# Mobility Management of Unmanned Aerial Vehicles in Ultra-Dense Heterogeneous Networks
## 4 Research Challenges
### General Challenges of Connected UAVs  
One of the main concerns is the dangers associated with monitoring airborne applications. Pilot preparation, flight length, climate conditions, and risk restrictions are all key factors when transporting a tracked flying machine [66; 67]. Connected UAVs and unmanned aerial system (UAS) technology can be used to place unmanned airships in situations where a human pilot cannot be placed due to various risks. UASs can also be used to gather extensive information regarding the progress of human activities to aid in risk mitigation and reduce the amount of time people spend in potentially dangerous situations. UAS is fully embraced by several development organizations to help mitigate the risks associated with various situations, such as foundation reviews, for instance. The \begin{table}
\begin{tabular}{c c c} \hline \hline
**No** & **Challenge Group** & **Summary of Challenges** \\ \hline \multirow{4}{*}{1} & \multirow{4}{*}{General and main challenges of connected UAVs} & \multirow{4}{*}{Connected UAV technology is used to place unmanned airships in situations where a human pilot cannot be placed due to risks. Maintenance personnel can employ UAS to conduct an initial inspection from the ground, avoiding perilous climbs and reducing casualties. The key concerns here are the risks connected with monitoring airborne applications. Pilot preparation, flight length, weather conditions, and risk constraints are all significant factors to consider. \\ \hline \multirow{4}{*}{2} & \multirow{4}{*}{UAV operations in LTE} & LTE technology is well suited to serve air vehicles, particularly at low altitudes, and this provides great potential for the rapid growth in the number of UAVs in use. This, in turn, creates numerous commercial opportunities for modern communications, which consequently requires improvements to LTE networks in the future to readily serve the anticipated rapid growth of aircraft. \\ \hline \multirow{4}{*}{3} & \multirow{4}{*}{Mobility in 3D} & Aerial and ground UEs are based on different assumptions. UAVs for network services are different from traditional networks in that they use a 3D model rather than a 2D model. UAVs are incredibly mobile, making control and decision-making difficult. As a result, advanced mobility solutions will be required. \\ \hline \multirow{4}{*}{4} & \multirow{4}{*}{UAV–ground channels} & One of the most complex design difficulties in producing cellular-connected UAVs is creating coexisting mechanisms between terrestrial and airborne users. UAV–ground interference management must be installed to achieve this coexistence. The communication channel between the ground BS and UAVs has extremely distinct interruption patterns. The elevation or angle of the UAV influences channel parameters such as shadowing and path loss exponents. These can be used in residential or sub–residential environments, depending on deployment. \\ \hline \multirow{4}{*}{5} & \multirow{4}{*}{Transmission protocols} & UAVs can scan and capture data while dropping data packets, according to several patent applications. Transmission Control Protocol/Internet Protocol (TCP/IP) will be insufficient for UAVs. As a result, new methods based on UAV mobility must be devised. \\ \hline \multirow{4}{*}{6} & \multirow{4}{*}{Dominance of LoS} & When aerial and terrestrial users work together, UAVs cause considerable BS disturbance. Existing UAV HO experiments have shown to possess several shortcomings. Due to their high mobility, UAVs are frequently susceptible to HOs and the ping-pong effect. \\ \cline{1-1} \cline{2-3}  & & \\ \cline{1-1} \cline{2-3}  & & \\ \cline{1-1} \cline{2-3}  & & \\ \cline{1-1} \cline{2-3}  & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of research challenges throughout the literature. vast majority of assessments rely on 'human eyes' on the ground to inspect the condition of basic components and determine whether or not maintenance is required.