Video Call Transfer Between PS and CS Domains
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Solution Overview
Problem
Existing methods for transferring video calls from a PS domain to a CS domain result in voice and video interruptions due to the need to convert video calls to voice calls and back, causing communication disruptions during handover processes.
Innovation Solution
Pre-negotiating video call parameters in the PS domain using IMS signaling to establish a CS video call directly after handover, avoiding the need for intermediate conversion and thus minimizing interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If video call conversion to voice call and back is performed during handover from PS domain to CS domain, then compatibility with CS domain is improved, but communication continuity deteriorates due to voice and video interruptions
Solution Approach 1:
The patent performs video call parameter negotiation in advance during the PS domain before handover occurs. By pre-negotiating the video parameters (such as codec type, resolution, bitrate) that will be needed in the CS domain, the system eliminates the need for conversion during handover. The terminal and network side agree on video parameters beforehand, so when handover to CS domain occurs, the video call can continue directly with the pre-agreed parameters, avoiding interruption and maintaining communication continuity.
2Reliability
If direct CS video call establishment after handover is implemented, then communication continuity is improved, but parameter negotiation complexity increases
Solution Approach 1:
The patent moves the parameter negotiation process to occur before handover in the PS domain, rather than during or after handover. This preliminary negotiation establishes all necessary video parameters in advance, simplifying the post-handover process to merely activating the pre-negotiated parameters. The complexity is front-loaded in a controlled environment where both parties are in the same domain (PS), making negotiation easier, while the actual handover becomes a simple state transition without complex negotiations.
Solution Approach 2:
The patent introduces an SCC AS (Service Continuity Application Server) as an intermediary to facilitate the pre-negotiation process. The SCC AS coordinates between the terminal and the network side during the PS domain, managing the video parameter negotiation and ensuring agreement is reached before handover. This intermediary simplifies the complexity by providing a dedicated coordination mechanism, separating the negotiation complexity from the handover execution.
3Adaptability or versatility
If video parameter negotiation is performed after handover to CS domain, then adaptability to CS domain is improved, but handover time increases causing communication interruption
Solution Approach 1:
The patent performs all video parameter negotiation activities before the handover event occurs, during the terminal's residence in the PS domain. By completing the negotiation of video parameters (codec selection, resolution, bitrate, etc.) in advance, the system eliminates any time delay that would occur if negotiation had to take place after handover. The terminal and network side establish agreement on all video parameters beforehand, so when handover to CS domain occurs, the transition is immediate and seamless, minimizing handover time and preventing communication interruption.
Data Source
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AI summary
The present invention discloses a method, a system, a terminal, an MSC server, and an SCC application server for transferring a video call between access networks. The method includes: pre-negotiating, in a PS domain and through IMS signaling, a CS video call parameter; and, after a video call of a terminal is transferred from the PS domain to a CS domain, establishing a CS video call according to the pre-negotiated CS video call parameter. By using the technical solutions of the present invention, the CS video call parameter is pre-negotiated before the video call of the terminal is transferred from the PS domain to the CS domain, and after transfer to the CS domain, the CS video call is established by directly using the pre-negotiated CS video call parameter. During a handover process of the video call of the UE from the PS domain to the CS domain, no voice or video interruption occurs, which improves user experience.