# Enabling Multi-Mission Interoperable UAS Using Data-Centric Communications
## 6 Conclusions  
In this paper, we explore the main contributions to UAS communications that can be provided by data-centric approaches, considering the open industry-standard developed by the OMG, i.e., DDS. Following our analysis of a set of motivating scenarios, which include multiple interconnected and heterogeneous UAVs, we conclude that DDS has the potential to enable interoperable UAS deployments. This is supported by the dynamic discovery of information publishers and subscribers, and the negotiation of a flexible set of QoS policies, which need to be satisfied for a successful publisher-to-subscriber communication. In addition, DDS eases the integration of new software and services with the utilization of a standardized middleware platform, this way enhancing the adaptability of the UAS to different mission objectives. To address the identified limitations of DDS in our motivating scenarios, regarding the utilization of network-level multicast (an enabling technology in DDS), we proposed the utilization of layer-2 virtual networks. We validated the feasibility of using DDS and layer-2 virtual networks over a heterogeneous UAS deployment, carrying out a number of practical experiments that served to support the conclusions of our practical analysis.  
Our future work includes the exploration of more dynamic alternatives to support layer-2 virtual networks, particularly Software Defined Networking (SDN). On the other hand, the paper addresses a functional validation of the benefits of using DDS in multi-UAV network environments. While this validation has been carried out using real equipment, there are still diverse aspects  
Figure 6: Measurements of the achieved throughput with: large PDU (**left**); and small PDU (**right**).  
that require consideration to support an operational deployment, particularly: automating the placement and configuration of DDS services as a prior step to the UAS deployment, dynamically configuring the network parameters of multi-UAV networks (e.g., network topologies and routes), and analyzing the overhead and the energy consumption implications when using the application-layer middleware of DDS. Additionally, the work in this paper is part of a research line where we are also exploring the adaptability of UAS deployments with the utilization of virtualization technologies [33]. Hence, besides the aforementioned aspects, our work in the short-term includes studying enhancements to interoperation and adaptability of UAS, with the automated orchestration of DDS-based virtualized services on UAV platforms.  
Funding acquisition, F.V. and A.Z.; Investigation, I.V., P.B., V.S.-A., J.G.-R., F.V., B.N. and A.Z.; Validation, V.S.-A. and B.N.; Visualization, V.S.-A. and B.N.; Writing--original draft, I.V., P.B. and J.G.-R.; and Writing--review and editing, I.V., P.B., J.G.-R., F.V. and A.Z.  
This article was partially supported by the European H2020 5 GRANGE project (grant agreement 777137), and by the 5 GCity project (TEC2016-76795-C6-3-R) funded by the Spanish Ministry of Economy and Competitiveness.  
The authors declare no conflict of interest.