CSI Measurement with Joint Reference Signals to Counter Channel Aging
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Solution Overview
Problem
In wireless communication systems, particularly in scenarios with terminal mobility, the rapid change in channel conditions leads to inaccuracies in uplink CSI measurement, resulting in a mismatch between the precoding matrix determined based on initial downlink CSI and the actual downlink CSI, which deteriorates the receiving quality of PDSCH.
Innovation Solution
A CSI measurement method involving joint measurement of uplink CSI using a first and second reference signal, where the antenna ports corresponding to these signals are at least partially the same, allowing for improved estimation of downlink CSI that matches the current channel conditions, thereby enhancing the precoding accuracy and improving PDSCH reception quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal periodically sends SRS with a fixed sending periodicity, then the base station can obtain uplink CSI through measurement, but in terminal mobility scenarios the channel changes rapidly causing the obtained downlink CSI to be far different from the actual downlink CSI when PDSCH is sent
Solution Approach 1:
The base station sends downlink reference signals (DL-RS) in advance before the terminal sends uplink SRS. The terminal uses these DL-RS to pre-obtain downlink channel information, which is then combined with uplink SRS measurement results. This preliminary action ensures that the downlink CSI is more current and accurate when needed for PDSCH precoding, reducing the time gap between channel measurement and actual usage.
2Productivity
If the base station determines precoding matrix based on first downlink CSI obtained from uplink CSI, then the precoding can be calculated, but the precoding matrix no longer matches the second downlink CSI that exists when PDSCH is sent
Solution Approach 1:
The patent combines downlink reference signal measurement results with uplink SRS measurement results to form a composite downlink CSI. By merging these two independent measurement sources, the system achieves more accurate and current downlink channel information, which improves the matching accuracy of the precoding matrix while maintaining calculation efficiency through unified processing of the combined CSI.
3Ease of operation
If a fixed SRS sending periodicity is configured, then the system operation is simple, but the channel aging problem causes receiving quality of PDSCH to deteriorate in mobile scenarios
Solution Approach 1:
The patent introduces dynamic adjustment mechanisms for SRS configuration based on terminal mobility states. The base station can adaptively adjust SRS sending periodicity and resource allocation according to the terminal's movement speed and channel conditions. This dynamic approach maintains ease of operation through automated adaptation while significantly improving PDSCH receiving quality by ensuring timely channel measurements in mobile scenarios.
Data Source
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AI summary
This application provides a CSI measurement method and an apparatus, and relates to the field of communications technologies. The method includes: A network device receives, from a terminal, a first RS used to measure uplink CSI and a second RS used to measure the uplink CSI. The first RS includes one or more RS ports, and the one or more RS ports correspond to one or more antenna ports of the terminal. Correspondingly, the second RS includes one or more RS ports, and the one or more RS ports also correspond to one or more antenna ports of the terminal. In addition, the one or more antenna ports, of the terminal, corresponding to the one or more RS ports included in the second RS are partially or completely the same as the one or more antenna ports, of the terminal, corresponding to the one or more RS ports included in the first RS. The network device may measure the uplink CSI based on the first RS or the second RS, to select, based on a requirement, an RS for measuring the uplink CSI. The network device may alternatively measure the uplink CSI based on the first RS and the second RS, and determine downlink CSI based on the uplink CSI, to avoid channel aging and improve receiving quality of receiving a PDSCH by the terminal.