# Communication Manager for Hyper-Connected RPAS Environments
## 2 Related Work
The adoption of softwarization technologies has been recently raised in the RPAS research area to provide solutions to this particular issue. The recent arrival of the 5G ecosystem has not only brought new radio technology as commonly thought but has also incorporated key software technologies such as Network Function Virtualization (NFV) and SDN. Our previous work has explored the use of NFV [7; 17], analyzing its strengths and weakness, but SDN-based solutions had not yet been explored by authors. Additionally, SDN has opened up new opportunities to automate the management of telecommunication services and verticals and facilitate achievement of the performance requirements imposed on 5G and beyond. For this reason, this article includes some SDN contributions to the RPAS research area. SDN brings significant advantages to multi-RPA environments, such as a centralized global network view or maintaining the status of the whole network, allowing for a flexible network reconfiguration based on different metrics. Therefore, forwarding decisions in each device may be based not on local conclusions, but rather on what happens in the rest of the network. SDN can help to address several inherent challenges of multi-RPA networks (e.g., architectural design, fluid topology, routing protocols, energy consumption) [18]. SDN can reconfigure the whole network (due to the global view of the SDN controller) under topological changes, which are quite frequent due to the intrinsic mobility of RPAs. For example, to reach RPS from RP4, there are several alternatives (e.g., RPA2 using radio, RPA3 using Wi-Fi or radio, 5G/4G/LTE). At some point, SDN could choose to go through RPA3, but if that link is lost, it may go to RPA2. SDN can also use different strategies for packet forwarding beyond the destination IP/MAC address, taking into account various parameters such as payload or packet types. SDN networks can also avoid network interference since it enables path/channel selection at any moment. Furthermore, SDN may select which channels are more reliable, based not only on instant parameters (e.g., signal level) but also on other representative information that cannot be considered in traditional routers (e.g., RPA mission planning input, historical data). The above-mentioned advantages slightly represent what the SDN paradigm can bring to multi-RPA networks. However, the design of legacy SDN technology was not done to fit into such specific environments like multi-RPA networks. Consequently, several challenges/issues must still be solved in order to involve SDN in this framework; in this regard, both academia [19; 20] and industry have increased their interest in this topic during the last years: authors in [21] propose an SDN and MQTT hybrid system for battlefield multi-RPA environments. Their proposal adapts to the periodic swarm topological changes, supports flexible data transmission among payloads, and improves swarm security. Authors in [22] design an SDN framework for the RPA backbone network. This framework monitors the RPA network to manage and analyze available information effectively. Authors in [23] investigate the deployment of an SDN RPA network providing a communication service. This article considers the placement of the SDN controller and its implications in terms of communication overhead and end-to-end delay. As the envisioned development of this article, the last references employ the SDN ecosystem as a key enabler technology for the correct operation of their systems. In order to maintain control over all the interfaces available in the devices (both the RPA and RPS) as well as the establishment and configuration of the communication networks, we developed the CIM (the evolution of the Interface Manager (IM) developed in [10]).