# Communication Interface Manager for Improving Performance of Heterogeneous UAV Networks
## 6 Obtained Results
### Application Evaluation
The best proportion was achieved by the IM in all scenarios as shown in Figure 8. This is also shown in the last column (Flow (n)) in Table 3. In all scenarios, the IM presented the best Tx and Rx packets relation with the highest number of packets trafficked, in the order of 3 \(\times 10^{6}\), 4.25 \(\times\)\(10^{6}\), and 3.75\(\times\)\(10^{6}\) with 1 \(\times\)\(10^{6}\), 5 \(\times\)\(10^{5}\), and 4.5 \(\times\)\(10^{5}\), for three, five, and eight nodes, respectively. This highlights that the IM produced almost twice the average throughput of both interfaces applied homogeneously. Another conclusion that can be obtained from Figure 8 is that although the 802.11p interface had the lowest flow rate in all scenarios presented in Figure 7, its packet productivity was similar to that of the 802.11n interface, even considering its lowest nominal bandwidth. This may have occurred because the packet production interval for this technology is shorter than that for 802.11n. The header size of the WAVE protocol requires a 32 \(\upmu\)s transmission time to the physical preamble, as opposed to the 96 \(\upmu\)s of 802.11n, as stated in [15]. Figure 7: Average network throughput. Figure 9 shows the resulting packet delivery ratio (PDR) (see Equation (5)) from the network packet generated by the U2U communication. This metric relates to the network packet delivery capacity. This capacity refers to the packets ratio delivered originating from the source node in its application layer, CBR, and the number of packages received by the CBR sink at the final destination [43]. It can be observed that the IM produced the best delivery rate in all scenarios, followed by the 802.11p interface. In this case, the IM presented the best PDR rate, 0.977, which was observed in the five-nodes scenario. In this scenario, the existence of intermediate waypoints allowed a significant increase in the amount of packets trafficked (as shown in Figure 8) and, consequently, an increase in the PDR. As the intermediate waypoints were applied to the UAVs, increasing their courses (UAV-2 and UAV-4 had intermediate waypoints), this allowed these nodes to stay longer within the neighbors' coverage area: UAV-1 and UAV-3 covered UAV-2, while UAV-3 and UAV-5 covered UAV-4. For the three- and eight-node scenarios, the IM presented PDRs of 0.760 and 0.571, respectively, which implies that more messages were exchanged during the flight compared with using the interfaces homogeneously. In practical terms, we concluded that the IM provided 76% (three-nodes scenario), 97% (five-node scenario), and 57% (eight-node scenario) of the effective capacity to exchange messages during the flight. This demonstrates that the switching resulting from the IM decisions between the available interfaces increases the effectiveness of the network in maintaining connectivity. \[PDR\left(\%\right)=Amount\ of\ Rx\ Packets/Amount\ of\ Rx\ Packets+Amount\ of\ Loss\ Packets \tag{5}\]  
A useful observation is that the IM performance in the five-node scenario, which included intermediate waypoints, highlights the idea that the use of relay UAVs or intermediate relay nodes can be beneficial for distances between vehicles greater than 70 m.  
Figure 8: Amount of packets (_n_) trafficked. Table 3 presents the average end-to-end delay, latency, and flow of messages in all three scenarios. Each message flow was composed of 1472 byte packages, which simulated a typical application message transmitted between UAVs. The end-to-end delay (ms) and the latency (ms) describe the average obtained from all received packets. As can be observed, the IM performed worse in end-to-end delay (highest value) in all scenarios. In terms of latency, the IM was last only in the three-node scenario, but was ranked second in the other scenarios (ahead of 802.11n). The 802.11p applied homogeneously produced the best performance in end-to-end delay and latency for all scenarios; one should recall, however, that this was achieved with a low messages flow.