  Zone-level occupancy counting is a critical technology for smart buildings
and can be used for several applications such as building energy management,
surveillance, and public safety. Existing occupancy counting techniques
typically require installation of large number of occupancy monitoring sensors
inside a building as well as an established network. In this study, in order to
achieve occupancy counting, we consider the use of WiFi probe requests that are
continuously transmitted from WiFi enabled smart devices. To this end, WiFi
Pineapple equipment are used for passively capturing ambient probe requests
from WiFi devices such as smart phones and tablets, where no connectivity to a
WiFi network is required. This information is then used to localize users
within coarsely defined occupancy zones, and subsequently to obtain occupancy
count within each zone at different time scales. An interacting multi-model
Kalman filter technique is developed to improve occupancy counting accuracy.
Our numerical results using WiFi data collected at a university building show
that utilization of WiFi probe requests can be considered a viable solution
tool for zone-level occupancy counting in smart buildings.
