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In urban Vehicular Ad-hoc Networks (VANETs), disseminating traffic data efficiently is challenging due to the dynamic and complex nature of the network. Multi-hop-based broadcasting approaches are commonly used to address this issue. However, selecting the optimal relay nodes poses a challenge and directly impacts network performance. Existing relay selection strategies, such as beacon-based methods, have limitations in scaling under different traffic conditions. This paper proposes a multi-attribute relay selection strategy for urban multi-hop VANETs to overcome these challenges. The strategy evaluates the rebroadcast capability of each receiving node based on its real-time status. It utilizes a fuzzy-BCM-based weight estimation strategy to determine the contribution of each attribute to the node's capability. The node with the highest broadcasting capability is given priority to access the channel and broadcast the data packet. The proposed scheme is evaluated through simulation tests in VANET simulation environments, considering various traffic flow and speed variations. Performance comparison with four benchmark methods is conducted. The results show that the proposed scheme improves the overall dissemination efficiency by 51.1% compared to the benchmarked methods. [ABSTRACT FROM AUTHOR]

In Vehicular Ad-hoc Networks (VANETs), fast and reliable dissemination of safety messages is a key step toward improving the overall road safety. In a highly dynamic VANET environment, safety message dissemination in a multi-hop manner is a challenging and complex problem that has gained significant attention recently. Many protocols and schemes have been proposed to efficiently share safety messages among vehicles. However, most existing techniques do not perform well under real-world traffic conditions, or perform adequately only under very limited scenarios and traffic conditions. This research proposes a highly efficient and reliable multi-hop broadcasting protocol, Intelligent Forwarding Protocol (IFP), that exploits handshake-less communication, ACK Decoupling, and an efficient collision resolution mechanism. In this research, IFP has been extensively studied and evaluated to establish its robustness and superiority over existing schemes. A key contribution of this paper is to present an in-depth analysis and optimization of IFP using theoretical modeling, thorough simulations, and extensive real-world experimentation. With IFP, the message propagation delay is significantly reduced and packet delivery ratio is drastically improved. [ABSTRACT FROM AUTHOR]

Vehicular safety applications based on DSRC/802.11p have strict reliability requirement (greater than 0.99). However, it is difficult to achieve high reliability in wireless medium as the transmission is vulnerable to various wave propagation issues. To the best of our knowledge, none of the existing emergency message dissemination schemes in the literature, achieves a predefined reliability in lossy channel. In this paper, we propose a novel scheme, called reliable emergency message dissemination scheme (REMD), which achieves a predefined reliability for message dissemination while satisfying delay requirements, for various channel conditions. We aim to guarantee very high reliability (e.g., 99%) in each hop, with low control overhead while keeping low end-to-end latency for time-critical applications. We employ zero-correlated unipolar orthogonal codes to combat hidden terminal problem. We exploit periodic beacons, to accurately estimate reception quality of 802.11p wireless link in each cell; then, we use this information to determine the optimal number of broadcast repetitions in each hop. In addition, to ensure reliability in multi-hop, we utilize cooperative communication. The simulation results show that REMD outperforms the existing well-known schemes in the literature. Furthermore, REMD satisfies latency requirements for time-critical vehicular applications and has less network overhead than the existing schemes. [ABSTRACT FROM AUTHOR]

Network congestion is a major issue affecting communications in Connected and Autonomous Vehicles (CAVs) under high vehicle density scenarios. The common idea used by emergency message broadcast protocols to overcome this challenge is to reduce the number of retransmissions. This is achieved by suppressing redundant retransmissions while maintaining broadcast reliability. In this paper, we analyze the problem of inaccurate suppression of redundant retransmissions in delay-based broadcast protocols and propose uHBS (unHurried Broadcast Suppression), a new more efficient broadcast suppression mechanism. uHBS avoids inaccurate decisions to suppress or forward an emergency message by considering the occurrence of duplicate receptions of this message and using an indication about the channel's busy status. Next, we use the proposed uHBS mechanism as a basis for designing uHBS-DP (uHBS based Dissemination Protocol), a novel delay-based protocol for broadcasting emergency messages in urban vehicular networks. The simulation results show that uHBS-DP, using the proposed broadcast suppression mechanism, significantly improves the efficiency of emergency message broadcasting by ensuring high reliability with low broadcasting overhead, compared to two other variants of uHBS-DP that use conventional suppression mechanisms. Furthermore, the results show a substantial improvement, compared to a well known protocol, in terms of reduced collision ratio (up to 36.57%), lower dissemination delay (up to 19.17%) and reduced broadcast overhead (up to 19.28%). [ABSTRACT FROM AUTHOR]

