# V2X Communications in Highway Environments: Scheduling Challenges and Solutions for 6G Networks
## 4 Simulation Environment  
The highway deployment scenario used in Figure 2 focuses on high-speed moving vehicles on a highway, simulating both high network load and high UE velocity.  
In the considered network model, a gNB is placed in the bottom center of a highway segment. Parameters regarding the highway are summarized in Table 3. The high-speed movement of the vehicles is performed on all lanes following the traffic characteristics of Table 4. Unfortunately, the algorithms necessary for the handover operation in the NR module have not been implemented yet; therefore, we had to reduce the size of the simulated area to 1 km to achieve a macro cell inter site distance (ISD) of 500 m. The following paragraphs outline the parameters used in the simulation scenarios and provide a brief introduction to the mobility models utilized.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Number of Vehicles & 40, 60, 80 \\ Max speed & 120 km/h \\ User Distribution & 100\% vehicles \\ Inter-vehicle distance & Average inter-vehicle distance (between two vehicles’ \\ centers) in the same lane is 0.5 s \\ Depart position & Random \\ \hline \hline \end{tabular}
\end{table}
Table 3: Highway parameters.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Number of lanes & 3 in each direction (6 lanes in total) \\ Lane width & 4 m \\ Simulation area size & 1000 m \(\times\) 24 m \\ \hline \hline \end{tabular}
\end{table}
Table 4: Vehicles and traffic characteristics.  
Figure 2: Highway configuration [23].  
The described topology was implemented using SUMO (Simulation of Urban Mobility), an open-source, highly portable, multi-modal traffic simulation package designed for vehicular networks. The vehicle flows are also modeled in SUMO and have the following characteristics.  
In the performed simulations, we used the latest release of ns-3 (v 3.42) along with the NR module (v 3.1). Ns-3 is a discrete-event network simulator that provides an open simulation environment for networking research, tailored to meet the simulation needs of modern networks. The NR module is a pluggable component for ns-3 that simulates 5G NR cellular networks. The network parameters used in the simulated scenarios are based on 3 GPP's technical report [23] and are summarized in Table 5. It is also important to mention that the delay presented in the results is measured end-to-end. This includes an additional 12 ms user plane delay for packets that pass through the core network and reach a V2X server. We have used the assumption that a packet faces a 3 ms delay each time it crosses a network interface (e.g., gNB to UPF to V2X AS to UPF to gNB) [6].  
In the initial network implementations, the PF scheduler was utilized in the OFDMA mode with the specified parameters. Three distinct cases of vehicle density were considered, with 40, 60, and 80 vehicles, respectively. As the number of vehicles increased, so did the demand for delay-sensitive UCs, aiming to represent various traffic congestion conditions on the highway. The simulation was then repeated using the SOVANET and SOVANET+ schedulers.