HARQ Feedback Transmission in LAA-LTE Unlicensed Spectrum
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Solution Overview
Problem
In Licensed-Assisted Access using Long Term Evolution (LAA-LTE) systems, there is no fixed uplink/downlink configuration, leading to challenges in transmitting Hybrid Automatic Repeat Request (HARQ) acknowledgement information, as the subframe selected by user equipment may not be an uplink subframe, resulting in transmission failures.
Innovation Solution
A method where the network device indicates a specific subframe for HARQ acknowledgement information transmission, using additional bits in the Downlink Control Information (DCI) to specify the subframe index or subframe window, ensuring that the user equipment sends HARQ feedback in known uplink subframes, thereby minimizing transmission failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If user equipment selects subframe for HARQ acknowledgement transmission autonomously, then transmission flexibility is improved, but transmission reliability deteriorates because the selected subframe may not be an uplink subframe
Solution Approach 1:
The network device acts as an intermediary by providing indication information (via DCI or RRC signaling) that guides the user equipment to select appropriate uplink subframes for HARQ acknowledgement transmission. This mediator approach resolves the contradiction by transferring the subframe selection authority from the user equipment to the network device, ensuring that only valid uplink subframes are used while maintaining system flexibility.
2Adaptability or versatility
If no fixed uplink/downlink configuration is used in LAA-LTE, then system adaptability to unlicensed spectrum is improved, but HARQ feedback mechanism deteriorates due to inability to determine valid uplink subframes
Solution Approach 1:
The patent implements a dynamic uplink/downlink configuration mechanism where the network device can flexibly indicate which subframes are uplink subframes through DCI or RRC signaling. This dynamic approach allows the system to adapt to varying unlicensed spectrum conditions while maintaining a functional HARQ feedback mechanism, resolving the contradiction between system adaptability and operational ease.
3Productivity
If HARQ acknowledgement is transmitted in dynamically determined subframes, then transmission efficiency is improved, but transmission success rate deteriorates due to potential selection of invalid subframes
Solution Approach 1:
The network device provides feedback in the form of indication information (DCI format 0 with specific bit patterns or RRC configuration) that tells the user equipment which subframes are valid for uplink transmission. This feedback mechanism ensures that HARQ acknowledgements are transmitted only in valid uplink subframes, maintaining both transmission efficiency and success rate.
Data Source
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AI summary
A method for transmitting HARQ acknowledgement information and a device are provided, to provide a manner of performing HARQ feedback in an LAA-LTE system. The method for transmitting HARQ acknowledgement information includes: sending, by a network device, first information to user equipment, where the first information is information used to indicate a subframe used by the user equipment to send HARQ acknowledgement information to the network device on an unlicensed carrier, and receiving, by the network device in the subframe indicated by the first information, the HARQ acknowledgement information sent by the user equipment.