Datalink Retry Timer Logic for Brief Interruption Delays
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Solution Overview
Problem
Current datalink communication systems in air traffic control experience message delays due to brief interruptions, as the retry timer logic continues to double and expire during hold mode, leading to longer propagation times than necessary.
Innovation Solution
Modifying the transport retry timer logic to pause or reset the retry timer during hold mode, ensuring the transport protocol data unit (TPDU) is transmitted as soon as connectivity is restored and the hold mode is exited, thereby preventing exponential timer increases and reducing propagation delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the retry timer logic continues to execute and double during hold mode, then the system maintains protocol compliance and handles retransmissions systematically, but the message propagation time increases significantly beyond the actual datalink interruption duration
Solution Approach 1:
The patent applies preliminary action by detecting hold mode conditions before the retry timer causes excessive delays. When hold mode is detected, the system preemptively pauses the retry timer logic, preventing the exponential timer increase from occurring in the first place. This allows the system to maintain protocol compliance while avoiding unnecessary delays.
Solution Approach 2:
The patent implements dynamics by making the retry timer logic conditional rather than static. The retry timer is dynamically paused when hold mode is detected and resumed when normal operation resumes. This dynamic adjustment allows the system to adapt its retransmission behavior based on the operational state, resolving the contradiction between maintaining protocol compliance and minimizing message propagation time.
2Reliability
If the system uses exponential backoff with doubling retry timer values, then retransmission attempts are spaced out to avoid network congestion, but during hold mode this results in delays much longer than the actual service interruption
Solution Approach 1:
The system performs preliminary detection of hold mode conditions before the exponential backoff mechanism can cause excessive delays. By detecting hold mode early and pausing the retry timer accordingly, the system prevents the harmful effect of prolonged delays while maintaining the benefit of systematic retransmission handling when normal operation resumes.
Solution Approach 2:
The patent changes the state parameter of the retry timer from active to paused based on the operational mode. When hold mode is detected, the retry timer parameter is changed to paused, preventing exponential increase. When normal operation resumes, the parameter is changed back to active. This parameter change resolves the contradiction by adapting the timer behavior to the operational context.
3Productivity
If the transport layer continues to execute retry logic during hold mode, then the system maintains continuous operation and protocol state management, but TPDU transmission is delayed until much later than necessary
Solution Approach 1:
The patent applies dynamics by conditionally pausing and resuming the retry timer logic based on operational mode. The system maintains continuity by keeping other transport layer functions active during hold mode, while dynamically pausing only the retry timer execution. This selective dynamic control maintains system productivity without sacrificing TPDU transmission speed once connectivity is restored.
Data Source
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AI summary
A method for minimizing datalink message propagation time comprises determining whether a datalink TPDU ready for transmission requires an acknowledgement; transmitting the TPDU, starting a transport retry timer, and setting a transmission count to one, when acknowledgement is required; determining whether acknowledgement is received after transmitting the TPDU; determining whether the retry timer has expired if acknowledgement not received; determining whether a hold mode is in effect when the retry timer has expired; determining whether a transport inactivity timer has expired when the hold mode is in effect; determining whether the hold mode is still in effect when the inactivity timer has not expired; when the hold mode is no longer in effect, incrementing the transmission count by one; and retransmitting the datalink TPDU and restarting the retry timer, when the transmission count is less than a predetermined maximum value and the inactivity timer has not expired.