Advice Of Charge - Information

Description

Advice Of Charge - Information (AOC-I) is a standardized 3GPP service that delivers charging information to users in real-time during active communication sessions. The service operates within the IP Multimedia Subsystem (IMS) architecture and leverages the Online Charging System (OCS) to calculate and provide cost estimates. AOC-I works by intercepting charging events during sessions, calculating the associated costs based on tariff information, and delivering this information to the user's device through standardized signaling protocols.

Architecturally, AOC-I involves several key network elements including the Serving-Call Session Control Function (S-CSCF) for session control, the Application Server (AS) for service logic execution, and the OCS for real-time charging calculations. When a user initiates a session, the S-CSCF identifies that AOC-I is required based on the user's service profile and routes the session to the appropriate AS. The AS then interacts with the OCS through the Diameter Ro interface to obtain charging information based on the session parameters such as destination, service type, and duration.

During session establishment and progression, the AS receives charging events from the OCS and formats them into appropriate messages for delivery to the user equipment. These messages are transported using SIP (Session Initiation Protocol) messages with specific headers and parameters defined in 3GPP specifications. The user equipment processes these messages and displays the charging information to the user through the device's user interface. The information typically includes cost per unit (minute, megabyte, or message), accumulated charges during the session, and currency information.

AOC-I supports multiple service types including voice calls, video calls, messaging services, and data sessions. For each service type, the charging calculation considers different parameters - for voice calls it's typically duration-based, for messaging it's per-message, and for data sessions it can be volume-based or time-based depending on the tariff plan. The system maintains session state to ensure accurate cumulative charging information throughout the session duration, with updates provided at configurable intervals or upon significant charging events.

The service operates in conjunction with other charging mechanisms including Advice Of Charge - Charging (AOC-C) which actually applies the charges, and Advice Of Charge - End of Call (AOC-E) which provides final charging information. AOC-I's real-time nature requires low-latency communication between network elements and efficient processing of charging events to ensure timely delivery of information without disrupting the user experience during active sessions.

Purpose & Motivation

AOC-I was developed to address the growing need for transparency in telecommunications charging, particularly as mobile services expanded beyond simple voice calls to include data services, messaging, and multimedia communications. Before AOC-I, users often received charging information only on their monthly bills, leading to 'bill shock' when unexpected charges accumulated. This lack of real-time visibility created customer dissatisfaction and increased support costs for operators dealing with billing disputes.

The service was introduced in 3GPP Release 7 as part of the IMS architecture evolution, which enabled more sophisticated service delivery and charging mechanisms. Prior approaches relied on post-session billing or required proprietary solutions that weren't interoperable across different networks and devices. AOC-I standardized the delivery of charging information across multi-vendor environments, ensuring consistent user experience regardless of the network operator or device manufacturer.

Beyond consumer protection, AOC-I serves important business purposes for network operators. It enables new tariff models and promotional offerings by allowing users to see the cost implications of different service options in real-time. This transparency builds customer trust and can reduce churn by demonstrating fair charging practices. Additionally, AOC-I supports regulatory requirements in many jurisdictions that mandate clear communication of service costs to consumers, particularly for premium services and international roaming.

Key Features

• Real-time charging information delivery during active sessions
• Support for multiple service types including voice, video, messaging, and data
• Integration with Online Charging System (OCS) for accurate tariff calculations
• Standardized SIP-based signaling for interoperability across networks
• Configurable update intervals and event-based charging notifications
• Currency and tariff plan awareness for accurate cost display

Evolution Across Releases

Defining Specifications