# Priority-Based Content Delivery in the Internet of Vehicles through Named Data Networking +
## 5 Simulation Settings  
A comprehensive simulation campaign has been performed under a wide range of settings as reported in Table 1 and detailed as follows. **Topology:** To create a realistic road layout, we used maps publicly available from the OpenStreetMap (OSM) project [39] and combined them with realistic vehicular mobility traces derived from SUMO [36]. In particular, similarly to [15], a map of the city of Rome has been chosen; the map has a size of nearly 3.2 \(\times\) 1.7 km\({}^{2}\); see Figure 6. The positions of public Wi-Fi APs deployed in an urban area are available from [40], and have been used to resemble the position of 802.11 OCB RSUs. The mobility traces of vehicles are given as an input to ndnSIM [41], the official NS-3 based NDN simulator, together with the RSUs' coordinates, available in latitude and longitude, converted in 2D positions. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Parameter** & **Value** \\ \hline \multirow{3}{*}{**Application**} & Content size & 1 MB \\  & Data payload & 1000 bytes \\  & Content popularity & Zipf distribution \\ \hline \multirow{3}{*}{**Topology**} & Area size & 3.2 \(\times\) 1.7 km\({}^{2}\) \\  & Number of vehicles & 200 \\  & Number of RSUs & 55 \\  & Mobility model & SUMO [36] \\ \hline
**Load** & Number of consumers & 8–24 \\ \hline \multirow{3}{*}{**802.11 OCB**} & Propagation model & Nakagami [37] \\  & Data rate & 6 Mbps [38] \\ \hline
**3G/LTE** & RTT & 150 ms \\ \hline \multirow{3}{*}{**NDN**} & Defer Window [27] & 511 \\  & DeferSlotTime [27] & 58 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. **Content features and request patterns:** A subset of vehicles (from eight to 24) request 1 MB-large content from a population of \(M=30\) content files (e.g., road pics, traffic maps, flyers, etc.). Such content is initially hosted at RSUs placed in the topology and acting as fog servers locally storing content [42] and also in remote servers accessible through the LTE connectivity. Although some preliminary works about the feasibility for LTE nodes to run ICN capabilities are available in the literature, e.g., [43], the topic is still at its infancy; thus, we assume that the eNodeB is not equipped with caching capabilities. Each content is fragmented into Data packets of 1000 bytes. Content popularity follows a Zipf-like distribution with parameter \(\alpha=0.8\)[44]. Without loss of generality, we assume that more popular content (i.e., with popularity index \(<5\)) is treated as HP content and named with the main prefix /high.This would be the case of road traffic-related data that are of interest for many vehicles. Other content is named with the main prefix /low. Each consumer vehicle chooses to download a single content file during the simulation. Interarrival times of content requests by different consumers are exponentially distributed with mean \(\lambda=0.5\). Each consumer issues a new Interest at the reception of the (previously requested) Data packet to request the subsequent one and retransmits an Interest when the RTO of the current Interest expires, until the retrieval is completed. **Access technologies:** The NDN instance in each vehicle runs over a multi-face device equipped with a dual-radio IEEE 802.11 OCB transceiver [3] and a cellular LTE interface. The first one is used for V2V and V2R communications, whereas the second one provides V2I connectivity towards the remote content server. For what concerns 802.11 OCB, we focus on a service channel, where NDN packets are only transmitted in broadcast. All RSUs and on-board units (OBUs) can listen to the packets within their vicinity of 802.11 signal reachability. By leveraging the OCB mode, there is no need for them to be in the same Service Set Identifier (SSID) domain. Radio signal propagation follows a Nakagami distribution with fading factor \(m\) equal to three to model medium fading conditions in vehicular environments [37].