CSI-RS Phase-Timing Calibration for Distributed MIMO Joint Transmission
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Solution Overview
Problem
Existing distributed MIMO systems face challenges in achieving accurate phase-timing calibration due to the difficulty in sharing reference signals across physically distant antenna panels or RRHs, which leads to phase drift and limited spectral efficiency, especially at lower frequency bands.
Innovation Solution
The implementation of over-the-air signaling mechanisms and calculation algorithms for phase-timing calibration using CSI-RS resources, enabling joint transmission between TRPs based on determined phase timing slopes and frequency bands, allowing for centralized processing of signals from distributed antenna panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If distributed antenna panels or RRHs are used to increase coverage and capacity, then network coverage and spectral efficiency are improved, but phase-timing calibration accuracy deteriorates due to physical distance making reference signal sharing difficult
Solution Approach 1:
The patent introduces CSI-RS resources as an intermediary mechanism that enables phase-timing calibration between distributed TRPs. Instead of directly sharing reference signals between physically distant antenna panels, the system uses downlink CSI-RS transmissions from each TRP that are received and measured by user equipment. The UE then provides feedback containing phase timing measurements that serve as the calibration reference, effectively mediating the calibration process across distributed locations without requiring direct signal sharing between TRPs.
Solution Approach 2:
The patent implements a feedback-based calibration mechanism where user equipment measures the phase timing of CSI-RS signals from different TRPs and reports these measurements back to the network. This feedback loop enables the system to determine phase timing slopes and perform calibration adjustments based on actual measured values rather than theoretical calculations, thereby maintaining calibration accuracy despite physical distance between distributed antenna panels.
2Reliability
If phase-timing calibration is performed using traditional reference signal sharing methods, then calibration can be achieved, but the method becomes infeasible for distributed TRPs due to the inability to share reference signals across physical distances
Solution Approach 1:
The patent inverts the traditional calibration approach by reversing the direction of measurement and feedback. Instead of having TRPs directly share reference signals with each other (TRP-to-TRP communication), the system has TRPs transmit CSI-RS to UE, and then UE measures and reports back to TRP (TRP-to-UE-to-TRP path). This inversion makes the calibration process feasible for distributed TRPs by eliminating the need for direct reference signal sharing between physically separated transmit-receive points.
3Productivity
If joint transmission is performed from multiple TRPs to improve spectral efficiency, then network capacity increases, but phase drift occurs due to timing mismatches between distributed antenna panels
Solution Approach 1:
The patent performs phase-timing calibration as a preliminary action before executing joint transmission from multiple TRPs. By determining phase timing slopes and applying calibration adjustments in advance, the system pre-compensates for timing mismatches between distributed antenna panels. This preliminary calibration ensures that when joint transmission subsequently occurs, the signals from different TRPs remain phase-coherent, preventing phase drift and maintaining stable composition of the transmitted signal.
Data Source
AI summary
A method performed by a network entity includes determining a target timing mismatch for a phase timing slope between first and second channel state information-reference signal (CSI-RS) resources, and determining, based on the target timing mismatch, a first band separation between a first calibrated phase for the first the second CSI-RS resource and a second calibrated phase for the first and the second CSI-RS resource. The method further includes determining a first frequency band for the first calibrated phase, and determining, based on the band separation, a second frequency band for the second calibrated phase. The method further includes determining, based on the band separation between the first calibrated phase the second calibrated phase, a first phase timing slope between the first the second CSI-RS resource, and performing joint transmission from a first TRP and a second TRP based on the first phase timing slope.