Multi-TRP CSI Reporting for Coherent Joint Transmission
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Solution Overview
Problem
Existing 5G/NR communication systems face challenges in achieving high spectral efficiency due to limited support for a large number of CSI-RS antenna ports at low frequencies, which restricts MU-MIMO spatial multiplexing gains, particularly in sub-1 GHz bands, necessitating improved CSI reporting methods for multi-TRP coherent joint transmission.
Innovation Solution
The proposed solution involves distributing antenna ports across multiple TRPs or RRHs, enabling CSI reporting across multiple CSI-RS resources, and incorporating methods for indicating reference values in Rel-18 MIMO Type-II CSI codebooks to support multi-TRP coherent joint transmission, enhancing CSI reporting in distributed MIMO systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If antenna ports are concentrated at a single TRP, then device complexity is reduced, but spectral efficiency and MU-MIMO spatial multiplexing gains are limited
Solution Approach 1:
The patent segments the antenna ports across multiple TRPs (Transmission Reception Points) instead of concentrating them at a single location. This segmentation enables the system to support a larger total number of antenna ports (e.g., 64 or 128 ports distributed across multiple TRPs), thereby achieving higher spectral efficiency and MU-MIMO spatial multiplexing gains while keeping each individual TRP's complexity manageable.
Solution Approach 2:
The patent introduces a spatial dimension by distributing antenna ports across multiple geographically separated TRPs. This dimensional expansion from a single-location architecture to a multi-location distributed architecture enables the system to achieve higher spectral efficiency through enhanced spatial multiplexing capabilities without proportionally increasing the complexity of any single node.
2Productivity
If the number of CSI-RS antenna ports is increased, then spectral efficiency improves, but measurement and reporting complexity increases
Solution Approach 1:
The patent segments the CSI-RS resources across multiple TRPs, allowing the UE to measure and report CSI for each TRP separately or in coordinated groups. This segmentation of the measurement and reporting process makes it more manageable to handle large numbers of antenna ports (64 or 128) by breaking down the complex single-step CSI calculation into multiple coordinated steps across different TRPs.
Solution Approach 2:
The patent enables partial CSI reporting where the UE can selectively report CSI for a subset of TRPs or antenna ports based on channel conditions and quality metrics. This partial action approach allows the system to achieve high spectral efficiency when conditions permit while reducing measurement and reporting complexity when resources are constrained or channel conditions are poor.
Data Source
AI summary
Apparatuses and methods for channel state information (CSI) reporting in multi-transmission reception point (TRP) operations in wireless networks. A method performed by a user equipment (UE) includes receiving information about a CSI report. The information indicates Ntrp CSI reference signal (CSI-RS) resources, where Ntrp>1. The method further includes, based on the information, measuring the Ntrp CSI-RS resources and determining the CSI report associated with N≤Ntrp CSI-RS resources, where N∈{1,2, . . . , Ntrp}. The CSI report includes a strongest coefficient indicator (SCI) for each layer l (SCIl). The SCIl indicates an index of a strongest coefficient amongKlNZcoefficients. l∈{1, . . . , v} is a layer index, v≥1 is a rank value, andKlNZis a total number of non-zero coefficients for a layer l associated with CSI-RS ports corresponding to the N CSI-RS resources. The method further includes transmitting the CSI report.