# Handover Management for Drones in Future Mobile Networks--A Survey
## 2 Drone Networks
### Drones Applications in Mobile Networks  
Drone usage has dramatically risen in recent years due to their contribution to a wide range of solutions in a variety of fields, as illustrated in Figure 1. Drones have unique characteristics such as high mobility in 3D space, autonomous operation, and flexible distribution. This makes them attractive solutions for numerous applications including civilian, general safety, Industrial IoT (IIoT) platforms, protection, defense sections, cyber-physical systems, and atmospheric and ecological observation [10; 34; 35]. Drones can be extremely useful in a variety of civic and business applications when combined with 6G communication service, as illustrated later.  
Drones can effectively provide wireless communication services by acting as BSs or as UEs in the sky. Drones can establish multiple connections, such as, Drone-to-Drone Networks, Drone-to-Ground mobile serving networks, Drone-to-Ground mobile users, and Drone-to-Satellite Networks. Ref. [36] examined drones serving as BSs in HetNets. The study focused on a solution for improving the wireless coverage of terrestrial UEs. This enables drones to be used in areas where communication is unavailable. Moreover, they can assist networks by acting as data relays between UEs and BSs. Drones are flying platforms that support adaptive height. Most emerging applications demand safe and reliable wireless communication systems with highly low-latency and well-organized information  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Item** & **Descriptions** & **Item** & **Descriptions** \\ \hline HD-SOHP & Handover Detection Self-Organizing & SGW & Serving Gateway \\  & Handover Parameters & & \\ HetNets & Heterogeneous Networks & SINR & Signal-to-Interference-Plus-Noise Ratio \\ HMIPV6 & Hierarchical Mobile IPv6 & SRS & Sounding Reference Signals \\ HOF & Handover Failure & SSM & Same Speed Model \\ HOs & Handovers & STRAW & Street Random Waypoint \\ HOM & Handover Margin & T-BS & Target Base Station \\ H-RRM & HO And Radio Resource Management & TCP & Transmission Control Protocol \\ HSS & Home Subscriber Server & TTT & Time-to-Trigger \\ IDT & Internet of Drone Things & U2I & UAV-to-Infrastructure \\ IIoT & Industrial IoT & U2U & UAV-to-UAV \\ IoE & Internet of Everything & UAVDRONEs & Unmanned Aerial Vehicles \\ IoT & Internet of Things & UCB & Unit Control Block \\ KPIs & Key Performance Indicators & UEs & User Equipment \\ LAANC & Low Altitude Authorization and & UPF & User Plane Function \\  & Notification Capability & & Ultrareliable Low-Latency \\ LAN & Local Area Network & URLLC & Communication \\ LoS & Line-of-Sight & UTM & Unmanned Aircraft Systems Traffic \\  & & & Management \\ LTE-A & Long-Term Evolution & V2V & Vehicle-to-Vehicle \\ MAHO & Mobile-Assisted Handoff & V2X & Vehicle-to-Everything \\ MANETs & Mobile Ad Hoc Networks & VANETs & Vehicular Ad Hoc Networks \\  & Mission-Critical Machine-Type & VIP & Vehicular IP \\ mcMTC & Communication & & \\ MEC & Mobile Edge Computing & VR & Virtual Reality \\ MIH & Media Independent HO & Wi-Fi & Wireless Fidelity \\ MIMO & Multiple-Input Multiple-Output & WLAN & Wireless Local Area Network \\ MIPv4 & Mobile IP Version 4 & WMNs & Wireless Mesh Networks \\ MME & Mobility Management Entity & XR & Extended Reality \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._exchanges with the BS [5]. In current applications, drones are often equipped with specialized communication equipment or sensors to provide various services such as low-altitude surveillance, logistical applications, post-disaster rescue, and communication support.  
Two primary work directions are thoroughly examined: the integration of drones in an appropriate cellular network scheme for smooth service, and universal connectivity for specific use cases. As seen in Figure 2, this integration allows drones to serve in three broad directions. The systemic and technical issues that arise as a result of this integration must also be analyzed.