I am reading Smartphone based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method, which is trying to estimate blood pressure from a PPG sensor and a small applied force finger sensor. I am not an engineer, so I'm unfamiliar with a lot of the terminology.
In this paper, they describe using the ppg sensor measurements to estimate an average heart rate. The single sentence that describes this process is "The average heart rate is determined from the blood volume waveform based on its spectral peaks within the frequency range of 0.5 to 3 Hz".
I have a ppg sensor, so I can take a time series measurement of the blood volume, but frankly, I have no idea what this sentence means other than it involves some kind of spectral analysis. I'm unable to find any similar descriptions of this algorithm in google scholar. I would really appreciate it if someone could interpret and translate this sentence into either an algorithmic, or statistical terminology, which I am much more familiar.