Trade-Offs in FMCW Radar-Based Respiration and Heart Rate Variability

2026-03-10

AI Summary

This study addresses the trade-off in non-contact vital sign monitoring using frequency-modulated continuous-wave (FMCW) radar between the accuracy of estimating mean respiratory and heart rates and the ability to capture their instantaneous variability. The authors systematically evaluate the performance of a low-cost FMCW MIMO radar across varying sensing distances and chirp counts. Through signal processing and statistical analysis, they provide the first quantitative assessment of how distance and chirp number influence monitoring accuracy. Experimental results show optimal performance at 70 cm, yielding mean absolute errors of 0.8 bpm for respiration rate and 3.2 bpm for heart rate. However, errors in variability metrics range from 15% to 30%, indicating limited capability for high-fidelity tracking of instantaneous fluctuations. These findings delineate the operational boundaries of this technology, highlighting its suitability for steady-state estimation but not for precise dynamic monitoring.

Technology Category

• Planning, Routing, and Scheduling: Activity and Plan Recognition
• Computer Vision: Motion & Tracking
• Intelligent Robots: State Estimation

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization

Abstract

This study presents a comprehensive experimental assessment of a low-cost frequency-modulated continuous-wave (FMCW) multiple-input multiple-output (MIMO) radar for non-contact vital sign monitoring, focusing on respiratory rate (RR) and heart rate (HR) estimation. The influence of sensing distance and number of transmitted chirps on measurement accuracy is systematically quantified. Results exhibit a U-shaped error profile with optimal performance near $70~cm$, achieving mean absolute errors of $0.8~bpm$ for RR and $3.2~bpm$ for HR. Accuracy deteriorates at short ($<60~cm$) and long ($>100~cm$) distances due to multipath, near-field, and signal-to-noise effects. Increasing chirp count enhances performance: RR errors converge asymptotically for $\geq96$ chirps, while HR requires at least 96 chirps for stable detection. Variability metrics, including heart and respiratory rate variability, remain less accurate ($>15$--$30\%$ error), indicating limited capability in capturing instantaneous fluctuations. These findings define a fundamental trade-off: the radar ensures robust estimation of average RR and HR but exhibits restricted precision in high-resolution beat-to-beat and breath-to-breath monitoring.

Problem

• FMCW radar
• respiration rate
• heart rate variability
• non-contact monitoring
• vital sign estimation

Innovation

• FMCW radar
• vital sign monitoring
• respiratory rate variability
• heart rate variability
• MIMO radar