Send Information For Incoming Call

Description

Send Information For Incoming Call (SIFIC) is a Circuit-Switched (CS) supplementary service defined in 3GPP specifications for GSM and UMTS networks. It operates within the framework of the Call Control (CC) protocol at the core network level. The service enables a calling party to attach additional information elements to a call setup request (SETUP message). When a call is routed to the called subscriber, the network delivers this supplementary information to the called User Equipment (UE) concurrently with or prior to the call alerting signal (ringing). The called party's terminal can then present this information on its display, providing context for the incoming call.

The technical flow involves several network entities. Originating from the calling UE, the SIFIC information is included in the FACILITY information element of the initial SETUP message sent to the Mobile Switching Center (MSC). The MSC, acting as the originating exchange, must recognize and support the SIFIC service. It then routes the call and the attached SIFIC data through the network via ISDN User Part (ISUP) signaling, ensuring the information is carried transparently to the terminating MSC serving the called subscriber. The terminating MSC checks the called subscriber's service profile to verify if SIFIC is provisioned and allowed. If so, it forwards the SIFIC information to the called UE within the SETUP message over the radio interface. The UE's Man-Machine Interface (MMI) software is responsible for parsing and displaying the received text or identifier to the user.

Key components in the architecture include the MSC, the Home Location Register (HLR) which stores the subscriber's service profile indicating SIFIC activation, and the UE's call control application. The service relies on precise signaling protocols (e.g., DTAP, ISUP) to transport the FACILITY information element end-to-end. SIFIC is distinct from Calling Line Identification Presentation (CLIP); while CLIP provides only the caller's number (if not restricted), SIFIC allows the caller to actively send a chosen piece of information. This service enhances basic telephony by adding a layer of context, allowing the called party to prioritize calls, prepare for the conversation, or decide to redirect the call based on the provided reason. Its implementation requires support from both the network infrastructure and the terminal devices.

Purpose & Motivation

SIFIC was developed to add intelligence and context to basic mobile voice calls, addressing the limitation of a simple 'ringing' notification. In early mobile networks, an incoming call provided minimal information—often just an indication of an incoming call, and if CLIP was supported and allowed, the caller's number. This left the called party with little context to decide the call's importance or urgency. SIFIC was created to solve this by allowing the caller to proactively communicate the purpose of the call, transforming the call alert into a more informative event.

The historical motivation stems from the era of feature phones and the expansion of supplementary services in GSM, aiming to mimic or exceed features available in advanced fixed-line ISDN networks. It addressed business and personal communication needs where knowing *why* someone is calling can be as important as knowing *who* is calling. For instance, a caller could send "Urgent" or "Meeting reminder," enabling the called party to make an immediate, informed decision about answering, rejecting, or forwarding the call to voicemail.

This service also aimed to reduce missed calls and unnecessary callbacks by providing immediate context. It was part of a suite of GSM Phase 2+ supplementary services designed to increase the value proposition of mobile networks beyond mere connectivity. While its usage was dependent on handset support and network provisioning, SIFIC represented an early step towards richer communication services that would later evolve into multimedia messaging and modern rich communication services (RCS), bridging the gap between simple voice and data-based context sharing.

Key Features

• Allows calling party to attach a text reason or identifier to a call setup message
• Delivers supplementary information to the called party's device before or with call alerting
• Operates as a Circuit-Switched supplementary service using FACILITY information elements
• Requires provisioning in the HLR subscriber profile and support in the terminating MSC
• Enhances call handling decisions by providing context beyond caller ID
• Relies on end-to-end signaling transparency across ISUP and radio interfaces

Evolution Across Releases

Defining Specifications