UE-Assisted OTA Calibration for Distributed FD-MIMO Phase Mismatch
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Solution Overview
Problem
Conventional centralized calibration techniques for FD-MIMO systems, especially in distributed FD-MIMO, face challenges due to physical separation of RF modules, leading to phase mismatch and increased cost, size, and power consumption, while also failing to exploit channel reciprocity effectively.
Innovation Solution
A UE-assisted over-the-air calibration method that eliminates dedicated calibration circuits by using sounding reference signals (SRS) and downlink CSI reference signals (CSI-RS) for joint calibration, allowing estimation of uplink and downlink channels without dedicated hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If centralized calibration circuits are used in FD-MIMO systems, then calibration accuracy is improved, but device complexity, cost, size, and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the dedicated centralized calibration circuits from the FD-MIMO system. Instead of using traditional calibration hardware, the system uses existing RF modules and signal processing capabilities to perform calibration through over-the-air transmission and reception of calibration signals, thereby removing complex calibration hardware while maintaining calibration functionality
Solution Approach 2:
The patent makes the RF modules serve dual purposes: both communication and calibration. The same RF modules that handle data transmission are used to transmit and receive calibration signals, eliminating the need for separate dedicated calibration circuits and reducing overall system complexity
2Productivity
If distributed FD-MIMO is implemented, then system capacity and coverage are improved, but phase mismatch increases due to physical separation of RF modules
Solution Approach 1:
The patent implements a feedback mechanism where the base station receives calibration signals from multiple distributed RF modules, processes the feedback information about phase and amplitude characteristics, and adjusts the calibration parameters accordingly. This closed-loop feedback allows the system to compensate for phase mismatches caused by physical separation while maintaining distributed architecture benefits
Solution Approach 2:
The patent changes the calibration parameters dynamically based on the physical separation characteristics of distributed RF modules. By measuring actual channel characteristics and adjusting calibration parameters accordingly, the system compensates for phase mismatches while preserving the advantages of distributed deployment
3Reliability
If dedicated calibration circuits are added to FD-MIMO base stations, then calibration performance is improved, but cost and power consumption increase
Solution Approach 1:
The patent enables the RF modules to perform self-calibration using their own transmission and reception capabilities. Each RF module transmits calibration signals and receives feedback, processes the information locally, and adjusts its own calibration parameters without requiring external dedicated calibration circuits, thereby reducing power consumption while maintaining calibration performance
Data Source
AI summary
A method includes receiving, by a base station, a sounding reference signal (SRS) symbol from a user equipment (UE). The method also includes estimating, by the base station, an uplink (UL) channel from the UE to a full dimensional multiple-input multiple-output (FD-MIMO) base station base band based on the received SRS symbol. The method also includes receiving, by the base station from the UE, an estimate of a downlink (DL) channel from the FD-MIMO base station base band to the UE. The method also includes performing, by the base station, a joint calibration by applying one or more calibration algorithms using channel state information (CSI) of the UL channel and the DL channel.