PDCP Decryption During Handover Using Source Security Variables
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Solution Overview
Problem
In wireless communication systems, particularly during handover in LTE systems, user equipment (UE) encounters decryption failures due to mismatched security variables between the source and target base stations, leading to incorrect deciphering of packets and impaired service quality.
Innovation Solution
The method involves using the security variables (Next_PDCP_RX_SN and RX_HFN) corresponding to the source base station to decipher packets received during handover and resetting them afterwards to ensure correct decryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE resets security variables (Next_PDCP_RX_SN and RX_HFN) during handover according to prior art, then the security variables are updated for the target base station, but the packets received from the source base station cannot be deciphered correctly due to mismatched security variables
Solution Approach 1:
The patent applies preliminary action by receiving and buffering packets from the source base station before completing the handover procedure. The UE maintains the old security variables (RX_HFN and Next_PDCP_RX_SN) during the handover transition to correctly decipher packets that were ciphered by the source base station. Only after successfully receiving and deciphering the packets does the UE reset the security variables for the target base station, ensuring no packet loss or deciphering errors occur during the transition.
2Reliability
If the UE uses non-reset security variables to decipher packets during handover, then packet deciphering is correct, but the security variables become desynchronized between the UE and the network
Solution Approach 1:
The patent applies dynamics by making the security variable state dynamic during handover. The UE temporarily maintains the old security variables only for the duration needed to decipher packets from the source base station, then transitions to the new security variables for the target base station. This dynamic state management ensures both correct packet deciphering during handover and proper synchronization with the network afterward, with the transition triggered by packet reception completion.
3Productivity
If the UE resets security variables immediately upon handover, then the handover procedure is completed quickly, but packets stored in the RLC layer cannot be correctly deciphered
Solution Approach 1:
The patent applies preliminary action by pre-buffering packets in the RLC layer before handover completion and maintaining the old security variables during the transition period. This allows the handover procedure to proceed quickly while ensuring that packets are deciphered correctly using the appropriate security variables. The security variable reset is deferred until after packet reception is confirmed, balancing speed and reliability.
Data Source
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AI summary
The present invention provides a method of handling data decryption for a packet data convergence protocol layer of a user equipment upon handover in a wireless communication system for increasing the validness of deciphering packages in the wireless communication system, which includes using a security variables corresponding to a source base station for deciphering the packets received from the source base station when the user equipment performs a handover procedure (402).