IMS Gateway Routing Without SIP-Trunk for UC-to-PSTN Sessions

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Solution Overview

Problem

Existing unified communications (UC) solutions face challenges in enabling real-time communication between users of different platforms or legacy networks like PSTN without the need for SIP-Trunk infrastructure, which adds load to the IMS network.

Innovation Solution

A communication system that establishes sessions between calling and called end devices using an IMS network without requiring user registration or a SIP-Trunk application server, utilizing gateway devices to convert and forward signaling information directly to the I-CSCF instance, and employing a number portability server to identify appropriate gateway devices for routing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If SIP-Trunk infrastructure is used to enable communication between UC platforms and legacy networks, then communication compatibility is improved, but device complexity and network load increase

Engineering Contradiction:
Improvecommunication compatibilityVSAvoidSIP-Trunk infrastructure complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent extracts the SIP-Trunk application server component from the traditional SIP-Trunk infrastructure and replaces it with a number portability server. This server only performs number lookup and gateway identification functions, significantly reducing the complexity and resource requirements while maintaining communication compatibility between UC platforms and legacy networks

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a number portability server as an intermediary component that sits between the UC platform and the IMS network. This mediator performs number lookup and gateway identification, enabling communication without requiring full SIP-Trunk infrastructure. The intermediary simplifies the overall system architecture while maintaining adaptability

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If SIP-Trunk application server is deployed for each user, then communication functionality is improved, but processing load on IMS network increases

Engineering Contradiction:
Improvecommunication functionalityVSAvoidIMS network processing efficiency
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent extracts the number lookup and gateway identification functions from the SIP-Trunk application server and implements them in a dedicated number portability server. This separation reduces the processing load on the IMS network by handling routine lookup operations externally, while the IMS network focuses on core call setup and management functions

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The number portability server performs preliminary number lookup and gateway identification before calls are routed to the IMS network. By pre-resolving number-to-gateway mappings, the system reduces the processing burden on the IMS network during actual call establishment, improving overall productivity

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP4113930B1Method and communication system for transmitting signaling information used for establishing a communication session between a calling end device and a called end device
Publication Date: 2025.12.17 DEUTSCHE TELEKOM AG
  • EP4113930B1 patent drawingFigure 1
  • EP4113930B1 patent drawingFigure 2
  • EP4113930B1 patent drawingFigure 3

AI summary

The present invention relates to method for transmitting signaling information used for establishing a communication session between a calling end device and a called end device via a communication system (10) comprising an IP Multimedia Subsystem (IMS, 20), the method comprising the steps of: a) receiving, at the first gateway device (50), first signaling information from the first unified communications (UC) platform (31), the first signaling information being associated with a calling end device (110) and including the calling number of a called end device (170), the calling end device (110) being configured to communicate with the unified communications (UC) platform (31), the calling end device (110) and the called end device (170) each forming an endpoint of a communication session to be established; b) transmitting, by the first gateway device (50), second signaling information including the calling number of the called end device (170) directly to the I-CSCF instance (22); c) retrieving, by the I-CSCF instance (22), in dependence of the calling number of the called end device (170) an information from a number portability server device (21) associated with the IP Multimedia Subsystem (20), the information identifying a gateway device (23, 24, 50, 60) configured to transmit signaling information destined for the called end device (170), the signaling information including the calling number of the called end device (170); and d) transmitting, by the I-CSCF instance (22), in response to the information retrieved at step c) third signaling information including the calling number of the called end device (170) directly to the gateway device (23) identified at step c).