## 5 Performance Evaluation
### Simulation
#### 5.2.2 Nonzero Resource Keeping Probability  
Here, we again assume that there is no population churn. It is to focus on the impact of the moving probability _probResourceKeep_. Figure 9 compares the collision probabilities of SPS and SPS/LA under various _probResourceKeep_, ranging from 0.2 to 0.8. To give the readers more direct sense of the performance differences, henceforth we use the linear scale on the \(y\)-axis. We present only the collision probability at the end of the simulation when the probability has been stabilized.  
First, we notice that there is impact from varying _probResourceKeep_ in SPS. Specifically, as the resource keeping probability increases, the collision probability decreases. This result is in line with other works [30]. Also, it confirms our earlier observation that the collisions are a direct consequence of blind reselection. Nevertheless, we cannot simply prohibit reselection to reduce the collision probability because the reselection also serves to accommodate topology dynamics in the vehicle traffic. In Section 5.2.3, we will observe the impact of _probResourceKeep_ under more dynamic population changes.  
Compared to SPS, the SPS/LA scheme rarely produces collisions under the light load. Specifically, the collision probability, if not zero, is frequently orders of magnitudes smaller than in SPS.  
Under heavier traffic loads in Figure 10, we first notice that the collision probability superlinearly increases in CBR in both schemes. Here again, increasing _probResourceKeep_ has a collision mitigating effect. We can also clearly observe that SPS/LA significantly reduces the collision probability, maintaining the order-of-magnitude performance gap.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**CBR** & \(\textbf{Mean}_{SPS}\) & 1 CI \({}_{SPS}\) & \(\textbf{Mean}_{SPS/LA}\) & 1 CI \({}_{SPS/LA}\) \\ \hline
10\% & \(4.34\times 10^{-4}\) & \(4.18\times 10^{-5}\) & \(3.16\times 10^{-6}\) & \(6.16\times 10^{-6}\) \\
20\% & \(2.11\times 10^{-3}\) & \(1.22\times 10^{-4}\) & \(2.27\times 10^{-5}\) & \(1.20\times 10^{-5}\) \\
30\% & \(5.24\times 10^{-3}\) & \(2.83\times 10^{-4}\) & \(5.08\times 10^{-5}\) & \(1.67\times 10^{-5}\) \\
40\% & \(1.08\times 10^{-2}\) & \(3.05\times 10^{-4}\) & \(1.15\times 10^{-4}\) & \(1.26\times 10^{-5}\) \\
50\% & \(1.96\times 10^{-2}\) & \(2.73\times 10^{-4}\) & \(2.27\times 10^{-4}\) & \(4.45\times 10^{-5}\) \\
60\% & \(3.36\times 10^{-2}\) & \(3.72\times 10^{-4}\) & \(4.10\times 10^{-4}\) & \(5.85\times 10^{-5}\) \\
70\% & \(5.49\times 10^{-2}\) & \(3.64\times 10^{-4}\) & \(7.56\times 10^{-4}\) & \(7.58\times 10^{-5}\) \\
80\% & \(8.65\times 10^{-2}\) & \(6.08\times 10^{-4}\) & \(1.69\times 10^{-3}\) & \(1.30\times 10^{-4}\) \\
90\% & \(1.28\times 10^{-1}\) & \(5.06\times 10^{-4}\) & \(5.76\times 10^{-3}\) & \(3.20\times 10^{-4}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Collision probability at \(t=100\) with 95% confidence interval (CI) width.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Application** & **Packet Size (B)** & **Reliability (\%)** & **Latency (ms)** \\ \hline Vehicle Platooning & 300–400 & 90 & 25 \\ Remote Driving & 300–400 & 99.99 & 5 \\ Autonomous Cooperative Driving & 1200 & 99.99 & 10 \\ Collective Perception of Environment & 1600 & 99 & 100 \\ Cooperative Collision Avoidance & 2000 & 99.99 & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Payload size, reliability, and latency requirements for prospective 5G eV2X applications.  
Figure 10: Collision probabilities under varying _probResourceKeep_, heavy load. (**a**) SPS. (**b**) SPS/LA.  
Figure 9: Collision probabilities under varying _probResourceKeep_, light load. (**a**) SPS. (**b**) SPS/LA.