Base Station Security Key Synchronization for Relay Node Mobility
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Solution Overview
Problem
In high-speed public transportation scenarios, the frequent handovers of relay nodes lead to excessive signaling overhead due to unnecessary security key synchronization between user equipment (UE) and the base station, causing throughput issues and potential integrity protection failures.
Innovation Solution
Implementing a method where the base station maintains two variables for each UE: the latest Next Hop Chaining Counter (NCClatest) and the NCC in use, triggering security key updates only when the delta between them exceeds a pre-configured threshold, using new S1AP messages for security key synchronization, reducing the frequency of security key updates and RRC Reconfiguration messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If security key synchronization is performed frequently during relay node handover, then security key synchronization between UE and base station is maintained, but signaling overhead increases excessively
Solution Approach 1:
The patent changes the parameter of security key update frequency by introducing a threshold mechanism. Instead of updating security keys at every relay node handover, the system compares the delta between NCC variables and only triggers updates when the threshold is exceeded. This parameter change reduces signaling overhead while maintaining security key synchronization reliability.
Solution Approach 2:
The patent applies partial action by performing security key synchronization only when necessary (when NCC delta exceeds threshold) rather than at every handover event. This selective approach avoids excessive signaling while ensuring security keys remain synchronized, resolving the contradiction between reliability and signaling overhead.
2Reliability
If security key updates are triggered at every relay node handover, then security synchronization is maintained, but network throughput decreases due to excessive signaling
Solution Approach 1:
The patent modifies the update frequency parameter by implementing threshold-based triggering. Security key updates occur only when the NCC delta exceeds the predetermined threshold, rather than at every handover. This parameter change reduces signaling overhead and improves network throughput while maintaining adequate security synchronization.
Solution Approach 2:
The patent implements periodic action through threshold-based triggering, where security key updates occur periodically based on accumulated NCC changes rather than continuously at every handover. This approach balances security requirements with network throughput by updating keys only when necessary.
3Device complexity
If NCC value range is limited from 0 to 7, then security key derivation is simplified, but NCC values round up after 8th handover causing desynchronization
Solution Approach 1:
The patent applies preliminary action by maintaining two NCC variables (latest NCC and NCC in use) in advance at the base station. This preparation allows the system to track and compare NCC values across handovers, detecting when the limited 0-7 range causes wrapping and enabling appropriate security key update decisions to prevent desynchronization.
Solution Approach 2:
The patent implements feedback by continuously comparing the latest NCC with the NCC in use at the base station. This feedback mechanism detects when NCC values have wrapped around due to the limited range, triggering security key updates to restore synchronization between UE and base station.
4Reliability
If intra-eNB handover is triggered for every terminal during relay node handover, then security configuration is synchronized, but RRC Reconfiguration messages and random access overhead increase
Solution Approach 1:
The patent changes the triggering parameter for intra-eNB handover from event-driven (every relay handover) to threshold-driven (when NCC delta exceeds threshold). This parameter change reduces the frequency of RRC Reconfiguration messages and random access procedures while maintaining security configuration synchronization.
Solution Approach 2:
The patent applies partial action by performing intra-eNB handover procedures only when necessary (when threshold is exceeded) rather than for every relay node handover. This selective approach reduces RRC Reconfiguration signaling overhead while maintaining adequate security synchronization.
Data Source
AI summary
The present disclosure relates to a base station and a method for security key synchronization during relay node (RN) mobility. In one embodiment, the base station may include a first transceiver configured to receive a Next Hop Chaining Counter in use, NCCin_use, sent from a source base station; a security key synchronization determining unit configured to determine that a security key synchronization criteria as follows is met: NCClatest−NCCin_use>Threshold, wherein NCClatest denotes a Next Hop Chaining Counter corresponding to the last Next Hop (NH) received from evolved packet core (EPC) for the user equipment (UE), and Threshold is a predetermined threshold; a second transceiver configured to send a security key update request to a relay node serving the UE, and to receive a security key update response from the relay node serving the UE; and a security key updater configured to update the NCCin_use as the NCClatest.