# A Practical Approach to Deploying a Drone-Based Message Ferry in a Disaster Situation +
## 4 Evaluation
### Experiment Setup  
The aim of the experiment is to confirm the data transfer rate between the message ferry and a standalone LACS that is installed in the disaster shelter. In addition, the performance evaluation confirms the effective transmission speed of the message ferry that can be achieved for transferring data from the local headquarters to the shelters. Figure 9 shows the experimental environment. As illustrated, we used the LACS prototype, a computer running Wireshark to capture traffic to/from the standalone LACS, and a mobile phone  
Figure 8: Demonstration test of the drone-based message ferry. (**a**) Take-off of a drone attached with LACS. (**b**) Drone attached with LACS in the air. Figure 7: The message ferry as a link in the LACS network. connected to the standalone LACS via Wi-Fi. Since the weight of LACS (i.e., around 4.5 kg) is more than the maximum weight the drone of the message ferry can safely carry, we conducted the experiment using a mobile phone (i.e., the drone mounted with LACS is replaced with a mobile phone in the experiment.) The development of a smaller and compact size LACS is ongoing and will be utilized in the actual demonstration test of the message ferry in the future. The LACS's access point [34] frequency band is set to 2.4 GHz and 5 GHz. For the 2.4 GHz frequency band, the protocol setting is changed to IEEE 802.11 b and 802.11 g, while the following protocols: IEEE 802.11 a, 802.11 n, or 802.11 ac is selected for the 5 GHz frequency band. The 5 GHz band has a maximum data rate (theoretically) of 866 Mbps for IEEE 802.11 ac and 400 Mbps for the 2.4 GHz band [35]. The protocol used for each part of the experiment is verified with a Wi-Fi analyzer. In addition, we changed the distance between the mobile phone and LACS from 3 to 18 m. At each distance, the LACS is used to transfer data to/from the mobile phone. The traffic transmitted between the LACS and the mobile phone is captured by the Wireshark running on the computer. The size of the data (i.e., information to be delivered/collected) transferred between the mobile phone and the standalone LACS is between 1 MB-300 MB. Table 1 shows the settings and the parameters for the experiment. In order to prevent interference from other radio waves, we performed the experiment in the anechoic chamber. Figure 10 show the measured results of the spectrum during the experiment. It was confirmed that there is no other wireless signal present during \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Number of LACS & 1 \\ \hline Protocol & b/g, \\  & 802.11 ac/n/a \\ \hline LACS AP frequency band & 2.4/5 GHz \\ \hline Channel width & 20/40/80 MHz \\ \hline Maximum Data rate & 11, 54, 300, 866 Mbps \\ \hline Number of movable LACS (mobile phone) & 1 \\ \hline Distance to LACS & 3–18 m \\ \hline Data Size & 1–300 MB \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experiment Parameters. Figure 9: Experimental environment. the experiment. As shown in Figure 10a, at a distance of 3 m, the spectrum analyzer confirms that the peak transmission power level of the wireless signal at a center frequency of 2.4 GHz on channel 6 is \(-\)40.0 dBm for 802.11 b. Furthermore, the distance between LACS and the mobile phone was increased to 18 m and the spectrum analyzer was placed in a fixed position during the experiment. It was confirmed that the transmission power of the wireless signal increased to a peak level of \(-\)22.5 dBm at a center frequency of 2.45 GHz on the same channel and protocol as shown in Figure 10b. The changes in the waveform observed in Figure 10b is as a result of the LACS using more transmission power (i.e., 17.5 dBm increase) to send a message to the mobile phone when the distance is changed from 3 to 18 m.  
The message ferry will be used to transfer the important information (i.e., to/from the standalone LACS) from the local headquarters to the disaster shelters. We measure the achievable data transfer rate of the inter-LACS data transfer between the message ferry and the standalone LACS.