Call Completion Service for Unregistered Users in SIP Networks

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Solution Overview

Problem

Current call completion services in SIP-based networks do not support completing calls to users who are not registered or unavailable, lacking a method to automatically retry calls without the user initiating new attempts.

Innovation Solution

A method for providing a Call Completion to a Not Registered/Not Available user (CCNReg) service, which involves monitoring the status of the called user through SUBSCRIBE and NOTIFY messages, assigning a Serving Call Session Control Function, and queuing the call attempt until the user becomes available, allowing automatic recall and call completion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If call completion services are provided for busy or absent users in PSTN/PLMN networks, then call completion capability is improved, but no similar service exists for not registered/not available users in SIP/IMS networks

Engineering Contradiction:

Improvecall completion service coverageVSAvoidcommunication availability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent extends the call completion service concept from traditional PSTN/PLMN networks (where it only handled busy/absent users) to SIP/IMS networks, making it universally applicable to not registered/not available users as well. The service now handles multiple user states (busy, absent, not registered, not available) through a unified mechanism using SUBSCRIBE/NOTIFY messages and call completion queues.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Extent of automation

If the network monitors user status and automatically recalls calling users, then call completion automation is improved, but the calling user must initiate repeated new attempts manually without automatic retry

Engineering Contradiction:

Improvecall completion automationVSAvoiduser operation simplicity

Core Design Contradiction:

Extent of automationVSEase of operation

Solution Approach 1:

The system enables automatic call completion through self-service mechanisms. When a called user becomes available, the network automatically recalls the calling user without requiring manual retry initiation. The calling user simply subscribes to the call completion service, and the system handles the entire process of monitoring, queuing, and automatic recall independently.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent implements a feedback mechanism where the network continuously monitors the called user's registration and availability status through SUBSCRIBE/NOTIFY messages. When the user status changes from not registered/not available to registered/available, the system provides feedback by automatically initiating recall of the calling user, eliminating the need for manual retry attempts.

Inventive Principle:

Principle #23Feedback

3Productivity

If call attempts are queued and completed in sequence, then multiple calling users can be served, but the system lacks capability to handle not registered users in SIP/IMS networks

Engineering Contradiction:

Improvecall handling capacityVSAvoidnetwork compatibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent implements preliminary action by establishing call completion queues in advance for both calling and called users. When a call attempt fails due to the called user being not registered or not available, the system proactively queues the call attempt rather than immediately rejecting it. This preliminary queuing mechanism enables subsequent automatic recall and call completion when the user becomes available.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary call completion service mechanism that bridges PSTN/PLMN and SIP/IMS networks. The service uses SUBSCRIBE/NOTIFY messages as intermediaries to monitor user status and maintains call completion queues as intermediary structures to store and manage pending call attempts, enabling seamless call completion across different network types including SIP/IMS networks that previously lacked this capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8359015B2Method of providing a call completion service to a not registered or not available user in a telecommunication network

Publication Date: 2013.01.22 ALCATEL LUCENT SA

AI summary

A method is disclosed of providing a call completion service to a not registered or not available user (CCNReg):—sending (9-10) a SUBSCRIBE message, from the originating application server (AS1) to the terminating I-CSCF, —then sending (11) a Location Information Request (LIR), from the terminating I-CSCF towards the HSS, requesting information about the terminating S-CSCF (S-CSCF2),—then sending (12) a Location Info Answer (LIA) containing S-CSCF capabilities or/and name, from the HSS to the terminating I-CSCF,—then assigning (13) a S-CSCF, referred to as the terminating S-CSCF (S-CSCF2), and forwarding the SUBSCRIBE message to said the terminating S-CSCF (S-CSCF2),—then sending (14) a Server Assignment Request (SAR) from the terminating (S-CSCF2) to the HSS,—then sending (15) a Server Assignment Answer (SAA) containing second user's profile info, from the HSS to the terminating S-CSCF (S-CSCF2),—then, forwarding (16) the SUBSCRIBE message to the terminating application server (AS2), for requiring to handle the CCNReg service),—and then sending (21-23) a NOTIFY with the indication that the CCNReg subscription to the CCNReg service is active, and that the CCNReg request for the first user (User A) to communicate with the second user (User B) has been queued.