# C-V2X Centralized Resource Allocation with Spectrum Re-Partitioning in Highway Scenario
## 5 Simulation Results
Moreover, for the short-distance links we observe the successful reception probability of almost 1 with frequency partitioning, while for the SB configuration the impact of interference, presented in Figure 4c, significantly affects the transmission success rate. In Figure 8, the differential PRR (D-PRR = PRR\({}_{PFR}\) - PRR\({}_{FRR}\)) values obtained comparing PFR with FFR techniques are visualized, to show the difference between them for the considered vehicle densities. The results show almost the same system performance for all vehicle densities (D-PRR is equal or close to zero) when the distance between the transmitters and the receiver is about 100 to 300 m. Furthermore, the performance of PFR starts to be higher than for FFR D-PRRs by around 1% when the distance between the transmitter and the receiver is around 400 m for vehicle densities \(\alpha=0.6\) and 0.7. A fast increase is observed in PFR over FFR (rising D-PRR) with all vehicle densities when the distance is around 500 to 600 m.  
of vehicles (referenced to the total number of vehicles) that are located in BCZs are given in Table 2 for FFR and Table 3 for SB, with respect to different vehicle densities. \(AFRD\) is calculated by averaging the distances between all vehicles that are using the same frequency resources in the nearest \(RSU\)-\(twins\). \(AFRD\) vs. the vehicle density factor, presented in Figure 10, shows a significant enhancement of the average frequency reuse distance for PFR compared with FFR, especially when the number of vehicles in the network is high. The impact of increasing \(AFRD\) has a positive effect on the PRR (see Figure 6) due to the increase in the observed signal-to-interference plus noise ratio, and thus, higher probability of correct reception of broadcast packets. In conclusion, the proposed frequency-domain partitioning of resources based on the geographical location of vehicles provides significant improvement in terms of reduced interference. Thus, it positively improves the likelihood of successful delivery of CAM packets broadcast to the neighbouring vehicles. Both proposed techniques yield significant gains compared with the conventional single-band configuration, where all vehicles share the same resources without any interference mitigation applied. The main purpose of the FFR and PFR techniques is to mitigate the impact of interference for C-V2X communications with support of dedicated infrastructure, such as the RSUs. While the proposed techniques are unable to fully mitigate the impact of interference, which is possible with centralized resource allocation in Mode 3, they can be utilized to employ autonomous resource allocation of the RC features (Mode 4 operation) to reduce the need to control signalling between the RSUs and the vehicles. With the geographical areas specified based on RSUs coverage, especially in the case of PFR where the inner and outer zones are considered, communicating cars can use different resource pools with the aim to reduce the impact of interference. Such an approach allows for reducing the need for control signalling compared to Mode 3 operation, while maintaining a significantly higher likelihood of successful reception than the standard Mode 4 operation in dense traffic scenarios. Certainly, the effectiveness of these methods is dependent on the location estimation accuracy of vehicles, as significant errors (that are possible, e.g., with low-quality GPS receivers) may result in wrong association with a geographical area. Figure 8: Difference in Packet Reception Ratio (D-PRR \(=\) PRR\({}_{PFR}\)\(-\) PRR\({}_{FRR}\)) between both FFR and PFR bandwidth partitioning techniques versus distance for different vehicle densities.