Wireless Communication UCI Feedback for Time-Varying Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In new radio (NR) systems, the precoding matrix indicator (PMI) fails to accurately reflect the channel state at low and medium Doppler frequency shifts, leading to performance loss in downlink transmission.
Innovation Solution
The terminal device reports indexes of Q time domain (TD) basis vectors in uplink control information (UCI), which reflects the time-varying characteristics of the channel, enabling the network device to perform improved downlink transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PMI is used for downlink transmission, then the transmission can be performed with simple feedback, but the transmission performance deteriorates at low and medium Doppler frequency shifts because PMI cannot accurately reflect channel state
Solution Approach 1:
The channel state information is segmented into multiple independent components: spatial domain basis vectors (SD), frequency domain basis vectors (FD), and time domain basis vectors (TD). Each component is reported separately through UCI, allowing the system to capture different aspects of channel characteristics independently. This segmentation enables more accurate channel representation compared to unified PMI feedback.
Solution Approach 2:
The patent extends the traditional PMI feedback by adding time domain dimension to the existing spatial and frequency domain basis vectors. By incorporating TD basis vectors that capture temporal variations, the system transitions from static channel representation to dynamic multi-dimensional channel characterization, particularly improving performance in time-varying channels.
2Loss of information
If traditional PMI feedback is used, then the feedback overhead is reduced, but the channel state representation becomes inaccurate leading to performance loss
Solution Approach 1:
The feedback structure is divided into three distinct segments: SD basis vector indexes, FD basis vector indexes, and TD basis vector indexes. Each segment serves a specific purpose in characterizing different dimensions of the channel, reducing information loss by ensuring comprehensive channel state representation across all relevant dimensions.
Solution Approach 2:
The multi-component feedback structure serves multiple functions simultaneously: SD vectors capture spatial characteristics, FD vectors capture frequency selectivity, and TD vectors capture temporal variations. This multi-functional feedback mechanism comprehensively characterizes the channel state while maintaining a structured and manageable feedback format.
3Reliability
If time-varying channel characteristics are not captured, then the feedback structure remains simple, but downlink transmission performance deteriorates due to inaccurate channel representation
Solution Approach 1:
The terminal device performs preliminary analysis of the channel state and pre-calculates the appropriate SD, FD, and TD basis vectors before feedback transmission. This preliminary action enables the system to proactively adapt to time-varying channel conditions, capturing temporal characteristics in advance and improving downlink transmission performance through forward-looking channel characterization.
Data Source
Figure 1~3
Figure 4~7
Figure 8~9
AI summary
Provided in the present application are a wireless communication method, a terminal device, and a network device. The terminal device reports indexes of Q TD base vectors in first UCl, that is, the first UCl can reflect a time variation characteristic of a channel within a period of time. Therefore, a network device can perform downlink transmission on the basis of the first UCI, thereby facilitating an improvement in the transmission performance. The wireless communication method comprises: a terminal device sending first UCI, wherein the first UCI comprises indexes of L SD base vectors, indexes of MV FD base vectors, and indexes of Q TD base vectors; each SD base vector is a two-dimensional DF'T vector with a length of N1N2; each FD base vector is a DF'T vector with a length of N3; each TD base vector is a DFT vector with a length of N4; and N1, N2, N3, N4, L, Mv and Q are all positive integers.