The growing size of cities and increasing population mobility have determined a rapid increase in the number of vehicles on the roads, which has resulted in many challenges for road traffic management authorities in relation to traffic congestion, accidents, and air pollution. Over the recent years, researchers from both industry and academia have been focusing their efforts on exploiting the advances in sensing, communication, and dynamic adaptive technologies to make the existing road traffic management systems (TMSs) more efficient to cope with the aforementioned issues in future smart cities. However, these efforts are still insufficient to build a reliable and secure TMS that can handle the foreseeable rise of population and vehicles in smart cities. In this survey, we present an up-to-date review of the different technologies used in the different phases involved in a TMS and discuss the potential use of smart cars and social media to enable fast and more accurate traffic congestion detection and mitigation. We also provide a thorough study of the security threats that may jeopardize the efficiency of the TMS and endanger drivers' lives. Furthermore, the most significant and recent European and worldwide projects dealing with traffic congestion issues are briefly discussed to highlight their contribution to the advancement of smart transportation. Finally, we discuss some open challenges and present our own vision to develop robust TMSs for future smart cities.

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A Communications-Oriented Perspective on Traffic Management Systems for Smart Cities: Challenges and Innovative Approaches

Vehicular Ad-hoc Networks (VANETs) are seen as the key enabling technology of Intelligent Transportation Systems (ITS). In addition to safety, VANETs also provide a cost-effective platform for numerous comfort and entertainment applications. A pragmatic solution of VANETs requires synergistic efforts in multidisciplinary areas of communication standards, routings, security and trust. Furthermore, a realistic VANET simulator is required for performance evaluation. There have been many research efforts in these areas, and consequently, a number of surveys have been published on various aspects. In this article, we first explain the key characteristics of VANETs, then provide a meta-survey of research works. We take a tutorial approach to introducing VANETs and gradually discuss intricate details. Extensive listings of existing surveys and research projects have been provided to assess development efforts. The article is useful for researchers to look at the big picture and channel their efforts in an effective way.

How Close are We to Realizing a Pragmatic VANET Solution? A Meta-Survey

Vehicular ad hoc networks are a special type of MANET providing vehicle to vehicle and vehicle to roadside wireless communications. Vehicular ad-hoc network (VANET) have been designed in order to assist drivers on the road with a variety of applications especially in preventing danger and saving lives. For such ends, broadcasting is a suitable scheme to convey emergency messages dissemination to the entire network. Broadcasting in VANETs is a challenging task due to the specific VANET features such as nodes mobility and frequent topology changes. VANET applications, especially those related with human life saving, are delay sensitive and have specific requirements in terms of performances and QoS. A QoS aware broadcasting scheme relies on different factors and has to deal with hard constraints. In this paper, we introduce a survey of broadcasting in vehicular networks and discussion of different performance and QoS related to broadcasting issues. Furthermore, a comparative study of QoS aware broadcasting protocols classifying them according to different taxonomies is elaborated. This survey specifies QoS requirements and performance metrics of VANET services. Furthermore, this survey focuses on QoS aware broadcasting as a challenging problem regrading VANET characteristics.

A survey and comparative study of QoS aware broadcasting techniques in VANET

In vehicular ad hoc networks (VANETs), network topology and communication links frequently change due to the high mobility of vehicles. Key challenges include how to shorten transmission delays and increase the stability of transmissions. When establishing routing paths, most research focuses on detecting traffic and selecting roads with higher vehicle densities in order to transmit packets, thus avoiding carry-and-forward scenarios and decreasing transmission delays; however, such approaches may not obtain accurate real-time traffic densities by periodically monitoring each road because vehicle densities change so rapidly. In this paper, we propose a novel routing information system called the machine learning-assisted route selection (MARS) system to estimate necessary information for routing protocols. In MARS, road information is maintained in roadside units with the help of machine learning. We use machine learning to predict the moves of vehicles and then choose some suitable routing paths with better transmission capacity to transmit packets. Further, MARS can help to decide the forwarding direction between two RSUs according to the predicted location of the destination and the estimated transmission delays in both forwarding directions. Our proposed system can provide in-time routing information for VANETs and greatly enhance network performance.

