# 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
This finding aligns with the real-world scenario. On the other hand, for the medium and lower speed ranges corresponding to Priority 2 and 3, the delay increases. Vehicles in the lower speed range need to wait for some time before sending data packets. This matches the initial design intention of this study. The specific data in Figure 10b are as follows: \([\overline{S_{1}};\overline{S_{2}};\overline{S_{5}}]=[4.837;7.992;18.85](*10^ {-4}\text{s})\), \([\overline{W_{1}};\overline{W_{2}};\overline{W_{3}}]=[1.756;4.952;13.84](*10^ {-7}\text{s})\), \([\overline{T_{1}};\overline{T_{2}};\overline{T_{3}}]=[4.839;8.002;18.89](*10^ {-4}\text{s})\). Comparing scenario 1, it can be observed that due to the increased arrival rate in the higher speed range, there is an increase in the number of vehicles and thus, an increase in the number of sent data packets. As a result, the average service time, average waiting time, and total  
Figure 8: Scenario 1 and 2 Vehicle Location MAP. (**a**) Scenario 1 and (**b**) scenario 2. Figure 9: Scenario 1 and 2 Speed Distribution Graph. (**a**) Scenario 1 and (**b**) scenario 2.  
delay for Priority 1 also increase compared to scenario 1. Additionally, the medium and lower speed ranges also experience an increase in delay due to the need to avoid the data packets from the higher speed range. This observation aligns with the requirements of this study. The specific data in Figure 11a are as follows \(\left[\overline{\mathrm{T}_{\mathrm{BBM1}}^{\mathrm{B}}};\overline{\mathrm{T}_{ \mathrm{BBM2}}^{\mathrm{B}}};\overline{\mathrm{T}_{\mathrm{BBM3}}^{\mathrm{B}} }\right]=\left[0.02261;0.06465;0.2839\right]\)(s). The vehicles in speed range 3, which represents the slowest speed, have a longer travel time within the UAV coverage area. However, due to their longer transmission or queuing time, the time interval between sending BSMs for these vehicles is longer compared to other speed ranges, and it shows an increasing trend. The specific data in Figure 11b are as follows: \(\left[\overline{\mathrm{T}_{\mathrm{BBM1}}^{\mathrm{B}}};\overline{\mathrm{T}_{ \mathrm{BBM2}}^{\mathrm{B}}};\overline{\mathrm{T}_{\mathrm{BBM3}}^{\mathrm{B}} }\right]=\left[0.0682;0.0772;0.0905\right]\)(s). Compared with scenario 1, it can be observed that due to the increased number of vehicles and thus, an increase in the number of high-priority data packets in the higher speed range, the time interval between sending BSMs increases in scenario 2. This is reasonable since more vehicles result in more data packets,  
Figure 11: Scenario 1 and 2 Interval of BSM For Each Section. (**a**) Scenario 1 and (**b**) scenario 2. Figure 10: Scenario 1 and 2 Delay Maps of Vehicles in Different Speed Ranges. (**a**) Scenario 1 and (**b**) scenario 2.  
which increases collision probability and thus, increases service and waiting times in the queue, leading to longer time intervals between packet transmissions. However, as shown in Figure 11a,b, for the medium and lower speed ranges, the delay time in the queue does not decrease but increases when the arrival rate and the number of vehicles and data packets decrease compared to scenario 1. Additionally, due to the reduced number of vehicles, there are fewer BSM data packets, resulting in similar time intervals between packet transmissions for Priority 2 compared to scenario 1 (as the arrival rate for Priority 2 remains unchanged), and shorter time intervals for Priority 3 but still higher than those for Priorities 1 and 2. Figure 12a,b demonstrates the practicality of the preemptive priority assignment scheme and MAC layer protocol design adopted in this paper by comparing preemptive and commonly used non-preemptive priority assignment schemes. Compared to non-preemptive schemes, preemptive schemes are more effective in managing and scheduling tasks in highly competitive resource environments, improving system responsiveness and throughput.