## 3 Experimental Results
### Varying Infrastructure Density Scenario
#### 3.2.1 Packet Delivery Ratio  
Figure 14a-d depict an impact of the infrastructure density deployment on the packet delivery ratio for the traffic intensity of 250 vehicles per hour and both investigated modes of the 4G-based C-V2X technology, i.e., the infrastructural mode and D2D mode (mode 3), respectively. As it can be clearly seen from Figure 14a,b, the impact is rather severe when it comes to the communication perimeter above 1000 m, as the reported PDR has increased from 85-90% to 100% by deploying 8 BSs. Moreover, there is no impact of the message generation frequency in this case. On the other hand, this impact is nicely visible for the D2D mode when it comes to the lowest message generation frequencies, i.e., 2 and 4, and a communication perimeter above 1000 m, see Figure 14c,d for more details. It is worth noting here that the longer communication perimeter above 1000 m has also played a role in the case of the remaining message generation frequencies. In other words, PDR has increased from 80-85% to 85-100% when 8 BSs were deployed. When it comes to the impact of the highest traffic intensity, i.e., 1500 vehicles per hour, and the infrastructural mode, the trend remains the same, but the PDR was slightly improved for the communication perimeter above 1000 m and less dense infrastructure deployment, i.e., 4 BSs, see Figure 15a,b for more details. The same is true also for the D2D mode, see Figure 15c,d for more details. Regarding the results obtained for the 5G-based C-V2X, they are reported in Figure 16a-d for the traffic intensity of 250 vehicles per hour and both modes of the 5G-based C-V2X technology, respectively. As we can clearly see from Figure 16a,b, the trend obtained for the infrastructural mode remains the same as that reported above for the 4G-based C-V2X, but the influence of the communication perimeter was slightly broadened. To be more precise, it is starting to play a role from 800 m. It should be noted here that the PDR values reported for the communication perimeter above 800 m are a bit lower than those reported for the 4G-based \begin{table}
\begin{tabular}{c c c c c} \hline
**C-ITS Service** & \multicolumn{2}{c}{**LTE-Infrastructural**} & **LTE-D2D** & **5G-Infrastructural** & **5G-D2D** \\ \hline \multicolumn{5}{c}{**Low frequency (1–2 Hz), low latency (<100 milliseconds) services**} \\ \hline Slow and stationary vehicle warning & ✓ & ✓ & ✓ & ✓ \\ Weather conditions warning & ✓ & ✓ & ✓ & ✓ \\ Intersection management & ✓ & ✓ & ✓ & ✓ \\ \hline \multicolumn{5}{c}{**Low frequency (1–2 Hz), high latency (<500 milliseconds) services**} \\ \hline Point of interest notification & ✓ & ✓ & ✓ & ✓ \\ Local electronic commerce & ✓ & ✓ & ✓ & ✓ \\ Media upload & ✓ & ✓ & ✓ & ✓ \\ Map updates & ✓ & ✓ & ✓ & ✓ \\ Cooperative flexible lane change & ✓ & ✓ & ✓ & ✓ \\ \hline \multicolumn{5}{c}{**High frequency (10 Hz), low latency (<100 milliseconds) services**} \\ \hline Electronic emergency break light & ✓ & ✓ & ✓ & ✓ \\ Emergency vehicle approaching & ✓ & ✓ & ✓ & ✓ \\ \hline \end{tabular}
\end{table} 
Table 4: Communication requirements of common Cooperative Intelligent Transport Systems (C-ITS) services and their fulfillment by the investigated communication technologies in the investigated context. Adapted from [39] and updated. C-V2X in the case of the both infrastructure density deployments. The difference is much more pronounced for the more dense infrastructure deployment, i.e., 8 BSs. Regardless, the gain of the increased infrastructure deployment is still nicely visible, see Figure 15(a),b for more details. Regarding the D2D mode of 5G-based C-V2X, the trend is similar to that reported above for the 4G-based C-V2X besides the fact that there is mostly negligible impact when it comes to the frequency of message generation. The impact of the communication perimeter was again broadened, becoming important from 600 m. The reported values are again a bit lower as in the 4G case.