SRVCC Handover for Non-Steady VoIP Calls
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Solution Overview
Problem
Current technologies do not effectively support Single Radio Voice Call Continuity (SRVCC) during a non steady state of a VoIP call, specifically when the call is in an earlier state before a 200 OK message is received, lacking a mechanism for handover from the Packet Switching (PS) domain to the Circuit Switching (CS) domain.
Innovation Solution
A method and network elements are introduced to manage SRVCC handovers by anchoring calls, storing provisional responses, and initiating handovers based on signaling bearers, allowing for seamless transitions from PS to CS domains even during non steady states by enhancing Mobility Management Entities (MME), eNodeB, and Service Centralization and Continuity Application Servers (SCC AS) to detect and handle IMS signaling bearers for SRVCC procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SRVCC handover is supported only during steady state calls, then the handover procedure is simple and well-defined, but call continuity cannot be maintained during non steady state calls
Solution Approach 1:
The patent applies preliminary action by storing the provisional response at the first network element before handover occurs. This allows the system to prepare the necessary signaling information in advance, enabling the handover procedure to continue seamlessly during non steady state calls. The stored provisional response is retrieved and forwarded to the third network element during the handover process, ensuring call continuity without requiring the call to be in a steady state.
2Reliability
If handover procedures are extended to non steady state calls, then call continuity is improved, but the complexity of the handover mechanism increases
Solution Approach 1:
The patent uses the first network element as an intermediary that anchors the call and stores the provisional response. This intermediary component simplifies the overall system architecture by centralizing the management of non steady state handover information. Instead of requiring complex modifications across multiple network elements, the first network element acts as a mediator that handles the storage and forwarding of provisional responses, thereby reducing overall system complexity while enabling non steady state handover.
3Adaptability or versatility
If provisional responses are stored and forwarded during handover, then non steady state handover is enabled, but additional signaling overhead is introduced
Solution Approach 1:
The patent applies the copying principle by storing a copy of the provisional response at the first network element. This copy is then forwarded to the third network element during handover, ensuring that the necessary signaling information is preserved and transmitted without loss. The copying mechanism allows the system to maintain the provisional response information efficiently, enabling non steady state handover while managing signaling overhead through intelligent replication and forwarding of critical signaling data.
Data Source
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AI summary
The present invention provides a method for handing over a terminal from a packet switching domain to a circuit switching domain during a non steady state of a call, a network element managing service centralization and continuity, an access device, a network element managing mobility of a terminal, as well as a communication system at least comprising at least a terminal, a network element managing service centralization and continuity, an access device and a network element managing mobility of a terminal. The method comprises a first network element anchoring the call based on the call setup request received from the terminal, and storing a provisional response returned to the terminal and the state of the call; the terminal detecting that a handover is necessary and sending a measurement report to an access network; the access network deciding to request a second network element for handover, upon detection of a signaling bearer while the measurement report meets handover condition; the second network element deciding to send the first network element a PS to CS handover request upon detection of the signaling bearer, after receiving a request for handover from the access network; and after reception of said handover request, if the first network element detects that the call is in the non steady state, then it checks the previously stored provisional response and sends the provisional response to a third network element, whereby completing the session handover procedure and updating the remote end.