellular service provider. Just like how a MAC address can tell the manufacturers name of the network interface card, the IMEI number does the same if not more than just the manufacturer. The IMEI number can also tell not just the manufacturer, but the model of the device as well. If the IMEI of the device that you just put the SIM into, states a model number not on the list of supported devices, it may not let you connect completely or at all onto the cellular network. This is even if your device supports the cellular bands for that network.

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