L1/L2 Security Key Derivation for Low-Latency Cell Mobility
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Solution Overview
Problem
Existing layer 1/layer 2 triggered mobility (LTM) in mobile communications lacks security key update mechanisms, leading to inefficiencies and increased latency during handover processes.
Innovation Solution
Implementing security key derivation methods during LTM procedures, including vertical and horizontal key derivation processes based on security key update information received from network nodes, to ensure seamless handovers with reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 based mobility is used for cell switch, then security is maintained through reconfiguration, but handover latency and signaling overhead increase
Solution Approach 1:
The patent performs security key derivation in advance during the LTM preparation phase before the actual cell switch occurs. The target security key is derived using the formula CKtarget = f(CKsource, targetCellID, targetPCI) before handover execution, so that when the cell switch happens, the security key is already ready and no additional signaling or processing delay is incurred during the actual handover.
Solution Approach 2:
The patent separates the security key derivation process from the traditional L3 reconfiguration process. By deriving security keys at the L1/L2 layer independently during preparation, it segments the security update from the upper layer reconfiguration, enabling faster handover execution without compromising security.
2Loss of time
If L1/L2 triggered mobility is implemented to reduce latency, then handover speed improves, but security key update mechanisms are lost
Solution Approach 1:
The patent introduces an intermediary security key derivation function that operates at the L1/L2 layer. This function uses the source security key, target cell ID, and target physical cell ID as inputs to generate the target security key, serving as a bridge between the fast LTM procedure and the security requirements traditionally handled by L3 reconfiguration.
Solution Approach 2:
The UE autonomously derives its own target security key using the predetermined formula and available information (source security key, target cell ID, target PCI) during the LTM preparation phase, without requiring network signaling for security key update. This self-service approach eliminates the security update bottleneck in LTM procedures.
3Reliability
If upper layer reconfiguration is performed during handover, then security is updated, but signaling overhead and processing complexity increase
Solution Approach 1:
The patent extracts the security key derivation function from the L3 RRC reconfiguration process and places it at the L1/L2 layer. By taking out the security update mechanism from upper layer signaling, it eliminates the need for complex RRC reconfiguration messages and processing, reducing both signaling overhead and device complexity while maintaining security updates.
Data Source
AI summary
Various solutions for security key derivation for layer 1/layer 2 triggered mobility (LTM) in mobile communications are described. A user equipment (UE) may receive security key update information from a network node during an LTM procedure. The UE may derive a security key for a target cell based on the security key update information. Also, the UE may perform an LTM cell switch to switch to the target cell. Furthermore, the UE may transmit a message encrypted with the security key to the target cell. Accordingly, the dynamic vertical security key update for LTM can be supported.