Calling Name Presentation

Description

Calling Name Presentation (CNAP) is a standardized supplementary service defined within the 3GPP framework that enables the display of the calling party's name on the called party's terminal. The service operates by querying a database containing name-to-number mappings when a call is initiated. This query occurs during call setup procedures, typically involving signaling between network elements to retrieve and forward the name information before the call is presented to the called subscriber.

Architecturally, CNAP leverages Intelligent Network (IN) capabilities, specifically utilizing the Customized Applications for Mobile network Enhanced Logic (CAMEL) framework in GSM/UMTS networks and Diameter-based interfaces in later 3GPP releases. The key network elements involved include the Home Location Register (HLR) or Home Subscriber Server (HSS) for subscriber data, the Mobile Switching Center (MSC) or Mobile Management Entity (MME) for call control, and specialized CNAP servers or databases that store and provide name information. When a call is placed, the serving network queries the appropriate database using the calling party's number as a key, retrieves the associated name, and includes it in the call setup signaling (such as in ISUP or SIP messages) toward the called party's terminal.

The technical implementation involves several protocol layers and interfaces. In circuit-switched domains, CNAP information is typically carried in the Calling Party Name parameter within ISDN User Part (ISUP) signaling messages. In packet-switched and IMS domains, it's conveyed via Session Initiation Protocol (SIP) headers, specifically the P-Asserted-Identity header with display name parameters. The service requires coordination between originating and terminating networks, potentially involving inter-operator queries when the calling and called parties belong to different networks. Privacy considerations are integral to the design, with mechanisms to respect calling party preferences regarding name display.

CNAP's role extends beyond basic caller identification to support various telecommunication services. It enables enhanced call screening, integration with contact lists, and support for business applications where caller identity verification is important. The service must handle international roaming scenarios, number portability cases, and different numbering plan formats while maintaining performance requirements for call setup times. Implementation variations exist between operators, but 3GPP standardization ensures basic interoperability and consistent user experience across different networks and device types.

Purpose & Motivation

CNAP was created to address the limitation of traditional caller identification that only displayed telephone numbers. Before CNAP, subscribers could only see the calling party's number, which required mental recognition or cross-referencing with contact lists to identify callers. This was particularly problematic for businesses receiving calls from unknown numbers or individuals trying to avoid unwanted calls. The service aimed to enhance user convenience and call management by providing immediate visual identification of callers.

The historical context for CNAP development includes the evolution of Intelligent Network services in the 1990s, where telecom operators sought to create value-added services beyond basic voice calls. As mobile phone adoption grew, the need for better call screening became apparent, especially with increasing spam and telemarketing calls. CNAP built upon existing Calling Line Identification Presentation (CLIP) services by adding the name dimension, creating a more user-friendly identification method that didn't require subscribers to memorize numbers or maintain extensive contact lists.

CNAP solves several practical problems in telecommunications. It helps users make informed decisions about answering calls, reducing interruptions from unwanted callers. For businesses, it enables better customer service by allowing agents to see caller names before answering. The service also supports regulatory requirements in some jurisdictions for caller identification. By standardizing CNAP across 3GPP networks, it ensures consistent functionality for subscribers roaming between different operators' networks, maintaining service continuity regardless of location or network technology.

Key Features

• Displays calling party name on called party's device
• Integrates with Intelligent Network (IN) architecture
• Supports both circuit-switched and packet-switched domains
• Includes privacy controls for calling parties
• Works across different network operators
• Maintains call setup performance requirements

Evolution Across Releases

Defining Specifications