20-07-2012, 12:22 PM
Realistic Mobility Models for Vehicular Ad hoc Network (VANET) Simulations
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ABSTRACT
Vehicular Ad-Hoc Network, or VANET, is a form of Mobile ad-hoc network, to
provide communications among nearby vehicles and between vehicles and nearby fixed
equipment, usually described as roadside equipment. InVANET, or Intelligent Vehicular Ad-Hoc
Networking, defines an Intelligent way of using Vehicular Networking. InVANET integrates on
multiple ad-hoc networking technologies such as WiFi IEEE 802.11 b/g, WiMAX IEEE 802.16,
Bluetooth, IRA, ZigBee for easy, accurate, effective and simple communication between
vehicles on dynamic mobility. Although there are many proposed solutions for routing in
VANET, it is still unclear as to what specific characteristics VANET routing protocols should
possess, since none of the proposed solutions achieves optimum performance in both urban and
highway, as well as sparse and dense environment. To shed light on these issues, we analyze
some of the most important QoS metrics in VANET. A vehicle in VANET is considered to be an
intelligent mobile node capable of communicating with its neighbors and other vehicles in the
network. For configuring the vehicle with a unique address, there is a need for address
reconfigurations depending on the mobility patterns; we have presented a centralized addressing
scheme for VANET using DHCP (Dynamic Host Configuration Protocol). By building up a P2P
overlay network on top of VANET's physical infrastructure, we effectively integrated P2P
network’s advantage on sustaining highly dynamic network into the design of VANET routing
protocol. By deploying passive VANET routing algorithms with innovative P2P routing
mechanisms, we propose a new kind of VANET routing protocol named Peer Computing based
Ad hoc On Demand Vector (PAV). A detailed description of the P2P decentralized naming,
route discovering, route querying and updating algorithm used in PAV is presented in this paper.
The simulation results indicate that PAV has an improved routing performance in comparison
with the popularly used AODV protocol.
COMPREHENSIVE STUDY ON TOPIC
Development in wireless communication networks has made Inter-Vehicular
Communications (IVC) and Road-Vehicle Communications (RVC) possible in Mobile Ad Hoc
Networks (MANETs). This has given birth to a new type of MANET known as the Vehicular Ad
Hoc Network (VANET). Governments and some car manufacturers, such as Toyota, BMW, and
Daimler- Chrysler have launched some important projects for VANET, for example, Advanced
Driver Assistance Systems(ADASE). The application of VANET includes the traffic control and
share of multimedia information. When VANET is applied to the traffic control, it can distribute
the information about the road situation, such as traffic accidents and road congestion, and is
helpful in avoiding accidents.
IP ADDRESS CONFIGURATION IN VANET
Vehicles in VANET are equipped with sensors and actuators to collect useful information
and to control the behavior of the vehicle. Information sent by these sensors is collected by a
centralized onboard controller. Based on the requirement, this information can also be shared
with the neighboring vehicles using the onboard radio device that is DSRC (Dedicated Short
Range Communications) capable. DSRC is a medium range communication service that supports
inter-vehicle and vehicle-to-roadside communication. Routing in VANET has attracted a lot of
interest. Some of the existing mobile ad-hoc network routing protocols like Dynamic Source
Routing (DSR), Ad-hoc On Demand Distance Vector (AODV) and Optimized Link State
Routing (OLSR) have been tested for vehicular ad-hoc networks. Addressing in vehicular
networks could be achieved by using Dynamic Host Configuration Protocol (DHCP), which is an
extensively used address configuration protocol in computer networks. Dynamic Host
Configuration Protocol (DHCP) is an application layer protocol used to configure hosts in the
computer communication network. DHCP supports automatic, dynamic and manual allocation of
addresses. In the automatic approach, permanent addresses are assigned to the hosts by the
DHCP server. In the dynamic approach, addresses are assigned by the DHCP server for a limited
period of time.
SIMULATION OF THE ROUTING PROTOCOLS IN VANET
According to the scheme to find route, existing MANET routing protocols can be
classified into two sorts, proactive and reactive routing protocols. Destination-Sequenced
Distance Vector (DSDV) protocol falls into the proactive ones. It broadcasts routing packets
periodically, and each node maintains the routes to all other nodes in the network. On contrary,
Dynamic Source Routing (DSR) protocol is a typical reactive routing protocol, which establishes
route by source node only when it needs, and the topology and routing table are also set up on
demand. Reactive protocols remain then passive until the established route becomes invalid or
lost.
Selecting appropriate level of details in the mobility model for a VANET simulation is a
critical decision. Developed a tool MOVE (Mobility model generator for Vehicular networks) to
facilitate users to rapidly generate realistic mobility models for VANET simulations. MOVE
provides an environment that allows the user to quickly pinpoint incorrect details and manage
details overhead. Our tool is built on top of an open source micro-traffic simulator SUMO.
MOVE allows user to conveniently incorporate realistic road maps into the simulation. In
addition, by providing a set of GUI that automate the simulation script generation.
CENTRALIZED ADDRESS CONFIGURATION
At first we assume that there is a central authority to control address distribution and
management. This responsibility can be taken up by vehicle manufactures or government
agencies. DHCP servers are installed in cities to cover a large area or an entire city depending on
vehicle densities. Redundant DHCP servers can be installed in order to provide fault tolerance.
Some of these servers might be capable of extending the lease for an IP address assigned by a
distant DHCP server. Such responsibilities can be assigned and managed by the central authority.
Access to these servers is provided by roadside units. Roadside units are equipped with access
points that provide Internet access to vehicles. These roadside units act as an interface between
vehicles and DHCP servers that dynamically assign IP addresses to vehicles.
REALISTIC MOBILITY MODELS FOR VANET SIMULATIONS
Several communication networking simulation tools already exist to provide a platform to test and evaluate network protocols, such ns-2, OPNET and Qualnet. However, these tool are designed to provide generic simulation scenarios without being particularly tailored for applications in the transportation environment. On the other hand, in the transportation arena, simulations have also played an important role. A variety of simulation tools such as PARAMICS, CORSIM, VISSIM etc have been developed to analyze transportation scenarios at the micro- and macro-scale levels.
CONCLUSION AND FUTURE WORK
The paper studied the application of VANET to the city road traffic control. The results have some value in the research and application of VANET to traffic control, and the design of a more suitable routing protocol for VANET is the next step of work.
The tool MOVE which is based on an open source micro-traffic simulator SUMO.
MOVE allows user to quickly generate realistic mobility models for vehicular network
simulations. MOVE is publicly available and can be downloaded via the following URL -
http://lens1.csie.ncku.edu.tw/MOVE/. It is shown that the details of a mobility model such as the
existence of traffic lights, driver route choice and car overtaking behavior can have a significant impact on the simulation results. The movements of vehicles are based on static configurations defined in the Vehicle Movement Editor. Based on the study of synergies between P2P network and VANET, proposed a new type of VANET routing protocol named PAV. By building up a P2P overlay network on top of VANET's physical infrastructure, PAV seamlessly integrates the functions of p2p overlay routing protocols operating in a logical namespace with those of VANET routing protocols operating in a physical namespace.