## 3 Experimental Results
### Fixed Infrastructure Density Scenario
#### 3.1.2 Average End-to-End Latency  
Compared to the study published in [16], the impact of the communication perimeter is greatly reduced in the case of the 4G-based C-V2X. So, in other words, the impact is negligible in this case. As it can be seen in Figures 8a, 9a, 10a, 11a, 12a and 13a, the average E2E latency of the messages sent by the 4G-based C-V2X in the infrastructural mode remains very low (below 0.5 ms) across all the simulated combinations of the simulation variables, i.e., the message generation frequency, communication perimeter and traffic intensity.  
The average E2E latency of the messages sent by the 4G-based C-V2X in the device-to-device mode 3 is also greatly reduced compared to the scenario with 2 cells reported in [16]. Here, a slight impact of the message generation frequency was observed, see Figures 8c, 9c, 10c, 11c, 12c and 13c for more detail, as the latency slightly decreases with the message generation frequency due to the more efficient resource scheduling. While noticeable in the figures, it is worth noting here that this decrease is so small in the absolute values that it has no practical implications.  
In the case of the 5G-based C-V2X in the infrastructural mode, a very minor increase of the E2E latency can be seen for the perimeters beyond 800 m, see Figures 8b, 9b, 10b, 11b, 12b and 13b for more detail. Again, the impact is so minimal, considering the scale, that it has no practical implication.  
The same can be stated for the 5G-based C-V2X in the device-to-device mode 3, see Figures 8d, 9d, 10d, 11d, 12d and 13d for more detail. The average message E2E latency increases linearly with the communication perimeter, however, the practical impact is essentially negligible.  
For both 5G modes, it can be said that the impact of the message generation frequency is practically not present. No noticeable impact of the traffic intensity on the average message E2E latency was observed in the case of both investigated technologies, i.e., 4G-based C-V2X as well as 5G-based C-V2X.  
Figure 7: PDR simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 1500 vehicles per hour.  
Figure 10: E2E latency simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 750 vehicles per hour.  
Figure 9: E2E latency simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 500 vehicles per hour.  
Figure 11: E2E latency simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 1000 vehicles per hour.  
Figure 12: E2E latency simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 1250 vehicles per hour.  
The obtained simulation results presented above in Figures 2-13 were put into the context of the communication requirements of the most popular V2I C-ITS services from the E2E latency and PDR perspective, coming from the renowned literature [39], which is based on [40; 41; 42]. So, this is to say that the obtained results were mapped to the above mentioned communication requirements to show whether the corresponding communication technologies fulfill those requirements in the context of the investigated V2I C-ITS services. This should help transport engineers to correctly deploy the corresponding technologies in reality.  
The experimental results indicate that all the investigated C-V2X technologies are able to fulfill the communication requirements of the most popular V2I C-ITS services, under assumption of sufficient infrastructure deployment in an urban scenario (see Table 4).  
Figure 13: E2E latency simulated for all the investigated modes of the 4G-based and 5G-based C-V2X technologies and traffic intensity of 1500 vehicles per hour.