Equipment Identity Register (EIR) within the Context of a 5G Network

The Equipment Identity Register (EIR) plays a crucial role in ensuring the security of a 5G network. It verifies the International Mobile Equipment Identity (IMEI) of mobile devices during access attempts and established calls, except for IMSI detach. If the EIR identifies a device as "black-listed" or "unknown," the network terminates the access attempt or ongoing call, alerting the user about an "illegal ME" event. This equates to an authentication failure, restricting the device to making only emergency calls and preventing it from responding to paging or updating its location.

EIR architecture

The Identity Check Procedure is an integral part of various network registration processes across different generations, including 2G, 3G, 4G, and 5G systems. The procedure's execution varies based on the network generation, with 5G utilizing HTTP2 links and involving the Access and Mobility Management Function (AMF) as the primary network element communicating with the EIR Service.

For 5G registration, a Permanent Equipment Identifier (PEI) is obtained from the User Equipment (UE), and the EIR validates it. The AMF operator queries the EIR to check if the PEI is on a banned list. The EIR's response informs whether the device is authorized or not, allowing the registration process to continue accordingly. This process also involves other network elements like UDM, SMF, and PCF.

In the case of the Diameter Attach Procedure, if a UE is unknown in both old and new MME/SGSN, the new MME/SGSN requests the IMSI from the UE, and an Identity Check procedure occurs. The ME-Identity-Check-Request/Answer (ECR/ECA) commands correspond to this procedure in the Diameter application.

For SS7/SIGTRAN MAP Attach Procedure, the EIR function is used to verify the IMEI when a handset attempts to register with an MSC or VLR. The identity check involves interactions between VLR, MSC, and the EIR, and it ensures the IMEI is recognized.

The EIR returns a response containing the device's status, indicating whether it's authorized, unauthorized, or not valid. The network element then takes appropriate action based on this status, either allowing or rejecting the device.

In summary, the Equipment Identity Register in 5G and other network generations plays a crucial role in verifying device identities, preventing unauthorized access, and maintaining network security during registration and call establishment processes.