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Cooperative intelligent transport systems (C-ITS) continue to be developed to enhance transportation safety and sustainability. However, the communication of vehicle-to-everything (V2X) systems is inherently open, leading to vulnerabilities that attackers can exploit. This represents a threat to all road users, as security failures can lead to privacy violations or even fatalities. Moreover, a high fatality rate is correlated with soft-mobility road users. Therefore, when developing C-ITS systems, it is important to broaden the focus beyond connected vehicles to include soft-mobility users and legacy vehicles. This work presents a new approach developed in the context of emerging hybrid networks, combining intelligent transport systems operating in 5.9 GHz (ITS-G5) and radio-mobile cellular technologies. Two protocols were implemented and evaluated to introduce security guarantees (such as privacy and integrity) in communications within the developed C-ITS hybrid environment. As a result, this work securely integrates G5-connected ITS stations and soft-mobility users through a smartphone application via cellular networks. Commercial equipment was used for this goal, including on-board and roadside units. Computational, transmission and end-to-end latency were used to assess the system's performance. Implemented protocols introduce an additional 11% end-to-end latency in hybrid communications. Moreover, workflows employing hybrid communications impose, on average, an extra 28.29 ms of end-to-end latency. The proposal shows promise, as it reaches end-to-end times below the latency requirements imposed in most C-ITS use cases. [ABSTRACT FROM AUTHOR]

Vehicle-to-X communication enables vehicles and other road users to exchange information in order to increase traffic efficiency and safety. All participants build a decentralized ad hoc network that can operate without the need for additional communication infrastructure. Two competing transmission technologies are available for this purpose. The WLAN-based approach ITS-G5 and the cellular-mobile-based LTE-V2X both enable the direct exchange of information between participants. Each of these technologies has individual advantages and disadvantages that recommend a specific technology for specific use cases. The hybrid usage of the two technologies in a common network can help to improve the reliability of transmissions for safety-critical applications by providing suitable transmission features for every use case, including dissemination range, latency, and channel throughput. The proposed hybrid V2X network approach provides participants with various options for selecting the transmission path to better adapt to the requirements of the specific use cases. The investigation is based on measurements of the transmission properties of ITS-G5 and LTE-V2X in real traffic environments as well as on simulations of hybrid V2X networks in a combined simulation environment for traffic and communication behavior. An important part of this investigation is the development of suitable dissemination models that describe the transmission behavior of both technologies. Initial results show that both technologies can be constructively combined to improve the reliability of communication for safety-critical applications in decentralized V2X networks.

Featured Application: The primary objective of introducing the proposed tools and methodology is to enable the accurate and comprehensive simulation of ITS-G5 radio channel load, thereby advancing the field of C-ITS network design and deployment. By leveraging these resources, stakeholders can gain critical insights into the intricate relationship between various C-ITS services, V2X penetration ratios, ITS-G5 radio channels, and network performance. These simulations can then be applied to optimize C-ITS network architecture, identify potential bottlenecks and points of failure, and support strategic decision making. Ultimately, the proposed tools and methodology can serve as a crucial asset for improving the reliability and efficiency of C-ITS networks. Transportation efficiency and safety are crucial development areas nowadays. Cooperative Intelligent Transport Systems (C-ITSs), relying on Vehicle-to-Everything (V2X) communication, are a promising group of technologies and applications aimed at solving several issues related to road safety or efficiency. The C-Roads Platform was brought to life to ensure the cross-border harmonization of C-ITS at a European level, guiding several pilot activities in national deployment projects and providing a harmonized pan-European C-ITS service perspective. Because of the safety relevance of V2X technologies, it is essential to ensure that the crucial parameters of wireless communication are within an acceptable range to serve C-ITS applications appropriately. In this work, we developed a simulation pipeline to evaluate future V2X deployments using the real-world traffic and map data of a C-Roads harmonized major Hungarian C-ITS deployment site. First, we selected three time periods representing different traffic patterns. Then, we reconstructed the flow-based traffic data from the real-world traffic counters for the selected time periods. We developed an approach based on linear equations to perform the conversion. Eventually, we used the real-world data to simulate the effects of various DSRC (ITS-G5-based) C-ITS services and V2X penetration rates on the Channel Busy Ratio (CBR) parameter of the radio access environment. [ABSTRACT FROM AUTHOR]

