SIP Representative Group Call Handling via NOTIFY Messages

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Solution Overview

Problem

Existing key telephone systems using SIP do not effectively implement representative group call reception and answering services, lacking specific sequences for simultaneous call ringing and stopping of unanswering phones.

Innovation Solution

A method involving a main unit transmitting a 'NOTIFY' message to all SIP telephones in a representative group, with an answering phone notifying the main unit and establishing a call session, and unanswering phones suspending call reception, utilizing 'NOTIFY', 'MESSAGE', or 'INFO' messages for event notification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If 'INVITE' messages are used for each SIP telephone in a representative group, then call sessions can be established, but system complexity increases due to administering multiple dialogs

Engineering Contradiction:

Improvecall reception operationVSAvoiddialog management complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent introduces a NOTIFY message as an intermediary mechanism between the main unit and SIP telephones for call reception notification. Instead of each telephone handling individual INVITE dialogs, the main unit sends a single NOTIFY message to all telephones in the representative group, which then ring simultaneously without requiring complex dialog administration. This mediator approach simplifies the overall system operation while maintaining establishable call sessions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of information

If simultaneous call ringing is implemented across all SIP telephones, then user notification is improved, but control complexity increases

Engineering Contradiction:

Improvecall notification completenessVSAvoidcall control sequence complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The patent implements preliminary action by having the main unit send a NOTIFY message to all SIP telephones in the representative group before actual call establishment. This preliminary notification triggers simultaneous ringing at all telephones, ensuring complete user notification. The call control sequence remains simple because the main unit only needs to send one NOTIFY message rather than managing complex sequential or simultaneous INVITE exchanges with multiple telephones.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If multiple INVITE dialogs are administered for representative group calls, then individual call sessions can be established, but processing overhead increases

Engineering Contradiction:

Improvecall session establishmentVSAvoidcall processing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent merges the call notification function for multiple SIP telephones into a single NOTIFY message sent by the main unit. Instead of administering separate INVITE dialogs for each telephone in the representative group, the system combines the notification into one message that triggers simultaneous ringing at all target telephones. This merging approach maintains reliable call session establishment while significantly improving call processing efficiency by reducing the number of dialog management operations required.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8184559B2Key telephone system using a SIP and method of receiving and answering an incoming call for a representative group in the key telephone system

Publication Date: 2012.05.22 NEC PLATFROMS LTD

AI summary

In a key telephone system including SIP telephones forming a representative group, a main unit transmits, upon reception of an incoming call for the representative group, a “NOTIFY” message to all of SIP telephones forming the representative group to perform a calling operation. An answering SIP telephone answers the main unit by sending a “NOTIFY” message to the main unit. The main unit transmits a “200 OK” message to the answering telephone alone and transmits a “NOTIFY” message to an unanswering SIP telephone.