Voice Call Continuity via Dual RAT Fallback in Wireless Communications
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Solution Overview
Problem
Wireless communication systems experience radio link failures (RLF) during voice calls, leading to dropped calls, which result in poor user experience and increased power consumption, especially when users are in areas with fast fading conditions such as tunnels or elevators.
Innovation Solution
Implementing techniques that allow user equipment (UE) to maintain voice call continuity by establishing concurrent connections with different radio access technologies (RATs) and using drop call timers to transfer calls to available connections, ensuring minimal disruption and power conservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE maintains concurrent connections with multiple RATs to prevent call drops, then call continuity is improved, but device complexity increases
Solution Approach 1:
The patent segments the connection management by separating the monitoring function (performed on the first RAT connection) from the fallback function (performed on the second RAT connection). This allows the UE to maintain call continuity through structured, modular connection handling rather than monolithic management, reducing operational complexity while improving reliability
Solution Approach 2:
The patent applies preliminary action by establishing a second connection with a second RAT in advance before the first connection fails. This pre-configured backup connection is monitored and ready to take over immediately upon detecting radio link failure on the first connection, ensuring call continuity without requiring complex real-time decision-making during failure events
2Reliability
If the UE attempts to re-establish connection after RLF, then call continuity is improved, but time loss increases due to re-dialing
Solution Approach 1:
The patent performs preliminary action by pre-establishing a second connection with a second RAT before the first connection fails. When radio link failure occurs on the first connection, the UE can immediately transfer the voice call to the pre-configured second connection without time-consuming re-dialing or connection establishment procedures, thus reducing call re-establishment time while maintaining continuity
Solution Approach 2:
The second connection with the second RAT acts as an intermediary backup path. When the primary first connection fails, this intermediary connection provides an immediate alternative route for voice traffic, avoiding the time loss associated with initiating new connection procedures and enabling seamless call continuation
3Reliability
If the UE monitors multiple RATs for connection availability, then call continuity is improved, but power consumption increases
Solution Approach 1:
The patent applies local quality by differentiating the monitoring intensity and scope for different connections. The UE performs comprehensive monitoring on the primary first connection while maintaining a simpler, lower-power monitoring approach on the second backup connection. This localized differentiation of monitoring quality reduces overall power consumption while maintaining call continuity through selective, targeted monitoring rather than uniform high-intensity monitoring across all connections
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that provide for call continuity following radio link failure (RLF) through re-establishment of a voice call using a same or different radio access technology (RAT) before the call is dropped. Upon detection of RLF on a connection supporting a voice call, a UE may initiate a drop call timer and scan for available connections. The voice call may be attempted to be re-established if a connection is available on using a RAT of an existing connection. The voice call in such cases may continue without the call being dropped. Upon expiration of the drop call timer, the UE may attempt to establish a connection using a RAT identified during the duration of the drop call timer.