Inter-CU Layer 1/2 Mobility With Selective Radio Bearer Key Updates
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Solution Overview
Problem
Existing radio resource control (RRC) signaling does not support the distinction between security key update required and not-required radio bearers, limiting the implementation of inter-centralized unit (inter-CU) Layer 1/Layer 2 triggered mobility (LTM) without security key change.
Innovation Solution
A method for inter-CU LTM that involves receiving configuration information of candidate cells, performing mobility cell switches, and applying unused derived security keys for radio bearers when necessary, while maintaining current keys when identifiers match, using MAC CE for new security key derivation indications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing RRC signaling is used for mobility management, then the signaling structure remains simple and compatible with current systems, but it cannot distinguish between security key update required and not-required radio bearers, limiting inter-CU LTM without security key change
Solution Approach 1:
The patent segments the mobility management signaling by introducing separate indication fields for different radio bearers. Each radio bearer can be independently marked with a security key update requirement indicator, allowing the system to handle security updates selectively per bearer rather than globally, thus enabling inter-CU LTM without unnecessary security key changes while maintaining signaling structure organization
Solution Approach 2:
The patent applies preliminary action by configuring security key update indicators in advance during RRC connection setup or reconfiguration. The network pre-configures which radio bearers require security key updates during mobility, allowing the WTRU to perform selective PDCP re-establishment only for indicated bearers during inter-CU LTM, avoiding unnecessary security procedures and enabling seamless mobility
2Productivity
If security key updates are performed for all radio bearers during inter-CU mobility, then communication security is maintained, but mobility efficiency decreases due to unnecessary PDCP re-establishment operations
Solution Approach 1:
The patent applies local quality by differentiating security key update requirements for individual radio bearers rather than applying a uniform security policy to all bearers. Each radio bearer is independently evaluated and marked with a security key update indicator, allowing the system to perform PDCP re-establishment only where necessary (local security updates) while maintaining overall communication security, thus improving mobility efficiency without compromising security reliability
Solution Approach 2:
The patent enables self-service by allowing the network to autonomously determine and indicate which radio bearers require security key updates through RRC signaling. The WTRU automatically performs PDCP re-establishment only for bearers marked with security key update indicators, eliminating the need for manual security policy configuration and enabling efficient, adaptive security management during inter-CU LTM
3Adaptability or versatility
If existing RRC signaling is used without modifications, then implementation complexity remains low, but it cannot support the distinction between inter-CU and intra-CU LTM operations
Solution Approach 1:
The patent segments the mobility operation types by introducing distinct indication mechanisms for inter-CU and intra-CU LTM scenarios. The RRC signaling structure is enhanced with specific fields that indicate the type of mobility operation, allowing the system to differentiate and handle inter-CU and intra-CU LTM operations separately with appropriate security and procedure configurations
Solution Approach 2:
The patent applies preliminary action by pre-configuring mobility type indicators and security parameter associations in the RRC signaling before mobility execution. The network provides advance information about whether the mobility operation is inter-CU or intra-CU, enabling the WTRU to prepare appropriate security procedures and PDCP re-establishment actions in advance, thus supporting differentiated inter-CU and intra-CU LTM operations
Data Source
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AI summary
In an embodiment, a method implemented in a WTRU comprises receiving, from a source cell, a first message comprising configuration information of one or more candidate cells, wherein the configuration information indicates a plurality of radio bearers of each candidate cell and of the source cell, wherein each radio bearer of the plurality of radio bearers is associated with an identifier; receiving, from the source cell, a mobility cell switch command message comprising information indicating a mobility cell switch to a candidate cell; performing the mobility cell switch to the candidate cell; and on condition that a first identifier associated with a radio bearer of the source cell differs from a second identifier associated with a corresponding radio bearer of the candidate cell, performing a PDCP re-establishment for the corresponding radio bearer associated with the second identifier to apply an unused derived security key for the radio bearer.