UE-Assisted Phase Calibration for Distributed MIMO Systems
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Solution Overview
Problem
Current wireless communication systems face challenges in achieving robust phase calibration for distributed MIMO systems, particularly due to the distribution of antenna ports across multiple locations, which limits spectral efficiency and increases deployment complexity, especially at lower frequency bands where antenna form factor constraints restrict the number of CSI-RS antenna ports.
Innovation Solution
The implementation of UE-assisted on-demand robust phase calibration methods using multi-port CSI-RS PMI feedback, where network entities and user equipment collaborate to perform iterative calibration operations, adjusting phases and determining converged calibrated phases through over-the-air signaling mechanisms, enabling effective phase alignment among distributed antenna panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If antenna ports are distributed across multiple locations in distributed MIMO systems, then coverage and capacity are improved, but phase calibration robustness deteriorates and deployment complexity increases
Solution Approach 1:
The patent implements feedback mechanisms where UEs report channel state information (CSI) including phase measurements back to the network entity. The network entity uses this feedback to iteratively adjust and calibrate phases of distributed antenna ports, achieving robust phase alignment despite spatial distribution. This closed-loop feedback system enables continuous optimization of phase calibration accuracy.
Solution Approach 2:
The patent introduces reference signals (RS) as intermediaries to facilitate phase calibration. These reference signals are transmitted through distributed antenna ports and received by UEs, serving as a common reference for phase measurement and comparison. The reference signals act as a mediator that enables the network entity to indirectly measure and calibrate phase relationships across distributed locations.
2Shape
If antenna form factor constraints are considered at lower frequency bands, then device portability is improved, but the number of CSI-RS antenna ports is limited
Solution Approach 1:
The patent segments the antenna system into distributed antenna ports located at different spatial positions rather than concentrating all antenna ports in a single location. This segmentation allows the system to achieve equivalent or superior performance with fewer antenna ports per location, accommodating form factor constraints while maintaining communication capacity through spatial distribution.
Solution Approach 2:
The patent transitions from a single-location antenna array to a multi-location distributed antenna system, adding the spatial dimension of distribution. This dimensional change allows the system to overcome form factor limitations by distributing antenna functions across multiple locations, effectively increasing the total number of usable antenna ports without increasing the density at any single location.
3Measurement precision
If iterative calibration operations are performed with multiple CSI-RS transmissions, then phase calibration accuracy is improved, but signaling overhead and calibration time increase
Solution Approach 1:
The patent performs preliminary phase calibration operations before actual data transmission begins. The network entity pre-calibrates the phases of distributed antenna ports using reference signals and UE feedback, establishing accurate phase relationships in advance. This preliminary action ensures that when data transmission starts, the system is already optimized, reducing the need for frequent recalibration during operation.
Data Source
AI summary
A method of operating a network entity includes transmitting, via a first TRP and a second TRP, a first DL RS; receiving from a UE, based on the first DL RS, first CSI; determining, based on the first CSI, a calibrated quadrant; transmitting, via the first TRP and the second TRP, a second DL RS based on the calibrated quadrant; and receiving from the UE, based on the second DL RS, second CSI. The method further includes, for N iterations, determining, based on the (N+1)th CSI, an adjusted calibrated phase; transmitting, via the first TRP and the second TRP, an (N+2)th DL RS based on the adjusted calibrated phase; and receiving from the UE, based on the (N+2)th DL RS, (N+2)th CSI. The method further includes, after the N iterations, determining, based on a most recently received (N+2)th CSI, a converged calibrated phase.