Cooperative intelligent transport systems (C-ITS) continue to be developed to enhance transportation safety and sustainability. However, the communication of vehicle-to-everything (V2X) systems is inherently open, leading to vulnerabilities that attackers can exploit. This represents a threat to all road users, as security failures can lead to privacy violations or even fatalities. Moreover, a high fatality rate is correlated with soft-mobility road users. Therefore, when developing C-ITS systems, it is important to broaden the focus beyond connected vehicles to include soft-mobility users and legacy vehicles. This work presents a new approach developed in the context of emerging hybrid networks, combining intelligent transport systems operating in 5.9 GHz (ITS-G5) and radio-mobile cellular technologies. Two protocols were implemented and evaluated to introduce security guarantees (such as privacy and integrity) in communications within the developed C-ITS hybrid environment. As a result, this work securely integrates G5-connected ITS stations and soft-mobility users through a smartphone application via cellular networks. Commercial equipment was used for this goal, including on-board and roadside units. Computational, transmission and end-to-end latency were used to assess the system’s performance. Implemented protocols introduce an additional 11% end-to-end latency in hybrid communications. Moreover, workflows employing hybrid communications impose, on average, an extra 28.29 ms of end-to-end latency. The proposal shows promise, as it reaches end-to-end times below the latency requirements imposed in most C-ITS use cases.

With the growing importance of cooperative intelligent transport systems (C-ITS), 3GPP has standardized LTE-V2X (Long Term Evolution - Vehicle-to-everything) in Release 14 to address specifically vehicle-to-everything (V2X) connectivity. This standard introduces a mode 4, in which vehicles allocate radio resources autonomously without cellular infrastructure support for direct vehicle-to-vehicle (V2V) communications. However, as LTE-V2X is a recent technology (compared to WAVE and ITS-G5), it is not sufficiently evaluated in the literature. In this work, we propose an evaluation of LTE-V2X mode 4 performances considering the impact of the parameters of the sensing-based resource allocation mechanism, the traffic load and the Quality of service (QoS) mechanism. In addition, we propose a comparative study of LTE-V2X mode 4 with ITS-G5. Based on several simulation scenarios from 3GPP, we prove that the Sensing-based SPS mechanism parameters and the traffic load significantly impact the performance offered by LTE-V2X. In addition, we show that the QoS mechanism of LTE-V2X outperforms the ITS-G5 one in a realistic multi-application context.

Transportation efficiency and safety are crucial development areas nowadays. Cooperative Intelligent Transport Systems (C-ITSs), relying on Vehicle-to-Everything (V2X) communication, are a promising group of technologies and applications aimed at solving several issues related to road safety or efficiency. The C-Roads Platform was brought to life to ensure the cross-border harmonization of C-ITS at a European level, guiding several pilot activities in national deployment projects and providing a harmonized pan-European C-ITS service perspective. Because of the safety relevance of V2X technologies, it is essential to ensure that the crucial parameters of wireless communication are within an acceptable range to serve C-ITS applications appropriately. In this work, we developed a simulation pipeline to evaluate future V2X deployments using the real-world traffic and map data of a C-Roads harmonized major Hungarian C-ITS deployment site. First, we selected three time periods representing different traffic patterns. Then, we reconstructed the flow-based traffic data from the real-world traffic counters for the selected time periods. We developed an approach based on linear equations to perform the conversion. Eventually, we used the real-world data to simulate the effects of various DSRC (ITS-G5-based) C-ITS services and V2X penetration rates on the Channel Busy Ratio (CBR) parameter of the radio access environment.

