I. Introduction
Device-free localization (DFL) is continuously an attractive topic due to the booming of location-based services [1], [2]. Among existing hardware utilized for DFL [2]–[6], the pyroelectric infrared (PIR) sensor is much promising due to its advantages of low cost, low power consumption, and privacy protection. Typically, the price of a PIR sensor is less than 1 dollar, and the power consumption of a PIR sensor is only about [7]. In addition, since the PIR sensor only senses the intensity of infrared radiation, it usually causes less concern of privacy leakage than the camera-based systems.