Inter-CU SCG Layer 1/2 Mobility Security Updates for Fast Handover
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Solution Overview
Problem
Current L1/L2 based inter-central unit (CU) mobility in mobile communications does not support security updates during handover, leading to long latency, large signaling overhead, and interruption time.
Innovation Solution
Implement security key calculation based on LTM configuration for target secondary nodes, enabling encryption of messages during LTM cell switch procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If L1/L2 based inter-CU mobility is implemented without security update, then latency is reduced and signaling overhead is minimized, but security cannot be updated during handover
Solution Approach 1:
The patent applies preliminary action by pre-configuring the target secondary node with security parameters (KSN, sk-counter) before the actual handover occurs. The LTM configuration message includes security update information for the target SN, allowing the UE to perform security key calculation in advance. This enables security updates to be completed during the fast L1/L2 handover process without adding significant latency, as the security parameters are already prepared and transmitted as part of the mobility preparation.
2Reliability
If L3 based handover is used, then security update can be performed, but latency increases and signaling overhead increases
Solution Approach 1:
The patent merges the security update function with the L1/L2 mobility preparation process. Instead of separating security update from handover (as in L3-based approaches) or excluding it entirely, the security update parameters are integrated into the LTM configuration message. This allows security key calculation and update to occur concurrently with the mobility preparation and execution phases, achieving both fast handover and secure communication without the latency penalties of traditional L3 handover.
3Reliability
If LTM configuration includes security key calculation, then security updates are enabled during handover, but device complexity increases
Solution Approach 1:
The patent uses copying by having the UE derive the target SN security key (KSN) through a standardized calculation based on the master key (KgNB) and a counter value (sk-counter) provided in the LTM configuration. Instead of requiring complex key exchange protocols or direct key transmission, the system copies the security derivation mechanism from the existing L3 approach and adapts it for L1/L2 mobility. This maintains security while simplifying implementation, as the UE already has the necessary algorithms and key material (KgNB) from previous operations.
Data Source
AI summary
Various solutions for security update for secondary cell group (SCG) layer 1/layer 2 triggered mobility (LTM) in inter-central unit (CU) scenario in mobile communications are described. A UE may receive an LTM configuration associated with a secondary cell group (SCG) from a network node. Also, the UE may obtain a security key for a target secondary node (SN), in which the security key for the target SN is calculated based on the LTM configuration. Further, the UE may transmit at least one message encrypted with the security key to the target SN. In this way, the security update for inter-CU SCG LTM can be supported.