Abstract
Vehicle ad-hoc networks (VANETs), which support various important applications for intelligent transportation systems (ITSs), consist of vehicle-to-vehicle and vehicle-to-infrastructure communications based on vehicles and roadside units (RSUs). Medium access control (MAC) plays a critical role in providing efficient broadcast services for VANETs. Unlike other types of networks, VANETs suffer from rapid changes in topology, resulting in frequent network disconnections caused by the high mobility of nodes. Hence, adaptive MAC protocols, which dynamically adjust the interval according to the traffic conditions, are essential to VANETs. This study proposes a cooperative and reliable RSU-assisted IEEE 802.11p-based multi-channel MAC protocol for VANETs, called RAM. In our proposal, an RSU is used to both calculate the optimized interval and keep track of the safety packet transmission. We also present a cooperative scheme for the retransmission of safety packets that failed to broadcast because of hidden nodes. The simulation results show that the RAM not only allows safety packets to be broadcast more efficiently using the existing MAC protocols, but also outperforms the existing MAC protocols in terms of the packet delivery ratios for safety and control packets.
Highlights
Vehicle ad-hoc networks (VANETs) are designed to provide vehicular safety, reduce the number of traffic accidents and improve transportation efficiency; play an important role in intelligent transportation systems (ITSs) [1]
VANET applications can be grouped into the three following main applications based on the communications between the on-board units (OBUs) and between the OBUs and the road-side units (RSUs): safety, The associate editor coordinating the review of this manuscript and approving it for publication was Zhengguo Sheng
We propose a new IEEE 802.11-based multi-channel Medium access control (MAC) protocol that can resolve the limitations of the existing MAC protocols
Summary
Vehicle ad-hoc networks (VANETs) are designed to provide vehicular safety, reduce the number of traffic accidents and improve transportation efficiency; play an important role in intelligent transportation systems (ITSs) [1]. VANETs using the existing MAC protocols have several advantages [14], [15] They improve the throughput of non-safety applications and the packet delivery ratio because they can reduce the hidden and exposed terminal problems [14]. They guarantee the QoS for real-time applications by reducing the time delay of service packets They improve channel utilization because the interval length ratio can be dynamically adjusted between the control channel (CCH) and the service channels (SCHs) according to network conditions [15]. Despite these advantages, VANETs using the existing MAC protocols face some challenges [15]. The rest of this paper is organized as follows: Section II gives a short survey of the adaptive MAC protocol in VANETs; Section III describes the proposed RAM protocol in detail; Section IV presents a theoretical analysis on the optimal interval in the RAM protocol; Section V presents the performance evaluation; and Section VI concludes the paper
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