Description
GPRS-CSI is a collection of subscriber-specific data stored in the HLR that enables the CAMEL (Customised Applications for Mobile networks Enhanced Logic) feature for GPRS/UMTS packet-switched services. It defines triggers and information required for the SGSN to interact with a CAMEL Service Control Point (gsmSCP) during a PDP context activation or a specific packet data event. The key components include the GPRS-CSI data itself, which contains a gsmSCF address, a Service Key, and various trigger detection points (TDPs) for events like PDP Context Establishment. When a subscriber with GPRS-CSI initiates a data session, the SGSN, upon detecting a configured TDP, suspends the procedure and sends a CAP (CAMEL Application Part) message to the designated gsmSCF. The gsmSCF, hosting the service logic, can then instruct the SGSN on how to proceed, for instance, by applying specific charging rules, allowing or denying the context, or modifying QoS parameters. This architecture decouples service logic from the core network switches, allowing for rapid deployment of advanced, subscriber-centric services without requiring upgrades to every network node. The interaction is standardized via the CAP protocol over the Gs interface (between SGSN and gsmSCF) or indirectly via the Gr interface (HLR to SGSN) for data provisioning.
Purpose & Motivation
GPRS-CSI was created to extend the intelligent network (IN) capabilities of CAMEL, originally designed for circuit-switched voice, into the packet-switched domain introduced with GPRS and UMTS. Prior to its introduction, advanced, real-time service control for data sessions (like prepaid data or content-based charging) was difficult, often requiring proprietary solutions within the GGSN or external billing systems with limited real-time interaction. GPRS-CSI standardized the mechanism for the network to invoke external service logic during a data session, solving the problem of flexible and real-time service control for packet data. This enabled operators to offer sophisticated prepaid data plans, location-based services, and spend-control features directly within the packet core, generating new revenue streams and improving customer experience by allowing real-time balance checks and policy enforcement. Its creation was motivated by the commercial need to monetize GPRS data services with the same agility as voice services, addressing the limitations of static, subscription-based data billing.
Key Features
- Enables CAMEL service control for GPRS PDP context procedures
- Stored in HLR as part of subscriber profile and downloaded to SGSN
- Defines Trigger Detection Points (TDPs) for events like PDP Context Establishment
- Triggers CAP dialogue between SGSN and external gsmSCF
- Allows real-time charging control (e.g., prepaid data)
- Supports service logic for advanced packet data services
Evolution Across Releases
Introduced GPRS-CSI to provide CAMEL Phase 3 support for GPRS. It defined the initial architecture where the SGSN interacts with a gsmSCF using CAP. Key capabilities included basic control points for PDP context activation and the ability to apply advice of charge and charging correlation for packet data services.
Defining Specifications
| Specification | Title |
|---|---|
| TS 23.078 | 3GPP TS 23.078 |