In the coming years, connectivity between vehicles with autonomous driving features and roadside infrastructure will become more and more a reality on our roads, pursuing to improve road safety and traffic efficiency. In this regard, two main communication standards are considered as key enablers, that is ITS-G5 (based on IEEE 802.11p) and C-V2X (3GPP). To assess the real performance of these technologies, there is still need for an objective and independent one-to-one comparison of these technologies using off-the-shelf hardware under identical and real-life traffic conditions. Until today, performance evaluations are limited to simulations, emulations or individual technology assessments in real-life circumstances. In this paper, an exhaustive and fair evaluation of the technologies has been conducted in a real-life highway environment under identical conditions. Tailored evaluation tools in combination with our in-house CAMINO vehicular framework has been utilized to perform the tests and analyze the results for different well-specified test cases. The performance evaluation shows that for the short-range technologies, C-V2X PC5 has, in general, a higher range than ITS-G5, while ITS-G5 offers lower latency than C-V2X PC5 in low-density scenarios. Long-range 4G C-V2X can be considered as an alternative for certain use cases. The outcome of this experimentation study can be used as valuable information for the further development of future (5G) connected and autonomous driving. [ABSTRACT FROM AUTHOR]

The suggested benefits of automated vehicles are plentiful, but many of the benefits depend on connectivity with other vehicles and infrastructure to be useful to the society at large. This paper identifies two main research gaps: first, to identify whether ITS-G5 can be a reliable communication link for V2V communication. Second, to discuss which implications the results have for practitioners working with the future implementation of CAVs. We answer these research gaps by introducing a conceptualization of V2V communication operationalized through controlled experiments with vehicles on a closed runway. In the experiments, onboard ITS-G5 communication devices are used for measuring signal strength and package loss between the vehicles. The results indicate that ITS-G5 technology has some limitations, especially for long range communication (>1500 m), and in cases with other traffic shadowing the signal. We conclude that although ITS-G5 has high risk of reduced radio link in non-line-of-sight situations and in situations where the radio signal is shadowed by other traffic, the latency and operational range would be sufficient for safety critical services in line-of-sight situations. For policymakers and practitioners working with implementing communication for vehicles, the results imply that large-scale piloting is critical for testing the technology in a realistic environment outside of the laboratories. In such environments different stakeholders and disciplines can meet and collaborate to avoid siloed approaches.

The industry is providing vehicles with advanced features and technologies that allows vehicles to connect and communicate with their nearby environment. These technologies’ umbrella term, Cooperative Intelligent Transportation Systems (C-ITS) are aimed to enhance road traffic efficiency, safety and assist the drivers in multiple ways. The C-ITS communication system should be able to offer the functional benefits to different sets of use-cases, each having a particular sub-set of requirements. In this paper some of the relevant use-case scenarios utilizing road weather and traffic information are studied in terms of communication technology. The key requirements for C-ITS use-case scenarios are analyzed and an evaluation of the ITS-G5 protocol stack is performed. The performance of ITS-G5 in use-case scenarios is considered testing messages (alerts) on road weather and traffic information in realistic environments. The results indicate that the performance of ITS-G5 in tested use-case scenarios offers 90-98% success rate in the delivery of safety messages at a transmission frequency of 10Hz. Also, ITS-G5 delivers safety alerts with a minimum delay so that it satisfies the C-ITS use-case requirements in real environments. The C-ITS pilot platform also performs efficiently in terms of transmitting packets from a safe distance with minimum network latency and packet loss between vehicles and infrastructure. C-ITS pilot use-cases were tested on the platform developed and tailored by the Finnish Meteorological Institute (FMI).

