UE Call Handling During NR to LTE Fallback
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Solution Overview
Problem
Wireless communication systems face challenges in handling calls when user equipment transitions from dual active mode to dual standby mode, particularly due to fallback from New Radio (NR) to Long Term Evolution (LTE) for calls, leading to dropped calls and poor user experience due to inability to concurrently manage multiple subscriptions across different radio access technologies.
Innovation Solution
A method for user equipment (UE) to determine if a call request is associated with fallback from NR to LTE by searching a database and transitioning the subscription to a third RAT, such as WLAN, if fallback is detected, ensuring continuous communication and maintaining active sessions across different radio access technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE operates in dual active mode with NR for both subscriptions, then concurrent communication on both subscriptions is enabled, but fallback from NR to LTE for calls causes dropped calls when transitioning to dual standby mode
Solution Approach 1:
The UE proactively identifies serving cells associated with NR-to-LTE fallback through database searching before call establishment. By detecting fallback-capable cells in advance and checking call request sources against this information, the UE can prevent dropped calls that would occur during mode transitions, thereby improving call continuity while maintaining adaptability to different RAT scenarios.
2Reliability
If the UE rejects call requests from fallback-associated cells, then dropped calls are prevented, but call connectivity is reduced
Solution Approach 1:
The patent introduces a database as an intermediary layer between the UE and the network. This database stores information about fallback-associated cells and acts as a reference mechanism. The UE queries this intermediary database to determine whether to accept or reject call requests, enabling intelligent decision-making that balances call stability with connectivity opportunities rather than using simple rejection rules.
Solution Approach 2:
The UE dynamically changes its call handling behavior based on the source cell identification. By checking whether the serving cell is associated with NR-to-LTE fallback and modifying call acceptance/rejection decisions accordingly, the system adapts its operational parameters (call handling mode) to specific network conditions, achieving both reliability and productivity.
3Use of energy by moving object
If the UE transitions to dual standby mode, then power consumption is reduced, but the ability to concurrently manage multiple subscriptions is lost
Solution Approach 1:
The patent enables the UE to automatically identify fallback-associated cells through database searching and self-manage call request handling based on this identification. This self-service capability allows the UE to operate in dual standby mode with reduced power consumption while still maintaining effective multi-subscription management through automated fallback detection and intelligent call handling decisions.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, while the UE is in an active session using a first radio access technology (RAT) associated with a first subscription of the UE, a call request via the first RAT, wherein the call request is associated with a second subscription of the UE. The UE may determine that the call request is received from a serving cell that is associated with fallback from the first RAT to a second RAT for calls. The UE may reject the call request or transition the second subscription to a third RAT based at least in part on the determination that the call request is received via the serving cell that is associated with fallback from the first RAT to the second RAT for calls. Numerous other aspects are described.