# A Practical Approach to Deploying a Drone-Based Message Ferry in a Disaster Situation +
## 4 Evaluation
### Results and Discussion  
Figure 11 shows the measured average achievable data rate of inter-LACS data transfer on various IEEE 802.11 protocols when the data size transmitted are 1 MB, 5 MB, 10 MB, 100 MB and 300 MB. The average achievable inter-LACS data rate increases with the data size. The average achievable data rate is lower for both 802.11 b and g on 2.4 GHz frequency band compared to that of 802.11 a, n and ac on 5 GHz frequency band. An overall average inter-LACS data rate of 4 Mbps, 14 Mbps, 23 Mbps, 68 Mpbs, and 141 Mbps for 802.11 b, g, a, n, and ac respectively. A slight decrease in the measured inter-LACS data rate is observed when the data size is 5 MB, 100 MB, and 300 MB for 802.11 g, b and n. The cause of this slight decrease is the result of high delays possibly due to packet processing, packet segmentation, packet fragmentation and aggregation where packets are divided into equal/smaller fragments to the IP Maximum Transmission Units (MTUs) and reassembled at the destination. Figure 10: Spectrum analyzer of the experiment environment. (**a**) Spectrum image of 802.11 b at 3 m. (**b**) Spectrum image of 802.11 b at 18 m.  
To confirm the effective transmission speed that the message ferry can achieve to transfer messages from the local headquarters to each disaster shelter, we need to account for the time it will take the message ferry to carry the message from point A to point B (i.e., local headquarters and disaster shelter). Therefore, we derived Equation (1) considering the parameters of the message ferry. Equation (1) consists of two parts. The first part considered the inter-LACS data rate that can be achieved to transfer data between two LACSs. The second part is based on the time taken by the message ferry (i.e., based on parameters such as the size of the data, drone velocity, and the distance the message ferry need to cover) to carry the data from the local headquarters to the disaster shelter. We calculate the effective transmission speed of the message ferry at various distances of 1 m to 20,000 m using Equation (1), where \(TS\) [Mbps] is the effective transmission speed, \(R_{b}\) [Mbps] is the data rate utilized at a particular time, v [m/s] is the speed of the drone, \(DS\) [Bytes] denotes the data size and \(D\) [m] is the distance. Moreover, the evacuee upload/download data to/from the standalone LACS installed in the disaster shelter, we assume that the size of the data to be transferred between the message ferry and the standalone LACS will be large. Therefore, the transmission speed of our proposed message ferry is calculated based on data size of 1 MB, 10 MB, 100 MB and 300 MB. \[TS=\bigg{(}2\times\frac{1}{R_{b}}+\frac{D}{8\times DS\times v}\bigg{)}^{-1}. \tag{1}\]  
Figure 12 shows the effective transmission speed of the message ferry on the 802.11 protocols using the overall approximate average achievable data rate obtained from the experiment when the inter-LACS data transfer size is 1 MB, 10 MB, 100 MB and 300 MB. The results confirm that the effective transmission speed increases as the overall average achievable data rate and data size increase. At a distance of 1 km as shown in Figure 12a, when the inter-LACS data transfer size is 300 MB and the overall achievable inter-LACS data rate is 141 Mbps for 802.11 ac, the effective transmission speed of the message ferry increased to an approximate 18 Mbps. In comparison, the message ferry using 802.11 ac outperforms other protocols: 802.11 b = 2 Mbps, 802.11 g = 5 Mbps, 802.11 a = 8 Mbps and 802.11 n = 14 Mbps. Similarly, as shown in Figure 12b,c, the same trend is confirmed. At a distance of 5 km and 10 km, the message ferry achieves higher effective transmission speed when the data size is 300 MB compared to other protocols. Figure 11: Inter-LACS data rate. Furthermore, our proposed message ferry is advantageous when transferring large data size when compared to other technologies such as Wi-SUN on a maximum data rate of 50 kbps and LoRa on 250 kbps.