ACK/NACK Feedback Mechanism for Asymmetric LTE TDD Subframes
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Solution Overview
Problem
In LTE TDD systems, when the number of downlink sub-frames exceeds the number of uplink sub-frames, existing methods fail to efficiently feed back acknowledgement/negative acknowledgement (ACK/NACK) information, leading to potential DTX situations and erroneous data detection, resulting in lost downlink data and increased delay.
Innovation Solution
The method involves the eNodeB carrying a number value of downlink sub-frames in downlink control information, allowing user equipment to correctly receive and feedback ACK/NACK information on the physical uplink shared channel, even when the number of downlink sub-frames exceeds uplink sub-frames, by transmitting data across multiple continuous downlink subframes and using signaling to represent the index of uplink subframes for data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple downlink sub-frames are mapped to one uplink sub-frame for ACK/NACK feedback, then the feedback capacity is improved, but the reliability of data reception detection deteriorates due to DTX situations
Solution Approach 1:
The patent segments the bundled ACK/NACK feedback into individual sub-frame level feedbacks by introducing a downlink sub-frame number indicator. Instead of transmitting a single bundled acknowledgment for multiple downlink sub-frames, the system divides the feedback into separate units, each corresponding to a specific downlink sub-frame, allowing the eNodeB to detect DTX conditions at the individual sub-frame level.
Solution Approach 2:
The patent introduces a feedback mechanism where the UE not only sends ACK/NACK information but also includes a downlink sub-frame number indicator in the uplink transmission. This enhanced feedback allows the eNodeB to identify which specific downlink sub-frame experienced DTX, enabling more reliable detection and appropriate retransmission decisions.
2Productivity
If ACK/NACK information of multiple downlink sub-frames is transmitted together on PUSCH, then the feedback efficiency is improved, but the accuracy of error detection deteriorates
Solution Approach 1:
The patent segments the bundled acknowledgment information by associating each ACK/NACK bit with a specific downlink sub-frame number. The downlink sub-frame number indicator divides the feedback into distinguishable units, allowing the eNodeB to accurately detect errors at the individual sub-frame level while maintaining the efficiency of bundled transmission.
3Quantity of substance
If the number of downlink sub-frames exceeds uplink sub-frames, then the downlink data transmission capacity is improved, but the feedback mechanism becomes complex and unreliable
Solution Approach 1:
The patent makes the uplink control information structure universal by introducing a downlink sub-frame number indicator that can identify multiple downlink sub-frames. This single indicator mechanism serves multiple functions: it identifies the downlink sub-frame number, enables DTX detection, and maintains compatibility with existing uplink transmission structures, thereby managing complexity while supporting asymmetric configurations.
Data Source
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AI summary
A method for feeding back confirmation information on a physical uplink shared channel, this method includes: an eNodeB carries, in downlink control information, a number value of the downlink sub-frame corresponding to the confirmation information which is fed back by one uplink sub-frame, and transmits data on a plurality of continuous downlink sub-frames after the sub-frame carrying the downlink control information (S202), wherein the number of the downlink sub-frames which transmit the data is equal to an number of the downlink sub-frames corresponding to the confirmation information fed back by the one uplink sub-frame; after the user equipment receives the downlink sub-frame which carries the downlink control information, the data is received from the downlink sub-frame which transmits the data after this downlink sub-frame, and the confirmation information received is fed back to the eNodeB through a physical uplink shared channel through an uplink sub-frame (S204). By the present invention, the feedback efficiency and the system work efficiency can be improved, the characteristic of the uplink single carrier is ensured, the problem of the lost of downlink data is solved, the delay is reduced, and the capability of the system is ensured.