Type II CSI Reporting for High-Velocity Doppler Compression
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Solution Overview
Problem
Existing CSI frameworks in NR are inadequate for accurately reporting CSI for UEs moving at medium-to-high speeds, leading to degraded downlink MU-MIMO precoding performance due to outdated channel information, and current solutions incur significant signaling overhead or CSI reporting delays.
Innovation Solution
Implement a Type II CSI reporting framework that allows for dynamic determination of Doppler domain compression based on the number of CSI instances requested by the network, using criteria and signaling to decide when to apply or avoid Doppler domain compression, and feedback selected Doppler domain basis vectors when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI reporting frequency is increased to maintain accuracy for high-velocity UEs, then CSI relevance is improved, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential CSI parameters needed for high-velocity UE operation, specifically focusing on Type II codebook parameters that capture the most significant channel variations. By reporting only the critical components of CSI (such as selected beams, amplitude coefficients, and phase information) rather than complete channel state, the signaling overhead is reduced while maintaining adequate accuracy for mobile scenarios.
Solution Approach 2:
The CSI reporting is segmented into different components with different reporting frequencies and granularities. The patent divides CSI feedback into wideband parameters (reported less frequently) and subband parameters (reported more frequently), allowing the system to maintain accuracy where needed while reducing overhead in less critical dimensions. This segmentation enables differentiated reporting strategies for different parts of the frequency spectrum and different temporal intervals.
2Quantity of substance
If Doppler domain compression is applied to reduce overhead, then signaling overhead is reduced, but CSI reporting complexity increases
Solution Approach 1:
The patent applies parameter changes by transforming the CSI representation into the Doppler domain using discrete Fourier transform (DFT). This transformation compresses the temporal variations of the channel into a compact spectral representation, where only the dominant Doppler components need to be reported. By changing the domain of representation from time-sequential CSI reports to a compressed Doppler spectrum, the overhead is significantly reduced while the processing complexity is concentrated in the transformation step, which can be efficiently implemented.
3Measurement precision
If Type II codebook is used for high-velocity UEs, then CSI accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent implements dynamic adaptation of the Type II codebook parameters based on the UE's velocity and channel conditions. The codebook configuration is made flexible, allowing the number of selected beams (L), the rank (number of layers), and the frequency-domain granularity to be adjusted dynamically. This dynamic approach enables the system to use more complex Type II codebook structures when accuracy is critical (e.g., for high-velocity UEs) while falling back to simpler configurations when conditions permit, thereby balancing accuracy requirements with processing complexity.
Data Source
AI summary
Systems and methods of Channel State Information (CSI) reporting with Type II codebook for high velocity are provided. In some embodiments, a method includes determining when to apply Doppler domain compression and when to avoid Doppler domain compression when feeding back a CSI report; determining a signaled number of CSI instances, for which the network node requests the User Equipment (UE) to compute CSI; and based on the number of CSI instances, determining whether to apply CSI compression in the Doppler domain or not. Some solutions proposed allow the possibility for the network and the UE to support cases with Doppler domain compression and without Doppler domain compression under a single CSI reporting framework. Based on the signaling received from the network, the solutions allow the UE to determine when to feedback selected Doppler domain bases and when to avoid Doppler domain bases selection in the Type II CSI report.