Frequency Domain Basis Restriction for CSI Feedback Overhead
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing channel state information (CSI) reporting, particularly in reducing computation and feedback payload size, while leveraging reciprocity between downlink (DL) and uplink (UL) channels.
Innovation Solution
The proposed solution involves a method where a base station transmits a frequency domain basis restriction to a user equipment (UE), indicating a subset of frequency domain basis, and sends a precoded channel state information (CSI) reference signal (CSI-RS). The UE selects the precoded port based on the CSI-RS and transmits a precoding matrix indicator to the base station, which is based on the frequency domain basis subset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE reports the complete frequency domain basis set for CSI feedback, then the channel state information accuracy is improved, but the feedback payload size and computation burden increase
Solution Approach 1:
The patent extracts and reports only the selected frequency domain basis subset from the complete frequency domain basis set. The UE identifies and reports only the specific basis vectors that are actually used for precoding, rather than reporting the entire basis set. This extraction principle reduces feedback overhead while maintaining the necessary information for accurate channel state representation.
Solution Approach 2:
The frequency domain basis set is segmented into multiple subsets, where each subset corresponds to specific precoding ports or antenna groups. The UE reports frequency domain basis information separately for different segments (e.g., different port groups or antenna subsets), allowing selective and efficient feedback of only the relevant basis vectors for each segment.
2Loss of information
If the UE reports the complete frequency domain basis set, then the channel state information completeness is improved, but the computation complexity increases
Solution Approach 1:
The patent extracts only the essential frequency domain basis vectors that are actually utilized for precoding operations. By identifying and reporting only the active basis vectors rather than the complete basis set, the computation complexity for both selection and reporting is significantly reduced while maintaining channel state information completeness.
3Quantity of substance
If the system uses frequency domain basis restriction, then the feedback overhead is reduced, but the adaptability of CSI reporting decreases
Solution Approach 1:
The frequency domain basis restriction configuration is made dynamic and adaptable through higher layer signaling. The network can configure different restriction patterns based on channel conditions, traffic requirements, and antenna configurations. This dynamic configuration allows the system to adapt CSI reporting to different scenarios while maintaining reduced feedback overhead through the restriction mechanism.
Solution Approach 2:
The patent applies different frequency domain basis restrictions to different local contexts, such as different antenna groups, port groups, or frequency bands. Each local segment can have its own optimized restriction configuration, allowing the system to maintain adaptability at the local level while achieving overall feedback reduction through structured segmentation.
Data Source
AI summary
The frequency domain basis may be fed back in a CSI report from a user equipment (UE), with extra overhead and computation cost. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE configured to receive, from a base station, CSI reference signals (CSI-RS). The apparatus may be further configured to receive, from the base station, a configuration including a frequency domain basis restriction indicating a frequency domain basis subset, where the frequency domain basis subset is selected from a frequency domain basis set. The apparatus may be configured to prepare, upon receiving the frequency domain basis restriction, a CSI report based on the CSI-RS and the frequency domain basis subset. The apparatus may be further configured to transmit the CSI report to the base station.