## 2 Setup and Simulation Environment
### Simulation Settings  
To explore each technology's sensitivity to traffic volume/intensity, we varied the traffic intensity in 6 steps, ranging from 250 to 1500 vehicles per hour. The values of the traffic intensity were set according to the official data from a traffic survey that was conducted for the General Traffic Plan of the City of Zilina. A well-established microscopic car-following model based on [21] was used to model the inter-vehicular spacings. The vehicle flow generated was a Poisson process where \(\lambda\) was equal to the respective traffic intensity value. For the sake of the comparability of the results, the traffic flows--down to the level of individual vehicle dynamics--were kept identical between the simulation scenarios for each given level of traffic intensity. The message generation frequency was varied in 5 steps from 2 to 10 Hz to characterize different ITS services; see [22] for more details. To study the impact of distance on the measured parameters, i.e., the PDR and end-to-end delay, the communication perimeter was varied in 7 steps ranging from 200 to 1400 m. All of the simulation variables and their respective values are summarized in Table 1.  
Figure 1: Visualization of the simulation scenarios. The simulation parameters applied are detailed in Table 2. The vehicles periodically transmitted unacknowledged messages with a fixed length to the RSU, i.e., emulating the Cooperative Awareness Message (CAM) service over the UDP protocol. To prevent the possible distortion of the simulation results as a result of a change in the traffic flow, the RSU did not influence the intersection control in any way upon the successful receipt of a message. Apart from the periodic (CAM) messages, there was also event-triggered communication traffic present in the typical C-ITS system. Represented by Decentralized Environmental Notification Messages (DENMs) in Europe, these event-triggered messages are more likely to be generated with increasing traffic intensity. As their amount is highly stochastic and very specific to the scenario and application, we did not consider them in this study. It is worth noting here that frequent dissemination of DENMs can further congest the communication channel and induce collisions on the Medium Access Layer (MAC), especially in the case of DSRC. Each simulation run simulated 10 min of traffic with an additional 100 s to represent the initialization period used to populate the transport network with vehicles. Over this initialization period, the target communication performance indicators, i.e., the PDR and end-to-end delay, were not evaluated. The technology-specific communication parameters of LTE and DSRC used for the simulation experiments are presented in Tables 3 and 4, respectively. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Traffic intensity & 250, 500, 750, 1000, 1250, 1500 vehicles per hour \\ Message generation frequency & 2, 4, 6, 8, 10 Hz \\ Communication perimeter & 200, 400, 600, 800, 1000, 1200, 1400 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation variables. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Application protocol & CAM-like periodic fixed-length message exchange service \\ Transport protocol & UDP \\ Message length & 300 bytes (including a security header) \\ Simulation length & 600 s \\ Number of repetitions & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Frequency band & 2100 MHz \\ Channel bandwidth & 10 MHz \\ Transmit power & 40 dBm \\ Max. HARQ Retransmission & 3 \\ eNodeB height & 25 metres \\ Thermal noise & \(-104.5\) dBm \\ eNodeB antenna gain & 18 dBi \\ UE antenna gain & 0 dBi \\ eNodeB noise figure & 5 dB \\ UE noise figure & 7 dB \\ Cable loss & 2 dB \\ Number of fading paths (JAKES) & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: LTE-specific parameters.