Group Identifier (level 1)

Description

Group Identifier level 1 (GID1) is a standardized identifier within the 3GPP UICC (Universal Integrated Circuit Card) and USIM (Universal Subscriber Identity Module) application architecture. It is stored as a data object in a dedicated elementary file on the card, specifically EF(GID1). This file is part of the USIM's file system, which is hierarchically organized under the USIM Application Dedicated File (ADF). The GID1 value is a network-provided identifier, meaning it is typically written onto the UICC by the mobile network operator (MNO) during personalization or via over-the-air (OTA) provisioning.

Technically, the EF(GID1) is a transparent elementary file with a fixed length. The content is an identifier whose coding and semantics are defined by the operator. The network can read this identifier from the UE (which reads it from the USIM) during procedures like registration or service invocation. The mechanism works through standardized commands between the mobile equipment (ME) and the UICC. When the network or the ME itself requires the GID1 value, it issues a READ BINARY command for the file identifier (FID) corresponding to EF(GID1). The USIM application on the UICC processes this command and returns the stored data.

In the network architecture, GID1 is used by various network functions, primarily in the core network. For instance, a Home Location Register (HLR) or Home Subscriber Server (HSS) subscriber profile may be linked to a GID1 value. When the UE registers, the Mobile Switching Center (MSC) or Serving GPRS Support Node (SGSN) can forward the GID1 to the HLR/HSS. The HLR/HSS can then use this group identifier as a key to apply specific service logic, tariff plans, or access restrictions defined for that group. It acts as a subscriber categorization tool within the operator's business and operational support systems (BSS/OSS).

The role of GID1 is to enable group-based service differentiation without requiring individual provisioning for each subscriber. It is a foundational element for mass service deployment, corporate plans, and machine-to-machine (M2M) group management. By checking GID1, the network can instantly determine if a subscriber belongs to a 'premium' group, a 'machine-type communication' group, or a 'partner roaming' group, and apply the appropriate network policies, quality of service (QoS) profiles, or charging rules accordingly.

Purpose & Motivation

GID1 was introduced to provide mobile network operators with a flexible, SIM-based mechanism to manage and differentiate large cohorts of subscribers. Prior to such group identifiers, applying specific network policies or service packages often required maintaining complex, individualized profiles in the network databases or using less secure identifiers that could be spoofed. This was operationally cumbersome for managing corporate accounts, family plans, or emerging service categories like data-only devices.

The creation of GID1 (and GID2) addressed the need for a standardized, secure, and portable group attribute. Its storage on the tamper-resistant UICC/USIM ensures the group affiliation is tied to the physical subscription medium, making it more secure than network-only group associations. This allows services and restrictions to follow the subscriber's SIM card reliably, which is essential for roaming scenarios and device independence.

Historically, as mobile services evolved beyond simple voice, operators needed finer tools for service segmentation. GID1 provided a simple yet powerful hook in the subscriber identity module to trigger group-specific logic in the network. It solved the problem of scalable service management, enabling operators to create, modify, and market services for entire groups by simply programming or updating the GID value on the SIM cards, rather than reconfiguring millions of individual HLR records. This was particularly motivated by the growth of value-added services and the need for efficient bulk subscriber management.

Key Features

• Stored in the EF(GID1) elementary file on the USIM/UICC
• Operator-defined coding and semantics for flexible use
• Read by the network via standardized UICC commands (e.g., READ BINARY)
• Enables group-based service provisioning and policy enforcement
• Provides a secure, SIM-bound group identifier
• Facilitates mass management of subscriber categories (e.g., M2M, corporate users)

Evolution Across Releases

Defining Specifications