Occupant Entry and Exit Event Extraction Using Continuous Wave (CW) Doppler Radar and Wavelet Analysis

Occupancy estimation and occupant entry/exit detection can play a significant role in designing energy-efficient heating, ventilation, and air conditioning (HVAC) systems. Radar-based occupancy estimation is gaining attention as it is unobtrusive and does not give rise to privacy issues associated with video imaging. Most research is focused on estimating the number of occupants by employing frequency-modulated continuous wave (FMCW) radar using a micro-Doppler signature. Continuous wave (CW) radar has a simple architecture and fewer signal processing steps than FMCW radar and is mostly employed for sensing micro-Doppler signatures produced by human cardiopulmonary motion. This paper investigates the feasibility of using wavelet analysis to extract occupant entry and exit information from data produced by a single antenna 2.4 GHz CW radar occupancy sensor. Preliminary experimental results on a short scale demonstrated that maximum wavelet coefficient frequency (MWCF) and wavelet coefficient energy (WCE) vary significantly during the entry and exit event of occupants, and can provide a reliable indicator to estimate the number of occupants.