MIMO Antenna Array Calibration via Intra-Group Pilot Signaling
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Solution Overview
Problem
Existing methods for updating the calibration matrix of a MIMO transceiver are not well-suited for rapid changes in hardware impairment, requiring excessive spectral resources and typically occurring only periodically rather than in real-time, and often approximate the calibration matrix as diagonal or block-diagonal, neglecting off-diagonal elements.
Innovation Solution
The method involves partitioning the antenna array into groups, performing intra-array pilot measurements where each antenna in one group transmits a pilot signal and other groups receive, allowing for efficient detection and correction of sudden variations in the calibration matrix, particularly useful for arrays with four or more antennas, by evaluating or calibrating the array based on received signals to minimize reciprocity relation violations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If periodic recalibration methods are used, then device complexity is reduced, but measurement precision deteriorates because they cannot detect sudden variations in hardware impairment
Solution Approach 1:
The system performs preliminary calibration to establish a baseline calibration matrix, then uses this baseline to detect sudden variations through reciprocity relation checks. This preliminary action allows the system to maintain high measurement precision without continuous complex recalibration, as the baseline serves as a reference for detecting hardware impairment changes.
Solution Approach 2:
The system implements feedback by continuously checking reciprocity relations between uplink and downlink channels against the baseline calibration matrix. When deviations exceed a threshold, the system triggers recalibration. This feedback mechanism ensures measurement precision is maintained while avoiding unnecessary recalibrations, thus reducing device complexity.
2Measurement precision
If full array recalibration is performed frequently, then measurement precision is improved, but loss of time increases due to excessive measurement duration
Solution Approach 1:
Instead of performing full array recalibration frequently, the system applies partial action by only recalibrating when reciprocity relation deviations exceed a threshold. This selective approach maintains measurement precision when needed while minimizing calibration time during normal operation, resolving the contradiction between precision and time loss.
Solution Approach 2:
The system uses periodic checks of reciprocity relations against the baseline calibration matrix to determine when recalibration is necessary. This periodic monitoring approach ensures measurement precision is maintained through timely recalibration while avoiding continuous full array calibration, thus reducing overall calibration time.
3Productivity
If baseline calibration matrix is used for sudden variation detection, then productivity is improved through faster calibration, but measurement precision may worsen if baseline becomes outdated
Solution Approach 1:
The system dynamically adjusts the baseline calibration matrix based on detected hardware impairment variations. When sudden variations are detected through reciprocity relation checks, the baseline is updated to reflect the new hardware state. This dynamic adaptation maintains measurement precision while preserving the productivity benefits of using a baseline for rapid calibration.
Data Source
AI summary
Intra-array pilot measurements are performed with an antenna array of a MIMO transceiver. The antenna array comprises N transceive antennas. The antenna array is partitioned into K groups of antennas, Gk, k=1, . . . , K, wherein K≥2, each group Gk comprising Nk antennas, Aki, i=1, . . . , Nk, of the antenna array. For each k=1, . . . , K, Sk pilot measurements, Mks, s=1, . . . , Sk, are performed, wherein Sk≥1 and wherein each pilot measurement Mks comprises transmitting simultaneously by each antenna Aki, i=1, . . . , Nk, of the group Gk a pilot signal Pkis and generating by each antenna Ak′i′, i′=1, . . . , Nk′, of the other groups, Gk′, k′≠k, a received signal Ykk′i′s by receiving the pilot signals Pkis transmitted by the antennas Aki, i=1, . . . , Nk. The measurements can be performed in a mode for detecting whether current hardware impairment parameters are valid or in a mode for updating the hardware impairment parameters.