Soft Fall Detection With a Height-Tracking Method Based on MIMO Radar System

Radar-based fall detection technology has attracted much attention for its high accuracy, robustness, and privacy preservation potential. Detection of "Soft Fall," i.e., high-freedom fall, is the key to practical application. This letter proposes a novel height-tracking method based on a multiple-input multiple-output (MIMO) radar system to address this problem. First, the received signal was segmented into a time sequence with a sliding window along slow time. Next, fast Fourier transform (FFT) and multiple signal classification (MUSIC) algorithms were applied to estimate the general trend of the human body's time-varying range and pitch angle information. Then, they were fused with a geometrical relationship to describe height changes during fall motions using a height trajectory map. Two height-based features were extracted as input to support vector machine (SVM) to distinguish soft fall and fall-similar motions. Finally, experiments, including four soft fall and five typical fall-similar motions, were conducted to demonstrate its feasibility and superiority.