Autonomous Redirection for 5G to 4G Call Continuity
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Solution Overview
Problem
Conventional EPS FB methods are prone to call failures due to handover or redirection failures in the 5G to 4G network transition, leading to unreliable voice services in 5G networks.
Innovation Solution
A method where user equipment (UE) autonomously redirects to a 4G network if no handover or redirection command is received within a specified time threshold, selecting a target cell based on signal quality parameters and frequency points to ensure continued call connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover or redirection command is sent from 5G network to 4G network, then call connectivity is maintained, but call failure occurs when command is lost or failed
Solution Approach 1:
The UE proactively initiates autonomous redirection to 4G network when handover command is not received within expected time, before call failure occurs. This preliminary action prevents the harmful effect of call failure by taking corrective action in advance based on timing detection
Solution Approach 2:
The UE monitors whether handover or redirection command is received from 5G network and detects timing information. Based on this feedback, the UE determines whether to perform autonomous redirection, creating a closed-loop control that improves call reliability
2Reliability
If autonomous redirection is implemented by UE, then call connectivity is ensured, but additional time and processing are required
Solution Approach 1:
The UE starts a timer when receiving INVITE message to pre-establish the timing reference for autonomous redirection decision. This preliminary timing setup enables rapid autonomous redirection without extensive processing delay when command loss is detected
Solution Approach 2:
The system uses timer threshold parameters to control the autonomous redirection behavior. By adjusting the timer threshold, the system balances between early redirection (faster connectivity) and waiting for network command (potentially shorter time), optimizing the time-reliability tradeoff
Data Source
AI summary
A method for calling performed by a user equipment (UE) including establishing a call based on a first network in which the UE camps, determining whether a first command for handover or redirection to a second network is received from the first network, and performing an autonomous redirection in response to determining that the first command is not received and a duration between the establishing and the determining exceeds a first threshold, the autonomous redirection redirecting the UE to the second network for continuation of the call.