Transmission Buffer Window Stalling Prevention via Dual-Stage Acknowledgment
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Solution Overview
Problem
Existing communication network protocols face a high risk of transmission stalling due to false positive acknowledgments in error detection mechanisms, particularly in the Fast ACK/NACK reporting scheme, which can lead to data connection failures and inability to recover from stalling states.
Innovation Solution
Implement a method and transmitting unit that sets a data block's status as 'tentatively acknowledged' upon initial acknowledgment and only advances the transmission buffer window when a subsequent, more reliable acknowledgment message confirms the block's receipt, thereby preventing premature advancement and retransmission of incorrectly marked data blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a CRC-based PAN-field error detection is used for Fast ACK/NACK reporting, then the acknowledgment speed is improved, but the reliability of error detection deteriorates due to higher probability of false positive acknowledgments
Solution Approach 1:
The patent segments the acknowledgment process into two distinct stages: a fast but less reliable PAN-field acknowledgment stage, and a slower but more reliable PUAN/PDAN message stage. By dividing the single acknowledgment mechanism into sequential segments with different reliability characteristics, the system can achieve fast initial feedback while maintaining overall reliability through the second verification stage.
Solution Approach 2:
The patent introduces an intermediary verification mechanism where the PUAN/PDAN message acts as a mediator between the fast PAN-field acknowledgment and the final transmission decision. This intermediary layer validates the initial acknowledgment, filtering out false positives while preserving the speed benefit of the PAN-field mechanism.
2Productivity
If the transmission buffer window is advanced immediately upon receiving an acknowledgment, then the productivity is improved, but the risk of transmission stalling increases due to false positive acknowledgments
Solution Approach 1:
The patent applies preliminary action by setting the data block status to 'tentatively acknowledged' upon receiving the PAN-field acknowledgment, rather than immediately advancing the transmission window. This preliminary status marks the block for potential retransmission verification, allowing the system to prepare for productivity improvement while maintaining a safety mechanism against false positives.
Solution Approach 2:
The patent provides beforehand cushioning by maintaining the ability to retransmit data blocks that are tentatively acknowledged but not yet confirmed by the more reliable PUAN/PDAN message. This cushioning mechanism protects against transmission stalling by preserving a safety net for false positive acknowledgments while still enabling progress when acknowledgments are valid.
3Device complexity
If a single acknowledgment message is used to confirm data block receipt, then the device complexity is reduced, but the measurement precision of acknowledgment status deteriorates
Solution Approach 1:
The patent segments the acknowledgment confirmation into two distinct message types: the PAN-field for fast initial acknowledgment and the PUAN/PDAN message for reliable verification. This segmentation allows the system to maintain relatively simple protocol structures at each stage while achieving high measurement precision through the combined two-stage process.
Solution Approach 2:
The patent implements a feedback mechanism where the PUAN/PDAN message provides feedback on the validity of the initial PAN-field acknowledgment. This feedback loop enhances measurement precision by allowing the system to verify and correct initial acknowledgment decisions, ensuring high accuracy in determining whether data blocks were successfully received.
Data Source
AI summary
According to a method for reducing a risk of transmission stalling between a transmitting unit and a receiving unit, data blocks are transmitted to the receiving unit from the transmitting unit. Each data block includes a block sequence number (BSN). The transmitted data blocks are stored in a transmission buffer. A flow of retransmission of transmitted data blocks is controlled with a transmission buffer window comprising an acknowledge state variable (ASV) that contains the BSN value of the oldest data block that has not been positively acknowledged by its peer. If a BSN corresponding to the ASV is acknowledged in a first type of acknowledgment message, a status of the BSN is set as tentative acknowledged. If the block sequence number is acknowledged in a second type of acknowledgement message, the status of the BSN is set as acknowledged, and the transmission buffer window is advanced to the ASV.