Key Handling for Inter-Domain Handover Failures
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Solution Overview
Problem
In inter-domain handovers, particularly during Single Radio Voice Call Continuity (SR-VCC) and other multi-RAT environments, key mismatches can occur due to differing criteria for handover completion between network and user equipment, leading to connection failures or poor audio quality, as one side may store the old key set while the other retains the new key set.
Innovation Solution
A method and apparatus that determine potential key mismatches by monitoring failures in handover completion acknowledgments and layer 1 synchronization, and invalidate the new key set to prevent communication failures, ensuring the most recent valid key set is retained for subsequent connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the network and user equipment use different criteria for determining handover completion, then the handover process can be completed more flexibly, but key mismatches occur leading to connection failures
Solution Approach 1:
The patent implements feedback mechanisms where the network monitors for handover completion messages from the UE and sends acknowledgments. The UE waits for network acknowledgment before considering handover complete, creating a closed-loop feedback system that synchronizes key set updates between network and UE, preventing key mismatches while maintaining flexible handover criteria
Solution Approach 2:
The patent applies preliminary action by having the network prepare and send new key sets to the UE before the handover is fully complete. The network stores the new key set in advance and provides it to the UE through the handover command, ensuring both parties have the same key set ready before the handover completion is finalized, thus preventing key mismatches
2Reliability
If the UE sends a handover complete message that is not received by the network, then the UE stores the new key set but the network retains the old key set, but implementing robust message delivery mechanisms increases system complexity
Solution Approach 1:
The patent uses feedback by implementing an acknowledgment mechanism where the network sends a handover acknowledgment message to the UE after receiving the handover complete message. This feedback loop confirms successful message delivery and triggers the UE to store the new key set, ensuring synchronization without requiring complex redundant message delivery mechanisms
Solution Approach 2:
The patent employs the handover acknowledgment message as an intermediary that mediates the key set synchronization process. This intermediary message serves as proof of successful handover completion message delivery and triggers the key set update at the UE side, simplifying the overall message delivery mechanism while ensuring reliability
3Reliability
If a new key exchange is initiated to resolve key mismatch, then communication continuity is restored, but additional authentication procedures increase handover time
Solution Approach 1:
The patent applies preliminary action by having the network generate and provide the new key set to the UE in advance through the handover command, before the handover completion is finalized. This preliminary key provision eliminates the need for time-consuming key exchange procedures after handover failure, as the keys are already synchronized and ready for immediate use
Solution Approach 2:
The patent converts the potential harm of handover failure into benefit by using the handover failure scenario as a trigger to enforce strict key set synchronization through feedback mechanisms. This prevents key mismatches from occurring in the first place, transforming what could be a harmful situation requiring time-consuming recovery into a benefit where key synchronization is proactively ensured
Data Source
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AI summary
A method of enabling key handling for a handover between different domains may include determining whether an indication of a potential key mismatch is present responsive to an attempt to conduct a handover between a first domain and a second domain, and defining validity of a most recent key set used for ciphering communication between a mobile terminal and a network device based on a result of the determining.