Over-the-Air Distributed MIMO Calibration for Phase Drift
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Solution Overview
Problem
Existing distributed MIMO systems face challenges in achieving precise phase calibration due to the use of different local oscillators in physically separated antenna modules, leading to phase drift and limited spectral efficiency, especially in low-frequency bands where antenna form factor constraints restrict the number of CSI-RS ports.
Innovation Solution
Implement over-the-air signaling mechanisms and calculation algorithms for phase calibration among distributed antenna modules, utilizing UL RS transmission, DL RS reception, and CSI reporting to estimate and correct phase mismatches, enabling coherent joint transmission across multiple TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If distributed antenna modules use different local oscillators to enable physical separation and flexibility, then deployment flexibility is improved, but phase drift occurs leading to poor phase calibration accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the network entity receives PMI reports from the UE containing measured phase offsets, processes these feedback signals to determine phase mis-match values, and uses these values to adjust the phase calibration between distributed TRPs. This closed-loop feedback enables continuous compensation for phase drift caused by different local oscillators.
Solution Approach 2:
The patent changes the phase parameter dynamically by calculating phase mis-match values based on feedback PMI reports and applying these corrections to the phase calibration. The network entity adjusts phase offsets and timing differences as parameters to maintain synchronization despite using different local oscillators in distributed antenna modules.
2Productivity
If the number of CSI-RS ports is increased to improve spectral efficiency, then spectral efficiency is improved, but antenna form factor constraints in low-frequency bands limit the physical implementation
Solution Approach 1:
The patent segments the antenna system into multiple distributed TRPs, each with a subset of antenna ports. Instead of requiring a single large antenna structure with many ports, the system distributes functionality across multiple smaller TRPs located at different positions, overcoming the form factor constraints of low-frequency bands while maintaining high spectral efficiency through coordinated joint transmission.
Solution Approach 2:
The patent transitions from a single-location antenna system to a multi-location distributed system, adding the spatial dimension to the antenna configuration. By distributing TRPs across different physical locations, the system effectively increases the number of usable antenna ports beyond what a single compact form factor could accommodate, thereby improving spectral efficiency.
3Reliability
If phase calibration is performed to enable coherent joint transmission across multiple TRPs, then transmission reliability is improved, but additional calibration procedures and signaling overhead are required
Solution Approach 1:
The patent implements self-service calibration where the UE autonomously measures phase offsets by receiving CSI-RS from multiple TRPs and generating PMI reports containing the measured phase information. The network entity then automatically processes these reports to determine phase mis-match values and applies corrections, eliminating the need for manual calibration procedures while maintaining coherent joint transmission reliability.
Data Source
AI summary
A method of operating a network entity includes receiving, via a first TRP and a second TRP, information associated with a SRS from a UE, and estimating a channel based on the information associated with the SRS. The method further includes, for N iterations: transmitting, via a first CSI-RS port from a CSI-RS resource, from the first TRP, a CSI-RS; transmitting, via a second CSI-RS port from the CSI-RS resource, from the second TRP, the CSI-RS with a controlled phase offset; receiving a PMI report associated with the CSI-RS including a measured phase offset between the first CSI-RS port and the second CSI-RS port; and updating the controlled phase offset, based on the measured phase offset. The method further includes, after the N iterations, based on the controlled phase offset and the measured phase offset, determining a phase mis-match for phase calibration between the first TRP and the second TRP.