Spending-Limit-Request

Description

Spending-Limit-Request (SLR) is a supplementary service defined in 3GPP specifications, primarily in the 22-series and 23-series. It allows a mobile subscriber to specify a maximum amount of money that can be spent on services within a given period. When the spending limit is reached, the network can restrict further usage or notify the subscriber. SLR is part of the Advice of Charge (AoC) family of services and is often used in prepaid or hybrid billing scenarios.

The SLR service operates through signaling between the UE and the network. The subscriber can activate, deactivate, or modify the spending limit using Unstructured Supplementary Service Data (USSD) or other supplementary service control mechanisms. The network maintains the spending limit and monitors the accumulated charges in real-time. When the limit is approached or exceeded, the network may send a notification to the UE and take action, such as barring outgoing calls or data sessions.

SLR is implemented in the core network, specifically in the Service Control Point (SCP) or the Online Charging System (OCS). The OCS interacts with the Gateway GPRS Support Node (GGSN) or the Packet Data Network Gateway (PGW) to enforce the spending limit. For circuit-switched services, the Mobile Switching Center (MSC) enforces the limit. The service is defined in specifications such as 22.024 (Advice of Charge) and 23.086 (Advice of Charge supplementary services).

Over the releases, SLR has evolved to support various bearer types, including GPRS, UMTS, LTE, and 5G. In 5G, the charging architecture is based on the Service-Based Architecture (SBA), and SLR is supported through the Charging Function (CHF) and the Policy Control Function (PCF). The spending limit can be applied to different service types, such as voice, data, and SMS, and can be configured per subscriber or per session.

SLR is particularly important for prepaid subscribers who want to control their spending without constantly monitoring their balance. It also enables operators to offer tiered pricing and parental controls. The service is standardized to ensure interoperability between different network vendors and to provide a consistent user experience.

Purpose & Motivation

SLR was introduced to give subscribers control over their spending on mobile services, addressing the need for real-time cost management in prepaid and postpaid environments. Before SLR, subscribers had limited options to set spending limits, often relying on manual balance checks or operator-specific solutions. SLR provides a standardized way to set, modify, and enforce spending limits, enhancing user experience and reducing the risk of bill shock. It also helps operators manage credit risk and offer flexible pricing plans.