Location System Billing Function

Description

The Location System Billing Function (LSBF) is a specialized logical function within the 3GPP architecture for Location Services (LCS). It operates as part of the network's billing domain, specifically tailored to handle the unique charging requirements associated with determining and reporting a mobile subscriber's geographical position. The LSBF is not necessarily a standalone physical node; its functionality can be integrated into existing billing systems or dedicated service platforms. Its core responsibility is to collect charging data related to location requests, process this data into appropriate billing records, and forward these records to the network's billing system for subscriber invoicing or inter-operator settlement.

Architecturally, the LSBF interfaces with the Location System Control Function (LSCF), which is the central coordinating entity for location requests. When a location service is invoked—whether by the subscriber themselves (Mobile Originated Location Request), by an external client (Mobile Terminated Location Request), or by the network for an emergency call—the LSCF manages the positioning process. Upon successful completion (or failure) of a location attempt, the LSCF generates a charging data record (CDR) or similar event report containing details such as the requesting client, the target subscriber, the type of service (e.g., emergency, commercial), the accuracy achieved, the positioning method used, and timestamps. This charging data is then transferred to the LSBF.

The LSBF processes these raw charging events. Its key internal components include charging data collection, event correlation, tariff application, and record formatting modules. It applies the relevant tariff policies based on the service type, subscriber profile, and network operator's rules. For example, an emergency service location request might be charged at a zero rate or generate a record for government reimbursement, while a high-accuracy commercial request for a navigation service would incur a fee. The LSBF formats the final billing record, typically a standardized CDR, and transfers it to the network's central billing system or accounting function. This separation allows the LCS architecture to remain focused on positioning technology while delegating complex commercial and regulatory charging logic to the dedicated billing domain.

Its role in the network is critical for the commercial viability and regulatory compliance of location services. By accurately capturing and rating location events, the LSBF enables operators to offer paid LCS to enterprises and consumers. It also ensures that legally mandated services, like locating callers during emergency (E911/eCall) scenarios, can be billed appropriately to authorities or absorbed as a cost of service. Furthermore, in roaming scenarios, the LSBF (in the visited network) may generate billing records for settlement with the subscriber's home network, facilitating inter-operator charging for location services used abroad.

Purpose & Motivation

The LSBF was created to address the specific billing challenges introduced by location-based services in cellular networks. Traditional voice and data services have relatively straightforward charging models based on duration, volume, or event. However, location services introduce new dimensions for charging: the type of request (emergency, value-added), the required accuracy, the response time, and the underlying positioning technology used (e.g., Cell-ID, OTDOA, A-GPS). The LSBF exists to translate these technical service parameters into billable events, solving the problem of how to monetize and account for the network resources consumed in determining a subscriber's position.

Historically, location services emerged from regulatory requirements for emergency caller location (E911 in the US, E112 in Europe). These mandates required networks to provide location information to emergency services, but the associated costs needed to be tracked and potentially reimbursed. The LSBF provided a standardized mechanism for this. Subsequently, with the rise of commercial LCS for navigation, fleet tracking, and location-based advertising, a flexible and robust billing function became essential for business models. Prior to its definition, operators lacked a standardized way to charge for these services, leading to proprietary and non-interoperable solutions.

The motivation for the LSBF was driven by the need for a clear separation of concerns within the LCS architecture. The positioning control (LSCF) and execution (e.g., SAS, SMLC) functions are complex and technology-specific. By offloading all charging logic to a dedicated LSBF, the overall system becomes more modular and scalable. This separation allows billing rules and tariffs to be updated independently of the positioning technology, and it enables consistent charging across different access networks (GERAN, UTRAN, E-UTRAN). It addresses the limitation of earlier, ad-hoc approaches where charging data was an afterthought, potentially leading to revenue leakage or an inability to comply with regulatory charging requirements for emergency services.

Key Features

• Generates and processes Charging Data Records (CDRs) specifically for location service events.
• Interfaces with the Location System Control Function (LSCF) to receive charging triggers and event reports.
• Applies tariff policies based on service type (emergency, commercial), accuracy, and subscriber profile.
• Formats billing records for transfer to the network's central billing system or accounting function.
• Supports charging for both mobile-originated and mobile-terminated location requests.
• Facilitates inter-operator billing for location services in roaming scenarios.

Evolution Across Releases

Defining Specifications