SR-VCC Codec List Handling for Seamless LTE to CS Handover
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Solution Overview
Problem
In Single Radio Voice Call Continuity (SRVCC), the enhanced Mobile Switching Center (MSC) faces challenges in obtaining the supported codec list from the User Equipment (UE) for seamless handover between LTE and Circuit-Switched (CS) domains, as the UE is not involved in SRVCC preparation.
Innovation Solution
The UE sends its supported CS codec list during LTE attachment, which is then forwarded to the Mobility Management Entity (MME) and subsequently to the enhanced MSC, enabling the MSC to set up proper handover signaling with the target 2G/3G radio access network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the UE is not involved in SRVCC preparation, then the handover can be performed automatically by the network, but the MSC cannot obtain the supported codec list from the UE
Solution Approach 1:
The UE sends its supported CS codec list to the MME during LTE attachment, before the handover occurs. This preliminary action ensures that the codec information is already available in the network when handover is needed, eliminating the need for UE involvement during the actual SRVCC preparation phase.
Solution Approach 2:
The MME acts as an intermediary that collects the codec list from the UE during attachment and forwards it to the MSC when handover is required. This mediator approach allows the MSC to obtain necessary information without directly interacting with the UE during the handover process.
2Reliability
If the UE sends codec list during attachment, then the MSC obtains codec information for handover, but additional signaling messages are required
Solution Approach 1:
The codec list information is merged into the existing LTE attachment signaling procedure. By combining the codec list transmission with the attachment process, the patent avoids creating separate dedicated signaling messages, thus reducing overall signaling complexity while ensuring reliable information delivery.
Data Source
AI summary
A Circuit Switched (CS) domain codec list for Single Radio Voice Call Continuity (SR-VCC) is provided. A apparatus providing such a list can include preparing a list of include preparing a list of circuit switched capabilities of a terminal device, sending the list to a network device during attachment, receiving the list at the network device, storing the list in the network device, sending the list to a second network device, receiving the list at the second network device, and using the list in handing over the terminal device to the second network device.