Terminal Device CQI Feedback for Downlink Reliability
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Solution Overview
Problem
In wireless communications, especially in LTE and future 5G systems, the reliability of downlink data transmission is compromised when channel quality is poor, as the base station's initial modulation and coding scheme may not ensure correct reception of retransmitted data, leading to inefficiencies in data correctness and reliability.
Innovation Solution
The terminal device reports a channel quality indicator (CQI) along with an acknowledgement or negative acknowledgement message to the base station, allowing the base station to adjust the modulation and coding scheme to match the current channel conditions, thereby improving data correctness and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station uses the same MCS level for retransmitted data as for the initial transmission, then the transmission process is simple, but the reliability of data reception cannot be ensured when channel quality is poor
Solution Approach 1:
The terminal device feeds back channel quality information (CQI) to the base station, enabling the base station to adjust the MCS level according to actual channel conditions. This feedback mechanism ensures that retransmitted data uses an appropriate MCS level matching the current channel quality, thereby improving reception reliability without requiring complex blind adaptation schemes
Solution Approach 2:
The MCS level is made dynamic rather than static, allowing it to be adjusted based on real-time channel quality feedback from the terminal. This dynamic adaptation enables the system to respond to changing channel conditions, ensuring optimal reception reliability for retransmitted data while maintaining system simplicity through standardized adjustment rules
2Reliability
If the base station dynamically adjusts MCS based on real-time channel quality feedback, then the reliability of downlink data transmission is improved, but the feedback overhead and system complexity increase
Solution Approach 1:
The channel quality information is reported selectively based on local conditions - specifically when NACK feedback is generated indicating poor channel quality. This localized reporting approach provides necessary feedback information for MCS adjustment while avoiding continuous full-channel quality reporting, thereby reducing feedback overhead while maintaining transmission reliability
Solution Approach 2:
The system changes the reporting parameters of channel quality information based on transmission outcomes. Instead of reporting CQI continuously, the terminal reports CQI specifically when data reception fails (NACK condition), changing the reporting frequency and timing parameters to match actual needs, thus reducing feedback overhead while ensuring reliability when needed
Data Source
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AI summary
This application discloses a channel quality indicator feedback method and device. The method includes: determining, by a terminal device, a response message of data and a channel state, where the response message includes an acknowledgement message and/or a negative acknowledgement message; determining, by the terminal device, first channel state information based on the response message of the data and the channel state; and sending, by the terminal device, the response message and the first channel state information to the network side device. According to the method and apparatus provided in this application, reliability of downlink data from a base station can be improved.