Mobile Station Key Update Handling During Radio Link Failure
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Solution Overview
Problem
In mobile communication systems, particularly during handover and re-establishment procedures, the failure of radio base stations to receive completion signals leads to unsuccessful key updates, resulting in security vulnerabilities and system instability.
Innovation Solution
A mobile communication method that updates keys only after receiving delivery acknowledgement information or when a predetermined time has passed, ensuring successful handover and re-establishment procedures even if the target radio base station fails to receive completion signals, by using a key updating unit that calculates new keys based on a master key and sequence numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the mobile station updates the first key immediately upon receiving MAC RA Response, then the key update speed is improved, but the system reliability deteriorates when the target radio base station fails to receive completion signals
Solution Approach 1:
The target radio base station performs preliminary actions by generating and storing the new first key (K eNB[n+1]) in advance before the mobile station completes the handover. This allows the base station to be prepared with the correct key before the mobile station attempts to use it, ensuring that even if completion signals are lost, the key update can succeed when the mobile station re-establishes connection.
Solution Approach 2:
The system implements feedback mechanisms where the target radio base station monitors whether it has successfully received the RRC HO Complete signal. Based on this feedback, the base station determines whether to wait for the mobile station's re-establishment request before proceeding with key verification, thereby adapting the key update process to the actual communication status.
2Object-affected harmful factors
If the mobile station deletes the old first key immediately after handover, then the security vulnerability window is reduced, but the system stability deteriorates when key updates fail
Solution Approach 1:
The mobile station retains the old first key (K eNB[n]) as a backup after updating to the new key, rather than immediately deleting it. This cushioning mechanism ensures that if the new key update proves problematic or if communication failures occur, the mobile station can fall back to using the old key to maintain connection stability and avoid complete system failure.
3Measurement precision
If the target radio base station waits for RRC HO Complete signal before acquiring the new first key, then the key verification accuracy is improved, but the handover completion time increases
Solution Approach 1:
The target radio base station generates and stores the new first key in advance during the handover preparation phase, before waiting for the RRC HO Complete signal. This preliminary key generation eliminates the need to wait for completion confirmation before having the key ready, thus reducing handover completion time while maintaining verification accuracy when the signal is eventually received.
Data Source
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AI summary
A mobile communication method according to the present invention is to communicate between a mobile station (UE) and a radio base station (eNB) by using a certain key generated using a first key. The mobile communication method includes the steps of: updating, at the mobile station (UE), the first key upon receiving a handover command signal from the radio base station (eNB); transmitting, from the mobile station (UE) to the radio base station (eNB), a handover complete signal by using the certain key generated using the updated first key; and performing, at the mobile station (UE), a cell selection processing when failing to transmit the handover complete signal and detecting a radio link failure, and transmitting, from the mobile station to a selected re-establishment target cell, a re-establishment request signal by using the first key before being updated.