CSI Feedback Configuration for FD-MIMO Vertical Beamforming
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Solution Overview
Problem
Current cellular systems with horizontally arranged antennas cannot achieve optimal performance due to fixed downtilt in vertical direction, leading to suboptimal beamforming and increased inter-cell interference, as they lack the ability to adjust beams vertically, and terminals struggle to determine the appropriate CSI feedback approach for both FD-MIMO and non-FD-MIMO modes.
Innovation Solution
The network device indicates a CSI feedback configuration group to the terminal, allowing it to determine and perform CSI measurement and feedback based on the configured approach, supporting both FD-MIMO and non-FD-MIMO modes by selecting an optimum CSI feedback configuration and providing location information for vertical beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If horizontal antenna arrangement with fixed downtilt is used, then device complexity is reduced, but system performance deteriorates due to inability to adjust vertical beam direction
Solution Approach 1:
The patent transitions from traditional horizontal-only beamforming to three-dimensional beamforming by adding vertical dimension control. The network device determines vertical beamforming vectors and horizontal beamforming vectors separately, enabling independent optimization in both dimensions. This dimensional expansion allows beams to be precisely oriented in 3D space, resolving the contradiction between simple horizontal arrangement and optimal system performance.
2Measurement precision
If terminal reports CSI for each CSI feedback configuration, then measurement precision is improved, but loss of information increases due to inability to identify optimum configuration
Solution Approach 1:
The patent extracts the optimum CSI feedback configuration from the set of all CSI feedback configurations by introducing location information. The terminal reports not only CSI values but also the location (index) of the optimum configuration. This extraction allows the network device to identify which specific configuration yields the best performance, preventing information loss while maintaining measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the terminal feeds back both CSI measurements and location information about the optimum configuration. This dual feedback enables the network device to understand both the quality metric and the specific configuration achieving it, resolving the information loss problem while preserving measurement precision.
3Ease of operation
If terminal determines CSI feedback approach autonomously, then ease of operation is improved, but reliability deteriorates because terminal cannot know network device capabilities
Solution Approach 1:
The patent introduces location information as an intermediary that bridges the terminal and network device. The terminal reports location information indicating which CSI feedback configuration is optimum, and the network device uses this intermediary data to understand terminal capabilities and adjust its CSI feedback configuration accordingly. This intermediary mechanism enables reliable capability matching while keeping the operation simple for the terminal.
Data Source
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AI summary
A channel state information, CSI feedback method and a terminal are provided to enable the terminal to determine a CSI feedback approach based on received information for CSI feedback and perform CSI measurement and CSI feedback. A network device indicates a CSI feedback configuration group for CSI feedback to the terminal. After receiving the CSI feedback configuration group, the terminal determines the CSI feedback approach corresponding to the CSI feedback configuration group.