https://journals.sagepub.com/doi/pdf/10.1155/2015/374391

A machine learning system for routing decision-making in urban vehicular ad hoc networks

Vehicular Ad Hoc Network (VANET) is formed by a number of moving vehicles that are equipped with wireless interfaces. It is a kind of Mobile Ad Hoc Network (MANET) in which communication takes place between moving vehicles on the road. VANETs are heterogeneous in nature as they provide wireless communication among moving vehicles (V2V) and vehicle to Road Side Units (RSU). It has become an exciting area of research as it is anticipated to improve Intelligent Transport System (ITS). To exploit effective communication among vehicles, routing is the key factor which needs to be investigated. This paper intends to analyze the performance of AODV and GPSR routing protocols in a VANET in various scenarios under different traffic conditions with respect to Packet Delivery Ratio (PDR) and average End-to-End Delay (E2ED). Simulation is performed using NS-2.35 in combination with Vanet MobiSim. It has been found that AODV performs better with respect to PDR and GPSR outperforms AODV with respect to E2ED. Also, the performance of both the routing protocols varies from one scenario to another and traffic types. The performance of both AODV and GPSR is improved by using IEEE 802.11p instead of IEEE 802.11.

Scenario Based Performance Analysis of AODV and GPSR Routing Protocols in a VANET

Vehicular Ad Hoc Networks (VANET) is a subclass of Mobile ad hoc networks which provides a distinguished approach for Intelligent Transport System (ITS). The survey of routing protocols in VANET is important and necessary for smart ITS. This paper discusses the advantages/disadvantages and the applications of various routing protocols for vehicular ad hoc networks. It explores the motivation behind the designed, and traces the evolution of these routing protocols. This paper discusses the main 5 types of protocols for VANET Topology Based, Positioned Based, Geo Cast, Broad Cast, Cluster Based Protocols.

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Study of Various Routing Protocols in VANET

Vehicular Ad Hoc Networks (VANET) is a subclass of Mobile ad hoc networks which provides a distinguished approach for Intelligent Transport System (ITS). The survey of routing protocols in VANET is important and necessary for smart ITS. This paper discusses the advantages / disadvantages and the applications of various routing protocols for vehicular ad hoc networks. It explores the motivation behind the designed, and traces the evolution of these routing protocols. This paper discusses the main 5 types of protocols for VANET Topology Based, Positioned Based, Geo Cast, Broad Cast, and Cluster Based Protocols. It also discusses the types of Broadcast Protocols like multi hop and reliable broadcast protocols. Keywords: VANET , ITS, MANET, UMB, DV-CAST.

https://www.iiste.org/Journals/index.php/NCS/article/download/1245/1166

Broadcasting Routing Protocols in VANET

  Abstract—VANET (Vehicular adhoc network) research field is growing very fast. It has to serves a wide range of applications under different scenario (City, Highway). It has various challenges to adopt the protocols that can serve in different topology and scenario. This paper presents a comparative study of the adhoc routing protocols. The main objective of Vehicular adhoc networks is to build a robust network among mobile vehicles so that vehicles can talk to each other for the safety of human beings. VANET hits the protocol's strength due to its highly dynamic features. Thus in testing a protocol suitable for VANET implementation, we have selected different routing protocols. In this paper, an attempt has been made to compare four well-known protocols AODV, DSR, OLSR and DSDV by using three performance metrics packet delivery ratio, average end to end delay and routing overhead. The comparison has been done by using simulation tool NS2 which is the main simulator, Network animator (NAM) and excel graph which is used for preparing the graphs from the trace files.

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Poonam Dhamal

Papers

Study of Various Routing Protocols in VANET

Broadcasting Routing Protocols in VANET

Performance Evaluation of Proactive and Reactive Protocols in VANET