Reciprocity-Based Type-II Codebook PUCCH Reporting
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Solution Overview
Problem
The high number of Precoding Matrix Indicator (PMI) bits and Channel State Information Reference Signals (CSI-RS) ports in New Radio (NR) Rel. 16 Type-II codebook leads to increased system complexity and resource overhead, necessitating a reduction to improve efficiency, especially in Frequency-Division Duplexing (FDD) mode where uplink-downlink channel reciprocity is partial.
Innovation Solution
The implementation of a reciprocity-based Type-II codebook with reduced CSI-RS ports and a spatial beamforming process, utilizing discrete Fourier transform-based CSI compression and partial CSI omission to minimize feedback overhead, while ensuring accurate channel estimation through precise timing and frequency alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of CSI-RS ports is reduced via spatial beamforming, then the system complexity and resource overhead are reduced, but the channel estimation accuracy may deteriorate
Solution Approach 1:
The patent segments the channel estimation process by separating spatial beamforming from channel estimation. The gNB performs beamforming for downlink transmission while the UE performs channel estimation using uplink reference signals. This segmentation allows the system to reduce the number of CSI-RS ports while maintaining estimation accuracy through the reciprocity principle.
Solution Approach 2:
The patent introduces uplink reference signals as an intermediary to enable downlink channel estimation. Instead of directly estimating the downlink channel using downlink reference signals, the system uses uplink reference signals transmitted by the UE, leveraging channel reciprocity to infer the downlink channel characteristics. This intermediary approach enables accurate estimation with fewer reference signal ports.
2Quantity of substance
If the number of PMI bits is reduced, then the feedback overhead is reduced, but the precoding accuracy may deteriorate
Solution Approach 1:
The patent changes the parameter representation from traditional PMI indices to a combination of beam indication and coefficient feedback. Instead of feedbacking complete precoding matrices with many bits, the system feeds back beam indices (from a codebook) plus a set of coefficients, significantly reducing the number of bits while maintaining precoding accuracy through the compressed representation.
Solution Approach 2:
The patent extracts only the essential information needed for precoding by using channel reciprocity. The UE extracts channel state information from uplink reference signals and feeds back only the necessary coefficients and beam indications, omitting redundant information that would be present in full PMI feedback. This extraction approach reduces feedback overhead while preserving the essential precoding characteristics.
Data Source
AI summary
Apparatuses, systems, and methods for PUCCH reporting of reciprocity-based type-II codebook are disclosed. One apparatus (1100) includes a transceiver (1125) that receives, from a network entity, a channel state information (“CSI”) reporting configuration comprising a codebook type associated with a precoding matrix and CSI reference signals over a set of CSI reference signal (“CSI-RS”) resources based on the CSI reporting configuration. The apparatus (1100) includes a processor (1105) that identifies a set of co-efficients associated with the codebook based on the received set of CSI-RS resources. The transceiver (1125) transmits a CSI report on a physical uplink control(“PUCCH”) or a physical uplink shared channel (“PUSCH”) and based on the codebook type, the CSI report comprising CSI and the set of coefficients, wherein to transmit the CSI report on the PUCCH is based on a value of a sub-configuration or the CSI reporting configuration.