Session Control Signaling Path for Circuit-Switched Multimedia Calls
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Solution Overview
Problem
Current technologies face challenges in effectively interworking circuit-switched and multimedia subsystems to control calls and provide multimedia services, particularly in maintaining quality of service across different network domains.
Innovation Solution
The method involves establishing a session control signaling path between a user element supported by a circuit-switched subsystem and a remote user agent, utilizing a CS Access Adaptation Function to facilitate message and protocol conversion for session control signaling between the circuit-switched and multimedia subsystems, allowing calls to utilize bearer paths through the circuit-switched subsystem while maintaining control via the multimedia subsystem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuit-switched subsystem is used for call bearer path, then call reliability and quality of service are improved, but multimedia service control capability and network flexibility are limited
Solution Approach 1:
The system separates the call control function from the bearer path. The multimedia subsystem (IMS) handles session control signaling while the circuit-switched subsystem handles the actual call bearer path. This segmentation allows each subsystem to operate in its optimal domain, with the IMS providing flexible multimedia control and the circuit-switched network providing reliable voice transmission.
Solution Approach 2:
The invention introduces an intermediary mechanism (session control signaling path) that connects the multimedia subsystem and circuit-switched subsystem. This intermediary enables the IMS to control calls in the circuit-switched domain without requiring the user element to be fully IMS-capable, thus bridging the gap between legacy and next-generation networks.
2Adaptability or versatility
If multimedia subsystem controls session signaling, then service flexibility and multimedia capability are improved, but compatibility with circuit-switched terminals is reduced
Solution Approach 1:
The invention uses the circuit-switched network itself as an intermediary transport mechanism for IMS signaling. By utilizing existing circuit-switched signaling channels (such as USSD or SMS) to carry IMS session control messages, the system enables IMS service control without requiring new terminal hardware or software modifications in circuit-switched devices.
Solution Approach 2:
The system makes the circuit-switched signaling infrastructure serve multiple functions: traditional telephony control and IMS session control signaling. This multi-functionality allows legacy circuit-switched networks to support next-generation multimedia services without requiring dedicated new infrastructure for signaling.
3Adaptability or versatility
If interworking between circuit-switched and packet-switched subsystems is implemented, then network reach and service coverage are improved, but system complexity and protocol conversion requirements increase
Solution Approach 1:
The invention introduces a gateway function that acts as an intermediary between the circuit-switched and packet-switched domains. This gateway handles protocol conversion and signaling translation, shielding the complexity of interworking from both the user elements and the core networks. The gateway translates IMS signaling protocols to circuit-switched signaling protocols and vice versa.
Solution Approach 2:
The invention extracts the protocol conversion and interworking complexity from the user elements and terminal devices, concentrating it in network-side gateway functions. This extraction allows simple legacy terminals to interwork with IMS services without requiring complex protocol stacks or conversion capabilities in the terminal itself.
Data Source
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AI summary
The present invention allows calls that are controlled by a multimedia subsystem (MS) to employ bearer paths that are supported in whole or in part by a circuit-switched subsystem (CS). As such, calls controlled by the MS can have a portion of the bearer path provided through the CS when needed or desired. To facilitate such control, a session control signaling path is established between a user element currently supported by the CS and a remote user agent (RUA), which represents the user element in the MS. While a portion of the bearer path for the call is supported by the CS, the session control signaling path extends the reach of the MS to the user element.