# A Preemptive-Resume Priority MAC Protocol for Efficient BSM Transmission in UAV-Assisted VANETs
## 5 Numerical Results
#### Analysis of Delay and Processed Packet Volume under Different Arrival Rates
By assigning different priorities to tasks, preemptive schemes can ensure that high-priority tasks are executed in a timely manner, thereby meeting the requirements of applications with higher real-time performance demands. Additionally, it is worth noting that based on the data, the preemptive scheme reduces latency compared to the non-preemptive high-priority scheme by 8.17% and overall system by 24.92%. In terms of frequency, the preemptive scheme is 23.55% stronger than the non-preemptive scheme. Therefore, the preemptive priority assignment scheme and MAC layer protocol design adopted in this paper are very useful and can effectively improve system performance and network transmission quality, meeting the requirements of different application scenarios. As shown in Figure 13a, this study compares the preemptive priority allocation scheme employed in this paper with the priority-based MAC layer modification scheme proposed in reference [34], demonstrating the practicality of the priority allocation scheme and MAC layer protocol design utilized in this work. Compared to reference [34], our proposed scheme exhibits significant advantages in terms of overall system delay performance, achieving a 68.8% higher overall efficiency. This further validates the novelty and effectiveness of our approach. By introducing a priority allocation mechanism, our proposed scheme better meets the real-time and reliability requirements of different types of data in vehicular communication, thereby enhancing system performance and efficiency. This positions our paper as a valuable point of comparison and provides beneficial insights for research and practice in the field of vehicular networking. Figure 12: Comparison of Non-preemptive and Preemptive Sections. (**a**) Delay and (**b**) interval of BSM. As depicted in Figure 13, this study presents a comparison between our proposed scheme and a paper published in the Sensor journal under MDPI [35]. Both studies focus on modifying the 802.11P protocol using queuing theory and 2D Markov models. However, our proposed scheme incorporates a priority allocation mechanism, which enhances the timeliness of high-priority vehicles and significantly improves the overall system performance. Additionally, our proposed scheme better caters to the communication requirements of different vehicles, optimizing system performance and efficiency. Comparative analysis reveals that our proposed scheme outperforms the approach presented in paper [35], resulting in a 22.7% higher overall system efficiency. This further validates the novelty and practicality of our proposed scheme, offering valuable insights for research and applications within the vehicular networking domain. This finding suggests that the priority classification in this study achieves the expected results of prioritizing higher priority vehicles, i.e., those in the higher speed range, to use limited resources, and allows for speed limiting measures to be taken for these vehicles to ensure normal UAV operation. The small change in numbers is mainly due to the limited number of data packets and vehicles and insufficient arrival rate parameters, which is in line with realistic scenarios [49, 50]. * Congestion: In situations with high vehicle arrival rates, the number of vehicles on the road may exceed the road capacity, leading to congestion. This can cause traffic jams and reduce vehicle speeds. When the arrival rate approaches or exceeds the road capacity, vehicle speeds often significantly decrease. * Traffic safety: On highways, vehicle speeds may be limited to maintain safe distances and prevent accidents. If the vehicle arrival rate increases but the road capacity cannot accommodate it, traffic management authorities may take measures to restrict vehicle speeds to ensure safety. * Road infrastructure and design: Road structures, signs, speed limits, and other factors can affect vehicle speeds. Even if the arrival rate increases, if the road design and facilities do not support high-speed travel, vehicle speeds may still be limited.