# Designing a Softwarized Network Deployed on a Fleet of Drones for Rural Zone Monitoring
## 2 Video Monitoring Platform Description
### Platform Elements  
As shown in Figure 1, the video monitoring platform is constituted by a backbone mesh network and a number of video transmitter devices. The backbone mesh network, whose nodes are the backbone node drones (BND), is a flying ad-hoc network (FANET), an ad-hoc network that is a particular class of Mobile Ad-hoc NETworks (MANET), also classifiable as a subset of Vehicular Ad-hoc NETworks (VANET) [34]. Generally, FANETs nodes may be highly mobile, so causing connectivity problems and frequent topology changes. However, for the scenario we are considering in this paper, where the only target is to cover a given rural area, we can assume that they follow a global path plan, that is, all the BNDs slowly move on a predetermined path with a regular mobility model. Moreover, by timely designing of network node density, it is possible to guaranteeing connectivity even in case of failures of some nodes. Therefore, their number, protocols and techniques they apply to setup and maintain connectivity, and the relative routing and battery recharging policies are out of the scope of this paper, and can be considered as a matter of future work. Interested readers can refer to the wide literature regarding FANETs [23; 24; 25] and data communications in unmanned aerial vehicles (UAV) [16; 48]. The architecture of the backbone mesh network nodes is presented in Figure 2. Their target is not only providing connectivity at the network level, but also running the virtual service elements constituting the platform at the application level, that is, the acquirers and the edge streamers comprising the video broadcasting infrastructure described in Section 2.2. For this purpose, they are equipped with one or more computing units hosting an NFV infrastructure (NFVI) point of presence (POP). A general-purpose x86 hardware, like for example Intel Nuke MiniPC or even RaspberryPi, can be used to deploy a virtualization environment that allows running virtual machines (VM). Each VM is used to host a specific virtual network or application function (VNF and VAF, respectively), according to the NFV paradigm. VM Dom0 is always running to host the operating system. A virtual SDN-compliant software switch (e.g., an OpenvSwitch [49]) is also installed and run on each backbone node drone to connect local VMs to each other, to the ones running on the neighboring backbone network node drones, and to some transmitter and receiver devices, all under the centralized control  
Figure 1: Reference scenario. of a remote SDN Controller. A WiFi network interface equipped with an omnidirectional antenna allows physical communications in the wireless mesh network. In our prototype, we used CentOS release 6.4 as host operating system (OS), directly installed on the bare metal, whereas we have chosen Xen Hypervisor [50] as a VM hypervisor. It behaves as a middleware software, enabling both virtual system management and hardware resource sharing with the aim of executing multiple computer operating systems on the same hardware concurrently. Xen Hypervisor is a free and open-source software developed by the University of Cambridge Computer Laboratory, available for x86-64, IA-32 and ARM architectures, and supporting a form of virtualization known as para-virtualization. Thanks to the para-virtualization paradigm, it is possible to obtain a faster execution of the VMs as compared with the traditional approaches. More in detail, Xen Hypervisor allows virtual machines to share with each other the x86-64 hardware directly, without the need to specify the resources to be allocated for the virtualized hardware preventively. Thanks to this peculiarity, the host OS only acts as a console to operate with the virtualization manager, enabling commands as create, destroy and migrate. Video transmission is realized with video transmitter drones and fixed wireless IP cameras, all sending video of portions of the considered rural area.