# Through-Floor Vital Sign Searching for Trapped Person Using Wireless-Netted UWB Radars
## 4 Results
### Experimental Results  
As shown in Figure 8a, the performance of the proposed vital sign searching based on different observation is verified and evaluated using a through-floor experiment, in which four wireless-netted connected UWB life-detection radars are adopted. The size of the floor is 3.2 m \(\times\) 4 m, with one pipeline inside. The position of the simulated trapped person is marked by the yellow diamond in Figure 8c. One human test subject lay on the ground with weak respiration, acting as a trapped person (see Figure 8b), and the radar echoes are obtained from 10 time detections (see Figure 8c). To confirm the spatial location of the human test subject, we can select any four time detections to form an available vital sign searching path, which is marked by the green arrow in Figure 8c.  
The detailed experimental results in such a vital sign searching process are listed in Table 3. Firstly, the detection results from the No. 7, No. 8, No. 9, and No. 10 radars are  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Searching Path** & **Observation Point 1** & **Observation Point 2** & **Observation Point 3** & **Observation Point 4** \\ \hline  & (\(-\)3.75 m, 4.58 m, 0 m) & (0.42 m, 2.92 m, 0 m) & (2.08 m, \(-\)1.25 m, 0 m) & (3.75 m, \(-\)2.92 m, 0 m) \\ \hline No. 1 radar result & 13.4 m & 9.69 m & 5.8 m & 4.26 m \\ No. 2 radar result & 12.61 m & 8.84 m & 5.15 m & 4.27 m \\ No. 3 radar result & 13.89 m & 8.71 m & 5.73 m & 3.96 m \\ No. 4 radar result & 12.28 m & 8.56 m & 4.5 m & 3.98 m \\  & (0.31 m, 1.72 m, 11.76 m) & (0.94 m, \(-\)3.19 m, 6.63 m) & (3.52 m, \(-\)3.88 m, 4.27 m) & \\ Output & (0.31 m, 9.14 m, 11.69 m) & (0.94 m, 1.28 m, 8.48 m) & (3.52 m, \(-\)1.53 m, 5.04 m) & \\  & (4.67 m, 1.72 m, 9.73 m) & (3.57 m, \(-\)3.19 m, 5.26 m) & (4.61 m, \(-\)3.38 m, 4.08 m) & (3.72 m, \(-\)3.75 m, 3.77 m) \\  & (4.67 m, 9.14 m, 8.44 m) & (3.57 m, 1.28 m, 8.30 m) & (4.61 m, \(-\)1.53 m, 4.29 m) & \\ \hline \hline \end{tabular}
\end{table}
Table 2: The simulated result for the vital sign searching path.  
Figure 7: The simulated result of searching for a trapped person along a searching path.  
performed to calculate the next possible observation point. The corresponding observation point 1 is (0.8 m, 1.2 m, 3.75 m). The output result of (\(-\)0.38 m, 0.02 m, 4.19 m) indicates that the next observation point might be \"observation point 2 (\(-\)0.4 m, 0 m, 3.75 m)\". Subsequently, the final observation point might be \"observation point 3 (\(-\)0.4 m, 0.8 m, 3.75 m)\", and the output result of (\(-\)0.47 m, 0.79 m, 3.76 m) should be the spatial location of the vital sign of the trapped person, which is in accordance with the experimental setup. Similar to the simulation, this process can also be illustrated by Figure 9. The vital sign searching path composed of three observation points can be formed (marked by the green arrows).  
Figure 8: The experimental setup. (**a**) The four wireless-netted UWB life-detection radars deployed on a floor; (**b**) the human test subject acting as a trapped person; (**c**) the top view of the 2D observation aperture and the vital sign searching path.