HARQ Feedback Mode Selection for TDD LTE Networks
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Solution Overview
Problem
In Time Division Duplexing (TDD) LTE networks, the fixed delay between data transmission and Hybrid Automatic Repeat Request (HARQ) ACK/NACK is not maintained due to variable uplink and downlink subframe configurations, leading to performance degradation in existing HARQ feedback modes.
Innovation Solution
A method to optimize the selection of HARQ feedback modes based on TDD uplink/downlink configuration, transmission mode, cell load, and traffic type, allowing for dynamic configuration of HARQ feedback modes such as HARQ-ACK bundling, multiplexing, and PUCCH Format 3, to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If TDD UL/DL configuration is used to accommodate variable uplink and downlink subframes, then the network can support flexible traffic patterns, but the fixed delay between data transmission and HARQ ACK/NACK cannot be maintained
Solution Approach 1:
The patent applies dynamics by making the HARQ feedback mode configurable and adaptable based on TDD UL/DL configuration. Instead of a fixed feedback mechanism, the system dynamically selects between bundling, multiplexing, or individual feedback modes depending on the subframe allocation, thereby maintaining flexibility while managing timing variations.
Solution Approach 2:
The patent changes the parameter of HARQ feedback timing and mode based on the TDD configuration. By adjusting the feedback mode (bundling, multiplexing, or individual ACK/NACK) according to the number of downlink subframes and their association with uplink subframes, the system adapts to different timing scenarios while supporting flexible traffic patterns.
2Productivity
If multiple HARQ ACK/NACK messages are transmitted in a single uplink subframe, then all downlink transmissions can be acknowledged, but the complexity of HARQ feedback mode selection increases
Solution Approach 1:
The patent segments the HARQ feedback mechanism into three distinct modes: bundling (logical AND operation), multiplexing (spatial bundling across codewords), and individual feedback (PUCCH Format 3). This segmentation allows the system to handle multiple ACK/NACK messages by selecting the appropriate level of aggregation, thereby managing complexity while maintaining productivity.
Solution Approach 2:
The system dynamically selects among different HARQ feedback modes based on the TDD configuration and traffic requirements. The network can adaptively choose between bundling, multiplexing, or individual feedback, making the complexity manageable through conditional selection rather than requiring all modes to be simultaneously active.
3Device complexity
If HARQ-ACK bundling is used to simplify feedback transmission, then the feedback mechanism becomes simpler, but performance degrades when bundled subframes have different channel conditions
Solution Approach 1:
The patent makes the HARQ feedback mode dynamic rather than fixed. The system can switch between bundling (simpler but less reliable under varying conditions) and multiplexing or individual feedback (more complex but better performance) based on the actual TDD configuration and channel conditions, thereby resolving the contradiction between simplicity and reliability.
Solution Approach 2:
The patent changes the aggregation level parameter of HARQ feedback based on conditions. When channel conditions are similar across bundled subframes, bundling is used for simplicity. When channel conditions vary significantly, the system can adjust to multiplexing or individual feedback modes, changing the parameter of feedback granularity to maintain reliability.
4Reliability
If PUCCH Format 3 is used for individual HARQ feedback per codeword and subframe, then throughput performance is improved, but the cell load capacity is reduced
Solution Approach 1:
The patent applies local quality by allowing different HARQ feedback modes to be configured for different wireless devices or different subframe groups within the cell. High-priority devices or those with specific traffic patterns can use PUCCH Format 3 for individual feedback to maximize throughput, while other devices can use simpler modes, thereby maintaining overall cell load capacity while improving performance where needed.
Solution Approach 2:
The system changes the feedback mode parameter based on device-specific requirements and cell load conditions. PUCCH Format 3 is not universally applied but selectively configured for devices that benefit most from individual feedback, allowing the network to balance throughput performance improvements against cell load capacity constraints.
Data Source
AI summary
Systems and methods related to optimized selection, or determination of, Hybrid Automatic Repeat Request (HARQ) feedback modes for downlink transmissions by considering Time Division Duplexing (TDD) uplink/downlink (UL/DL) configuration, transmission mode, cell load, and/or traffic type are disclosed. In this manner, performance can be improved.