# Ground Control System Based Routing for Reliable and Efficient Multi-Drone Control System
## 2 Related Work  
Several previous studies have considered aerial networks, such as unmanned aeronautical ad-hoc networks [14], airborne network [15], UAV ad-hoc network [16], etc. However, despite the different names, these have largely only considered aerial ad-hoc networks. The flying ad-hoc network (FANET) was subsequently defined [17], where all UAVs constituted an ad-hoc network but only a subset communicated with the GCS. FANET nodes fundamentally move more freely and have higher mobility than nodes in traditional networks such as MANETs or vehicular ad-hoc networks (VANETs). Thus, it is essential to guarantee reliable peer-to-peer connection among FANET nodes for collaboration and coordination between multiple UAVs. Since FANET is a new form of MANET, most studies modified existing MANET routing protocols, i.e., proactive (PRP) and reactive (RRP) routing protocols, to make them suitable for FANET. For example, [PERSON] et al. proposed directional optimized link state routing protocol (DOLSR) [8] based on optimized link state routing protocol (OLSR) [18], one of widely used PRPs, that minimized the number of multipoint relays by using UAVs equipped with directional antennas. They verified that DOLSR reduced both end-to-end delay and the number of overhead packets by simulation. In contrast, [PERSON] et al. developed a FANET testbed [9] based on a commonly employed RRP, dynamic source routing (DSR) [19]. [PERSON] et al. also proposed a routing protocol using time slot allocation to coordinate communication between UAVs [10] based on ad-hoc on-demand distance vector routing (AODV) [20]. Simulation results showed that the proposed routing protocol minimized packet drops and improved communication quality of service. Thus, the various routing protocols were not ideal for FANET where link quality rapidly changes and node (drone) mobility is high. Previous protocols also failed to consider GCS, which is the most significant FANET component. In a typical FANET scenario, GCS is essential to monitor UAV information and control them [11]. However, previous protocols were not able to utilize GCS because they were fundamentally based on existing MANET protocols. Consequently, the protocols inherited MANET protocol limitations, such as constant exchange of HELLO message and repetitive path finding, which significantly degrade FANET performance. To overcome these limitations, we propose GCS-routing designed for FANET to maximize GCS utilization. GCS-routing has advantages compared to previous approaches from several perspectives. * In contrast to previous routing protocols that were based on MANET protocols, GCS-routing was fundamentally designed for FANET and makes full use of the GCS, enabling FANET to overcome MANET limitations. The proposed routing can predict topology changes and react to them immediately, since the GCS knows the drone movement schedules. Removing the requirement for periodic HELLO messages for neighbor discovery or link cost estimation means that GCS-routing significantly reduces current protocol overheads, making it suitable for high mobility drones. * Most previous protocols were only evaluated through simulations, without experiments using real drones, even though general network simulators cannot fully support aerial conditions and specifications [17]. Implementing drone networks in the real world is challenging, and development of new routing protocols for drones is difficult. In contrast to the existing work, we implemented GCS-routing on real drones and GCS, and verified the performance of GCS-routing in various experiments. As discussed above, GCS-routing improves overall network performance by reducing network overhead. Thus, it is compatible with systems or algorithms for networks composed of multiple nodes.