# Ground Control System Based Routing for Reliable and Efficient Multi-Drone Control System  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)  
[PERSON]  
1 School of Electrical Engineering, Korea University, Seoul 02841, Korea; [EMAIL_ADDRESS] (W.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (K.K. ); [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (S.P)
communication for network disabled areas. In this study, drones are equipped with an additional network interface to provide network access to users and Internet of Things (IoT) devices, even in disaster areas or emergency situations, as shown in Figure 1. To actualize drone assisted wireless communications, it is most important to guarantee connectivity among drones and GCS. Since connection loss means that the GCS loses control of drones in a multi-drone control system, it is essential to construct a reliable and efficient network. However, messages are generally exchanged via wireless ad-hoc network, which is unreliable and frequently disconnected, and drone mobility aggravates network instability. Many studies have modified existing routing protocols, such as the mobile ad-hoc network (MANET), to provide a suitable network for drone systems [8; 9; 10]. However, there are fundamental differences between existing MANET and drone system network requirements. 1. Drones can move in any direction in three-dimensional air space, in contrast to ground nodes that can effectively only move in two-dimensions. Thus, drones can be deployed at any three-dimensional location forming significantly more complicated network topologies. 2. Drones have much higher level of mobility than MANET nodes, hence network topology frequently and significantly changes. 3. Line of sight (LoS) is usually assured in the air since there are usually no obstacles. Thus, communication range between drones can be significantly larger than between ground nodes, and link cost estimation can be simplified. 4. Guaranteed connections among drones are essential. Disconnection of any link may cause critical problems because control messages are transmitted through multi-hop communication. Therefore, MANET based routing protocols fundamentally have significant limitations, as follows. * They are not ideal for drone systems, where link quality rapidly changes and node mobility is high, since their original target nodes have limited mobility. * They cannot utilize GCS, which is a significant component of drone systems, because they are fundamentally based on MANET protocols. * They inevitably incorporate fundamental MANET protocol limitations, such as constant exchange of HELLO message and repetitive path finding. These limitations significantly degrade drone system performance, hence MANET based routing protocols are unsuitable for drone networks.