The objective of vehicular communication is to improve road safety and traffic efficiency through various cooperative intelligent transport system (C-ITS) services. These services allow information exchange between vehicles and other communication entities (e.g., vehicles, infrastructure, pedestrians). In addition, many advanced services are envisaged to support autonomous vehicles and safety applications. Therefore, the performance requirements of such services are considered highly critical for road safety. However, all these services increase the channel load, and thus, it isn’t easy to differentiate which service has a higher priority for accessing communication channels. In this paper, we focus on the classification of C-ITS services, which allows the cohabitation of all services considering the strict performance requirements for some services. The aim is to classify C-ITS services based on their packet delay requirements to define higher priority for critical services to ensure their dissemination, especially under congestion conditions. Then, we present protocols and quality of service (QoS) mechanisms that can map this classification to the available vehicular networks.

In this paper we report the implementation and experimental evaluation of a proposed hybrid communication ecosystem for CCAM applications such as cooperative adaptive cruise control (CACC) and smart intersections. Three wireless technologies have been suggested for communications between vehicles and intelligent traffic lights and are evaluated in this work: ITS-G5 based on IEEE 802.11p and LTE sidelink with PC5 air interface for direct short range links, and regular mobile LTE with LTE Uu air interface for long range or indirect links. The applications used are independent of the communication channel, to enable a comparison on the application level of the different communication technologies. Field experiments were carried out with two CACC-equipped vehicles and three intelligent traffic lights in two field test locations under ideal, i.e., no-traffic, conditions and with real traffic. Experimental results related to CACC show that the best performance in terms of latency is achieved by the ITS-G5 system, while LTE PC5 and LTE Uu links show a penalty of 20 and 50 ms respectively. However, experimental results show that all three communication technologies were still able to guarantee string stable performance of the vehicle platoon. Regarding the smart intersections, an analysis based on field measurements and comparison between long- and short-range solutions is proposed; the analysis includes the impact of each channel on the applications such as speed advisory and green light prediction. The reported experimental evaluation shows the potential of current mobile technologies for CCAM use cases and highlights the way for further CCAM applications based on 5G and beyond mobile networks.

The critical nature of vehicular communications requires their extensive testing and evaluation. Analytical models can represent an attractive and cost-effective approach for such evaluation if they can adequately model all underlying effects that impact the performance of vehicular communications. Several analytical models have been proposed to date to model vehicular communications based on the IEEE 802.11p (or DSRC) standard. However, existing models normally model in detail the MAC (Medium Access Control), and generally simplify the propagation and interference effects. This reduces their value as an alternative to evaluate the performance of vehicular communications. This paper addresses this gap, and presents new analytical models that accurately model the performance of vehicle-to-vehicle communications based on the IEEE 802.11p standard. The models jointly account for a detailed modeling of the propagation and interference effects, as well as the impact of the hidden terminal problem. The model quantifies the PDR (Packet Delivery Ratio) as a function of the distance between transmitter and receiver. The paper also presents new analytical models to quantify the probability of the four different types of packet errors in IEEE 802.11p. In addition, the paper presents the first analytical model capable to accurately estimate the Channel Busy Ratio (CBR) metric even under high channel load levels. All the analytical models are validated by means of simulation for a wide range of parameters, including traffic densities, packet transmission frequencies, transmission power levels, data rates and packet sizes. An implementation of the models is provided openly to facilitate their use by the community. [ABSTRACT FROM AUTHOR]

V2X (Vehicle to everything) communications can be currently supported by standards based on IEEE 802.11p (e.g. DSRC or ITS-G5) or LTE-V2X (also known as Cellular V2X or C-V2X) technologies. There has been an intense debate in the community on which technology achieves best performance. However, existing studies do not take into account the variability present in the generation and size of V2X messages. This variability can significantly impact the operation and performance of the Medium Access Control (MAC). This study progresses the state of the art by conducting an in-depth evaluation of both technologies under different message traffic patterns. In particular, we consider aperiodic and periodic messages of constant or variable size based on the standardized ETSI Cooperative Awareness Messages (CAMs). This study considers different scenarios and possible configurations of IEEE 802.11p and LTE-V2X. We demonstrate that IEEE 802.11p can better cope with variations in the size and time interval between messages. We also demonstrate (and characterize) that the LTE-V2X sensing-based semi-persistent scheduling faces certain inefficiencies when transmitting aperiodic messages of variable size. These inefficiencies result in that IEEE 802.11p generally outperforms LTE-V2X when transmitting aperiodic messages of variable size except when the channel load is very low.

