CQI Feedback Mapping for Reliable 5G Link Adaptation
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Solution Overview
Problem
In wireless communications systems, particularly in 5G ultra-reliable and low latency communications (URLLC), ensuring high data transmission reliability is challenging due to the lack of feasible solutions for link adaptation and channel quality indicator (CQI) reporting, especially when the base station does not know the channel quality before sending downlink data.
Innovation Solution
A terminal device measures channel quality and selects a reference CQI index from a prestored mapping table, feeding it back to the network device, which determines the modulation order, code rate, or spectral efficiency to improve data transmission reliability by using a mapping table that correlates CQI indices with these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station sends downlink data without knowing channel quality, then the system operation is simple, but data transmission reliability is poor
Solution Approach 1:
The terminal device performs preliminary channel quality measurement and CQI calculation before the base station sends downlink data. The terminal pre-calculates the CQI index based on channel quality metrics (RSRP, SINR) and spectral efficiency requirements, and feeds this information back to the base station in advance, enabling the base station to make informed modulation and coding scheme decisions.
Solution Approach 2:
A feedback mechanism is established where the terminal device measures channel quality, calculates CQI index, and feeds this information back to the base station. The base station uses this feedback to select appropriate modulation order and code rate, then sends data with optimized parameters. This closed-loop feedback ensures high reliability while maintaining manageable system complexity through standardized procedures.
2Reliability
If the terminal device feeds back CQI index, then data transmission reliability is improved, but uplink signaling overhead increases
Solution Approach 1:
The invention changes the parameter representation from continuous channel quality metrics to discrete CQI indices (0-15). This quantization reduces the information that needs to be transmitted while preserving the essential channel quality information needed for reliable data transmission. The mapping table approach converts complex channel state information into compact index values.
Solution Approach 2:
Instead of feeding back complete channel state information (CSI) including channel matrix, correlation matrix, and other detailed parameters, the invention selectively feeds back only the CQI index which is locally optimized for spectral efficiency and reliability decisions. This selective feedback approach reduces overhead while maintaining the quality of information most critical for data transmission.
3Adaptability or versatility
If multiple mapping tables with different BLER targets are used, then adaptability to different reliability scenarios is improved, but device complexity increases
Solution Approach 1:
The system dynamically selects appropriate mapping tables based on the required block error rate (BLER) target. Different mapping tables are prepared for different BLER scenarios (e.g., 10%, 1%, 0.1%), and the terminal device can switch between them according to service requirements. This dynamic adaptability allows the system to optimize for ultra-reliable scenarios when needed while maintaining simplicity for standard scenarios.
Solution Approach 2:
Multiple mapping tables with different BLER targets are pre-configured in the terminal device before operation. This preliminary preparation allows rapid switching between different reliability scenarios without real-time computation, reducing the computational burden during actual data transmission while maintaining high adaptability to different service requirements.
Data Source
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AI summary
This application provides a method for sending a channel quality indicator CQI or a modulation and coding scheme MCS. In an example method, a terminal device obtains a modulation order, a code rate, or spectral efficiency, selects an index of a reference CQI (or an index of a reference MCS) from a prestored mapping table based on the obtained modulation order, code rate, or spectral efficiency, and reports the index of the reference CQI (or the index of the reference MCS) to a network device, where the mapping table includes a mapping relationship between a CQI index (or an index of a reference MCS) and a modulation order, a code rate, or spectral efficiency. The terminal device may process uplink or downlink data based on the determined modulation order, code rate, or spectral efficiency, and the network device may determine, based on the mapping table, a modulation order, a code rate, or spectral efficiency that is used to send data, thereby improving data transmission reliability.