Direct WLAN-to-LTE Handover for Voice Call Continuity
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Solution Overview
Problem
Existing wireless communication systems face challenges in maintaining voice call continuity when transitioning from a WLAN to a WWAN, particularly due to the need for multiple handovers that result in call muting and dropping, especially when the LTE RAT network has a lower priority relative to 5G NR, leading to poor user experience.
Innovation Solution
The UE is configured to perform a reselection procedure to directly handover from a deteriorating WLAN to an LTE RAT network, bypassing a potentially higher-priority 5G NR network, and to de-prioritize 5G RAT networks upon handover rejection, ensuring timely reestablishment of voice calls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE follows standard handover procedures from WLAN to 5G NR and then to LTE RAT network, then the network priority rules are satisfied, but the voice call experiences multiple handovers causing call muting and dropping
Solution Approach 1:
The patent applies preliminary action by having the UE perform reselection to the LTE RAT network before the WLAN connection deteriorates below the threshold. This proactive approach allows the UE to establish the handover target in advance, avoiding the need for multiple sequential handovers (WLAN→5G NR→LTE) and thereby reducing call muting time while maintaining network priority rules.
2Reliability
If the UE performs multiple handovers from WLAN to 5G NR and then to LTE RAT network, then network priority rules are followed, but call dropping occurs due to excessive handover complexity
Solution Approach 1:
The patent extracts the problematic intermediate 5G NR handover step from the standard procedure. By directly selecting LTE RAT network as the handover target from WLAN without requiring 5G NR involvement, the patent simplifies the handover path to WLAN→LTE, eliminating the complex multi-step process while still respecting network priority rules through the reselection mechanism.
3Productivity
If the UE de-prioritizes 5G RAT networks upon handover rejection, then voice call reestablishment is accelerated, but network resource allocation may be impacted
Solution Approach 1:
The patent applies dynamics by making the UE's RAT selection flexible and adaptive. The UE dynamically adjusts its network selection based on real-time conditions - preferring 5G NR when available and conditions permit, but switching to LTE RAT network when handover rejection occurs or connection deteriorates. This dynamic behavior accelerates voice call reestablishment while the network maintains overall resource allocation through coordinated management.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for improving voice call continuity from a wireless local area network (WLAN) to a wireless wide area network (WWAN). An example method performed by a user equipment (UE) includes performing, while a session is active on a first radio access technology (RAT) network, reselection to a second RAT network from a third RAT network, performing a handover to the second RAT network, after detecting a condition impacting the session on the first RAT network, and resuming the session on the second RAT network.