# On the Performance of a UAV-Aided Wireless Network Based on NB-IoT
## 5 Results and Discussion
In Figure 13, the value of \(\Delta\tau_{\text{avg}}\) is affected more by increasing UAB speeds rather than increasing UAB heights. Figure 5.4 Percentage of served IoT nodes for different UAB speeds and heights in the TSP path. To summarize our findings into three main points, which reflect the previously mentioned key contributions, we can state that:  
Figure 5.5 Energy consumption of IoT nodes for different UAB speeds and heights in the TSP path. Figure 5.6 Access rate for different UAB speeds and heights in the TSP path. Figure 5.7 Perceived latency of IoT nodes for different UAB speeds and heights in the TSP path. Simulations performed have accounted for all the described NB-IoT standard parameters, from the random access procedure to the precise scheduling in uplink transmission with the three NB-IoT coverage classes;
* we jointly investigated a number of performance metrics related to the IoT field, namely (i) the number of completely served nodes, (ii) the achieved network throughput, (iii) the perceived latency and (iv) energy consumption of nodes. Numerical values achieved are related to the scenario under consideration and may scale accordingly. Different IoT applications may prefer one metric over the others as its main requirements, but our results show that pursuing one usually improves also the other metrics;
* as evinced from the analyzed results, the TSP trajectory performs better than the others in terms of successful transmissions, latency and throughput, making it the most promising among the three for cellular IoT (e.g., NB-IoT) applications. As expected, the prevailing trajectory in terms of performance is scenario-dependent. Moreover, in our results, one can extract the behaviour of UAV networks with respect to speed and height; in particular, the UAV speed should be taken under control, since it might abruptly decrease the performance metric if kept too high. Thanks to our number of outcomes and simulations (and the variety of real scenarios that could apply to our system model), we can discuss results further and broaden our findings to different cases. In the numerical evaluation, we first identify which are the relevant factors an operator must take into account when deploying this kind of system. First, the speed undergoes a trade-off between average perceived latency and throughput from one side to total number of successfully served nodes on the other. In this sense, the NB-IoT protocol plays a relevant role, since too higher speeds do not allow the completion of the RA procedure, and therefore the scheduling of uplink resources in the NPUSCH. Moreover, though a larger altitude would grant an increased NB-IoT nodes connectivity, increases the transmitter-receiver distance, which has again a negative impact on the successful completion of the RA procedure. From our results, we can also infer conclusions on the trajectory selection. We can state that the circular trajectory, as would be for any path that travels the perimeter of a convex figure, is neither an effective trajectory in terms of latency nor a robust choice for the service of a massive number of IoT nodes. In fact, it is not able to follow the particular deployment of nodes for a given service area. On the other hand, a Paparazzi trajectory seems a good alternative, since it ensures to scan the overall service area. This might be a fair solution if a mobile operator does not know a priori the location of nodes. However, because of the fact that this information is usually easy to retrieve and that the Paparazzi trajectory becomes expensive in terms of energy consumption and latency, is probably not desirable. This confirms the expectations on the robustness of the TSP path. If we want to achieve the 100% successfully served nodes, the use of multiple UABs might be necessary. However, this can apply only for those trajectories reaching full nodes connectivity, as for the case of TSP and Paparazzi. In fact, an n-th UAB, following the path of its predecessors, will address only those nodes not previously served.