EPS Fallback Signaling for Voice Bearer Continuity Across Networks

The patent applies preliminary anti-action by having the core network device send indication information to the target network device before the UE completes the area crossing, explicitly requesting that the PDN connection not be deleted. This preemptive measure prevents the service interruption that would otherwise occur when the UE crosses into a new area and the target device would normally delete the connection.

The patent implements preliminary action by establishing the indication information exchange mechanism in advance, so that when the UE triggers EPS fallback and crosses areas, the target network device is already instructed to preserve the PDN connection. This ensures service continuity without requiring reactive measures after the interruption occurs.

The patent applies local quality by differentiating the treatment of PDN connections based on local conditions - specifically, whether EPS fallback is triggered. When EPS fallback occurs, the indication information is sent to preserve the PDN connection for audio/video services. This allows area-based IP address management to function normally in regular scenarios while providing exceptional protection for critical services during fallback events.

The patent implements dynamics by making the PDN connection deletion behavior conditional rather than static. The target network device dynamically adjusts its behavior based on the received indication information - deleting the connection in normal area crossings but preserving it when EPS fallback is detected. This dynamic approach reconciles area management requirements with service continuity needs.