HFN Offset Synchronization for RoHC De-synchronization Recovery
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Solution Overview
Problem
In wireless communication systems, de-synchronization between a base station and a user equipment (UE) due to dropped frames or poor channel conditions leads to failures in deciphering and decompressing data, causing communication disruptions.
Innovation Solution
The UE detects consecutive failures to decipher compressed RoHC packets and transmits a negative acknowledgment (NAK) message, triggering the transmission of a RoHC initialization and refresh (IR) packet with full header information, allowing the UE to re-synchronize by adjusting the hyper frame number (HFN) offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE uses compressed RoHC packets for efficient data transmission, then data transmission efficiency is improved, but de-synchronization occurs under poor channel conditions leading to deciphering failures
Solution Approach 1:
The patent applies preliminary action by transmitting an RoHC initialization and refresh (IR) packet before normal compressed data transmission resumes. This IR packet contains full header information and synchronization data that re-establishes the HFN offset at the UE before compressed RoHC packets are transmitted again, preventing deciphering failures that would occur under poor channel conditions.
Solution Approach 2:
The patent implements feedback through the transmission of status information from the UE to the base station regarding deciphering success or failure. When the UE detects de-synchronization through failed deciphering attempts, it sends feedback that triggers the base station to transmit an IR packet for re-synchronization, creating a closed-loop system that maintains reliability while using compressed packets.
2Measurement precision
If the UE transmits NAK messages upon detecting deciphering failures, then synchronization accuracy is improved, but communication overhead increases
Solution Approach 1:
The patent extracts only the essential synchronization information into separate IR packets that are transmitted independently from the main data stream. The NAK message extracts only the critical failure indication, while the full re-synchronization data is contained in the IR packet, minimizing overhead while maintaining precision.
3Reliability
If the UE adjusts HFN offset values to re-synchronize, then communication reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the UE to autonomously detect deciphering failures, adjust its HFN offset values, and recover from de-synchronization without requiring complex network-side intervention. The UE independently manages its synchronization state by detecting failures and processing IR packets to re-establish the correct HFN offset.
Data Source
AI summary
Methods, systems, and devices are described for wireless communication at a user equipment (UE). In some examples, the UE may identify an initialization and refresh (IR) packet at the radio link control (RLC) layer based the size of the IR packet, where the IR packet comprises a larger ciphered PDU size than a compressed RoHC packet. Accordingly, once the UE identifies the received packet as an IR packet, the UE may attempt to decipher the IR packet using one or more HFN offset values. In one example, the UE may determine whether the IR packet is deciphered correctly based on cyclic redundancy check (CRC) value of the deciphered IR packet. As a result, the present disclosure allows the UE to re-synchronize with the transmitting device by at least one of incrementing or decrementing an HFN value at the receiving device.