Transmit Beamforming Codebook Selection With Reduced Feedback Overhead
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Solution Overview
Problem
Existing MIMO systems face challenges in codebook selection for transmit beamforming, leading to increased computation complexity, insufficient performance gain, power fluctuation, and large overhead for feedback in existing algorithms.
Innovation Solution
A method for selecting a codebook involves constructing an estimated channel matrix, selecting a channel submatrix, calculating a selection matrix, and assigning a steering matrix based on the optimal codebook, which reduces computation complexity and improves performance by using algorithms like Shannon Capacity maximization and incremental selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing algorithms (SVD, TxZF, TxMMSE, etc.) are used to calculate the steering matrix, then the beamforming performance can be achieved, but the computation complexity increases and the transmitter and receiver design becomes more complex
Solution Approach 1:
The patent divides the codebook into multiple subcodebooks, each corresponding to different channel conditions or antenna groups. This segmentation allows the system to select only the relevant subcodebook for current channel conditions, reducing the effective codebook size and simplifying the computation at both transmitter and receiver while maintaining beamforming performance.
Solution Approach 2:
The patent performs preliminary channel quality indication (CQI) feedback from the receiver to the transmitter before the actual data transmission. This preliminary action allows the transmitter to pre-select the appropriate codebook or subcodebook based on channel conditions, avoiding the need for complex real-time calculations during data transmission and simplifying the overall system design.
2Reliability
If a large codebook is used to improve beamforming accuracy, then the signal-to-noise ratio gain increases, but the feedback overhead increases
Solution Approach 1:
By segmenting the large codebook into multiple smaller subcodebooks, the system can represent the same steering matrix using combinations of smaller codebook entries. This reduces the feedback overhead because fewer bits are needed to index into smaller subcodebooks compared to a single large codebook, while still achieving the same SNR gain through selective subcodebook combination.
Solution Approach 2:
The patent uses partial codebook information for feedback. Instead of feeding back the entire steering matrix or full codebook index, the system feeds back only the necessary subcodebook selection information or partial steering matrix parameters, reducing feedback overhead while maintaining sufficient beamforming accuracy for the current channel conditions.
3Reliability
If complex algorithms are used to select the optimal steering matrix, then the beamforming directivity improves, but the computation complexity increases
Solution Approach 1:
The patent segments the codebook selection process into multiple simpler stages. Instead of searching through the entire large codebook to find the optimal steering matrix, the system first selects relevant subcodebooks based on channel conditions, then performs a simplified search within each subcodebook. This segmentation reduces computation complexity at each stage while maintaining the ability to achieve optimal beamforming directivity through the combined selection.
Solution Approach 2:
The patent performs preliminary channel estimation and quality assessment before the actual codebook selection and beamforming computation. This preliminary action provides the transmitter with channel quality information that guides the codebook selection process, allowing for simpler and faster computation of the optimal steering matrix while still achieving high beamforming directivity.
Data Source
AI summary
A method select a codebook for transmit beamforming. The method constructs an estimated channel matrix based on a codebook, selects a channel submatrix from the estimated channel matrix, calculates a selection matrix from the channel submatrix; and assigns a steering matrix based on the selection matrix. There may be multiple codebooks and the method may construct an estimated channel matrix, select a channel submatrix, and calculate a selection matrix for each of the codebooks, then select an optimal codebook. The steering matrix is assigned based on the optimal codebook. The steering matrix may be used in steering a transmitted packet. The method may also calculate a post-MIMO equalizer signal-to-noise ratio for a data stream, based on the estimated channel matrix and the selected codebook. A related system is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.