The VANET (Vehicular Ad hoc Network) is a collection of mobile nodes forming a temporary network on variable topology, operating without base station and without centralized administration. Communication is possible between vehicles within each other's radio range as well as with fixed components on road side infrastructure. The characteristics of VANET network that distinguishes it from other ad hoc networks, such as high mobility and communication with the infrastructure to support security or comfort applications, have prompted researchers to develop models and mobility specific protocols. The main goal of this chapter is firstly to compare the performance of three Ad hoc routing protocols: OLSR, AODV and DSDV, and secondly to examine the impact of varying mobility, density and pause time on the functionality of these protocols. The results of this chapter demonstrate that AODV have better performance in terms of Throughput and Packets Delivery Rate (PDR), whereas OLSR have best performance in terms of Packet Delivery Time (Delay).
TopIntroduction
The integration of wireless communications technology between vehicles has begun some years ago and has led to Vehicular AdHoc Network (VANET). This technology is derived from mobile ad hoc networks (MANET), which also gave birth to the Wireless Sensor Networks (WSN). Thus, the practicality of MANETs is applied in WSNs and VANETs. If WSNs are spatially distributed to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. VANETs are used in intelligent transport systems (ITS). ITSs are designed to offer to passengers and vehicles, road safety services (accident alert, driver assistance, traffic flow optimization, congestion reduction, etc.) and comfort services (Internet access, games, etc.) (Singh & Verma, 2013). One of the challenges of VANET networks is the efficient and timely dissemination of information with reasonable use of resources. Road safety applications are the main motivation of vehicle networks and have two major requirements, speed and reliability. Multi-hop communication is an important component of these applications.
In VANETs environment, a few issues and requirements are imposed, such as driver’s behavior, different road topology, size of the network, multi-path and roadside obstacles, trip models, mobility and varying vehicular speed, etc. For these various reasons, Deploying and testing VANETs involves high cost, intensive labor and security constraints in real world, so simulation is a useful alternative in research prior to real implementation.
Figure 1 shows a part of VANET networks constraint.
Figure 1.
Future of Intelligent Transport Systems (ITS)
Simulating a VANET involves two different aspects, the First, is related to the communication among vehicles and the second is related to the mobility of the VANET nodes. To achieve author’s simulation objective, we have chosen three widely used simulators, NS-2.34 as network simulator and Move-2.92 and Sumo-0.12.3 as mobility simulator.
The routing process in the VANTE networks is an important issue that requires a thorough study before network deployment, the data packets are routed from the source node to the destination node using the vehicles available as relays, the large number of Vehicles, high dynamic and frequent change in vehicle density increase the challenge of the routing process.
Traffic lights and vehicle movement conditions cause frequent partitions in VANET networks and make routing a more difficult process. In our chapter, we will proceed to comparative study of two types of routing protocols belonging to topology based routing protocol class, proactive and reactive protocols.
The remainder of the chapter is organized as follows: Section III briefly discusses the ITS for Rail. Section IV discusses the ITS for VANET and precisely, the processes and constraints of routing in VANET, classification of different VANET routing protocols and an overview of the three routing protocols AODV, DSDV and OLSR. The section V shows the simulation results and performance comparison of the three above said routing protocols.