Performance Evaluation of VANET Under Realistic Vehicular Traffic Assumption
Vehicle-to-vehicle communication has become a very challenging topic in recent years. Vehicles equipped with devices capable of short-range wireless connectivity can form a mobile ad hoc network, called a Vehicular Ad-hoc NETwork (VANET). In such networks
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y. Vehicle-to-vehicle communication has become a very challenging topic in recent years. Vehicles equipped with devices capable of short-range wireless connectivity can form a mobile ad hoc network, called a Vehicular Ad-hoc NETwork (VANET). In such networks, two vehicles which are not in the radio range of each other can communicate by using other vehicles as relay. Our work focuses on the efficiency of routing algorithm in VANET. A routing algorithm is a distributed algorithm used by the nodes to learn the route to potential destinations. There exists standardized routing protocols designed for ad-hoc networks. VANET is a particular ad hoc network where the nodes (vehicles) move very fast. This introduces a high dynamism in the network topology which is difficult to manage. So, we compare the performances of different existing routing protocols in this context. We use two different simulators. The first is a traffic simulator which emulates the vehicular traffic on a highway. It uses microscopic simulations. The second is a network simulator (NS2) which simulates all the protocols (wifi, IP, UDP and the routing protocols) used by the nodes to communicate. The simulations show that reactive protocols are most efficient compared with geographical routing in a VANET. The remainder of the paper is organized as follows. In Section 1, we present the microscopic traffic simulator. We present the network simulator and simulation parameters in Section 2. Different routing protocols are presented in Section 3. The simulation results are discussed in Section 4.
1 Traffic Simulator The objective of our study is to analyze and evaluate the performance of ad hoc routing protocols with a realistic simulation of traffic. The simulator we use to model the traffic is a microscopic simulator. It emulates the individual behaviour of vehicles taking into account the interaction between them. We use a microscopic model in our simulations because we are interested about the impact of individual characteristics (speed, geographical location, . . . ) of vehicles on the performance of routing protocols. The location of vehicle
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Mabiala Muriel, Anthony Busson, and V´eronique V´eque
is defined by the co-ordinates x, y, where the parameter y represents the lane of vehicle. The model we use is presented in [1]. The trajectory of a vehicle is determined by two models: lane changing model and a car-following model. The car-following model includes three modes: emergency model, car-following and free flow regime. If the time of contact with the vehicle ahead is smaller them a certain threshold, the vehicle is in the emergency regime. The acceleration an is given by: (vn −vn−1 )2 , vn > vn−1 ; min a− n , an−1 − 0.5 gn an = − − min(an , an−1 + 0.25an ), vn ≤ vn−1 . If the time of contact with the vehicle ahead is larger than another threshold, the car is in free flow regime. In this regime, the vehicle is not obstructed by other vehicle. So, it tries to reach a certain desired speed. The acceleration an is then given by: ⎧ + target ; ⎪ ⎨ an , if vn < vn target
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