Incremental Redundancy Control Under Reverse Link Degradation
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Solution Overview
Problem
In wireless communication systems, especially those employing multiple access techniques like TDMA, FDMA, and CDMA, ensuring reliable packet transfer is inefficient due to varying channel conditions, leading to high packet latency and incorrect termination of transmissions caused by misinterpreted ACK/NACK messages, particularly in systems with growing user numbers.
Innovation Solution
Implementing a mechanism to determine channel degradation, allowing the access point to transition to a non-incremental redundancy mode by ignoring ACK/NACK messages and instructing access terminals to cease transmission, thereby reducing interference and maintaining system synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental redundancy transmission is used to improve reliability, then packet transfer reliability is improved, but packet latency increases due to repeated transmissions
Solution Approach 1:
The system dynamically switches between incremental redundancy mode and non-incremental redundancy mode based on reverse link channel conditions. When channel quality is good, incremental redundancy is used for reliability; when channel quality degrades, the system transitions to non-incremental mode to reduce latency, thus adaptively balancing reliability and latency requirements
2Reliability
If ACK/NACK messages are transmitted to ensure reliable packet transfer, then transmission reliability is improved, but system interference increases due to unnecessary message transmissions
Solution Approach 1:
The patent extracts and removes ACK/NACK message transmissions when the system is operating in non-incremental redundancy mode. By identifying situations where ACK/NACK messages would be unnecessary (when already in non-incremental mode), the system eliminates these messages to reduce system interference while maintaining transmission reliability through the mode selection mechanism
3Reliability
If incremental redundancy mode is maintained to ensure reliable delivery, then delivery reliability is improved, but synchronization issues occur when channel conditions degrade
Solution Approach 1:
The system implements feedback mechanisms by monitoring reverse link channel conditions and using this information to determine when to transition between incremental and non-incremental redundancy modes. This feedback-driven approach ensures that the system adapts to changing channel conditions, maintaining synchronization between access point and terminal while preserving delivery reliability through appropriate mode selection
Data Source
AI summary
Method and apparatus for transmission of information in multiple access communication system is claim. Information using incremental redundancy is transmitted. A determination is made as to whether reverse link performance drops below a predetermined threshold. Determination of reverse link performance may be done in variety of ways, including use of a filter percentage of ACK erasures, measured error rates on the reverse link control channel, reverse link data channel error rates, and other methods. Upon determination of channel degradation, the access point can decide whether to ignore messages sent from the access terminal to instruct the access terminal to cease transmission.