# Enabling Multi-Mission Interoperable UAS Using Data-Centric Communications
## 5 Functional Validation  
This section presents a practical experience on the deployment of DDS in a UAS testbed (see Figure 2). Our testbed includes real network equipment from the TCP/IP communication system of an existing tactical surveillance system called SIVA [3], an UAS from the Spanish Ministry of Defense  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Feature** & \multicolumn{2}{c}{**Alternative IP-Based Solutions**} & \multicolumn{1}{c}{**DDS**} \\ \hline Location of data & \(\bullet\) & IP addresses are necessary for consumers to contact hosts that store content. & After consumers subscribe to topics, the DDS middleware is in charge of delivering data to such subscribers (spatial decoupling between data producers and consumers). \\ \hline QoS negotiation & \(\bullet\) & Requires the use of additional protocols (e.g., [23]). & Requires the use of additional protocols (e.g., [23]). & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Quality support is standardized and one of the strongest aspects of the rich DDS middleware aspects of the rich DDS middleware & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. \\ \hline Efficient data dissemination & \(\bullet\) & Both unicast and IP multicast could be used. The optimal mechanism depends on the expected number of consumers for the same content (there is a tradeoff between bandwidth consumption and maintenance costs of multicast delivery trees). & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. \\ \hline Mobility management & \(\bullet\) & Not considered by design in the TCP/IP stack. Diverse existing solutions (e.g., Mobile IP [26], Proxy Mobile IP [27] and SIP mobility support [28]). Increases the complexity of the deployment and may impact the performance of data distribution (e.g., signaling/data overhead and data path delay). & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. & Equality support is standardized and one of the strongest aspects of the rich DDS middleware solution. (we carried out the design and implementation of the TCP/IP communication system of the SIVA in our prior work [8]). The UAS testbed integrates network equipment corresponding to the SIVA UAV and the SIVA GCS (see Figure 2). The UAV router is an embedded system following the PC/104 industry standard (Intel Core i7 2.3 GHz, 8 GB RAM, 128 GB SSD, 4 GbE ports, operating with Ubuntu 16.04.3 LTS, 64 bits). This system integrates an Ethernet switch that allows the interconnection of local on-board equipment, such as a data acquisition unit (DAU) and a camera. It also integrates a GbE port that implements a data-link with the GCS. The data acquisition unit (DAU), deployed as a computer in the testbed, is capable of serving different telemetry patterns towards a workstation in the GCS (emulating information captured from the different on-board sensors of the UAV, and also the video stream captured from the camera).