Event-driven Safety Messages Research Articles

A Review of Congestion Control Schemes for Vehicular Ad-Hoc Network (VANET) Communication

Intelligent Transportation Systems (ITS) are built on top of self-organizing networks, known as Vehicular Ad hoc Networks (VANET). In VANET, each vehicle equipped with communication devices represents a node and is allowed to send and receive safety messages through wireless communication channels. These messages are either periodic (beacons) or event-driven. Beacons are transmitted periodically while the event-driven messages are generated when an abnormal condition or an imminent danger is detected. The event-driven messages should be delivered to neighbouring nodes with high reliability and limit time as a single delayed or lost message could result in loss of lives. In dense network, the periodic messages broadcast lead to broadcast storm/blind flooding problem in VANETs. It is very important to keep the communication channel free from congestion in order to ensure timely and reliable delivery of event-driven safety messages. This study presents a review of existing congestion control schemes for VANETs with the aim of discussing the contributions and drawbacks of the algorithms.

Analysis of Multi-Hop Probabilistic Forwarding for Vehicular Safety Applications on Highways

Safety applications based on the dedicated short-range communication (DSRC) in vehicular networks have very strict performance requirements for safety messages (in terms of delay and packet delivery). However, there is a lack of systematic approach to achieve the performance requirements by leveraging the potential of multi-hop forwarding. This paper proposes a generic multi-hop probabilistic forwarding scheme that achieves these requirements for event-driven safety messages, is compatible with the 802.11 broadcasting protocol and inherits some of the best features of solutions proposed so far for vehicular safety applications. In addition, we develop a unified and comprehensive analytical model to evaluate the performance of the proposed scheme taking into account the effect of hidden terminals, vehicle densities, and the spatial distribution of the multiple forwarders, in a one-dimensional highway scenario. Our numerical experiments confirm the accuracy of the model and demonstrate that the proposed protocol can improve the packet delivery performance by up to 209 percent, while maintaining the delay well below the required threshold. Finally, the utility of the analytical model is demonstrated via an optimal design for the coefficients of a forwarding probability function in the proposed scheme.

A novel context-aware variable interval MAC protocol to enhance event-driven message delivery in IEEE 802.11p/WAVE vehicular networks

Vehicular Ad hoc NETworks (VANETs) are the key to the future of Intelligent Transportation Systems (ITS). In VANETs, event driven safety messages, generated for example when an abnormal condition or an imminent danger is detected, have stringent requirements on delay. However, due to the inherent drawbacks of CSMA which is used in VANETs, such messages will not be able to meet the timing constraints in dense traffic scenarios. In this paper, we introduce a Context Aware Variable Interval MAC (CAVI-MAC) protocol for IEEE 802.11p/WAVE VANETs which utilizes multichannel access scheduling in a novel way. We differentiate between event driven and periodic messages by assigning priorities and also suggest a probabilistic model for addressing interference from hidden terminals. We also use a novel atomic model to analyze the propagation of event driven messages. Extensive simulations over lower Manhattan city scenario for a variety of metrics indicate that CAVI-MAC provides better performance (packet delivery ratio) than any of the existing protocols.

Modeling Event-Driven Safety Messages Delivery in IEEE 802.11p/WAVE Vehicular Networks

A stochastic model is designed to assess the delivery performance of event-driven safety messages in IEEE 802.11p/1609.4 vehicular ad-hoc networks (VANETs). The study focuses on the case of a vehicle detecting an unpredictable hazard and broadcasting the alert in the one-hop neighborhood. The model aims at providing quick insights into the impact of the latest WAVE specifications (i.e., traffic differentiation, channel switching) on the delivery of such short-lived alert messages. Results prove that it is accurate in capturing the effect of relevant parameters and show that repeating the alert transmission on the control channel helps to achieve reliable delivery.

Performance Evaluation of VeMAC Supporting Safety Applications in Vehicular Networks

Vehicular ad hoc networking (VANET) is an emerging paradigm that is expected to increase the public safety standards and enhance the safety level of drivers/passengers and pedestrians on roads through a variety of applications. We have recently proposed VeMAC, a medium access control protocol that supports a reliable one-hop broadcast service necessary for high priority safety applications in VANETs. This paper explains how the VeMAC protocol can deliver both periodic and event-driven safety messages in vehicular networks and presents a detailed delivery delay analysis, including queueing and service delays, for both types of safety messages. The probability mass function of the service delay is first derived; then, the D/G/1 and M/G/1 queueing systems are used to calculate the average queueing delay of the periodic and event-driven safety messages, respectively. In addition, a comparison between the VeMAC protocol and IEEE 802.11p standard is presented via extensive simulations using the network simulator ns-2 and the microscopic vehicle traffic simulator VISSIM. A real city scenario is considered and different performance metrics are evaluated, including the network goodput, protocol overhead, channel utilization, protocol fairness, probability of a transmission collision, and message delivery delay.

Formal Verification of Congestion Control Algorithm in VANETs

A Vehicular Ad-Hoc Networks (VANETs) is the technology that uses moving cars as nodes in a network to create a mobile network. VANETs turn every participating car into a wireless router, allowing cars of each other to connect and create a network with a wide range. VANETs are developed for enhancing the driving safety and comfort of automotive users. The VANETs can provide wide variety of service such as Intelligent Transportation System (ITS) e.g. safety applications. Many of safety applications built in VANETs are required real-time communication with high reliability. One of the main challenges is to avoid degradation of communication channels in dense traffic network. Many of studies suggested that appropriate congestion control algorithms are essential to provide efficient operation of the network. However, most of congestion control algorithms are not really applicable to event-driven safety messages. In this paper we propose congestion control algorithm as solution to prevent congestion in VANETs environment. We propose a complete validation method and analyse the performance of our congestion control algorithms for event-driven safety messages in difference congested scenarios. The effectiveness of the proposed congestion control algorithm is evaluated through the simulation using Veins simulator.

Congestion Control Framework for Disseminating Safety Messages in Vehicular Ad-Hoc Networks (VANETs)

The purpose of this study is to propose a new congestion control framework for uni-priority of event-driven safety messages in VANETs. The uni-priority congestion is caused by the traffic of the same priority. Many of event-driven safety applications developed for VANETs is required real-time communication with high reliability and must be delivered before certain time deadline. In high load traffic, the CCH communication channel easily congested. Many studies [2,10,11,12] recommended congestion control approach to control the load and congestion on the wireless channel in VANETs. Our proposed congestion control will reserve the CCH communication channel for event-driven safety messages if the number of safety messages in the queue exceeds a defined threshold or the congestion control detect event-driven safety message. In normal traffic, the CCH communication channel is not reserve for event-driven safety messages. This research will adapt priority-based Earliest Deadline First (EDF) scheduling algorithms in proposed congestion control to schedule uni-priority of eventdriven safety messages. In addition, to provide reliability performance for event-driven safety messages, we will develop a new rebroadcasting scheme to prevent broadcast storm. In next phase of study, we plan to test and evaluate performance of our congestion control approach using network simulator e.g. NS-3.