Codebook Subsets for Wireless Feedback Overhead Reduction
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Solution Overview
Problem
Current multiple-antenna wireless communication systems face high feedback overhead in closed-loop transmission modes due to the need for extensive feedback information to select appropriate precoding matrices, which is not optimized for open-loop and closed-loop transmission modes separately.
Innovation Solution
The method involves specifying separate codebook subsets for open-loop and closed-loop transmission modes, allowing for the selection of precoding matrices based on the specific requirements of each mode, reducing feedback overhead by using different subsets and optimizing codebook usage for each mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single codebook is used for both open-loop and closed-loop transmission modes, then the system can maintain simplicity in codebook management, but feedback overhead increases due to the need to support all precoding matrices for closed-loop mode
Solution Approach 1:
The codebook is segmented into two separate subsets: a first codebook subset for open-loop transmission mode and a second codebook subset for closed-loop transmission mode. This segmentation allows each subset to be optimized for its specific transmission mode, reducing the feedback overhead required for closed-loop mode while maintaining simplicity in overall codebook management through unified codebook structure.
2Loss of information
If separate codebook subsets are specified for open-loop and closed-loop transmission modes, then feedback overhead is reduced, but the system complexity increases due to mode-dependent codebook selection
Solution Approach 1:
The codebook selection is made dynamic based on the transmission mode. The system adaptively selects between the first codebook subset and the second codebook subset according to whether open-loop or closed-loop transmission mode is used. This dynamic selection reduces feedback overhead by providing appropriate codebook granularity for each mode while managing complexity through mode-based selection logic.
3Reliability
If a larger codebook subset is used to provide more precoding matrix options, then precoding performance is improved, but feedback overhead increases due to more bits required to indicate the selected matrix
Solution Approach 1:
Different codebook subsets are provided for different transmission modes, with the second codebook subset for closed-loop mode containing a carefully selected number of precoding matrices that balances performance and feedback overhead. This local optimization ensures that each subset has the appropriate quality and size for its specific transmission mode, improving precoding performance where needed while controlling feedback overhead.
Data Source
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AI summary
A method for transmitting signals to reduce feedback overhead and a method for transmitting feedback information for the same are described. In transmitting signals through precoding, different codebook subsets are used in an open-loop transmission mode and a closed-loop transmission mode, thereby reducing feedback overhead. In this case, it is assumed that the codebook subsets for the respective transmission modes are optimized according to each transmission mode.