HFN Correction and Dynamic Discard Timer for LTE Handover
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Solution Overview
Problem
In mobile communication systems, especially in LTE, the current discard timer lacks consideration for handover, leading to inconsistent application and excessive packet discard due to changes in ciphering parameters, particularly in bad propagation environments, where packets are delayed beyond the timer's maximum limit of 1,500 milliseconds.
Innovation Solution
The method and apparatus for error correction in ciphering/deciphering between enhanced Node B (eNB) and User Equipment (UE) involve acquiring and comparing partial Hyper Frame Numbers (HFN) to perform HFN correction and setting discard timers based on handover requests, ensuring consistent timer application across eNBs during handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed discard timer of 1,500 milliseconds is used in the current system, then packet discarding can be controlled in good propagation environments, but packets are discarded excessively in bad propagation environments where transmission delays exceed the timer limit
Solution Approach 1:
The discard timer is transformed from a fixed value to a dynamic value that adapts to different propagation environments. The timer is adjusted based on handover detection and propagation conditions, allowing it to extend beyond the standard 1,500 milliseconds when needed while maintaining the original limit in good conditions.
Solution Approach 2:
The discard timer parameter is changed from a constant 1,500 milliseconds to a variable value that can be modified based on system conditions. The invention introduces a mechanism to detect handovers and adjust the timer parameter accordingly, enabling it to accommodate varying transmission delays in different propagation environments.
2Reliability
If the discard timer value is increased to accommodate bad propagation environments, then packet loss is reduced, but it becomes difficult to control packet transmission effectively
Solution Approach 1:
The discard timer becomes a dynamic parameter that automatically adjusts based on detected conditions rather than being manually configured. The system dynamically extends the timer only when handover is detected or propagation conditions warrant it, maintaining ease of operation through automated adaptation.
Solution Approach 2:
The invention introduces feedback mechanisms that monitor propagation conditions and handover events, using this information to automatically adjust the discard timer value. This feedback loop enables the system to maintain control while adapting to changing conditions, as the timer is modified based on actual system state rather than fixed configuration.
3Adaptability or versatility
If ciphering parameters change during handover, then network mobility is supported, but error correction capability is lost and erroneous packets are continuously forwarded
Solution Approach 1:
The invention performs preliminary detection of handover conditions before ciphering parameter changes take effect. By detecting handover events in advance, the system can prepare error correction mechanisms and maintain data integrity checks during the transition, preventing erroneous packets from being forwarded.
Solution Approach 2:
The system implements feedback mechanisms that monitor ciphering parameter changes during handover. When parameter changes are detected, the feedback loop triggers error correction procedures and data integrity verification, ensuring that mobility is supported while maintaining reliability during the transition.
Data Source
AI summary
A method for error correction deciphering of a receive apparatus in a mobile communication system includes receiving a Packet Data Convergence Protocol (PDCP) packet. The method also includes, when error correction ciphering is set, acquiring a partial Hyper Frame Number (HFN) from the PDCP packet. The method further includes comparing the partial HFN and the receive apparatus's own lower HFN of a constant bit count. The method still further includes, if the partial HFN and the receive apparatus's own lower HFN of the constant bit count are different from each other, performing an HFN correction function.