## 4 Performance Evaluation
### Simulation Results  
The results of this investigation into 5G NR sidelink C-V2X communication make it clearly evident that increasing distance has an important effect on collision probability. These insights are particularly crucial as they take into account the generation time of the sidelink channel, offering a deeper understanding of how distance and time inter-relate in the context of collision occurrences in this advanced communication framework. In Figure 2a, the collision probability clearly decreases as the distance between UEs grows. This drop is due to the longer propagation delays, which give each UE more time to finish transmitting its packet without interfering with the transmissions of other UEs, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value** & **Unit** \\ \hline Simulator & NS-3/5G-LENA/SUMO & - \\ Packet Size & 1 & Kilobyte \\ Scenario & Houghton-MI & - \\ Speed & Variable & Km/h \\ Channels & ITS Band 5.9 & GHz \\ Bandwidth & 10 & MHz \\ Transmission Power & 13 & dBm/MHz \\ Density & 6 & dBm \\ Noise Figure & LOS Fading Model & - \\ Beacon Size & 300 & byte \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. accounting for the sidelink channel generation time. In addition, it was shown that, when the generation time is taken into account, there is a distance which is close to 400 m at which the likelihood of a collision is significantly reduced. Beyond this range, the propagation delays grew unacceptably long, significantly increasing the time required to generate a packet. In contrast, given the limitations of generation time, if the distance was too close, the propagation delays were insufficient to effectively avoid collisions. Achieving a low collision probability in 5G NR sidelink CV2X communication requires the establishment of an optimal distance between UE, acting as a balancing mechanism amidst propagation delays, packet generation times and collision avoidance. This optimal distance is vital, as it helps mitigate interference, maintaining communication reliability. Minimizing propagation delays is essential for real-time information relay in vehicular communications and managing packet generation times is crucial to avoid network congestion and subsequent collisions. Hence, determining this ideal distance, while incorporating effective collision avoidance mechanisms and considering generation times and propagation delays, is pivotal for enhancing the reliability and efficiency of CV2X communications. This effect can be understood as follows:  
* When UEs are closer together, the propagation delay is short, meaning their transmissions may overlap more frequently, leading to higher collision probabilities. Figure 2: Probability of collision based on the distances between two UEs. (**a**) Unlimited RBs; (**b**) 1 RB. As distance increases, the propagation delay increases, allowing more time for transmissions to complete before another UE begins transmission, reducing interference and lowering collision probability. * However, beyond a certain distance (around 400 m in our study), the propagation delay becomes excessively long, which may negatively impact packet generation and transmission efficiency, introducing new challenges such as increased latency. In Figure 2b, where the resource block is set as a constant, we observe that the likelihood of a collision increases as the distance between the UE decreases. When only one resource block (RB) is available for allocation (set as a constant), all the UEs have to contend for this single RB to transmit their data. Conversely, the probability of a collision diminishes as the distance between the UEs increases. This phenomenon can be attributed to the fact that when the UEs are farther apart, there are instances where one of the UEs falls outside the effective range of the RB. This results in fewer collisions occurring, as the UEs are less likely to interfere with each other's transmissions.