The proper utilization of road information can improve the performance of relay-node selection methods. However, the existing schemes are only applicable to a specific road structure, and this limits their application in real-world scenarios where mostly more than one road structure exists in the Region of Interest (RoI), even in the communication range of a sender. In this paper, we propose an adaptive relay-node selection (ARNS) method based on the exponential partition to implement message broadcasting in complex scenarios. First, we improved a relay-node selection method in the curved road scenarios through the re-definition of the optimal position considering the distribution of the obstacles. Then, we proposed a criterion of classifying road structures based on their broadcast characteristics. Finally, ARNS is designed to adaptively apply the appropriate relay-node selection method based on the exponential partition in realistic scenarios. Simulation results on a real-world map show that the end-to-end broadcast delay of ARNS is reduced by at least 13.8% compared to the beacon-based relay-node selection method, and at least 14.0% compared to the trinary partitioned black-burst-based broadcast protocol (3P3B)-based relay-node selection method. The broadcast coverage is increased by 3.6−7% in curved road scenarios, with obstacles benefitting from the consideration of the distribution of obstacles. Moreover, ARNS achieves a higher and more stable packet delivery ratio (PDR) than existing methods profiting from the adaptive selection mechanism.

To enhance traffic safety with efficient transportation, a vehicle public safety system is designed and implemented for collision avoidance and emergency warning. The proposed architecture for the system combines On Board Unit development with publicly available inter-vehicle wireless communication systems and also positioning devices. A communication routing scheme is proposed based on multi-hop broadcasting scheme with a dissemination model and a suppression technique. Field test of the On Board Unit prototype and simulation model of the proposed communication routing scheme demonstrates the capability of the system to improve traffic safety with low latency, wider coverage and collision avoidance. [ABSTRACT FROM AUTHOR]

Vehicular Ad-hoc Networks (VANETs) are highly dynamic and self-organized ad hoc wireless networks that enable vehicles to set up and maintain communication without any central base station. In multi-hop-based VANETs, messages are disseminated throughout the network through a relaying. However, the dissemination of time-critical emergency warning messages remains challenging due to the broadcast storm problem. The widely proposed broadcast suppression strategies are either beacon-based, which demands extra bandwidth or do not scale well under different traffic conditions. Thus, this paper proposes a multi-criteria-based broadcast suppression scheme for multi-hop VANETS. The proposed scheme utilizes multiple node attributes, including relative velocity, traffic density, lane weight (moving lane), link stability, movement angle and distance to sender, to estimate a node's quality. Upon receiving a new message, each node can contend for the next-hop relay position using its quality value such that a high-quality node is granted the earliest channel access to broadcast the data packet. The performance of the proposed scheme is validated using data generated from traffic simulation in the OMNET++ environment under different traffic conditions. The results from the simulation claim that the proposed strategy alleviates broadcast overhead by 30% and significantly improves the overall dissemination efficiency by 48.97% compared to the bench-marked methods. The results showed that the objectives are met by significantly improving dissemination efficiency with increased reachability, reduced broadcast overhead and end-to-end delay. Moreover, the scheme enables each receiving node to evaluate its broadcasting suitability autonomously, making the relay selection process dynamic and adaptive to any traffic condition. [ABSTRACT FROM AUTHOR]

The proper utilization of road information can improve the performance of relay-node selection methods. However, the existing schemes are only applicable to a specific road structure, and this limits their application in real-world scenarios where mostly more than one road structure exists in the Region of Interest (RoI), even in the communication range of a sender. In this paper, we propose an adaptive relay-node selection (ARNS) method based on the exponential partition to implement message broadcasting in complex scenarios. First, we improved a relay-node selection method in the curved road scenarios through the re-definition of the optimal position considering the distribution of the obstacles. Then, we proposed a criterion of classifying road structures based on their broadcast characteristics. Finally, ARNS is designed to adaptively apply the appropriate relay-node selection method based on the exponential partition in realistic scenarios. Simulation results on a real-world map show that the end-to-end broadcast delay of ARNS is reduced by at least 13.8% compared to the beacon-based relay-node selection method, and at least 14.0% compared to the trinary partitioned black-burst-based broadcast protocol (3P3B)-based relay-node selection method. The broadcast coverage is increased by 3.6–7% in curved road scenarios, with obstacles benefitting from the consideration of the distribution of obstacles. Moreover, ARNS achieves a higher and more stable packet delivery ratio (PDR) than existing methods profiting from the adaptive selection mechanism. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks have been identified as a key technology for enabling safety and infotainment applications in the context of smart and connected vehicles. In this sense, diverse approaches of multi-hop broadcast protocols have been proposed to collect and disseminate context information through the network. However, before vehicular ad hoc networks applications fulfill their expected potential to connect smart vehicles, several issues must be addressed. Among these issues, those related to security are of particular importance. In this article, the main security issues of broadcast message dissemination in vehicular ad hoc networks are discussed. Moreover, a review of the most relevant threats and proposed solutions to secure broadcast message dissemination in vehicular ad hoc networks is presented and discussed. As mentioned, security is an important topic which has not been fully addressed in vehicular ad hoc networks; therefore, the aim of this article is to introduce security issues and proposed solutions related to three main security concerns associated with the message dissemination process in vehicular ad hoc networks: network access, data consistency, and broadcast protocols. [ABSTRACT FROM AUTHOR]