# Cellular and Virtualization Technologies for UAVs:
## 4 Testbed Experimentation  
### Communication Performance Evaluation  
In this section, the UAVs communication performance has been evaluated to guarantee that it meets the requirements defined by the 3 GPP in Release 15 (TR 36.777) [50]. These requirements are based on three network parameters: (i) data rate, which should be set between60 and 100 Kbps for command and control in both downlink and uplink; (ii) reliability, which should be below \(10^{-3}\) of packet error rate in both downlink and uplink; and (iii) latency, which should be below 50 ms (100 ms of RTT) in the downlink. It should be noted that these KPIs are related to management assignments (C2). Each particular service will have its individual KPIs (for example, real-time video streaming KPIs are quite different). We have first tested the quality of the Internet connection with the well-known Ookla speed test (Ookla speed test: [[https://www.speedtest.net/](https://www.speedtest.net/)]([https://www.speedtest.net/](https://www.speedtest.net/)) (accessed on 27 April 2020)). The speed test uses public servers to perform a quick and realistic diagnosis of Internet connectivity. In this context, the network performance was also tested from the UAV upon the UAV-controller since, in practical experimentation, the minimum values have to be met against this entity. Other limiting factors may arise in the second experiment, such as using a VPN service (since all the traffic should traverse the VPN server). Experiments have been replicated with the three available mini PCIe and a commodity smartphone (Xiaomi Redmi Note 95). The purpose of repeating the same experiments employing different devices is to determine if the potential limiting factors are procured from either the cellular network characteristics, e.g., the status of the network, the antennas used, the strength of the signal at certain points of time, or the devices themselves (i.e., checking if the devices could be limiting the quality of the connection due to a hardware/software limitation). Likewise, experiments have been conducted using two different Internet Service Providers (ISP) to check if connectivity performance varies depending on the network operator. The selected ISPs are Movistar and Yoigo (the first and the fourth operator in Spain ranked by the number of users). Twenty repetitions of the experiment have been conducted at different time intervals randomly distributed throughout the day to ensure that the external effects are not reflected (or at least mitigating their effect as much as possible) in the results. The main purpose of these measurements is not to characterize the network, as this would require an extensive set of measurements with varied coverage areas and having an insight of the network infrastructures involved to rule out any other factors having an effect on the results achieved. The main purpose instead is to verify whether the results fulfill the 3 GPP KPIs. As it can be appreciated in Figure 3(a) both downlink and uplink are considerably limited for the Telit mini PCIe due to its technical characteristics, which define a nominal rate of 10 Mb/s in downlink and 5 Mb/s in the uplink, regardless of the selected ISP. On the other side, experiments with Qualtec mini PCIe should not be so limited since its nominal rate is 150 Mb/s and 50 Mb/s in downlink and uplink, respectively. However, after comparing with the smartphone and SIMCom PCIe results, both the downlink and uplink appear to be limited despite its technical characteristics (i.e., it has been demonstrated with the SIMCom results that the performance of the network is superior to that obtained by Qualtec PCIe). Finally, the SIMCom PCIe results improve the results obtained with the smartphone, which can be considered the benchmark. It should be noted that the Waveshark HAT, in combination with the SIMCom modem, has a notably higher price than the rest of the selected equipment, so we can infer that the performance is better because it belongs to an upmarket product.