Codebook Subset Selection for High-Speed MIMO Feedback
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Solution Overview
Problem
In high-speed movement scenarios, both open-loop MIMO and closed-loop MIMO transmission schemes face challenges, with open-loop MIMO unable to adaptively adjust transmission parameters to channel changes, leading to a lack of beamforming and precoding gains, and closed-loop MIMO experiencing system performance deterioration due to mismatched transmission parameters.
Innovation Solution
Combining closed-loop and open-loop precoding techniques, where the transmitting terminal determines a code book based on channel measurements, using transformed construction matrices to ensure beams are oriented in the same direction, allowing for adaptive adjustment of transmission parameters and feedback of Channel Quality Indicators (CQI) to match actual channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If closed-loop precoding technique is used, then beamforming gain and precoding gain can be obtained, but system performance deteriorates at high speed due to invalid feedback information
Solution Approach 1:
The codebook is segmented into multiple codebook subsets, each corresponding to different terminal movement scenarios (low-speed, medium-speed, high-speed). The terminal selects an appropriate codebook subset based on its movement state, allowing the system to adaptively choose the most suitable precoding matrices for the current channel conditions, thereby maintaining reliability across different speed regimes while preserving beamforming gain where applicable
Solution Approach 2:
The system dynamically adapts the codebook selection based on terminal movement speed. By introducing movement-speed-dependent codebook subsets and enabling dynamic switching between them, the system transitions from a static codebook approach to a dynamic one that automatically adjusts to changing channel conditions, resolving the contradiction between maintaining beamforming gain and ensuring system performance at high speeds
2Reliability
If open-loop MIMO transmission scheme is used, then system performance is maintained at high speed, but beamforming gain and precoding gain cannot be obtained due to lack of adaptive adjustment
Solution Approach 1:
Different codebook subsets with different local qualities (precoding characteristics) are provided for different movement scenarios. Low-speed subsets offer high beamforming gain with closed-loop precoding, while high-speed subsets provide more robust open-loop compatible options. The terminal selects the locally optimal subset for its current speed, achieving local optimization that resolves the global contradiction
Solution Approach 2:
The system changes the codebook parameter (subset selection) based on terminal movement speed. By introducing speed-dependent parameter changes in the codebook structure and selection criteria, the system can switch between closed-loop optimized subsets (for beamforming gain at low speed) and open-loop compatible subsets (for reliability at high speed), thereby resolving the contradiction through parameter adaptation
3Speed
If terminal moves at high speed, then channel state changes rapidly, but feedback information becomes invalid and transmission parameter mismatch occurs
Solution Approach 1:
Multiple codebook subsets are prepared in advance for different movement scenarios. The terminal performs preliminary assessment of its movement speed and selects the appropriate pre-prepared codebook subset before feedback transmission. This preliminary action ensures that the feedback information is generated using the most appropriate codebook for the current speed regime, preventing information invalidity
Solution Approach 2:
The system implements speed-adaptive feedback mechanisms where the terminal monitors its movement speed and adjusts its codebook subset selection accordingly. This feedback loop ensures that the transmitted PMI always references precoding matrices appropriate for the current channel conditions, maintaining feedback validity even during high-speed movement by continuously adapting the reference codebook
Data Source
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AI summary
The present application provides a method and a device for transmitting feedback information. The method includes: determining, by a transmitting terminal, a first code book in accordance with a channel measurement result, precoding matrices included in the first code book being obtained through transformation of a same construction matrix; calculating, by the transmitting terminal, to obtain a first CQI in accordance with all or part of the precoding matrices in the first code book; and transmitting, by the transmitting terminal, first indication information for indicating the first code book and second indication information for indicating the first CQI to a receiving terminal.