Multi-Stage UL Precoding Matrix Update Mechanism
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently indicating high-resolution uplink precoding with low overhead, particularly due to limitations in exploiting UL channel correlations across scheduling time instants and providing coarse precoding matrices, which degrades uplink transmission performance.
Innovation Solution
The introduction of a multi-stage UL precoding mechanism that generates UL precoding matrices based on an update matrix and a previous precoding matrix, using adaptive/multi-stage codebooks to select finer resolutions and exploit channel correlations, thereby reducing indication overhead and improving transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution UL precoding is indicated using traditional methods, then precoding accuracy is improved, but signaling overhead increases
Solution Approach 1:
The precoding matrix is segmented into a base precoding matrix (selected from codebook) and a differential update component (indicated via signaling). This segmentation allows the system to transmit only the essential update information rather than the complete high-resolution precoding matrix, thereby reducing signaling overhead while maintaining precoding accuracy.
Solution Approach 2:
The base precoding matrix is pre-selected from a codebook and stored at both the gNB and UE. This preliminary action eliminates the need to signal the entire precoding matrix, as only the differential update from the base matrix needs to be transmitted, significantly reducing signaling overhead while preserving high-resolution precoding capability.
2Loss of information
If coarse precoding matrices are used, then signaling overhead is reduced, but uplink transmission performance degrades
Solution Approach 1:
The system employs feedback mechanisms where the UE measures the downlink channel and reports channel state information (CSI) to the gNB. This feedback enables the gNB to select an appropriate base precoding matrix from the codebook that matches the current channel conditions, ensuring that the differential update from the base matrix achieves high-resolution precoding performance optimized for the specific channel state.
Solution Approach 2:
The system dynamically changes the base precoding matrix selection based on channel conditions (through CSI feedback). By adapting the base matrix to match current channel parameters, the differential update can achieve high-resolution precoding performance tailored to each channel state, preventing performance degradation that would occur with fixed coarse precoding matrices.
3Device complexity
If channel correlations across scheduling time instants are not exploited, then system complexity is reduced, but precoding resolution is limited
Solution Approach 1:
The base precoding matrix is pre-selected from a codebook based on historical channel information and correlations across scheduling time instants. This preliminary action leverages temporal channel correlation to establish a reliable base matrix that captures the dominant channel characteristics, allowing the differential update to achieve high-resolution precoding without requiring complex real-time processing of channel correlations.
Solution Approach 2:
The system adapts the base precoding matrix selection based on observed channel correlation patterns over time. By changing the base matrix selection strategy to exploit temporal correlations, the system achieves higher precoding resolution while maintaining manageable complexity through codebook-based selection rather than full channel estimation and optimization at each scheduling instance.
Data Source
AI summary
Apparatuses and methods for multi-stage UL precoding are provided. The method includes receiving configuration information about resource allocation for an uplink (UL) transmission, the configuration information indicating: allocated resources for an UL transmission, and UL precoding information for the UL transmission on the allocated resources, wherein the UL precoding information indicates: an update precoding matrix V, and basis vectors and coefficients for the update precoding matrix V; determining an UL precoding matrix for the UL transmission based on the update precoding matrix V and a previous UL precoding matrix; and performing UL transmission on the allocated resources using the UL precoding matrix.