## 3 Validation of MANTiS-32 Sensing Performance
### Wireless Communication Performance Assessment of the MANTiS-32 System  
In wireless structural monitoring systems, communication range and transmission stability are key determinants of data reliability. Civil infrastructure, such as bridges, often exists in environments where unforeseen physical obstructions can disrupt signal paths, resulting in data degradation. To ensure accurate and continuous monitoring of structural behavior, especially under high-frequency sampling conditions, the wireless system must maintain consistent and robust communication performance. The MANTiS-32 system was designed to operate over the 2.4 GHz Wi-Fi band, with the specific objective of sustaining reliable data transmission even in obstructed or partially enclosed environments. This capability is particularly critical for field applications, where environmental variability and structural complexity pose significant challenges to long-range wireless communication. To evaluate the system's communication performance, a series of experiments were conducted to assess the transmission range, received signal strength, and data acquisition rate under various sampling frequencies. As illustrated in Figure 9, the distance between the MANTiS-6050 sensor module and the MANTiS-32 unit was incrementally increased from 20 m to 100 m, in steps of 20 m. A 3 dBi external antenna was employed to support signal propagation, and excitation was applied using an electrodynamic shaker, as shown on the left side of Figure 9. To simulate a realistic obstructed environment, a temporary partition wall was installed between the MANTiS-32 hub and the access point (AP), creating a semi-enclosed space representative of field conditions. This setup was intended to verify the MANTiS-32's ability to maintain high-fidelity wireless data transmission under shielded environment conditions, further validating its applicability to complex civil infrastructure monitoring scenarios. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Division**} & \multicolumn{3}{c}{**Excitation**} & \multicolumn{3}{c}{**Measurement Results**} \\ \hline \multirow{2}{*}{**Sensor No.**} & \multirow{2}{*}{**Axis**} & **Amp.** & **Freq.** & **Amp.** & **Error** & **Freq.** & **Error** \\  & & **(g)** & **(Hz)** & **(g)** & **(\%)** & **(Hz)** & **(\%)** \\ \hline \multirow{4}{*}{5} & \(x\) & 0.5 & 7.0 & 0.50 & 0.0 & 6.97 & 0.43 \\ \cline{2-8}  & \(y\) & 1.1 & 10.0 & 1.09 & 0.9 & 9.95 & 0.50 \\ \cline{2-8}  & \(z\) & 1.7 & 13.0 & 1.67 & 1.8 & 12.95 & 0.39 \\ \hline \multirow{4}{*}{6} & \(x\) & 0.6 & 7.5 & 0.59 & 1.7 & 7.49 & 0.13 \\ \cline{2-8}  & \(y\) & 1.2 & 10.5 & 1.19 & 0.8 & 10.45 & 0.48 \\ \cline{1-1} \cline{2-8}  & \(z\) & 1.8 & 13.5 & 1.76 & 2.2 & 13.45 & 0.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 9: Schematic of wireless communication performance test by distance and signal strength. At each measurement point, the Received Signal Strength Indicator (RSSI) was measured ten times, and the average signal strength was computed using Equation (1). To further evaluate communication performance, the sampling frequency was systematically increased to 20 Hz, 50 Hz, 100 Hz, and 200 Hz at each distance interval. The data acquisition rate was quantified by calculating the proportion of successfully received data relative to the total transmitted data, thereby assessing transmission reliability as a function of both distance and sampling frequency. \[Signal\ Strength(\%)=\frac{RSSI_{average}-RSSI_{min}}{RSSI_{max}-RSSI_{min}} \times 100 \tag{1}\]  
Here, \(RSSI_{average}\) denotes the average value of the 10 measurements conducted under identical conditions, while \(RSSI_{min}\) and \(RSSI_{max}\) represent the minimum and maximum values observed, respectively. As summarized in Table 3, the measured signal strength remained above 80% at up to a distance of 40 m, with average RSSI values of 88% at 20 m and 85% at 40 m (Figure 10).