User Controlled PLMN Selector

Description

The 7.2 feature, formally known as User Controlled PLMN Selector, is a standardized capability defined in 3GPP specifications 31.122 and 31.127 that resides within the UICC (Universal Integrated Circuit Card) or USIM (Universal Subscriber Identity Module). It provides a structured mechanism for storing and managing a user-defined list of preferred Public Land Mobile Networks (PLMNs) that the mobile device consults during network selection procedures. This functionality operates independently from the operator-controlled PLMN selector (feature 7.1), giving subscribers direct influence over which networks their devices attempt to connect to, particularly in roaming scenarios or areas with multiple network operators.

Architecturally, the User Controlled PLMN Selector is implemented as a dedicated file (EFPLMNwAcT) within the USIM application on the UICC. This file contains a prioritized list of PLMN codes (MCC-MNC combinations) along with associated access technology indicators (e.g., GSM, UMTS, LTE, NR). When the mobile device performs network selection—either automatically after power-on, after losing coverage, or manually when the user initiates network search—it consults this user-controlled list before falling back to the operator-controlled list or other selection algorithms. The device processes the PLMNs in the order specified in the list, attempting registration with each until successful.

The mechanism works through a well-defined interaction between the mobile equipment (ME) and the UICC/USIM. During network selection, the ME reads the EFPLMNwAcT file from the USIM and extracts the prioritized PLMN list. The device then scans for available networks and compares detected PLMNs against the user's list. If a match is found, the device attempts to register with that network using the specified access technology. The user can typically manage this list through the device's network settings menu, where they can add, remove, or reorder PLMNs based on personal preference, cost considerations, or performance requirements.

Key components include the EFPLMNwAcT file structure, which defines the format for storing PLMN entries with associated access technologies; the network selection algorithms in the device that prioritize user-controlled PLMNs; and the user interface mechanisms that allow subscribers to modify their preferred network list. The feature plays a crucial role in enhancing user autonomy in network selection, particularly valuable for frequent travelers, business users with specific roaming agreements, or subscribers in border regions where multiple networks are available.

Purpose & Motivation

The User Controlled PLMN Selector was created to address the limitation of purely operator-controlled network selection, which often prioritized the home operator's roaming partners without considering user preferences or cost factors. Before its introduction, subscribers had limited control over which networks their devices selected when roaming, potentially leading to unexpected roaming charges or suboptimal network performance. This feature empowers users to make informed decisions about network selection based on personal criteria such as cost, coverage quality, or specific service requirements.

Historically, network selection was primarily governed by the operator-controlled PLMN list (feature 7.1) stored on the SIM card, which reflected commercial agreements between operators. While this ensured basic roaming functionality, it didn't account for individual user needs. The 7.2 feature emerged in Release 8 as part of 3GPP's broader effort to enhance user control and personalization in mobile networks. It recognized that different users might have different priorities—some might prioritize cost-effective networks, while others might prefer networks with specific technical capabilities or service quality.

The feature solves several practical problems: it allows users to avoid expensive roaming networks by manually selecting more affordable alternatives; it enables selection of networks with better coverage or performance in specific locations; and it provides a mechanism for users to maintain connectivity preferences that persist across different devices when using the same USIM. This is particularly valuable in regions with multiple competing operators or complex roaming environments, giving subscribers agency over their connectivity experience while maintaining compliance with network selection standards.