The VANET simulators that have been developed in recent years have contained some of the requirements of the VANET environment, but not all. This is because most of the research and development has evolved in non-connected groups. Traffic and Network Simulation Environment (TraNS) is an open-source simulation that aims to connect these groups together.
Developing a realistic VANET simulation is important due to the costly deployment of a real-world environment. Simulations need to enable virtual vehicles to exchange active safety, transportation efficiency, and other application data. Most of these applications need to be tested on a large scale network with hundreds or thousands of vehicles. There needs to be repeatable experiments which are almost impossible in a real-world environment.
Most current VANET simulations are based on the Network Simulator version 2 (ns2), as the network simulator with a set of road mobility models. This, however, doesn’t reflect the true characteristics and features of VANETs. TraNS is designed to fix this issue by combining Simulation of Urban Mobility (SUMO), a traffic simulator, and ns2, a network simulator. This allows ns2 to use realistic mobility models and influence the behavior of SUMO, based on the communication between vehicles (Piorkowski, 2008). Active safety and traffic efficiency applications have also been implemented in the simulation. TraNS goal is to have simulation results that closely resemble real-world experiments.
TraNS has two modes of operation: network-centric and application-centric. Network-centric is used to evaluate VANET communication protocols that don’t influence in real-time the mobility of nodes like music or travel information (Piorkowski, 2008). Application-centric is used to evaluate VANET applications that influence node mobility in real-time and during traffic simulation runtime like active and public safety applications (Piorkowski, 2008). In network-centric mode, TraNS provides realistic mobility models to ns2 from SUMO. Its main component is the parser that resides in between the road traffic simulator and ns2. The parser translates the dump file of the road network map to a format readable for ns2.
In Application-centric mode, ns2 is allowed to control the mobility of certain vehicles in the simulation runtime. Traffic Control Interface (TraCI) is an interface that is used to couple road traffic and networking simulators. This allows the user to evaluate VANET applications that influence the mobility of vehicles. TraCI runs on a feedback loop that makes it possible to modify mobility of individual vehicles due to information exchange within VANET (Piorkowski, 2008). It uses atomic mobility commands like stop, change lane, and change speed to manipulate vehicle’s mobility. This allows complex vehicle mobility patterns to be broken down into a set of consecutive atomic mobility actions.
In the upcoming versions of TraNS, there will be a simple driver behavior model which will take decisions upon reception of messages exchanged between vehicles (Piorkowski, 2008). It will allow more sophisticated behavior patterns of drivers. The next version will also support large-scale simulations of 10,000 nodes or more, as well as modeling the cost of implementing security into the VANET protocols. There will also be a comparison to other simulators with an objective benchmark of VANET simulators.
Link:
http://nsl.csie.nctu.edu.tw/NCTUnsReferences/trans_poster.pdf
