PLMN Access barring list

Description

The PLMN Access barring list is a feature defined in 3GPP specifications (22.071, 22.935, 23.171, 23.271) that allows a mobile network operator to restrict location-based services (LCS) for specific subscribers. It is an optional list of Mobile Station International Subscriber Directory Numbers (MSISDNs) per Public Land Mobile Network (PLMN) where any LCS Client is not allowed to locate any MSISDN in the list, except for certain exceptional cases (e.g., emergency services). This list is used to protect the privacy of subscribers who do not wish to be located by commercial or third-party location services.

The PLMN Access barring list is typically stored in the Home Subscriber Server (HSS) or a similar subscriber database as part of the subscriber's profile. When an LCS Client requests the location of a target MSISDN, the network checks the barring list before proceeding. If the MSISDN is on the list, the request is denied unless it falls under an exception, such as an emergency call or lawful interception. The list can be managed by the operator and may be updated dynamically.

In terms of architecture, the PLMN Access barring list interacts with the Gateway Mobile Location Center (GMLC), which is the entry point for LCS requests from external clients. The GMLC queries the HSS to retrieve the subscriber's privacy profile, including the barring list. If the target is barred, the GMLC rejects the request. The list is per PLMN, meaning that a subscriber may be barred in one network but not in another, depending on roaming agreements and local regulations.

The PLMN Access barring list is a key component of location privacy. It complements other privacy mechanisms, such as the LCS Client privacy class and the subscriber's own privacy settings. The exceptional cases are defined in 3GPP specifications and typically include emergency services, lawful interception, and certain value-added services that the subscriber has explicitly opted into.

Operators use the PLMN Access barring list to comply with regulatory requirements and to offer privacy options to their subscribers. It is particularly important in regions with strict privacy laws, such as the European Union. The list can be provisioned via the Operations and Maintenance (O&M) system and can be updated in real-time. Overall, the PLMN Access barring list provides a flexible and standardized way to control access to location information.

Purpose & Motivation

The PLMN Access barring list was created to address privacy concerns related to location-based services. As LCS became more prevalent, subscribers demanded control over who could locate them. The barring list provides a simple yet effective mechanism for operators to honor these preferences by maintaining a list of MSISDNs that are off-limits to LCS clients.

Before the introduction of this feature, location privacy was managed on a per-request basis or through client-specific settings, which were not standardized and could be inconsistent. The PLMN Access barring list standardizes the process, ensuring that privacy preferences are respected across different networks and clients. It also allows operators to meet regulatory mandates, such as the EU's ePrivacy Directive, which requires explicit consent for location tracking.

The list is optional, giving operators flexibility in how they implement privacy controls. It is designed to be scalable and easy to manage, with the ability to handle large numbers of subscribers. The exceptional cases ensure that critical services like emergency calls are not blocked, balancing privacy with public safety.