Person to Application

Description

Person to Application (P2A) is a service paradigm standardized in 3GPP Release 18 and beyond, focusing on direct communication between a human user and an application server. This model is a subset of the broader Person-to-Person (P2P) and Application-to-Person (A2P) communication frameworks, but specifically addresses scenarios where the interaction is initiated by the person and targets an application, such as a conversational AI, virtual assistant, or automated service platform. The architecture leverages existing IMS (IP Multimedia Subsystem) core or 5G core network capabilities, including session control, media handling, and service enablers, to establish and manage these sessions. Key network functions involved include the P-CSCF (Proxy-Call Session Control Function), S-CSCF (Serving-CSCF), and application servers (AS) that host the conversational logic. The service may utilize protocols like SIP (Session Initiation Protocol) for signaling and RTP (Real-time Transport Protocol) for media transport, supporting voice, video, or text-based interactions.

From a technical perspective, P2A sessions are established similarly to traditional voice or video calls but are routed to an application server instead of another user endpoint. The network identifies the P2A service request through initial filter criteria (IFC) or service identification mechanisms, directing the session to the appropriate AS. The application server then processes the user's input—which could be speech, text, or DTMF tones—using natural language processing or predefined logic, and generates a response. Media resources, such as speech-to-text conversion or text-to-speech synthesis, may be provided by network-based Media Resource Function (MRF) or integrated within the AS. Quality of Service (QoS) mechanisms ensure low latency and high reliability for real-time interactions, which is critical for user experience in services like voice assistants.

The role of P2A in the network extends beyond basic call setup; it enables new revenue streams for operators by facilitating advanced conversational services. It integrates with network APIs (e.g., CAPIF - Common API Framework) to expose network capabilities like user authentication, location, or presence to the application, allowing for context-aware interactions. Security is paramount, with measures such as TLS for signaling encryption and SRTP for media protection, as defined in relevant 3GPP security specifications. P2A also supports regulatory requirements like lawful interception and emergency service handling, ensuring compliance in deployed networks. Overall, P2A represents a convergence of telecom and IT, enabling seamless human-machine communication over standardized cellular networks.

Purpose & Motivation

P2A was introduced to address the growing demand for interactive, application-driven communication services where users directly engage with automated systems. Prior to its standardization, such interactions were often implemented using proprietary solutions or over-the-top (OTT) applications, leading to fragmentation, inconsistent quality, and limited integration with network capabilities. This made it difficult for mobile operators to offer standardized, carrier-grade conversational services like voice-activated assistants or customer service bots with guaranteed performance and security. The motivation for P2A in 3GPP Release 18 stems from the evolution towards 5G Advanced, which emphasizes enhanced service enablers and network APIs to support new use cases beyond traditional telephony.

Historically, communication services were primarily P2P (e.g., voice calls) or A2P (e.g., SMS alerts), but the rise of AI and conversational interfaces created a need for a hybrid model where a person initiates a session with an application. Existing mechanisms, such as unstructured supplementary service data (USSD) or interactive voice response (IVR) systems, were limited in functionality, media support, and scalability. P2A standardizes this interaction within the 3GPP ecosystem, leveraging IMS and 5G core networks to provide a unified framework. This allows operators to deploy services with consistent QoS, security, and interoperability across different vendors and regions, reducing development costs and time-to-market.

Furthermore, P2A solves challenges related to service discovery, routing, and media handling in person-to-application scenarios. By defining clear architectural roles and procedures in specifications like TS 23.228 and TS 24.186, it ensures that applications can reliably interact with users over cellular networks, supporting features like session continuity, billing integration, and regulatory compliance. This enables innovative services in areas such as healthcare (virtual health assistants), automotive (in-car voice controls), and smart cities, driving the digital transformation of communication networks.

Key Features

• Standardized interaction between human users and application servers
• Support for multiple media types including voice, video, and text
• Integration with IMS and 5G core network for session control
• Quality of Service (QoS) guarantees for real-time conversational services
• Security mechanisms including encryption and authentication
• Exposure of network capabilities via APIs for context-aware applications

Evolution Across Releases

Defining Specifications