Vehicle speed and trajectories play an important role in influencing fuel consumption, gas emissions and travel time. ITS services are often proposed in order to reduce the impact of these issues on the environment and the comfort of drivers. Cooperative Intelligent Transport Systems (C‐ITS) introduced many services that target traffic efficiency management and road safety. Green Light Optimal Speed Advisory (GLOSA) is one of the traffic efficiency services that can significantly cut fuel consumption and decrease waiting time while crossing intersections. When approaching a signalized intersection, GLOSA informs the driver of an advisory speed to respect in order to reach the intersection while the traffic light is green. In this paper, we propose an Efficient Path Planning GLOSA‐based (EPP‐GLOSA) approach using Dijkstra greedy algorithm and GLOSA service. EPP‐GLOSA aims at proposing the fastest path for the driver to follow in order to reach its destination. The estimated duration to reach the destination takes into consideration the state of traffic lights along the path on top of Dijkstra algorithm. The proposed approach is evaluated under a large scale scenario in free flow and rush‐hour conditions. Our findings show that EPP‐GLOSA offers a balanced scale between travel time reduction and fuel saving especially in free flow conditions. [ABSTRACT FROM AUTHOR]

The arrival of the connected and/or autonomous cars offers countless opportunities for both the user and service provider. In this paper, we present a novel solution for tolling transaction using ITS-G5 technology. Specifically, it investigates how to secure tolling transactions performed with the cooperative intelligent transportation system (C-ITS) equipment and the tolling server as a trusted party. In this novel solution, we consider ITS components using the ITS-G5 technology with features specified by the European Telecommunication Standardization Institute (ETSI): RoadSide Unit (RSU), On-Board Unit (OBU), and the standardized architecture of the Electronic Fee Collection by the International Organization for Standardization (ISO). To perform the tolling transaction, a point-to-point protocol must be established between the RSU of the infrastructure and the OBU embedded in the vehicle. Therefore, we design an efficient architecture that ensures the security of exchanges is guaranteed by the security back office of the tolling server as a trusted party. From the application to the service and until its usage, some security requirements are verified: mutual authentication between all entities involved in the transaction, confidentiality, integrity, and non-repudiation of all exchanged information. The certificate usage combined with the signature process certifies the mutual authentication between each entity: the OBU with the RSU, the payer with the service provider and the RSU with the tolling server. The encryption of the messages and the verification of the signatures ensure the confidentiality, the integrity and the non-repudiation of all exchanged information. The safety and efficiency of the proposed method are validated through its formal verification using the security protocols verifier tool AVISPA (Automated Validation of Internet Security Protocols and Applications). Furthermore, the proposed architecture requires reasonable resources which will be suitable for vehicle-to-infrastructure (V2I) communications.

Connected and Automated Vehicles (CAVs) utilize a variety of onboard sensors to sense their surrounding environment. CAVs can improve their perception capabilities if vehicles exchange information about what they sense using V2X communications. This is known as cooperative or collective perception (or sensing). A frequent transmission of collective perception messages could improve the perception capabilities of CAVs. However, this improvement can be compromised if vehicles generate too many messages and saturate the communications channel. An important aspect is then when vehicles should generate the perception messages. ETSI has proposed the first set of message generation rules for collective perception. These rules define when vehicles should generate collective perception messages and what should be their content. We show that the current rules generate a high number of collective perception messages with information about a small number of detected objects. This results in an inefficient use of the communication channel that reduces the effectiveness of collective perception. We address this challenge and propose an improved algorithm that modifies the generation of collective perception messages. We demonstrate that the proposed solution improves the reliability of V2X communication and the perception of CAVs. [ABSTRACT FROM AUTHOR]

