## 3 Experimental Results
### Varying Infrastructure Density Scenario
#### 3.2.2 Average End-to-End Latency  
The influence of the infrastructure deployment on the E2E latency reported for traffic intensity of 250 vehicles per hour is shown in Figure 18a-d for both investigated modes of the 4G-based C-V2X, respectively. We can clearly see from Figure 18a,b that the impact of the infrastructure density deployment in terms of latency is negligible for the infrastructural mode. Moreover, neither the message generation frequency nor the communication perimeter play a role in this case. The former is also true for the D2D mode. On the other hand, only the message generation frequency has a significant impact on the E2E latency in the D2D mode and for both infrastructure densities, see Figure 18c,d for more details. When it comes to the highest traffic intensity, i.e., 1500 vehicles per hour, and the infrastructural mode, no change in comparison to the traffic intensity of 250 vehicles per hour was observed, see Figure 19a,b for more detail. For the D2D mode, as it can be seen from Figure 19c,d, the behavior has remained the same, but some spikes have appeared. When it comes to the 5G-based C-V2X, we can clearly see in Figure 20a-d that the impact of the more dense infrastructure deployment is negligible for both modes, similarly as in the LTE case. Moreover, both the message generation frequency and communication perimeter have no impact on the reported E2E latency values, even for the D2D mode. Regarding the higher traffic intensity, i.e., 1500 vehicles per hour, the behavior is completely the same as reported above for the traffic intensity of 250 vehicles per hour, see Figure 21a-d for more detail. It should be noted here that slightly higher values are reported for the infrastructural mode deploying 4 BSs, i.e., the less dense infrastructure deployment, and longer communication perimeter above 1000 m in comparison to the lowest traffic intensity, see Figures 20a and 21a for more detail. Similarly to the fixed infrastructure density scenario, see Section 3.1 for more detail, we have put the obtained results into a context of communication requirements of the most popular V2I C-ITS services, see [39] for more detail. Regarding the 4G-based C-V2X as well as the infrastructural mode, we can see from Table 5 that more dense infrastructure deployment is very beneficial in the context of all the considered types of the V2I services,  
Figure 17: PDR simulated for the both modes of the 5G-based C-V2X technology, both infrastructure density deployments and traffic intensity of 1500 vehicles per hour. i.e., the low-frequency and low-latency services, low-frequency and high-latency services and high-frequency and low-latency services. To be more precise, when at least 4 BSs are deployed, no limitations when it comes to the communication perimeter and traffic intensity (the low-frequency and low-latency services) or the communication perimeter (the low-frequency and high-latency services) are present in the case of all the considered services. Moreover, a great improvement, i.e., from no service support to a full support without the limitations, is achieved for the high-frequency and low-latency services. The similar situation, i.e., the transition from no service support to the full support without the limitations, is also obtained in the D2D mode 3 of the 4G-based C-V2X for all the services when more than 4 BSs are deployed, see Table 6 for more detail. Regarding the 5G-based C-V2X and the infrastructural mode, the transition is even more perceived for all the considered services, in comparison to the LTE case, as the transition from no coverage to the full support without the limitations can be seen here when the more dense infrastructure deployments, i.e., 4 and 8 BSs, are applied, see Table 7 for more detail. The same behavior, see Table 8 for more detail, was reported for the D2D mode 3 of the 5G-based C-V2X. It should be noted in this context that no coverage is meant here as no coverage for resource scheduling, not for transmitting the data packets.