ACK/NACK Bundling for Wireless Uplink Feedback
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Solution Overview
Problem
In wireless communication systems, especially in TDD mode, the limited uplink radio resources restrict the number of ACK/NACK signals that can be transmitted, leading to potential packet loss and reduced recovery capability due to the asymmetry between downlink and uplink subframes.
Innovation Solution
A method where a user equipment (UE) receives a bundling indicator to determine if downlink subframes are missed, generating a representative ACK/NACK signal based on successful reception of codewords across bundled subframes, and transmitting this signal on an uplink channel, allowing for efficient ACK/NACK bundling and reduced feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ACK/NACK signals are transmitted for each downlink packet individually, then packet loss is minimized and recovery capability is maximized, but the number of required uplink feedback resources increases beyond available resources
Solution Approach 1:
Multiple ACK/NACK signals corresponding to different downlink packets are merged into a single bundled ACK/NACK signal. The UE groups feedback for multiple downlink transmissions and transmits them collectively through one uplink signal, reducing the total number of feedback signals while maintaining reliability through the bundling mechanism
2Adaptability or versatility
If the number of uplink subframes is reduced to accommodate asymmetric service requirements, then service asymmetry is improved, but the number of available feedback resources decreases leading to potential packet loss
Solution Approach 1:
The invention enables multiple downlink packets to be acknowledged through a single uplink subframe by bundling ACK/NACK signals. This allows the system to maintain asymmetric uplink-downlink subframe allocation for service requirements while still providing sufficient feedback capacity through the bundled acknowledgment mechanism
3Quantity of substance
If ACK/NACK bundling is implemented to reduce feedback signals, then uplink resource usage is optimized, but the complexity of determining representative ACK/NACK signals increases
Solution Approach 1:
The bundling process is segmented into distinct functional steps: receiving the bundling indicator, counting detected downlink packets, comparing the count with the indicator value, and generating the representative ACK/NACK signal. This segmentation simplifies the overall complexity by breaking down the determination process into manageable, sequential operations
Data Source
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AI summary
A method of performing HARQ performed by a user equipment (UE) is provided. The method includes receiving a bundling indicator which indicates the number of bundled downlink subframes, determining whether at least one bundled downlink subframe is missed by comparing the bundling indicator with the number of detected bundled downlink subframes, generating a representative ACK/NACK signal when no bundled downlink subframe is missed, and transmitting the representative ACK/NACK signal on an uplink channel. Recovery capability is maximized and the packet loss is reduced in such a situation that less number of ACK/NACK signals are fed back than that of downlink packets.