Differential Precoding Matrix Indicator Feedback for MIMO Systems
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Solution Overview
Problem
The existing 3GPP LTE R8 system has low accuracy in feedback Precoding Matrix Indicators (PMI) due to its fixed codebook design, primarily suited for Single User MIMO, which limits the adaptability and precision of data transmission in changing channel conditions.
Innovation Solution
A method and apparatus for obtaining a precoding matrix indicator by using differential codebooks and channel information, such as long-term channel covariance matrices, to enhance feedback accuracy, involving eigenvalue decomposition, normalization, and QR decomposition, allowing for adaptive feedback that utilizes channel correlations across frequency and time domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed codebook is used in 3GPP LTE R8 system, then the system complexity is reduced and ease of operation is improved, but the PMI feedback accuracy deteriorates
Solution Approach 1:
The codebook is segmented into multiple codebooks corresponding to different ranks. Each codebook contains codewords organized in groups, where each group corresponds to a specific rank. This segmentation allows the system to select the appropriate codebook and codeword group based on the current channel rank, improving PMI accuracy while maintaining manageable complexity through structured organization.
Solution Approach 2:
The codebook selection and codeword group selection are dynamically adapted based on channel conditions and rank indicators. The system transitions from a static fixed codebook to a dynamic codebook selection mechanism where the appropriate codebook and codeword group are chosen according to the current transmission rank, enabling accurate PMI feedback that adapts to changing channel conditions.
2Adaptability or versatility
If a fixed codebook designed for SU-MIMO is used, then the system design is simplified, but the adaptability to MU-MIMO and changing channel conditions deteriorates
Solution Approach 1:
The codebook structure is designed to be universal and support multiple MIMO modes including both SU-MIMO and MU-MIMO. The same codebook framework with rank-adaptive codeword groups can be used across different MIMO scenarios, providing versatility while maintaining a unified design approach that reduces overall system complexity.
Solution Approach 2:
The codebook parameters such as codebook selection and codeword group selection are changed based on channel conditions and rank indicators. The system adjusts the effective codebook subset dynamically by selecting appropriate codewords from different groups within the codebook, enabling adaptation to varying channel conditions and MIMO modes without requiring completely different codebook designs.
3Manufacturing precision
If codebook-based precoding is used, then the implementation is simplified and ease of manufacture is improved, but the precision of beam forming deteriorates
Solution Approach 1:
The codebook is pre-configured with codewords organized in groups corresponding to different ranks. This preliminary organization of codewords allows the system to quickly select the appropriate codeword group based on the rank indicator without complex real-time calculations, improving beam forming precision while keeping the implementation relatively simple through pre-computed optimal precoding vectors.
Data Source
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AI summary
The present invention discloses a method and an apparatus for obtaining a precoding matrix indicator, and relates to the field of communication technologies. The method includes: obtaining a first rotation matrix according to first channel information; obtaining a first differential matrix according to the first rotation matrix and a currently-obtained instantaneous beam forming matrix/precoding matrix; and quantizing, according to a first differential codebook, a pre-acquired first rank indicator, and preset quantization criteria, the first differential matrix to obtain a differential precoding matrix indicator. The apparatus includes: a first rotation matrix obtaining module, a first differential matrix obtaining module, and a differential precoding matrix indicator obtaining module. In the present invention, the differential PMI is obtained according to the channel information, and the differential PMI is used for feedback, which not only reduces an overhead, but also improves feedback accuracy.