Björn Schünemann

V2X-Based Traffic Congestion Recognition and Avoidance

Vehicular traffic congestion is a global phenomenon that has increased in importance in the last decades and has caused economically and ecologically negative effects. Thus, finding a way to improve traffic efficiency is a high-frequented problem to be solved by scientists and politicians worldwide. One new promising approach is the usage of decentralized wireless vehicle to vehicle communication based on the Vehicle-2-X (V2X) technology. The idea is that vehicles share information about the current local traffic situation and use this information to optimize their routes. In this paper, we introduce a new algorithm that can be used by navigation systems to calculate routes circumnavigating congested roads. For this purpose, each vehicle transmits its average speed of a road segment to vehicles in the neighbourhood. As a result, vehicles receiving this information can recalculate their routes based on the knowledge about the current possible speeds in the road segments of their neighbourhood. To evaluate the improvements that can be achieved by our algorithm, simulations have been done. Our results show that navigation systems using the V2X technology for a more intelligent route calculation can improve the traffic efficiency of future transport systems.

V2X simulation runtime infrastructure VSimRTI: An assessment tool to design smart traffic management systems

The V2X simulation runtime infrastructure - VSimRTI - enables the preparation and execution of V2X simulations. It is a flexible system which simulates traffic flow dynamically. VSimRTI couples different simulators, thus, allowing the simulation of the various aspects of future intelligent transportation systems. The easy integration and exchange of simulators enables the utilization of the most relevant simulators for a realistic presentation of vehicle traffic, emissions, wireless communication, and the execution of V2X applications.

Realistic Simulation of V2X Communication Scenarios

Vehicle-2-X (V2X) Communication provides the foundation for new applications that enhance both safety and traffic efficiency. Before V2X applications can be deployed in practice, their in-depth analysis is necessary. For this end, detailed and realistic simulations are essential. Depending on the simulated V2X Communication application, particular simulators have to be coupled. For this purpose, we have developed the V2X Simulation Runtime Infrastructure (VSimRTI) offering the flexibility to combine arbitrary simulators. The VSimRTI is derived from concepts of the High Level Architecture (HLA). It synchronizes the simulators and enables the communication among them. Another feature of our simulation environment is the emulation of the environment of V2X Communication applications in real vehicles. As a result, we can integrate real V2X Communication applications without modifications.

Efficient traffic simulator coupling in a distributed V2X simulation environment

For the simulation of all aspects of V2X Communication scenarios, different simulators have to be combined and an interaction among them at runtime of the simulation has to be enabled. Hence, we have developed the V2X Simulation Runtime Infrastructure (VSimRTI) which couples discrete event-based simulators, e.g. for communication network, traffic, and V2X application simulation. The flexibility of VSimRTI allows us to vary the composition of integrated simulators depending on the specific requirements of a scenario. Moreover, optimistic synchronisation mechanisms enable us to decrease simulation time. In this paper, we combine both traffic simulators VISSIM and SUMO. VISSIM is used to achieve a highly accurate simulation of the most interesting region, whereas the more efficient traffic simulator SUMO simulates surrounding areas. We shall show that this simulator coupling reduces the overall simulation time without any decrease in accuracy. This work has been carried out within the PRE-DRIVE C2X project.

A Novel Approach for Realistic Emulation of Vehicle-2-X Communication Applications

New applications in future intelligent transportation systems are to enhance both safety and traffic efficiency. Wireless vehicular communication is to provide the basis for the new Vehicle-2-X communication applications. However, field tests are necessary to make them usable and validate the improvements that are to be achieved. Since the realization of the field tests is rather complex and expensive, detailed simulations are essential to prepare the tests in the real world and reduce their costs. Currently, software simulators do not support all aspects necessary for a proper validation of Vehicle-2-X applications. In this paper, an integrated software simulation environment that fulfils the special requirements of Vehicle-2-X applications is presented. Furthermore, our testbed architecture that allows simulating Vehicle-2-X communication under real physical conditions is introduced.

The influences of communication models on the simulated effectiveness of V2X applications

In this article, we aim to evaluate the influences of different propagation models on the results of V2X simulations. First, we analyze how the models free space propagation, Rayleigh fading, and Ricean fading in synthetic scenarios with and without background communication influence the simulation of communication in general. After that, we investigate the impact of the models on the simulated behavior of a V2X traffic efficiency application in a real inner city scenario. Our results show that the selection of the propagation model affects the number of delivered messages, but exerts no significant influence on the simulated effectiveness of a V2X traffic efficiency application in urban areas. Under those circumstances, a simplified propagation model is sufficient.

Improving V2X simulation performance with optimistic synchronization

The simulation framework VSimRTI provides the integration of multiple heterogeneous simulators to enable V2X application simulations. In order to increase the performance and scalability of complex V2X simulations, a new time management service has been implemented that enables optimistic synchronization in federated simulations. This paper presents the underlying mechanisms as well as the resulting system architecture. To evaluate the improvements that can be achieved, different experiments with highly configurable virtual federates as well as real simulators have been realized. Our experiments show the conditions for an improvement by optimistic synchronization mechanisms and demonstrate the performance increase that can be achieved.

Realistic simulation of vehicular communication and vehicle-2-X applications

In future intelligent transport systems, wireless vehicular communication will provide the basis for new applications to enhance safety, traffic efficiency, and provide infotainment services. In the near future, field tests are to be carried out to verify the improvements that could be achieved by these new Vehicle-2-X applications. However, the realisation of such field tests is very complex and expensive. Therefore, detailed simulations are necessary to prepare the tests in the real world and reduce their costs. Current simulation tools do not support all aspects necessary for Vehicle-2-X applications. In this paper, we present an integrated software simulation environment that fulfils the special requirements of Vehicle-2-X applications. Furthermore, we introduce our testbed architecture that allows simulating vehicular communication under real physical conditions.

Simulation Tools and Techniques for Vehicular Communications and Applications

In the domain of Inter-Vehicle Communication (IVC), even though first field operational tests are already going on, performance evaluation is still dominated by simulation experiments. Yet, they require a very specific methodology as well as adapted tools and models not straightforwardly found in other domains. In this chapter, we first describe the required methodology in terms of scalability and applicability to select the right models and their interactions. In particular, we classify each class of models as in increasing level of granularity, and discuss in detail the trade-off between scalability and applicability typical to IVC simulations. We then introduce some of the most widely used and openly available simulation frameworks applicable to the domain of IVC, and emphasize their capabilities related to the required methodology. In particular, we present the IVC simulation toolkits Veins, iTETRIS, and VSimRTI, three prominent simulation platforms openly available for IVC simulations. To provide guidelines for efficient and scalable simulations of IVC applications, we discuss the appropriate selection of models and their level of granularity as function of the IVC application requirements, and provide an overview of their corresponding support in each of toolkit.

A Sensitive Metric for the Assessment of Vehicular Communication Applications

The technical evaluation of Vehicle-2-X communication properties in the field operational test simTD delivered first results. However, the need for new metrics arose to be able to measure the influences of communication characteristics on the application performance more precisely. Hence, we proposed the Consecutive CAM Period (CCP) as a suitable metric. In this paper we discuss the advantages of using the CCP compared to the classical communication metrics as the Packet Delivery Ratio (PDR). In a short evaluation study we furthermore present a method that helps to approach two issues. 1) The time and space dependent nature of the CCP facilitates to detect if use cases actually exist or not. 2) Particularly, the evaluation of the maximum CCP guaranties that certain situations are not missed compared to the usage of metrics with an arithmetic mean calculation.