## 2 Related Works
### Open Issues  
The reviewed literature shows that there are multiple ways to use UAVs in different environments for activities that are mostly related to data collection, either by using sensors or for monitoring purposes (which involve the usage of sophisticated cameras embedded as part of the UAV itself). However, as far as the application domain in our paper is concerned, there are very few examples on how UAVs can be used, and none of them are conceived as a fully functional prototype the way it has been built and described in this paper. Table 1 shows the advantages and drawbacks of each of the studied proposals in relation to the ideas that we put forward as authors of this study. In a more specific way, the open issues can be described as follows:  
1. It is uncommon to use UAVs for the purposes and aims shown in this paper; many of the examples included deal with other aspects that, even when they show remarkable developments, do not intend to cover the purpose of measuring mobile network signals and parameters with a UAV. This creates a situation where there are multiple valid solutions that, unfortunately, cannot be applied or ported to the application domain shown in this paper. 2. Additionally, some of the papers studied in the reviewed literature rely on simulations to validate the hypotheses put forward. Although, depending on the context, this may be a valid methodology (it might even be that it is the only reasonable methodology to be used), it is usually more accurate and closer to reality using an actual prototype that will count on design, implementation and testing works to realize the contributions that are made to the existing state-of-the-art. 3. There is a degree of solution customization that is missing. This is due to the fact that, in several cases, instead of offering a system tailored for the purposes of the paper that is describing the research carried out, an already built UAV is used. This might \begin{table}
\begin{tabular}{c c c} \hline \hline
**Authors** & **Advantages** & **Disadvantages** \\ \hline
[10] & Usage of UAVs for wireless network measurements. & Simulated environment for some tailored use cases rather than actual prototype. \\ \multirow{4}{*}{[11]} & Antijam and accurate antenna parameters’ measurement framework is created. & No scope with open-source tool to perform mobile network measurements. \\ \multirow{4}{*}{[12]} & Autonomous Aerial Refuelling system designed. & Outside of the scope of this paper. Large UAV required for the application domain. \\ \multirow{4}{*}{[13]} & UAV can be used as a Mobile Measurement Platform (MMP). & No information or instructions regarding the application domain of this paper. \\ \multirow{4}{*}{[14]} & Proves that UAVs can be used for mobile network-related applications. & Focus oriented on the usability of UAVs as mobile base stations. \\ \multirow{4}{*}{[15]} & High precision aeromagnetic measurement equipment. & Requires large, oil-powered UAV. \\ \multirow{4}{*}{[16]} & UAV used for monitoring and parameter measurement in a natural environment. & Application domain far from the scope of this paper. \\ \multirow{4}{*}{[17]} & System created for Large-Scale Statistical Modelling of Air-to–Air Wireless UAV Channels. & Communications follow an Air-to-Air pattern; no GUI is provided. \\ \multirow{4}{*}{[18]} & Thorough study on how UAVs operate in congested wireless environments. & Application domain far from the scope of this paper. \\ \multirow{4}{*}{[19]} & Usage of UAV for measuring even fill and inter-fill erosion on the European loess belt. & Application domain far from the scope of this paper. \\ \multirow{4}{*}{[20]} & Usage of UAV for Normalized Difference Vegetation Index measurement & Application domain far from the scope of this paper. \\ \multirow{4}{*}{[21]} & UAV-based methodology to measure tree height for intensive forest monitoring & Application domain far from the scope of this paper. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advantages and disadvantages shown in the studied UAV-based applications.