Suppose an operator has provided LTE SIM cards with GSM access to its subscribers. Currently, this operator plans to prohibit the access and connection of subscribers to the 3G and 4G networks, and subscribers can only connect to the 2G network. What methods are available to the operator to apply such a restriction?
In my opinion, this issue can be investigated in two different areas.
The first area is related to SIM card facilities. As far as I know, each SIM card has a standard file structure and includes applets for network authentication. According to my research, there are three specific files on the SIM card that can determine the radio access technology. These three files include OPLMN, UPLMN, and HPLMN. Of course, these three files can only suggest the priority of connecting to a network along with its access technology. There is another file called FPLMN that allows us to block connections to the networks that are mentioned in its list. But there is no ability to determine the access technology in this file (FPLMN). On the other hand, there are services on the SIM card that are active or disabled, as specified in the USIM Service Table (UST) file. Is there a way to prohibit subscriber’s connections to the 3G and 4G networks by changing files via the OTA commands or disabling or activating services on the SIM card?
The second area is related to the features available in the core of the operator’s network. Does the operator have the ability to prohibit the subscriber connection to 3G and 4G through the network-side platforms? (either in roaming mode or in home network connection mode) when the subscriber Mobile Station performs the network registration process, can the operator send the message “registration not allowed” according to the type of access technology in response to that request?
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