1. A method comprising: transmitting, via at least one transmitting antenna, ultra-wide band (UWB) radio frequency (RF) signals at an environment including at least one human, and receiving, via at least one receiving antenna, echo signals from the environment; processing the received echo signals to yield a range-bin-based slow signal that is spatially characterized over a plurality of spatial range bins; removing motion related components from the slow signal and deriving a range-bin power spectrum therefrom to identify a respiration-related region of interest; deriving from the respiration-related region of interest a respiration signal; applying a PCA (principal component analysis) on earlier-derived slow signals to estimate a respiration signal; extracting the at least one respiration feature from the respiration signal; and classifying the at least one respiration feature to indicate a respiration mode of the at least one human.