Supplementary Service Notification CAMEL Subscription Information

Description

Supplementary Service Notification CAMEL Subscription Information (SS-CSI) is a specific type of CAMEL (Customised Applications for Mobile networks Enhanced Logic) subscription data. CAMEL is a 3GPP standard for intelligent network (IN) services in mobile networks, allowing the home network operator to define and control value-added services for their subscribers even when they are roaming. SS-CSI is a trigger mechanism that links the occurrence of a Supplementary Service (SS) event to the invocation of a CAMEL service logic, which is executed on a dedicated node called the CAMEL Service Environment (CSE) or Service Control Point (SCP).

Architecturally, SS-CSI is one of several CSI (CAMEL Subscription Information) data sets stored in the subscriber's profile within the Home Location Register (HLR). When the subscriber's profile is downloaded to the Visitor Location Register (VLR) or Serving GPRS Support Node (SGSN) during registration, the SS-CSI is included. The key functional entities involved are the HLR (data storage), the MSC or GMSC (the Service Switching Function - SSF, which detects the trigger condition), and the gsmSCF (GSM Service Control Function, i.e., the SCP, which executes the custom service logic). The interface between the SSF and the gsmSCF is the CAP (CAMEL Application Part) protocol.

The mechanism works as follows: When a mobile subscriber performs an operation related to a Supplementary Service—such as activating Call Forwarding Unconditional (CFU), deactivating Call Barring, or receiving a notification that Call Waiting is invoked—the MSC (acting as SSF) checks the subscriber's profile for the presence of SS-CSI. If SS-CSI is present and the specific SS event matches the trigger criteria defined within it, the MSC suspends the normal SS processing and sends a CAP message (e.g., InitialDP) to the gsmSCF indicated in the SS-CSI data. This message includes details about the SS event, such as the type of Supplementary Service (e.g., CFU), the subscriber's identity, and any relevant parameters (like the forwarded-to number).

Upon receiving the trigger, the gsmSCF executes its custom service logic. This logic could perform various actions. A common use case is specialized charging: the home network might want to apply a different tariff when a subscriber activates call forwarding to an international number. The gsmSCF can instruct the MSC to apply a specific charging rate via CAP messages. Another use case is notification: the home network might want to send an SMS notification to the subscriber or to a management system whenever a high-value SS like call barring is changed, for security auditing purposes. After the CAMEL logic is executed, the gsmSCF processes the event. It can then instruct the MSC (via CAP Continue or other operations) to proceed with the normal SS processing, or it might apply custom logic. For example, the gsmSCF could generate a charging record for the SS activation, send an SMS notification to the subscriber confirming the change, or even modify the SS operation parameters based on business rules (e.g., only allow Call Forwarding to specific numbers). After receiving instructions, the MSC resumes and completes the Supplementary Service procedure.

Purpose & Motivation

SS-CSI was created to extend the power and flexibility of the CAMEL intelligent network platform to cover events related to Supplementary Services. Before CAMEL, the control and charging for Supplementary Services were largely static and built into the core network switches (MSCs). Operators lacked the ability to easily introduce customized, real-time interactions based on SS usage. SS-CSI solves this by providing a standardized trigger point that allows the home network's service logic (on the SCP) to be invoked precisely when a subscriber interacts with a Supplementary Service.

The primary motivations were enhanced service control, sophisticated charging models, and improved customer interaction. For service control, an operator could use SS-CSI to implement business rules, such as preventing Call Forwarding to international numbers for prepaid subscribers or requiring a PIN for activating certain barring services. For charging, it enabled detailed, event-based billing for SS usage. For example, an operator could charge a small fee each time a subscriber activates Call Forwarding or uses Multi-Party Conferencing, which would be difficult with traditional call-detail-record-based billing alone.

Furthermore, SS-CSI enabled proactive customer care and notification services. When a subscriber roamed to a foreign network and activated Call Forwarding, the home network's SCP could be notified via SS-CSI and immediately send an SMS to the subscriber's phone confirming the activation and perhaps informing them of any associated charges. This improved the transparency and user experience, especially in roaming scenarios where subscribers might be uncertain about service availability and costs. In essence, SS-CSI bridged the gap between the standardized, switch-based world of Supplementary Services and the flexible, programmable world of intelligent network services, allowing operators to differentiate their offerings and manage services more granularly.

Key Features

• A CAMEL trigger subscription parameter stored in the HLR/VLR that links Supplementary Service events to intelligent network logic
• Invokes the home network's gsmSCF (Service Control Point) when a subscriber activates, deactivates, or invokes a Supplementary Service
• Uses the CAP (CAMEL Application Part) protocol for communication between the MSC (SSF) and the gsmSCF
• Enables customised charging, notification, or control policies for Supplementary Service usage
• Operates transparently to the subscriber and does not alter the standardised SS behaviour unless instructed by the gsmSCF
• Particularly valuable for managing and monetising SS usage in roaming scenarios

Evolution Across Releases

Defining Specifications