Abstract
Traffic density around the globe is increasing on a day-to-day basis, resulting in more accidents, congestion, and pollution. The dynamic vehicular environment induces challenges in designing an efficient and reliable protocol for communication. Timely delivery of safety and non-safety messages is necessary for traffic congestion control and for avoiding road mishaps. For efficient resource sharing and optimized channel utilization, the media access control (MAC) protocol plays a vital role. An efficient MAC protocol design can provide fair channel access and can delay constraint safety message dissemination, improving road safety. This paper reviews the applications, characteristics, and challenges faced in the design of MAC protocols. A classification of the MAC protocol is presented based on contention mechanisms and channel access. The classification based on contention is oriented as contention-based, contention-free, and hybrid, whereas the classification based on channel access is categorized as distributed, centralized, cluster-based, cooperative, token-based, and random access. These are further sub-classified as single-channel and multi-channel, based on the type of channel resources they utilize. This paper gives an analysis of the objectives, mechanisms, advantages/disadvantages, and simulators used in specified protocols. Finally, the paper concludes with a discussion on the future scope and open challenges for improving the MAC protocol design.
Highlights
This paper represents a comprehensive study on media access control (MAC) protocols in vehicular ad hoc networks (VANETs), the challenges, and issues related to the design of an efficient MAC protocol
When a node receives a packet for the first time, a time slot is allocated to the node and the node is re-broadcasted with a probability of 1; for re-broadcast, priority is given to the farther node
A node with higher signal-to-interference-plus-noise ratio (SINR), transmission rate, and channel condition sends back CAM, and the optimal relay is selected from nodes sending CAM
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A basic model diagram of VANETs includes vehicles and other infrastructures communicating via V2V, V2I, Road Side Units (RSUs), and Onboard Units (OBUs) These communications play a vital role in the transportation system to improve traffic efficiency and safety. Some of the challenges tackled by MAC protocol design in VANETs are (1) the provision of low latency safety services and high throughput non-safety services, (2) the elimination of hidden/exposed terminal problems due to rapid mobility of nodes in VANETs and topology changes, (3)proper resource and bandwidth allocation in single-channel as well as multi-channel for load balancing and better network throughput. In [14], the authors assessed foreground multi-layer challenges for better performing VANETs, with a focus on different layers, and proposed solutions along with the limitations and future work
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have