CSI Codebook Grouping for Multi-TRP Coherent Joint Transmission
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Solution Overview
Problem
Existing 5G/NR communication systems face challenges in achieving high spectral efficiency due to limitations in supporting a large number of CSI-RS antenna ports at low frequencies, leading to reduced MU-MIMO spatial multiplexing gains, especially in sub-1 GHz bands, where deploying large antenna form factors is difficult.
Innovation Solution
The proposed solution involves distributing antenna ports across multiple transmission reception points (TRPs) for multi-TRP coherent joint transmission (C-JT), enhancing CSI reporting by indicating reference values and using a modified CSI codebook that includes components W1, W2, and Wf to support multi-TRP C-JT scenarios, allowing centralized processing of signals from distributed TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of antenna ports are deployed at a single TRP to achieve high spectral efficiency, then MU-MIMO spatial multiplexing gain is improved, but device complexity and hardware constraints are worsened
Solution Approach 1:
The patent segments the antenna ports across multiple TRPs instead of concentrating them at a single location. Each TRP is equipped with a reduced number of antenna ports, and the system achieves high spectral efficiency through coordinated joint transmission across multiple TRPs. This segmentation approach resolves the contradiction by maintaining high productivity while reducing device complexity at each individual TRP.
Solution Approach 2:
The patent transitions from a single-TRP system to a multi-TRP system, adding the dimension of spatial distribution. By utilizing multiple TRPs in different spatial locations, the system achieves enhanced MU-MIMO spatial multiplexing gain without requiring a large number of antenna ports at any single TRP, thus resolving the contradiction between spectral efficiency and device complexity.
2Productivity
If antenna ports are distributed across multiple TRPs for multi-TRP C-JT, then spectral efficiency is improved, but CSI reporting complexity is worsened
Solution Approach 1:
The patent segments the CSI reporting process by associating each TRP with a specific group of antenna ports. The UE reports CSI for each TRP separately, with each TRP's CSI corresponding to its associated antenna port group. This segmentation reduces CSI reporting complexity compared to reporting for all antenna ports simultaneously, while still enabling multi-TRP C-JT for high spectral efficiency.
Solution Approach 2:
The patent introduces TRP grouping as an intermediary mechanism between the physical antenna ports and the CSI reporting process. By grouping antenna ports according to their associated TRPs, the system simplifies CSI reporting while maintaining the benefits of distributed antenna deployment. The grouping structure acts as a mediator that organizes the complexity of multi-TRP CSI reporting.
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 associated with Ntrp groups of antenna ports, where Ntrp>1 and, based on the information, determining the CSI report associated with N≤Ntrp groups of antenna ports, where N∈{2, 3, . . . , Ntrp}. The CSI report includes a first indicator indicating, for each layer l=1, . . . , v, indices of Mv vectors including columns of a frequency-domain (FD) basis matrix Wf,l, where v≥1 is a rank value and a second indicator indicating an index of a FD offset value φr for each of the N groups of antenna ports, where r∈{1, . . . , N}, r≠r* and r* is an index of a reference group of antenna ports. The method further includes transmitting the CSI report including the first and the second indicators.