Most V2X (Vehicle-to-Everything) applications rely on broadcasting awareness messages known as CAM (Cooperative Awareness Messages) in ETSI or BSM (Basic Safety Message) in SAE standards. A large number of studies have been devoted to guarantee their reliable transmission. However, to date, the studies are generally based on simplified data traffic models that generate awareness messages at periodic intervals or with a constant message size. These models do not accurately represent the real generation of CAM messages that follow specific mobility-based rules. Using simplified and unrealistic traffic models can significantly impact the results and validity of the studies, and hence accurate models for the generation of awareness messages are necessary. This paper proposes the first set of models that can realistically generate CAM messages. The models have been created from real traces collected by two car manufacturers in urban, sub-urban and highway test drives. The models are based on mth order Markov sources, and model the size of CAMs and the time interval between CAMs. The models are openly provided to the community and can be easily integrated into any simulator. [ABSTRACT FROM AUTHOR]

Vehicular networks require vehicles to periodically transmit 1-hop broadcast packets in order to detect other vehicles in their local neighborhood. Many vehicular applications depend on the correct reception of these packets that are transmitted on a common control channel. Vehicles will actually be required to simultaneously execute multiple applications. The transmission of the broadcast packets should hence be configured to satisfy the requirements of all applications while controlling the channel load. This can be challenging when vehicles simultaneously run multiple applications, and each application has different requirements that vary with the vehicular context (e.g., speed and density). In this context, this paper proposes and evaluates different techniques to dynamically adapt the rate and power of 1-hop broadcast packets per vehicle in multi-application scenarios. The proposed techniques are designed to satisfy the requirements of multiple simultaneous applications and reduce the channel load. The evaluation shows that the proposed techniques significantly decrease the channel load, and can better satisfy the requirements of multiple applications compared to existing approaches, in particular the message handler specified in the SAE J2735 DSRC Message Set Dictionary. [ABSTRACT FROM AUTHOR]

In the automotive domain, Cooperative Localization (CLoc) is a new promising paradigm that aims at outperforming conventional Global Navigation Satellite Systems (GNSS) in terms of positioning accuracy, robustness, and service continuity, by relying on Vehicle-to-Vehicle (V2V) communications and hybrid data fusion. However, the growing number and the variety of the sensors aboard vehicles raise unprecedented challenges, especially in the context of distributed fusion approaches. This paper thus compares parametric and nonparametric Bayesian data fusion engines (e.g., based on cooperative variants of the Extended Kalman Filter (EKF) and Particle Filter (PF), respectively), while validating a CLoc scheme suitable to Vehicular Ad Hoc Networks (VANETs). More particularly, absolute position information from both onboard GNSS receiver and ITS-G5 V2V messages, as well as relative distance measurements based on the Impulse Radio–Ultra-Wideband (IR–UWB) technology, are combined into a single location solution that is hopefully more robust and more accurate than that of standalone GNSS. First, we investigate V2V ranging accuracy on a highway under real mobility conditions. In the same environment, we then provide offline validations of CLoc positioning, confirming significant performance gains through cooperation over conventional GNSS, even in case of poor initialization. In this specific context, the PF solution is thus shown to yield even better accuracy in comparison with EKF, thanks to its fine robustness against faced non-linear dynamics and non-Gaussian noise processes. Finally, we illustrate the resilience of the proposed solution under temporary GNSS denial. [ABSTRACT FROM AUTHOR]

