Rating Region Table

Description

The Rating Region Table (RRT) is a service-layer concept specified within the 3GPP framework for the Multimedia Telephony Service for IMS (MTSI), primarily documented in TS 26.917. It functions as a configurable database or table used by an application server, typically a Telephony Application Server (TAS), to determine the appropriate charging rate or policy for a communication session based on the geographical location of the users involved. The core mechanism involves mapping a 'Rating Region' identifier to a specific set of charging rules. A Rating Region is a logical area, such as a country, a group of countries, a state, or a specific network operator's service area. When an MTSI call or session is established, the serving network node (e.g., the MTSI Application Server) can ascertain the location of the calling and/or called party, often derived from network-provided location information or subscription data.

Upon determining the relevant geographical context, the server consults the RRT. The table lookup yields the specific rating policy applicable for that session. This policy defines parameters such as the tariff (cost per minute, per data volume, or per event), the billing currency, any time-of-day or day-of-week rate variations, and potentially the responsible charging system (e.g., Online Charging System - OCS, or Offline Charging System - OFCS) to be invoked. The RRT thus acts as a critical translation layer between the physical/network location of a session and the commercial logic governing its cost. Its implementation allows for a single service platform to support a complex, multi-region commercial deployment without requiring hard-coded logic for every possible location combination.

Architecturally, the RRT is a functional component within the service stratum, separate from the core network charging interfaces like Diameter Ro/Rf. It is provisioned and managed by the service provider, often through operational support systems. The table's contents are dynamic and can be updated to reflect new tariff plans, regulatory changes in specific regions, or promotional offers. During session setup, the MTSI AS uses the RRT output to construct the appropriate charging information, which is then forwarded to the core network's charging functions via standardized mechanisms. This enables precise, location-aware charging events to be generated, ensuring subscribers are billed correctly according to where they are using the service. The RRT is a key enabler for commercial Voice over LTE (VoLTE) and Video over LTE (ViLTE) services, allowing operators to implement differentiated pricing for domestic, international, and roaming scenarios seamlessly.

Purpose & Motivation

The Rating Region Table (RRT) was created to address the commercial and operational complexity of charging for IP-based multimedia telephony services, like VoLTE, in a globalized and roaming-enabled environment. Traditional circuit-switched telephony had relatively static charging models often tied to the called number's prefix (e.g., country code, area code). However, with IMS-based services, the concept of location becomes more fluid—a user can be physically in one country but registered with their home network (roaming), and the service logic is decoupled from the underlying transport. This created a challenge: how to apply the correct tariff for a call where the caller might be roaming, the callee might be in a different country, and the service is delivered via a packet-switched IP connection.

The RRT solves this by introducing a flexible, configurable mapping between logical geographical regions and charging policies. Its purpose is to separate the service logic from the complex, frequently updated rules of commerce and regulation. Without such a table, application servers would need embedded, hard-coded logic for every possible location pair, making tariff updates cumbersome, error-prone, and slow to deploy. The RRT allows operators to define and modify rating regions and their associated policies centrally, enabling rapid response to market changes, new roaming agreements, or regulatory requirements in specific jurisdictions.

Historically, its introduction in Release 14 as part of the enhanced MTSI specifications was motivated by the large-scale commercial deployment of VoLTE/ViLTE. Operators needed a standardized, robust method to implement sophisticated charging schemes that could differentiate between home and visited network usage, apply special rates for specific regions (like a "home zone" or partner networks), and support complex inter-operator settlement models for roaming. The RRT provides this necessary abstraction layer. It empowers service providers to create competitive and fair pricing models that reflect the true cost and value of the service in different contexts, which is fundamental for the commercial success of IMS-based telephony as a replacement for legacy circuit-switched voice.

Key Features

• Maps logical geographical regions (Rating Regions) to specific charging tariffs and policies
• Enables dynamic, location-aware charging for IMS-based multimedia telephony (MTSI/VoLTE)
• Decouples service logic from commercial tariff rules for easier updates and management
• Supports complex scenarios including roaming, international calls, and regional promotions
• Integrates with core network Online Charging System (OCS) and Offline Charging System (OFCS)
• Configurable and provisionable by the service provider's operational support systems

Evolution Across Releases

Defining Specifications