# Communication Interface Manager for Improving Performance of Heterogeneous UAV Networks
## 6 Obtained Results
### Application Evaluation  
Network throughput is the first of the application metrics to be discussed. This metric was chosen to evaluate the data flow of the nodes and, consequently, the effective exchange of messages during the flight, considering their different adopted speeds (equal to or greater than 10 m/s). The average network throughput was calculated based on the average throughput obtained by the amount of messages received by the nodes in each network experiment, as stated in Equation (4). \[\textit{Average Network Throughput}=\frac{\sum_{k=1}^{N}\frac{\textit{ Amount of Rx Bytes}(k)}{\textit{Last Time Rx Packet (k)+First Time Tx Packet (k)}}}{N} \tag{4}\]  
This is composed of bytes received in each message exchanged (amount of Rx bytes (\(k\)), i.e., data flow), considering the last packet reception time and the first packet transmitted of each data flow (\(k\)), divided by the amount of network traffic (\(N\)). Figure 7 shows the average network throughput from each experimental scenario. The IM performed best in all three scenarios. Another aspect of this experiment was that the throughput ratio decreased while the number of nodes increased. This was expected because the CBR data rate was divided by the number of nodes. Thus, the IM presented 2.5 Mbps in comparison with 0.5 Mbps for 802.11p and 1 Mbps for 802.11n for the three-nodes experiment. In the fives-nodes experiment, the IM presented 1.55 Mbps in comparison with 0.25 Mbps and 0.4 Mbps for 802.11p and 802.11n, respectively. Finally, for the eight-nodes experiment, the IM presented 0.62 Mbps against 0.15 Mbps (802.11p) and 0.25 Mbps (802.11n). Another observation was that the 802.11n interface, in all three scenarios, always produced twice the 802.11p throughput. This highlights the intrinsic difference in the channel bandwidth of these interfaces, 20 MHz for 802.11n and 10 MHz for 802.11p. The 802.11n interface can have a bandwidth up to 40 MHz using two frequency channels. However, to perform a fair comparison, this was reduced to 20 MHZ with the use of only one frequency channel. Analyzing the three- and eight-node scenarios, with the average throughput obtained by the network using the IM system, in the three-node experiment, it would be possible to send about 260.41 samples of GPS coordinates per second, considering the use of a GPS device with 9600 bps resolution and about five frames per second of a 640 \(\times\) 420 (480p) resolution video. For the eight-nodes experiment, it would be possible to send 83.33 samples of GPS coordinates per second and about 1.6 frames per second of the same video. We concluded that this amount of GPS samples is favorable for the proposed SAR experimentation scenarios. In the case of the three-node experiment, the resolution and frames obtained from a possible video transmission by an MP4 resolution camera were satisfactory. However, for the eight-node scenario (more sparse scenario), some method of signal relay should be adopted for this video transmission resolution. Improving this will be the focus of future investigation. Figure 8 presents the amount of packets (\(n\)) trafficked in the network considering all the network traffic generated by the complete mission execution. The total amount of packets transmitted and received over the network during the three experiments represents the total volume of data trafficked by the network and, implicitly, the amount of packets lost (total of packets transmitted minus the amount of packets received). This metric describes the productivity of the network, that is, the more packets delivered, the more productive the adopted network settings. It allows a higher message recovery rate and, consequently, a higher volume of effective messages.