# Fall Detection Based on Continuous Wave Radar Sensor Using Binarized Neural Networks
## 2 Experimental Setup and Measurement  
Data measurements were performed with 24 GHz CW radar from Infineon's Sense2 GoL Development Kit [23]. The detailed specifications of the radar are listed in Table 1. The radar sensor and experimental environment are shown in Figure 1. The size of the experimental environment is 3 \(\times\) 2.5 m\({}^{2}\). The radar was positioned 1.3 m above the ground. Further, because only micro-Doppler signatures were used, the distance between the radar and the participants was flexible. The distance was set between 1 and 4 m to account for the indoor environment while remaining within the radar's maximum measurement range. Additionally, lighting conditions were adjusted to simulate both daytime and nighttime scenarios, and the indoor temperature was varied by opening or closing the window. Five male and female participants with varying heights, weights, and ages participated in the experiment. The Doppler effect, which measures the speed of radar, varies depending on the direction of motion of the target relative to the radar. However, as falls can occur in any direction, we configured the actions in various directions and measured data at different speeds, even within the same action. For example, when standing, a fall can occur in any direction. To account for this, the cases of 0\({}^{\circ}\) (forward), \(\pm\)90\({}^{\circ}\) (left/right), and 180\({}^{\circ}\) (backward) were selected based on the radar's line of sight. Conversely, when sitting on a chair or sofa, only the cases of 0\({}^{\circ}\) (forward) and \(\pm\)90\({}^{\circ}\) (left/right) were considered, taking the backrest into account. Examples of the actions are shown in Figure 2. There were five fall actions, labeled (a)-(e), and six non-fall actions, labeled (f)-(k).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Frequency & 24.125 GHz \\ Minimum speed & 0.5 km/h \\ Maximum speed & 30 km/h \\ Maximum distance & 15 m \\ Horizontal \(-\)3 dB beamwidth & 80\({}^{\circ}\) \\ Elevation \(-\)3 dB beamwidth & 29\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Radar specifications.  
Figure 1: Radar sensor used and experimental environment: (**a**) radar sensor; (**b**) experimental environment.  
Figure 2: Examples of actions: (**a**) standing and then falling forward; (**b**) standing and then falling to the left/right; (**c**) standing and then falling backward; (**d**) sitting and then falling forward; (**e**) sitting and then falling to the left/right; (**f**) walking slowly without moving arms; (**g**) walking quickly whites winging arms; (**h**) squatting; (**i**) sitting on a chair; (**j**) standing up from sitting on a chair; (**k**) lying down and then lifting the upper body. Arrows indicate the direction of movement of the upper body or arm.  
The results are summarized in Table 2. The total number of data points was 2192, with 1017 and 1175 representing fall and non-fall data, respectively. For (b), there were 306 data points, with 153 for falling to the left and the remaining 153 for falling to the right. Similarly, for (e), out of 270 data points, 135 fell to the left, and the remaining 135 fell to the right.