# Transport-Layer Limitations for NFV Orchestration in Resource-Constrained Aerial Networks
## 2 Background and Related Work
The work in [12] presents several architectures for creating a computing platform based on several aircraft, discussing the possibility of using UAVs for data collection in wireless sensor networks as well. In [13], a UAV network architecture is presented to relay data traffic for ground vehicles, which also supports data collection functionalities. However, we want to highlight that according to our previous research on this area, there is still a lack of consensus from the research community and the industry on a standard design for SUAVs that using existing protocols and technologies, enables the flexible execution of general-purpose telecommunication services and functionalities [14]. Despite the market opportunities in this area, commercial SUAV products are typically proprietary solutions, i.e., usually manufactured to accomplish specific missions. In our future view, swarms combining UAVs of different sizes and characteristics might be positioned over delimited geographic areas, and provide a baseline resource infrastructure, capable of flexibly executing different network functions and services, which could then be offered on-demand by a service provider over that areas. As an example, a telecommunication operator could deploy several SUAVs to temporarily provide Internet access over a specific geographic location, for instance because the access network infrastructure of the telecommunication operator in that area is unavailable (e.g., as a consequence of a natural disaster) or insufficient (e.g., in a crowded event). In these cases, SUAV platforms could enable a cost-effective deployment of network functionalities (e.g., wireless access points, routing functions, IP telephony servers, etc.) over a target geographic area. This way, SUAVs could be used to complement the available network infrastructure over specific areas, which could favor the provision of the network services expected for 5G. To realize this view, NFV emerge as an enabling technology to decouple network functions and services from the hardware they are deployed on: by using virtualization, network services can be executed independently of the hardware and software platforms used underneath. This would allow their execution on multiple and heterogeneous aircraft and devices, as long as these can support virtualization. This way, NFV has the potential to take fleets of SUAVs to a higher degree of flexibility in the provision of network functions and services. A degree of flexibility that can barely be achievedwith other specialized SUAV equipment that has been designed and/or configured offline to provide specific services. In addition to its inherent flexibility to adapt the SUAV functionalities to serve to different purposes, the use of NFV brings other relevant advantages in the field of the SUAV arena, particularly: simplifying the development cycle of functions and services, which may prototyped and tested in production-like virtualized environments; easing the evolution of these functions and their migration to production state, as they are implemented in software; and the facility to adapt the resources allocated to specific functions and services to better accommodate varying demands (e.g., an increasing number of users). In this respect, the research community is giving the first steps towards realizing the softwarization of network functions in aerial networks. Examples of this approach can be seen in works such as [15] where authors use Software-Defined Networking (SDN) techniques to manage a UAV network, [16] where authors provide efficient handover techniques using SDN, with the aircrafts being used as OpenFlow switches, or [17] where authors use SDN in aircraft to improve connectivity between aircraft of an aerial network.