transmitting, by a first wireless device, a wireless signal through a wireless multipath channel in a venue;
receiving, by a second wireless device, the wireless signal through the wireless multipath channel, wherein the received wireless signal differs from the transmitted wireless signal due to the wireless multipath channel and a movement of an object in the venue;
obtaining a time series of channel information (TSCI) of the wireless multipath channel based on the received wireless signal;
computing a spatial-temporal information (STI) based on a time-domain auto-correlation function (ACF) of channel information (CI) in a first sliding time window of the TSCI computed based on a first feature of each CI;
computing a gait score based on the STI;
computing a time series of resampled CI (TSRCI) by resampling the TSCI;
computing a proximity score based on a frequency-domain k-component correlation of resampled CI (RCI) in a second sliding time window of the TSRCI computed based on a second feature of each RCI; and
detecting a proximity state of the object to a target in the venue based on the gait score and the proximity score in a third sliding time window.