# Insights from the Experimentation of Named Data Networks in Mobile Wireless Environments
## 4 Experimentation Setup and Results
### NDN in Single Wireless Radio Scenarios  
To evaluate our solution in a real scenario, we have used a limited number of nodes belonging to the previously mentioned ATCLL infrastructure, consisting of four edge nodes (RSUs) capable of both wireless and wired communication, one backend router, which will act as a content Producer, and two mobile nodes, one posing as a vehicle moving through unpredictable traffic and the other as a pedestrian. At first, the vehicle maneuver through an itinerary that connects with all four considered RSUs at some point in time, with the sole purpose of retrieving content that it is interested in, under the form of real files consisting of images and text documents, caching them for future use (Figure 7a). After 574 s, the vehicle completes its fist itinerary and move towards the pedestrian which is placed outside the coverage of any given RSU, meaning that its only point of contact with the contents is through the moving vehicle. At this moment, the pedestrian downloads the content from the vehicle's Content Store (Figure 7b). Then, after 1000 s the vehicle starts a second trip around the city to retrieve the remaining contents from the RSUs. This second trip is shorter than the previous, and the vehicle contacts only with three RSUs (Figure 7c). Finally, the vehicle ends its journey next to the pedestrian, providing another opportunity for the pedestrian to retrieve the remaining contents from the vehicle's cache (Figure 7d). Figure 6: Messages exchanged following the NDN architecture and heterogeneous radio access technologies. Figure 7: Route performed by the mobile node in the first experiment. (**a**) Between \(t=0\) s and \(t=574\) s the vehicle connects with four RSUs. (**b**) Between \(t=574\) s and \(t=1000\) s both vehicle and pedestrian are in communication range. (**c**) Between \(t=1000\) s and \(t=1534\) s the vehicle travels around the city, connecting with three RSUs. (**d**) Finally, the vehicle ends its journey next to the pedestrian. Table 1 refers to the parameters considered in this scenario. Six files were considered with increasing size values which would be transmitted through ITS-G5 on the wireless section of the network. A single file will be under dissemination at a given time, meaning that only after the previous file is successfully downloaded, the next one will start its transmission. This approach aims to test two aspects: how the architecture behaves when multiple files are being delivered in consecutive manner, and the impact of the mobility in the delivery of large files, requiring the connection to multiple points of access to the infrastructure. The performance of the NDN solution in this scenario is discussed using the following indicators:  
* **Interest satisfaction ratio:** measures the number of Interest packets arriving at the Producer, and how many of the Data packets, sent upon the reception of the Interest packet, arrive at the Consumer. This helps us to understand if the heuristics set on the Forwarding module, responsible for decisions about the forwarding of Interest and Data packets, are properly defined;
* **Network overhead:** a mobile network node moving at uncertain speed and at an unpredictable rate of contact with the network has a direct influence on the number of packets exchanged with the network mostly due to the inevitable packet loss that will occur, increasing the need for Interest retransmission. The number of Interests and Data packets traversing the network will be considered in this indicator;
* **Network contact time:** despite the strategic placement of RSUs, due to the unknown behavior of the vehicle traffic and weather conditions, it is inevitable that disconnections will occur. To ascertain the efficiency of content forwarding when contact is available, and the impact this may have in the results, we verify how long a mobile node is connected to the network, in seconds, throughout the experience.