MIMO Channel Calibration Using Separate Tx/Rx Matrices
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Solution Overview
Problem
Calibrating multiple-input multiple-output (MIMO) antenna arrays is costly and complex due to the large number of virtual channels, requiring significant computing resources and memory, especially when mutual coupling and transmission line differences are considered.
Innovation Solution
Separate transmit and receive components of the virtual channels into vectors and compute calibration matrices for each, reducing the number of elements needed compared to full calibration matrices, thereby minimizing memory and computation requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full calibration matrices are used for all virtual channels in MIMO systems, then calibration accuracy is improved, but memory requirements and computational complexity increase significantly
Solution Approach 1:
The patent segments the calibration process by separating transmit and receive channel responses. Instead of calibrating all virtual channels simultaneously using a single large calibration matrix, the method divides the calibration into independent transmit calibration and receive calibration components. This segmentation reduces the computational burden and memory requirements while maintaining calibration accuracy for the overall MIMO system.
2Measurement precision
If full calibration matrices are used for all virtual channels in MIMO systems, then calibration accuracy is improved, but memory requirements increase significantly
Solution Approach 1:
The calibration matrix is segmented into separate transmit and receive components. The patent stores calibration data independently for transmit channels and receive channels rather than maintaining a single comprehensive calibration matrix for all virtual channels. This segmentation dramatically reduces the memory footprint required to store calibration information while preserving the accuracy needed for MIMO operations.
3Adaptability or versatility
If more physical channels are added to increase virtual channels, then system capability is improved, but calibration cost and complexity increase exponentially
Solution Approach 1:
The patent applies segmentation to decouple the calibration complexity from the number of virtual channels. By separating transmit and receive calibration into independent processes, the calibration complexity scales linearly with the number of physical channels rather than exponentially with the number of virtual channels. This enables MIMO systems to scale to higher capabilities without prohibitive calibration complexity.
Solution Approach 2:
The calibration method enables the MIMO system to self-calibrate by measuring and correcting transmit and receive channel responses independently. The system uses its own transmitted signals and received responses to generate calibration data, eliminating the need for external calibration equipment or procedures. This self-service approach reduces calibration cost and complexity while maintaining accuracy.
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AI summary
This document describes techniques and systems for independent transmit and receive channel calibration for multiple-input multiple-output (MIMO) systems. Antenna responses are collected from each virtual channel of a MIMO system at an angle respective to an object. The transmit components and the receive components of the virtual channels are separated and organized into vectors (one for the transmit components and one for the receive components). Calibration values for elements of the vectors are computed and maintained in a transmit calibration matrix and a receive calibration matrix, respectively. Together, the transmit calibration matrix and the receive calibration matrix may include fewer elements than a calibration matrix for the virtual channels and, therefore, may require less memory and fewer computations to calibrate a MIMO system than using other calibration techniques. As such, described is a less expensive and less complex way to calibrate MIMO system by accurately approximating an ideal antenna array.