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The V2X Simulation Runtime Infrastructure VSimRTI

VSimRTI - Smart Mobility Simulation

The V2X Simulation Runtime Infrastructure (VSimRTI) is a comprehensive framework for the assessment of new solutions for Cooperative Intelligent Transportation Systems. Vehicle movements and sophisticated communication technologies like Vehicle-2-X communication and cellular networks can be modeled in detail. VSimRTI is one of the most flexible systems available in the automotive research arena to dynamically simulate Smart Mobility applications and to assess their impacts and benefits.

VSimRTI couples different simulators to allow the simulation of the various aspects of future Intelligent Transportation Systems. The easy integration and exchange of simulators enables the substitution of the most relevant simulators for a realistic presentation of vehicular traffic, emissions, wireless communication (cellular and ad-hoc), user behavior, and the modelling of mobility applications. Furthermore, VSimRTI is currently extended to allow the simulation of electric mobility scenarios.

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VSimRTI Features

Smart Mobility applications and Cooperative Transportation Systems help to enhance safety and traffic efficiency. However, the simulation of corresponding scenarios is a challenge because different simulation worlds come together here: e.g. vehicular traffic, wireless network communication, and application modeling. To solve this problem, VSimRTI couples different simulators and enables the simulation of the various aspects of future Intelligent Transportation Systems. Consequently, VSimRTI simulations allow the analysis of novel mobility solutions before real field tests start.

Different simulations aspects modeled by VSimRTI
Different simulations aspects modeled by VSimRTI

The aim of the VSimRTI project is to make the preparation and execution of simulations as easy as possible for the users. Therefore, a comprehensive framework for simulator integration was created that facilitates the simulation of Smart Mobility scenarios. All simulator management tasks, such as synchronization, interaction and lifecycle management are handled completely by VSimRTI. Several optimization techniques, such as optimistic synchronization, enable high performance simulations. Special features, e.g. traffic lights, roadside stations, and CAM and DENM transmissions, are supported by VSimRTI. Moreover, various configuration, visualization and analysis tools assure maximum usability.

VSimRTI Concept

In contrast to existing fixed simulator couplings, the VSimRTI simulation infrastructure allows the easy integration and exchange of simulators. Thus, the high flexibility of VSimRTI enables the coupling of the most appropriate simulators for a realistic presentation of vehicular traffic, emissions, wireless communication (cellular and ad-hoc), user behavior, and the modelling of mobility applications. Depending on the specific requirements of a simulation scenario, the most relevant simulators can be used.

An example of a VSimRTI simulator coupling
An example of a VSimRTI simulator coupling

VSimRTI uses an ambassador concept inspired by some fundamental concepts of the High Level Architecture (HLA). Thus, it is possible to couple arbitrary simulation systems with a remote control interface. Attaching an additional simulator only requires that the ambassador interface is implemented and, then, the specified commands are executed. For immediate use, a set of simulators is already coupled with VSimRTI, for example:

The VSimRTI Application Simulator

The application simulator of VSimRTI is optimized for the simulation of Smart Mobility applications. Applications run in a sandbox which offers vehicle-like interfaces, e.g. for requesting sensor data or interacting with communication modules. Data provided by traffic, communication network and further connected simulators are transformed in a format used by components of real vehicles. To run an application, its logic is implemented in Java. Additionally, the VSimRTI application simulator supports various settings to specify the characteristics of an application and to configure its behavior.

Features of the VSimRTI Application Simulator
Features of the VSimRTI Application Simulator

The architecture of the Application Simulator is based on the ETSI ITS Standard. Besides the sandboxed Application Layer approach, it features a rich Facility Layer with Application, Information and Communication Support. The individual aspects should be explained in the following:

The VSimRTI Cellular Simulator

The VSimRTI cellular simulator enables the simulation of wireless transmissions via cellular networks. This simulator basically consists of two components: the GEO Server and the Cellular Network Simulation (CNS). In contrast to ad-hoc communication, cellular systems always require a deployed network infrastructure. The addressing between the nodes needs to be realized by IP. The GEO Server is a central server which is connected to the Gateway GPRS Support Node (GGSN). It has the task to maintain a table with all vehicles in the region. In this way, Geo addressing similar to geographic ad-hoc routing can be realized.

