Uplink Precoding Codebooks for Lower CSI Feedback Overhead
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently conveying channel state information (CSI) due to the high overhead and delay associated with raw CSI feedback, particularly in multiple-input and multiple-output (MIMO) technology, which strains network resources.
Innovation Solution
A method for uplink signal precoding and reporting using a reference signal to measure CSI, followed by a CSI report that indicates a transmit precoder matrix indicator (TPMI) for precoding signals, supporting up to 8-layer transmission with fully coherent antenna ports grouped into single or multiple panels, and utilizing dual-stage or single-stage reporting based on codebook modes to balance feedback overhead and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If raw CSI feedback is used to convey channel state information, then measurement precision is improved, but communication overhead increases and network resources are strained
Solution Approach 1:
The patent extracts only the essential precoding information (TPMI) from the complete channel state information, rather than transmitting raw CSI. The receiver calculates CSI, determines the optimal precoder matrix from a codebook, and feeds back only the TPMI index that identifies this matrix. This extraction approach maintains the necessary precision for precoding while dramatically reducing feedback overhead.
Solution Approach 2:
Instead of transmitting the actual precoder matrix, the system uses a TPMI index as a reference copy that points to the matrix in a pre-defined codebook at the transmitter. Both transmitter and receiver share the same codebook, so the receiver can indicate the desired precoder by transmitting only its index (TPMI) rather than the full matrix data. This copying mechanism reduces overhead while preserving the ability to convey precise precoding information.
2Adaptability or versatility
If codebook modes with more co-phasing values are used, then adaptability is improved, but feedback overhead increases
Solution Approach 1:
The patent implements dynamic adaptability through multiple codebook modes (Mode 1, Mode 2, Mode 3) that can be selected based on channel conditions and transmission requirements. Each mode offers different numbers of co-phasing values and different reporting periodicities, allowing the system to dynamically adjust the balance between adaptability and overhead. The dual-stage reporting mechanism further enables dynamic adaptation by reporting slow-changing parameters with low periodicity and fast-changing parameters with high periodicity.
Solution Approach 2:
The system changes key parameters including the number of co-phasing values, reporting periodicity, and codebook mode selection based on channel conditions and transmission requirements. By varying these parameters, the system can adapt to different scenarios: using more co-phasing values when adaptability is critical, and using fewer when overhead must be minimized. This parameter-based adaptation resolves the contradiction between versatility and overhead.
Data Source
AI summary
This disclosure provides a method, an apparatus, and a non-transitory computer-readable medium for wireless communication. In the method, a reference signal is sent from a first device to a second device. The reference signal is used for channel state information (CSI) measurement of a channel between the first device and the second device. A CSI report is received at the first device from the second device. The CSI report indicates a transmit precoder matrix indicator (TPMI) that indicates one of a plurality of precoder matrices. A to-be-transmitted signal is precoded based on the one of a plurality of precoder matrices indicated by the TPMI. Each of the plurality of precoder matrices is able to be used for up to 8-layer transmission.