Codeword-to-Layer Mapping for CSI Feedback Precision
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Solution Overview
Problem
Current LTE systems face limitations in data transmission precision and throughput due to the need to reflect channel quality of multiple layers with a single channel quality indicator (CQI), leading to inaccurate modulation and coding scheme selection and reduced multi-user multiple-input multiple-output (MU-MIMO) performance.
Innovation Solution
User equipment receives a first reference signal set to obtain CSI including a rank indicator (RI) and CQI based on a first codeword-to-layer mapping, and then receives data using a second codeword-to-layer mapping with fewer layers, allowing for more accurate channel quality feedback and improved scheduling precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a single CQI reflects channel quality of multiple layers, then the feedback overhead is reduced, but the scheduling accuracy and MCS precision deteriorate
Solution Approach 1:
The patent segments the channel quality feedback by introducing separate CQI parameters for different layer groups. Instead of using a single CQI to represent all layers, the system divides layers into multiple groups (e.g., first layer group and second layer group) and assigns dedicated CQI values to each group. This segmentation allows each CQI to accurately reflect the channel quality of its specific layer group without being diluted by other layers, thereby resolving the contradiction between reducing feedback overhead and maintaining scheduling accuracy.
2Device complexity
If a single CQI is used for multiple layers, then the feedback complexity is reduced, but the MCS selection precision deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the feedback structure into multiple CQI parameters corresponding to different layer groups. Each CQI parameter independently represents the channel quality of its associated layers, eliminating the need for complex aggregation algorithms while maintaining high MCS selection precision. This approach reduces feedback complexity compared to alternative solutions that would require detailed per-layer feedback.
3Device complexity
If fewer user equipment are paired in MU-MIMO, then the scheduling complexity is reduced, but the system throughput deteriorates
Solution Approach 1:
The patent introduces enhanced feedback mechanisms where user equipment provides separate CQI information for different layer groups. This detailed feedback enables the base station to make more informed pairing decisions for MU-MIMO transmissions. By accurately assessing the channel quality of each layer group, the system can identify more suitable user pairs that meet quality requirements, thereby increasing the number of paired users and system throughput without excessively increasing scheduling complexity.
Data Source
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AI summary
Embodiments of the present invention disclose a data transmission method, user equipment, and a base station. The method may include: receiving a first reference signal set sent by a base station; obtaining, based on the first reference signal set and a first codeword-to-layer mapping, CSI that includes a rank indicator RI and a channel quality indicator CQI, and sending the CSI to the base station; receiving a second reference signal set sent by the base station; and receiving, based on the second reference signal set and a second codeword-to-layer mapping, data sent by the base station, where a quantity of layers to which at least one codeword is mapped in the first codeword-to-layer mapping is less than a quantity of layers to which a codeword is mapped in the second codeword-to-layer mapping. According to the embodiments of the present invention, precision of an MCS used during data transmission may be improved, and a throughput of a communications system may be enhanced.