The architecture of the VSimRTI Cellular Simulator
The architecture of the VSimRTI Cellular Simulator

The second component of the VSimRTI Cellular Simulator is the Cellular Network Simulation (CNS), which is the most important component for the simulation of the Radio Access Network (RAN) and its connection to the IP-based core network. The CNS subdivides the simulation area into various regions to modulate a network with different coverage properties. For each region, three nested models are used to simulate the packet transmission: the Core Delay Model, the PDR Model, and the Bandwidth Model.

Further Components

Much attention is paid to comprehensive configuration possibilities to simulate realistic scenarios. In these terms, the Mapping Component and the Navigation Component play an important role. Besides, VSimRTI also offers the integration of the security simulator Agez.

Mapping Component

The VSimRTI Mapping component is used to de?ne the specific type of simulated vehicles, RSUs and intelligent traffic lights. This means that one or multiple applications, different communication parameterization and behavioral aspects can be mapped to the dedicated nodes (vehicles, RSUs, traffic lights) in the scenario. Either one or a ratio of all nodes can be selected. Therefore, a deterministic mapping (producing the exact same sequence of mapped vehicles in every simulation run with regard to the given ratios at each point in time the simulation) and a stochastic mapping (resulting in a random order of mapped vehicles) exist. In this manner, the Mapping Component offers a convenient way to set up simulation series e.g. with the respect to market deployment rates where 5%, 10%, etc. of all vehicles and traffic participants are based on the V2X communication technology.

Navigation Component

The VSimRTI Navigation Component is an important part of the VSimRTI simulation universe. It basically holds the map of the road network and supports the routing of the vehicles. In the scenario creation process, VSimRTI supports the conversion of OpenStreetMap based road networks for the traffic simulator. Advanced route-finding algorithms can be either used to define possible vehicle routes and alternatives before the simulation starts as well as calculate new routes at runtime, when the according events of a route change demand this action.

Agez (A Generic Security Solution)

Agez is a security simulator that can be integrated into advanced simulation environments for ITS. It supports major security measures such as the signing and verification as well as the encryption and decryption of messages and the concept of short-term identifiers that are used for privacy protection. Instead of re-implementing cryptographic operations that are used to apply the security measures and to perform security checks, Agez includes the Trusted Communications Testbed (TCT) which is an implementation of the IEEE 1609.2-2006 trial-use standard. This approach allows the reuse of a tested and validated security implementation, which reduces the risk of bugs that skew results.

Evaluation of V2X Applications with VSimRTI

VSimRTI has been used by various automotive companies and research institutes to evaluate V2X applications. The following two examples are a small excerpt from the wide range of simulation scenarios that VSimRTI has performed thus far:

The goal of the intelligent V2X-based navigation system is to recommend travel routes which avoid congested areas. In contrast to classical traffic management systems, V2X technology operates in near real-time. That means it is able to avoid congested roads and those which are about to become congested. The VSimRTI simulations helped to optimize the effectiveness of the algorithm and to reduce the travel time and vehicle emissions.

Vehicles use the V2X-based navigation system to recalculate new optimized routes which avoid congested areas.
Vehicles use the V2X-based navigation system to recalculate new optimized routes which avoid congested areas.

The V2X-based speed warning application aims to reduce accidents caused by bad weather conditions for example. Vehicles share information about dangerous road conditions such as ice roads or fog banks via V2X communication. This information helps to adapt speed, especially on road segments that are difficult to observe. To evaluate the application, an area with tight turns and often limited visibility in the Taunus Mountains was simulated. The VSimRTI results were used to improve the application and further reduce the number of speeding vehicles.

The V2X-based speed warning application allows vehicles to adapt their speed, especially on road segments which are difficult to observe.
The V2X-based speed warning application allows vehicles to adapt their speed, especially on road segments which are difficult to observe.

VSimRTI Workshop

Each year, the VSimRTI Workshop is hold in Berlin. The workshop provides an insight of how to setup and run simulations as well as discussions of state of the art methods and tools for the assessment of novel solutions for Cooperative Intelligent Transportation Systems.

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