“…Due to the non-directly observable nature of wireless signals, unlike directly visible videos or images, they can protect user privacy. Extensive recent efforts with various wireless signals, such as Wi-Fi [ 16 , 17 , 18 ], RFID [ 19 , 20 , 21 ], acoustic [ 22 , 23 , 24 ] and mmWave [ 25 , 26 , 27 ], have been devoted to inferring gestures. Wi-Fi devices can be easily and inexpensively deployed in most home and office environments, which makes them more promising.…”