HARQ ACK/NACK Bundling for Asymmetric TDD Feedback
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Solution Overview
Problem
In wireless communication systems, especially in TDD mode, the inefficiency in transmitting ACK/NACK signals due to the asymmetrical allocation of downlink and uplink subframes leads to restricted feedback resources, resulting in potential packet loss and reduced recovery capability when the number of ACK/NACK signals is less than the number of downlink packets.
Innovation Solution
A method where a user equipment (UE) receives a bundling indicator for downlink subframes, determines if any are missed, and generates a representative ACK/NACK signal to be transmitted on an uplink channel, with the signal being an ACK if all codewords are received successfully and a NACK if any are not, thereby optimizing the use of limited feedback resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TDD mode with asymmetrical allocation of downlink and uplink subframes is used, then asymmetric services such as Internet service can be efficiently supported, but the number of ACK/NACK feedback resources is restricted leading to potential packet loss
Solution Approach 1:
The patent applies ACK/NACK bundling where multiple ACK/NACK signals corresponding to different downlink subframes are combined and transmitted together in a single uplink subframe. This merging approach allows the system to accommodate the asymmetrical TDD subframe allocation while maintaining reliable feedback transmission by consolidating multiple feedback signals into one resource allocation.
Solution Approach 2:
The patent segments the ACK/NACK feedback process into two stages: first determining which downlink subframes were successfully received, then generating bundled ACK/NACK signals only for those successful subframes. This segmentation allows selective feedback transmission, ensuring that only necessary feedback signals are sent while efficiently utilizing the limited uplink feedback resources.
2Quantity of substance
If the number of ACK/NACK signals to be transmitted is less than the number of downlink packets, then feedback radio resources can be saved, but recovery capability is reduced and packet loss increases
Solution Approach 1:
The patent merges multiple ACK/NACK signals into a single bundled signal that conveys information about multiple downlink subframes. This allows the system to transmit feedback for multiple packets using a single feedback resource, maintaining recovery capability while reducing the quantity of individual feedback signals transmitted.
Solution Approach 2:
The patent implements a feedback mechanism where the UE transmits bundled ACK/NACK signals to indicate successful reception of multiple downlink subframes. This feedback approach allows the base station to understand which packets were successfully received and which require retransmission, maintaining recovery capability even with reduced feedback signal quantity.
Data Source
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.