## 4 Simulation of NDN Transport in V2X Scenarios
### Simulation Scenarios for V2X Communication  
In this section we summarize the most used scenarios for simulating V2X communication in literature and discuss their properties. A V2X communication scenario is defined by street alignment, environment geometry and environmental conditions, road users and infrastructure, incidents, and its use case. While street alignment, as well as environment geometry and environmental conditions impact simulation of V2X communication on a physical-level, road users and infrastructure, incidents, and use case influence network communication on a high-level basis. _Street alignment_. Additionally to highways and intersections, which are predominantly used street alignments in recent literature, we propose to simulate roundabouts, as traffic flow in roundabouts is fundamentally different to the intersection case. We found that SUMO currently does not correctly translate roundabouts, as they are interpreted as intersections. For an illustration of these basic street alignments, please refer to Figure 8. Please note that the number of lanes per direction is an additional variable of the simulation scenario. In addition to the literal street alignment, this dimension also defines the presence and position of classical traffic infrastructure, such as traffic lights or pedestrian crossings. At intersections, red traffic lights, and at pedestrian crossings, cars should share information for following cars, in order to optimize traffic flow and subsequently minimize travel time. _Environment geometry, environmental conditions_. Another factor with a big impact on the physical aspect of a simulation scenario is the geometry of the environment. This category defines attributes of possible obstacles for V2X communication, such as buildings or trees. While the position of an obstacle is self-explanatory, we identified surface character and physical shape as remaining important attributes of the environment geometry. Depending on these geometry attributes, channel model selection heavily impacts the simulation outcome for the scenario. Environmental conditions, such as weather street conditions affect physical data transmission (e.g., reflection properties) as well as physical simulation properties (e.g., stopping distance or sight distance). _Infrastructure and road users_. As already discussed in previous sections, several related work assume base stations or a fixed RSU in place (i.e., as in [14; 41; 43]). While the assumption of having base stations available in communication range is illusory for the fact of high hardware cost, we propose to use base stations for selected applications, such as signaling the availability of parking space. Infrastructure nodes thus act as a communication party providing potentially beneficial information for traffic safety and traffic flow. A major point of interest concerning fixed base stations is the kind and availability of provided data. In contrast to fixed infrastructure, road users are moving entities. We classify road users as vehicles, priority vehicles, public transport, cyclists, and pedestrians. Vehicles are traffic actors, with the goal to minimize travel time from source to destination location. They exchange relevant information in order to achieve the goal of safe and fast travel within the framework of road traffic regulations. Priority vehicles are vehicles which are exceptions to road traffic regulations, such as fire engines, the ambulance, or police cars. In order to allow these cars to quickly reach their destination, the communication with such vehicles has to be prioritized. Public transport, cyclists, and pedestrians are further special cases of road users as special road  
Figure 8: Basic street alignment types. Examples have been taken from SUMO TAPASCologne scenario. regulations apply. Especially in the case of cyclists and pedestrians, we can not assume active communication, so autonomously driving cars have to rely on (not necessarily their own) sensor data only.