5G-EIR — 5G Equipment Identity Register¶

Learning objectives¶

• Understand the role of the 5G-EIR, namely that it is the NF responsible for checking the state of the identifier PEI (IMEI, etc.) of the terminal (equipment) itself.
• Be able to explain the difference between the PEI (Permanent Equipment Identifier) and the SUPI (subscriber identifier), and the viewpoint of checking the "equipment" rather than the "subscriber."
• Understand the flow in which the AMF queries the state of the PEI (allowed/denied, etc.) via N5g-eir (SBI).
• Grasp the correspondence with the 4G/EPC EIR (S13/MME coordination).

Prerequisites¶

• Basics of the AMF and the registration procedure: AMF ／ Registration
• The concept of identifiers (SUPI/PEI, etc.): Identifier dictionary
• The concept of SBA/SBI: Curriculum

What you will learn in this chapter¶

• Why: Why a mechanism to check the "equipment itself," separate from the subscriber, is needed in order to exclude stolen terminals or type-uncertified equipment.
• What: Learn that the 5G-EIR retains and judges the state of the PEI (blacklist, etc.) and answers queries with the N5g-eir API.
• How: Learn the flow in which the AMF obtains the UE's PEI during the registration procedure and the like, and queries the 5G-EIR for the state to use as a basis for the connection-permission decision.

Why — Why it is needed¶

Whether communication is allowed is usually decided by "whether the subscriber (SIM/SUPI) is legitimate." However, even if the subscriber is legitimate, there are cases where you want to deny the connection if the terminal (equipment) being used is a stolen or type-uncertified item. Therefore, a mechanism is needed to check the "equipment itself" with the identifier PEI (IMEI, etc.), separate from the subscriber. The 5G-EIR fulfills this role and judges whether the PEI falls on a blacklist or the like.

Analogy: The 5G-EIR is the "window that queries the wanted list for equipment." Even if the subscriber's ID (SIM/SUPI) is correct, it handles the check of rejecting a terminal (PEI) if the held equipment is one for which a theft report has been filed.

Overview¶

• The AMF obtains the PEI (equipment identifier such as IMEI) from the UE during the registration procedure and the like.
• The AMF queries the 5G-EIR for the state of that PEI (allowed/denied, etc.).
• The 5G-EIR returns a judgment result against the list it retains (blacklist, etc.).
• The AMF uses that result as a basis for the connection-permission decision.

Note that whether a PEI check is performed, and the handling on denial, depend on the operator's policy (details to be confirmed).

Basic Concept — Explanation for beginners¶

The 5G-EIR is the "window" that queries the equipment blacklist. A smartphone has, separately from the SIM (subscriber), a terminal-specific number (a PEI such as an IMEI). The 5G-EIR has a ledger-like role that checks "has a theft report been filed for this terminal number?" When a new terminal connects, the AMF queries this window as needed and excludes problematic equipment.

Network Function details¶

Architecture¶

flowchart LR
    UE["UE"] -->|"present PEI (NAS)"| AMF["AMF (registration processing)"]
    AMF -->|"N5g-eir (query PEI state)"| EIR["5G-EIR (equipment identification)"]
    EIR -->|"judgment result (allowed/denied)"| AMF

How to read the diagram: The UE presents its PEI (IMEI, etc.) during the registration procedure and the like. The AMF queries the 5G-EIR for the state of that PEI via N5g-eir, and the 5G-EIR returns a judgment result such as allowed/denied against the list it retains. The AMF uses this as a basis for the connection-permission decision.

Interface¶

For details, see the Interface dictionary.

Appearance in procedures¶

Within the Registration procedure, the AMF obtains the UE's PEI and, as needed, queries the 5G-EIR for the state. Whether the query is required and its timing depend on the operator's policy. For the specific flow, see Registration and AMF (the detailed message order is to be confirmed).

Comparison with EPC¶

In 4G/EPC, the EIR handled the check of the ME Identity (IMEI) over the S13 interface (MME ⇔ EIR, Diameter-based). In 5G, this function is handled by the 5G-EIR and changed to being queried over SBI (N5g-eir) (the precise correspondence is to be confirmed).

Release differences¶

The 5G-EIR was defined as a basic function in Rel-15. Extensions in subsequent releases are to be confirmed.

3GPP Specification¶

• TS 23.501 defines the 5G-EIR (the individual section numbers in the TS 23.501 §6.2 family are to be confirmed).
• TS 23.502: Specifies procedures including the equipment-identity check (to be confirmed).
• TS 29.511: Specifies N5g-eir (EquipmentIdentityCheck) (individual section numbers to be confirmed).

Summary¶

• The 5G-EIR is the NF that judges the state of the terminal's equipment identifier PEI (IMEI, etc.).
• It checks the "equipment itself" rather than the subscriber (SUPI), used for the purpose of excluding stolen or unauthorized terminals.
• The AMF queries the state of the PEI via N5g-eir (SBI) and obtains a result such as allowed/denied.
• Whether the check is required and the handling on denial depend on the operator's policy.
• It corresponds to the 4G/EPC EIR (S13) and is queried over SBI (N5g-eir) in 5G.

Next Step¶

• AMF
• Registration
• Identifier dictionary
• NF dictionary
• Interface dictionary