What is GUMMEI in LTE?

The GUMMEI (Globally Unique MME Identifier) is a key identifier in LTE networks, uniquely identifying a Mobility Management Entity (MME) globally. It is essential for routing, mobility management, and secure identification of devices within the network.

Structure of GUMMEI.

The GUMMEI consists of three main components:

MCC (Mobile Country Code): Identifies the country.
MNC (Mobile Network Code): Identifies the network operator within that country.
MMEI (MME Identifier): Includes the MME Group ID (MMEGI) and the MME Code (MMEC).

The MMEI is constructed from:

MME Group ID (MMEGI): A 2-octet identifier assigned by the service provider.
MME Code (MMEC): A 1-octet identifier assigned by the service provider.

The complete structure of the GUMMEI is:

GUMMEI = MCC + MNC + MMEI (MMEGI + MMEC) + MME Code

Shared MME and Multiple GUMMEI.

A shared MME can have up to nine GUMMEI:

One for the Home PLMN (Public Land Mobile Network).
Up to eight for Shared PLMNs.

In these cases, the MMEI remains the same, but the MCC and MNC differ for each PLMN.

Paging and S-TMSI.

For paging purposes, the mobile device is paged using the S-TMSI (SAE Temporary Mobile Subscriber Identity). The S-TMSI is constructed from:

MMEC
M-TMSI (Mobility Management Temporary Mobile Subscriber Identity)

GUTI and Reallocation.

The GUTI (Globally Unique Temporary Identifier) is periodically reallocated by the operator’s network. When a UE (User Equipment) detaches from the network, it retains its GUTI. However, if a significant time passes, the MME might no longer recognize the GUTI and may request the IMSI (International Mobile Subscriber Identity) for re-attachment.

Other Identifiers.

Several other identifiers are used in LTE networks:

eNB S1AP UE ID: Identifies a UE on the S1 interface within the eNodeB, unique within the eNodeB.
MME S1AP UE ID: Identifies a UE on the S1 interface within the MME, unique within the MME.

Importance in LTE Networks

The GUMMEI is important identifier for the efficient operation of LTE networks, providing unique identification for MMEs, facilitating seamless mobility, and supporting robust network operations. It ensures reliable routing, effective mobility management, and secure device identification within the LTE infrastructure.