VANETs (Vehicular Ad hoc Networks) operating in conjunction with road-side infrastructure connecting road-side infrastructure are an emerging field of wireless communication technology in the vehicular communication’s domain. For VANETs, the IEEE 802.11p-based ITS-G5 is one of the key standards for communication globally. This research work integrates the ITS-G5 with a cellular-based 5G Test Network (5GTN). The resulting advanced heterogeneous Vehicular Network (VN) test-bed works as an effective platform for traffic safety between vehicles and road-side-infrastructure. This test-bed network provides a flexible framework to exploit vehicle-based weather data and road observation information, creating a service architecture for VANETs that supports real-time intelligent traffic services. The network studied in this paper aims to deliver improved road safety by providing real-time weather forecast, road friction information and road traffic related services. This article presents the implementation of a realistic test-bed in Northern Finland and the field measurement results of the heterogeneous VANETs considering the speed of vehicle, latency, good-put time and throughput. The field measurement results have been obtained in a state-of-the-art hybrid VANET system supporting special road weather services. Based on field measurement results, we suggest an efficient solution for a comprehensive hybrid vehicular networking infrastructure exploiting road weather information.

Human errors are probably the main cause of car accidents, and this type of vehicle is one of the most dangerous forms of transport for people. The danger comes from the fact that on public roads there are simultaneously different types of actors (drivers, pedestrians or cyclists) and many objects that change their position over time, making difficult to predict their immediate movements. The intelligent transport system (ITS-G5) standard specifies the European communication technologies and protocols to assist public road users, providing them with relevant information. The scientific community is developing ITS-G5 applications for various purposes, among which is the increasing of pedestrian safety. This paper describes the developed work to implement an ITS-G5 prototype that aims at the increasing of pedestrian and driver safety in the vicinity of a pedestrian crosswalk by sending ITS-G5 decentralized environmental notification messages (DENM) to the vehicles. These messages are analyzed, and if they are relevant, they are presented to the driver through a car’s onboard infotainment system. This alert allows the driver to take safety precautions to prevent accidents. The implemented prototype was tested in a controlled environment pedestrian crosswalk. The results showed the capacity of the prototype for detecting pedestrians, suitable message sending, the reception and processing on a vehicle onboard unit (OBU) module and its presentation on the car onboard infotainment system.

Tight coupling between the performance of vehicle-to-vehicle (V2V) communications and the performance of cooperative intelligent transportation system (C-ITS) safety applications is addressed. A cyber-physical system analytical framework is developed which links the characteristics of V2V communications (such as packet loss probability and packet transmission delay) with the physical mobility characteristics of the vehicular system (such as safe intervehicular distance). The study is applied to the Day 1 C-ITS application, emergency electronic brake lights, enabled by the European Telecommunication Standard Institute ITS-G5 and IEEE 802.11p standards. [ABSTRACT FROM AUTHOR]

The revolution of cooperative connected and automated vehicles is about to begin and a key milestone is the introduction of short range wireless communications between cars. Given the tremendous expected market growth, two different technologies have been standardized by international companies and consortia, namely IEEE 802.11p, out for nearly a decade, and short range cellular-vehicle-to-anything (C-V2X), of recent definition. In both cases, evolutions are under discussion. The former is only decentralized and based on a sensing before transmitting access, while the latter is based on orthogonal resources that can be also managed by an infrastructure. Although studies have been conducted to highlight advantages and drawbacks of both, doubts still remain. In this work, with a reference to the literature and the aid of large scale simulations in realistic urban and highway scenarios, we provide an insight in such a comparison, also trying to isolate the contribution of the physical and medium access control layers.

Cooperative awareness on the road is intended to support the road users by providing knowledge about the surroundings and relies on the information exchange enabled by vehicular communications. To achieve this goal the European telecommunication standard institute (ETSI) delivered the standard EN 302 637-2 for cooperative awareness messages (CAM). The CAM triggering conditions are based on the kinematics of the originating vehicle, which is checked periodically. In this paper, we show that the standardized ETSI protocol may suffer a decrease in communication performance under several realistic mobility patterns. The potential influence of the discovered phenomena on the IEEE 802.11p medium access control operation is studied. [ABSTRACT FROM PUBLISHER]