CSI Reporting with Linear Combination Codebooks for Lower Feedback Overhead
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Solution Overview
Problem
Current 3GPP Type-I and Type-II CSI reporting schemes in FDD systems suffer from high feedback overhead and computational complexity due to the need for UE to calculate and report beams and delays, leading to inaccurate precoder coefficients and reduced performance in downlink transmissions.
Innovation Solution
Utilize angular and delay information from uplink channel sounding measurements at the gNB to precode CSI-RS resources, allowing the UE to calculate and report precoder coefficients without calculating beams and delays, reducing feedback overhead and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE calculates and reports beams and delays for Type-II CSI reporting, then downlink transmission performance is improved through accurate precoder coefficients, but feedback overhead and computational complexity increase significantly
Solution Approach 1:
The patent extracts the beam and delay calculation tasks from the UE and relocates them to the gNB. The gNB performs channel sounding measurements and calculates the necessary beam and delay information locally, then provides this information to the UE for CSI reporting. This extraction significantly reduces the computational burden on the UE while maintaining accurate precoder coefficients for downlink transmission.
Solution Approach 2:
The patent introduces channel sounding measurements as an intermediary mechanism. The gNB performs these measurements to obtain angular and delay information, which then serves as input for CSI reporting. This intermediary approach allows the UE to report simplified CSI parameters without performing complex beam and delay calculations, thereby reducing computational complexity while maintaining transmission performance.
2Reliability
If UE calculates and reports beams and delays for Type-II CSI reporting, then downlink transmission performance is improved, but feedback overhead increases
Solution Approach 1:
The patent extracts the computationally intensive beam and delay calculations from the UE and performs them at the gNB through channel sounding measurements. The UE then reports only the essential CSI parameters (such as precoder coefficients) without including the full beam and delay information, significantly reducing feedback overhead while maintaining accurate downlink transmission performance.
Solution Approach 2:
The patent performs channel sounding measurements and beam/delay calculations in advance at the gNB before the actual CSI reporting. This preliminary action prepares the necessary information so that the UE can report simplified and reduced-size CSI parameters, thereby reducing feedback overhead without compromising transmission performance.
3Device complexity
If codebook-based precoding is used with limited resolution, then device complexity is reduced, but measurement precision of channel information is degraded
Solution Approach 1:
The patent introduces channel sounding measurements as an intermediary that enables high-resolution channel characterization at the gNB. These measurements provide accurate angular and delay information that can be used to construct precise precoder coefficients. The UE then reports these high-resolution coefficients without needing to perform complex calculations, maintaining both low complexity and high measurement precision.
Data Source
AI summary
A method performed by a UE for generating a CSI report in a wireless communication system, including receiving from a network node, a CSI report configuration information including at least one parameter, D, for indicating a first basis set of D basis vectors used for constructing for each transmission layer a precoding vector or matrix for a rank set; identifying a precoding vector matrix for each transmission layer based on the first basis set, a second basis set comprising P basis vectors, and a number of combining coefficients for combining selected vectors from the first and second basis set; generating a CSI report based on the CSI report configuration information for a RI, or v of the rank set; and transmitting the CSI report to the network node.