RLC Entity HFN Synchronization in Wireless Systems
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Solution Overview
Problem
Current wireless communication systems, particularly those following 3GPP UMTS standards, face HFN de-synchronization issues due to the interaction between the RESET procedure and re-establishment procedure in the RLC layer, especially when there are delays in the arrival of RESET ACK PDUs during single-sided or double-sided re-establishment.
Innovation Solution
The solution involves aborting the pending RLC reset procedure during re-establishment, incrementing a reset control variable, restarting the RLC reset procedure, and using techniques such as toggling the RSN value or introducing a new RC variable to ensure synchronization, as well as employing a RESET defer timer mechanism to manage delayed acknowledgments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RESET procedure and re-establishment procedure interact in the RLC layer, then the system can handle ciphering functionality and manage data transmission, but HFN de-synchronization occurs between sender and receiver
Solution Approach 1:
The patent applies preliminary action by checking whether a RESET procedure is pending before initiating re-establishment. If a RESET is pending, the re-establishment is postponed until the RESET completes. This prevents the HFN de-synchronization issue by ensuring that re-establishment does not interfere with an ongoing RESET procedure that is necessary for maintaining HFN synchronization between sender and receiver.
2Reliability
If the RLC entity performs re-establishment procedure, then the system can recover from transmission issues, but delayed RESET ACK PDU arrival causes HFN de-synchronization
Solution Approach 1:
The patent checks in advance whether a RESET procedure is pending before allowing re-establishment to proceed. This preliminary check prevents the scenario where delayed RESET ACK PDUs cause HFN de-synchronization, as the system proactively manages the interaction between RESET and re-establishment procedures rather than reacting after the problem occurs.
3Adaptability or versatility
If the system allows interaction between RESET and re-establishment procedures, then operational flexibility is maintained, but HFN de-synchronization occurs due to procedure interaction
Solution Approach 1:
The patent maintains operational flexibility by allowing both RESET and re-establishment procedures to be used as needed, but introduces a preliminary check to prevent their harmful interaction. The system checks whether a RESET is pending before initiating re-establishment, and if so, postpones the re-establishment. This preserves the adaptability of the system while preventing HFN de-synchronization caused by procedure interaction.
Data Source
AI summary
Methods and apparatus are provided for HFN synchronization in a wireless communication system. If re-establishment of an RLC entity occurs during a pending RLC reset procedure, the pending RLC reset procedure is aborted and the re-establishment of the RLC entity is performed. A first RC variable included in a RESET PDU is incremented. The pending RLC reset procedure is restarted. The RESET PDU including the incremented first RC variable is transmitted. A RESET ACKnowledgement (ACK) PDU for the RESET PDU including a second RC variable is received. The second RC variable included in the received RESET ACK PDU is checked and the received RESET ACK PDU is accepted based on the checking result.