LIPA PDN Connection Suspension for CSFB Voice Services
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Solution Overview
Problem
In LTE systems, the existing LIPA connection is unconditionally deactivated during CSFB, leading to service quality degradation and loss of IP connectivity for UE, as it cannot maintain the LIPA PDN connection during voice communication using legacy CS schemes.
Innovation Solution
A method and apparatus that allow suspending the LIPA PDN connection during CSFB, enabling continuous LIPA service by transmitting a suspend indicator from the Mobility Management Entity (MME) to the eNodeB, which notifies the UE that the connection is suspended rather than deactivated, allowing reactivation with the same IP address post-CSFB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LIPA PDN connection is unconditionally deactivated during CSFB, then voice communication using legacy CS schemes can be supported, but IP-based service quality degrades and the UE loses IP connectivity
Solution Approach 1:
The patent applies dynamics by transitioning the LIPA PDN connection from a static deactivated state to a dynamic suspended state. The connection can be suspended during CSFB and then reactivated, allowing the system to adapt to different operational modes (LTE data transmission vs. CS voice communication) while preserving the underlying connection state. This dynamic approach resolves the contradiction by maintaining adaptability for voice communication while preserving IP-based service quality through suspension rather than deactivation.
Solution Approach 2:
The patent changes the state parameter of the LIPA PDN connection from 'deactivated' to 'suspended'. This parameter change allows the connection to be temporarily paused during CSFB without being completely terminated. The suspended state preserves the connection context and IP address allocation, enabling quick reactivation afterward. This resolves the technical contradiction by maintaining the connection in a reversible state, thus preserving IP-based service quality while still supporting voice communication through CSFB.
2Ease of operation
If the LIPA PDN connection is deactivated during CSFB, then the UE can perform voice communication, but the UE must re-establish the connection and obtain a new IP address after CSFB terminates
Solution Approach 1:
The patent applies preliminary action by suspending the LIPA PDN connection before CSFB occurs, rather than deactivating it. This preliminary suspension preserves the connection state, IP address allocation, and session context in advance. When CSFB terminates and the UE returns to LTE, the connection can be quickly reactivated using the preserved context, avoiding the time-consuming process of re-establishing the connection and obtaining a new IP address. This resolves the contradiction by performing the suspension action in advance, thus reducing connection re-establishment time while maintaining voice communication capability.
3Device complexity
If the LIPA PDN connection is unconditionally deactivated, then mobility management is simplified, but service continuity is disrupted
Solution Approach 1:
The patent introduces a dynamic suspension state for the LIPA PDN connection during mobility management. Instead of unconditionally deactivating the connection, the system can suspend it temporarily during CSFB and restore it afterward. This dynamic approach maintains service continuity by preserving the connection state throughout the mobility event. The suspension mechanism adds minimal complexity to mobility management while significantly improving service continuity, thus resolving the contradiction between simplified mobility management and stable service composition.
Data Source
AI summary
A method for supporting local access and voice communication by a User Equipment (UE) in a wireless network, the method comprises transmitting a message for requesting a Circuit Switch (CS)-based voice service to a eNode B, the UE having a local Internet Protocol (IP)-based Packet Data Network (PDN) connection, and receiving, from the eNode B, a message including information indicating that the local IP-based PDN connection is suspended, if a server managing mobility of the UE determines that suspending the local IP-based PDN connection is supported in a local gateway.