CSI Feedback Overhead Reduction via PMI Vector Extraction
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Solution Overview
Problem
In LTE FDD systems, the current two-stage feedback mechanism for channel state information (CSI) results in high uplink resource wastage when the rank of the precoding matrix is greater than 2, leading to increased feedback overheads.
Innovation Solution
A method where the terminal device reports a first precoding matrix indicator (PMI) and a second PMI that indicates some column vectors in the precoding matrix W2, allowing the access network device to determine the precoding matrix W based on these indices, reducing the need to report all elements and thus minimizing feedback overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal device uses the traditional two-stage feedback mechanism to report all elements of the precoding matrix W2, then the precision of the precoding matrix is improved, but the feedback overhead increases and uplink resources are wasted
Solution Approach 1:
The patent extracts and reports only the essential components of the precoding matrix W2 (specific column vectors and their association relationships) rather than all elements. By identifying and reporting only the critical parts that define the matrix structure, the feedback overhead is significantly reduced while maintaining sufficient precision for the network device to reconstruct the precoding matrix.
Solution Approach 2:
The patent segments the precoding matrix W2 into distinct components: some column vectors that are directly reported via PMI, and remaining column vectors that are derived through association relationships. This segmentation allows the terminal device to report only necessary parts while the network device reconstructs the complete matrix, reducing overall feedback requirements.
2Reliability
If the terminal device reports all elements of the precoding matrix W2, then the downlink communication quality is improved, but the uplink resource efficiency deteriorates
Solution Approach 1:
The patent extracts only the essential information needed to reconstruct the precoding matrix W2, specifically reporting indexes of some column vectors and their association relationships rather than complete matrix elements. This extraction approach maintains downlink communication quality by preserving critical structural information while significantly improving uplink resource efficiency by reducing feedback data volume.
3Measurement precision
If the terminal device reports indexes of all elements in W2, then the accuracy of CSI feedback is improved, but the complexity of the feedback mechanism increases
Solution Approach 1:
The patent extracts and reports only the essential components needed to define the precoding matrix structure: indexes of some column vectors in W2 and their association relationships with remaining column vectors. This approach maintains CSI feedback accuracy by preserving the critical structural information while reducing feedback mechanism complexity by eliminating the need to report redundant elements.
Solution Approach 2:
Instead of reporting all elements directly, the patent inverts the approach by reporting a subset of elements and their relationships, allowing the network device to reconstruct the complete matrix. This inversion reduces the amount of information that needs to be transmitted while maintaining the ability to accurately represent the precoding matrix.
Data Source
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AI summary
This application provides a channel state information transmission method, an access network device, and a terminal device. The method includes: receiving, by an access network device, CSI reported by a terminal device, where the CSI includes a first PMI and a second PMI; and determining, by the access network device based on the first PMI and the second PMI, a precoding matrix W whose rank is greater than or equal to 2, where W meets W = W1 × W2, and the second PMI is used to indicate some column vectors in W2. According to the method in the embodiment, overheads of feeding back the CSI by the terminal device are effectively reduced.