# A Preemptive-Resume Priority MAC Protocol for Efficient BSM Transmission in UAV-Assisted VANETs
## 2 Related Works
[38] introduced a repetition-based cooperative broadcasting scheme to enhance the reliability and efficiency of message delivery in VANETs and mitigate the adverse effects of fading on message transmission. In this scheme, vehicles within the communication range form a cooperative group and collaborate to forward broadcast messages. Cooperation is achieved through the utilization of repetition techniques, where each vehicle retransmits the received message multiple times to increase the likelihood of successful message reception by other vehicles. In [39], a priority-based communication scheme for V2V communication is presented, which is realized in VANETs utilizing the IEEE 802.11p standard. This scheme focuses on enhancing the QoS mechanism and incorporates priority scheduling techniques to optimize communication efficiency and minimize latency. By assigning different priorities to various types of data and vehicles, the proposed scheme aims to prioritize critical information and improve the overall performance of vehicular communication systems. Ref. [40] presented a novel priority-based approach for emergency data dissemination in urban environments. This method is specifically designed to facilitate the swift propagation of critical information during emergency situations. By leveraging prioritization techniques, the proposed method enhances the speed and reliability of data delivery, ensuring that emergency data reach relevant entities promptly. This approach holds great potential for improving emergency response systems and enhancing the overall efficiency of urban communication networks. In [41], the authors propose a V2V emergency data transmission scheme based on TCP protocol and priority queue technology in VANETs. This scheme utilizes stable connections and priority queue techniques to achieve fast transmission of emergency data. Moreover, it incorporates mechanisms such as traffic control and congestion control to ensure the stability and reliability of the transmission. Ref. [42] presents a novel dynamic resource allocation algorithm for optimizing the utilization of limited UAV and spectrum resources. The proposed algorithm takes into account both the communication demands of vehicles and the current network conditions. By considering factors such as vehicle-specific communication requirements and energy constraints, the algorithm intelligently allocates UAV resources to ensure efficient resource utilization. This approach holds significant potential for enhancing the overall performance and effectiveness of UAV-assisted communication systems in scenarios with limited resources. Our work is based on the computational model of drone-assisted vehicular networks proposed in papers [18; 19]. Furthermore, Refs. [20; 21; 22; 23] provide strong evidence that supports the superiority and effectiveness of drones as relay nodes in vehicular networks. Currently, there are two main approaches to address the BSM traffic congestion control problem we are interested in: one is by adjusting the generation frequency, as discussed in Refs. [24; 25; 26] and the other is power control, as explored in Refs. [27; 28]. Our proposed solution focuses on designing a MAC layer protocol that minimizes latency through preemptive priority and queuing theory and subsequently adjusts the generation frequency. The limitations of Refs. [24; 25] lie in their focus on real-time congestion monitoring and optimizing network utilization efficiency without modifying the MAC layer or providing system-wide optimization. While real-time congestion monitoring is an effective method, it does not solve the fundamental problem. On the other hand, Ref. [26] mainly emphasizes vehicle-to-vehicle communication, overlooking the auxiliary role of drones or road test units. Our research centers around designing a MAC layer protocol to adjust the 802.11P protocol in vehicular networks, incorporating key aspects such as Markov chain modeling, queuing theory, and priority design. Unlike Refs.