CSFB Bearer Preservation via Non-3GPP Access Routing
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Solution Overview
Problem
During circuit switched fallback (CSFB) operations in mobile communications, packet switched bearers are often dropped or handed over to networks that cannot accommodate them, leading to service degradation or failure, and there is a lack of control over which radio access technology (RAT) to use for handovers, resulting in suboptimal quality of service.
Innovation Solution
The implementation of a mechanism that allows user equipment (UE) to indicate which packet switched bearers should be preserved from handover to cellular RATs, using explicit bearer indications and preference settings, ensuring that bearers are not dropped and can be routed through more suitable access networks like WLAN, and that RAT preferences are differentiated based on policy and network conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packet switched bearers are handed over to cellular RATs during CSFB operation, then network handover is achieved, but bearers may be dropped or routed through networks that cannot accommodate them
Solution Approach 1:
The UE provides explicit bearer indications to the network before CSFB handover occurs, specifying which bearers should be preserved from handover to cellular RATs. This preliminary action allows the network to prepare appropriate routing decisions in advance, ensuring bearers are not dropped and are routed through suitable access networks like WLAN that can accommodate them.
Solution Approach 2:
The patent introduces an intermediary mechanism where the UE's bearer indication messages act as mediators between the UE's quality of service requirements and the network's handover execution. These indications enable the network to differentiate between bearers that should be handed over to cellular RATs and those that should be preserved and routed through alternative access networks.
2Reliability
If explicit bearer indications are implemented to preserve bearers during CSFB, then bearer drop prevention is achieved, but signaling complexity increases
Solution Approach 1:
The bearer indication mechanism is integrated into existing CSFB signaling procedures, allowing the same signaling framework to serve multiple functions: triggering CSFB, indicating bearer preservation requirements, and coordinating handover execution. This multi-functionality reduces the need for separate dedicated signaling protocols and minimizes overall signaling complexity.
3Ease of operation
If RAT preferences are differentiated based on policy and network conditions, then quality of service is optimized, but control mechanism complexity increases
Solution Approach 1:
The patent enables differentiated RAT selection by applying quality of service policies at the individual bearer level rather than uniformly across all bearers. Each bearer can have its own preservation indication based on its specific QoS requirements, allowing the network to route different bearers through different access networks (cellular RATs or WLAN) according to their specific needs while using a unified signaling mechanism.
Data Source
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AI summary
Methods and apparatus to provide packet switched service continuity during circuit switched fallback operation are described. One example method includes determining that a target system does not support packet switched handover; determining if non-3GPP access for packet switched service is available; and triggering handover to the non-3GPP access.