Microcontroller Based RR-Interval Measurement Using PPG Signals for Heart Rate Variability based Biometric Application

Heart Rate Variability (HRV) is a natural property of heart rate. Medical science since last two decades has been viewing at it as a diagnostic and prognostic tool. This study is intended towards harnessing the HRV property of heart for person identification. The highest peak in the ECG signal as well as PPG signal as seen in Figure 1, is known as the R-peak, while the time duration between two adjacent R-peak is known as RR-Interval. RR-Intervals are the only requirement for HRV analysis. Traditionally it is measured from an Electrocardiography (ECG) signals, but we used photoplethysmography (PPG) based pulse sensor and in-house designed microcontroller based RR-Interval measurement system. PPG sensors come in two basic types, one uses transmission and the other one makes use of reflection. We have tested the hardware with both transmission and reflection type sensors. This article is intended to document the performance analysis of both types of PPG sensors. And also present results of biometric identification based on RR-Intervals collected at the fingertips. Classification is done using KNN classifier.