IMS Registration Retry Across High-Priority RAT Cells
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Solution Overview
Problem
Existing configurations in 5G wireless communication systems do not adequately address scenarios where voice over Internet Protocol (IP) multimedia subsystem (IMS) becomes unavailable, leading to unnecessary connection to low priority radio access technologies (RATs) due to voice-centric user equipment (UE) disabling high priority RATs, resulting in detrimental user experience.
Innovation Solution
The UE is configured to synchronize IMS registration failure causes with RAT disable types, attempt IMS registration on all available high priority RAT cells before disabling, and periodically re-evaluate radio conditions to re-enable the high priority RAT when conditions improve, using synchronized timers and interworking capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE disables the high priority RAT (5G) when voice over IMS becomes unavailable, then voice service availability is maintained by falling back to low priority RAT (LTE), but the UE remains connected to the low priority RAT longer than necessary, degrading user experience
Solution Approach 1:
The UE implements periodic re-evaluation of radio conditions by starting a timer (T3109) when disabling the high priority RAT. The timer is periodically checked to see if the high priority RAT has become available again, allowing the UE to switch back when conditions improve, thus avoiding prolonged connection to low priority RAT
Solution Approach 2:
The system uses feedback from radio condition monitoring and IMS registration status to dynamically control RAT selection. When IMS registration succeeds on the high priority RAT or radio conditions improve, the UE receives feedback to re-enable and switch back to the high priority RAT, optimizing the connection duration on low priority RAT
2Loss of time
If the UE attempts IMS registration on all available high priority RAT cells before disabling, then unnecessary connection to low priority RAT is avoided, but the complexity of cell evaluation and registration attempts increases
Solution Approach 1:
Before disabling the high priority RAT, the UE performs preliminary actions by attempting IMS registration on all available cells of the high priority RAT. This preliminary registration attempt ensures that the UE has exhausted all options on the high priority RAT before falling back to low priority RAT, reducing unnecessary connection duration
Solution Approach 2:
The UE segments the cell evaluation process by individually attempting IMS registration on each available high priority RAT cell. This segmentation allows systematic exploration of all cells while maintaining organized control flow, balancing thoroughness with manageable complexity
Data Source
AI summary
This disclosure describes a user equipment device (UE). The UE includes one or more antennas; one or more radios configured to perform cellular communication using a plurality of radio access technologies (RATs) that support voice over an Internet protocol (IP) multimedia subsystem (IMS); and one or more processors coupled to the one or more radios. The one or more processors are configured to cause the UE to perform operations including: sending, to a communications network associated with a first RAT of the plurality of RATs, a first request for IMS registration, wherein the UE is camped on a first cell of the first RAT; determining, based on an IMS rejection failure, that the IMS registration failure is due to a temporary radio failure; and responsively attempting to perform the IMS registration on at least one other cell of the first RAT.