TRS-Based CSI Reporting for Time-Domain Channel Tracking
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Solution Overview
Problem
Downlink MU-MIMO precoding performance degrades when co-scheduled UEs move faster than a few km/h due to outdated channel information, and existing Type-II CSI feedback is complex and not suitable for multi-TRP operations, leading to high UE complexity.
Innovation Solution
Configure UEs to measure time domain information using Tracking Reference Signals (TRS) for CSI reporting, allowing low-complexity estimation of time domain channel properties, which can be combined with CSI-RS for spatial and frequency domain measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Type-II CSI feedback is used for MU-MIMO precoding, then precoding performance is improved, but UE complexity increases significantly
Solution Approach 1:
The patent segments the channel state information into two independent parts: spatial/frequency domain CSI (from CSI-RS) and time domain properties (from TRS). This segmentation allows the UE to report only the time domain properties using simple TRS measurements, while the network combines these with CSI-RS data for complete precoding, thereby reducing UE complexity while maintaining precoding performance.
Solution Approach 2:
The patent introduces TRS as an intermediary reference signal that mediates between the UE and network for time domain property measurement. The TRS enables the UE to obtain time domain information without requiring complex Type-II CSI feedback, acting as a simplified intermediary that reduces UE processing burden while providing necessary time-varying channel characteristics.
2Reliability
If channel measurement resources are increased to track fast-moving UEs, then precoding robustness to speed is improved, but reference signal overhead increases
Solution Approach 1:
The patent makes the TRS serve multiple functions: it provides synchronization signaling and simultaneously enables time domain property measurement for CSI reporting. This multi-functionality eliminates the need for separate dedicated measurement resources, reducing reference signal overhead while maintaining the ability to track fast-moving UEs effectively.
Solution Approach 2:
The patent changes the measurement parameter focus from full Type-II CSI (which requires extensive resources) to time domain properties only (which can be measured using minimal TRS resources). This parameter change enables robustness to higher UE speeds without proportionally increasing reference signal overhead.
3Measurement precision
If CSI-RS is used for time domain measurements, then spatial and frequency domain information is obtained, but time domain tracking capability is insufficient
Solution Approach 1:
The patent segments the measurement function between two different reference signals: CSI-RS handles spatial and frequency domain measurements, while TRS handles time domain property measurements. This segmentation allows each signal to be optimized for its specific domain, with TRS providing the necessary time domain tracking capability through its periodic structure and dedicated time domain property measurement support.
Data Source
AI summary
There is provided a method performed by a user equipment (UE). The method comprises: receiving a reference signal over multiple time instances; determining time domain properties of a channel, based on the received reference signal; and sending a report to a network node, the report comprising information about the determined time domain properties of the channel. A UE for implementing this method is also provided.