23-07-2012, 11:42 AM
Data dissemination in VANET
Data dissemination in VANET.doc (Size: 1 MB / Downloads: 72)
Abstract
Now a day’s vehicles are having the capability to communicate with each other. The vehicles continuously exchange the available information with each other which are in the range and cooperate together to ensure the safety. This inter vehicular communication capability of vehicles is the Vehicular Ad hoc network (VANET). VANET is a type of MANET to communicate with nearby vehicles and nearby fixed infrastructure. The dissemination of safety information to the drivers like traffic condition warning, service updates, route planning, accident, etc are plays an important role for safety application. To gather the critical information efficiently within the minimum time is very essential for safety application.
Here we study the different data dissemination techniques to disseminate the safety information like cooperative driving, accident, road condition warning. Here we will also study about the solution ensuring data dissemination in VANET for sparse and dense network. Also we will study the proposed agent based model for the information dissemination in VANET. The critical information dissemination is the major challenge in the VANET environment.
Introduction
About Vehicular ad hoc Network(VANET)
Vehicle is now the part of people’s life. Over wireless medium the vehicles communicate in Ad hoc manner. A VANET is an brief, rapidly changing wireless network formed among
vehicles and roadside units which are able to communicate with one another. To participate in a VANET, vehicles must be equipped with wireless transceivers and computerized control modules that allow them to act as network nodes. Stationary network nodes may be used in the form of roadside units. These roadside units may help with a wide variety of services for vehicular networks such as hosting location relevant data. Delivering the information to drivers about traffic condition, parking information, service updates, route planning. Providing the safety and critical information to the drivers is now major challenge in Vehicular Ad hoc Network (VANET). Consider the situation while driving into strange city. The vehicle navigation system checks the traffic condition on-demand and directs quickly through the city avoiding busy road and road blocks. For the time being vehicle navigation system requests the parking information in the neighbourhood of destination, so that you can drive straight to a free parking space. Having information about distant hazardous situations like an accident ahead or icy road, the driver can be warned in-time, thus being able to completely avoid the dangerous situation.
Literature Review
In this literature review we first present the different Network simulators required to generate the mobility trace using a vehicular mobility simulator and then input this trace to the network simulator in chapter 3. The eWorld is a framework to import mapping data from providers, such as OpenStreetMap.org (.OSM), visualize it, edit and enrich it with events or annotational attributes and pass it to traffic simulators, such as SUMO.
VANET Simulator
Vehicular simulators are tools to generate mobility traces from vehicular mobility models. These traces are than used for simulating existing or new protocols. They provide the opportunity to developers to do fast, well-configurable, cheap and repeatable simulation runs in order to evaluate results of new protocols or even whole systems. Simulations are not accounting for all the parameters of reality, but for selected ones to keep simulations feasible while keeping them accurate enough.
Either they both incorporate to a single simulator application like presented in [6] or the traffic simulator outputs traces for a networking simulator which than provides results of traffic and communication performance (e.g., average speed) and networking characteristics (e.g., inter-contact time, minimum transmission range [7], mean time to loss information [8]).
Data Dissemination in VANET
The major challenging task in the VANET is to disseminate the maximum possible data by utilizing the limited bandwidth. Many people have provided the various techniques to access the efficient data here we will study various technique of data dissemination. Xu et al. has proposed the data dissemination technique in which the data centre is periodically broadcasting the data, and then vehicles which are passing through the range of data centre they are receiving and storing the data [13]. Whenever two vehicles come into the range of each other’s transmission range then they exchange the data. In this V2V communication there is no need of infrastructure therefore it is very suitable for highly dynamic VANET. But in the Urban area vehicle density is very high therefore the data cannot be updated is the one drawback of this technique. If we use this scheme then the MAC layer collision [12] occurs.
Data pouring(DP) and buffering is one of the scheme proposed by Zhao, cao [8]. In this scheme select the road having the high density and the mobility of vehicles i.e. axis road and the data center delivers the data not only on the road but on the crossing roads if the vehicles are near to the intersection on another road.
Data Dissemination Techniques
Push Based Data Dissemination Technique:
In push based data dissemination technique the data is managed by data center. The data center collects the data from the outside world and makes it ready to deliver to the vehicles. The data center can be a computer having a wireless interface. Data center may be a wireless access point, or an infostation. Data center makes a list of the data items that has to be disseminated over network. It transmits this information on the road with header which stores all the necessary information like source id, source location, forwarding direction, packet generation time, etc.
Pull Based Data Dissemination Technique
The pull based dissemination technique is used to query the data for the specific response from data center or from other vehicles.
In this technique the data is managed by the data center and the vehicles which are moving on the road.
When any particular vehicle needs the data query then initially that vehicle sends the beacon message to find out the vehicles among his range.
In this technique the carry and forward method is used to deliver the data. In this method the data packets are carried by the vehicles and when they found and other vehicle moving in the direction of destination in his range, it forward that packet to this vehicle. This method takes tolerable delay to transfer data to the destination.
The vehicular ad hoc network is unpredictable in nature, so optimal path for successful routing cannot be computed before sending the packet. So the dynamic path selection is done throughout the packet forwarding process.
Vehicle in straightway mode
In this mode greedy approach is used to forward the packet to the destination in which packets waits for vehicles moving in the direction of destination and as it finds such vehicle it forwards the packet to that vehicle. The delivery ratio of the H-VADD protocol provides best delivery ratio of all other protocols. Delay in H-VADD is equivalent to the MD-VADD when the vehicle density is low as it depends more on D-VADD protocol to avoid the routing loops and when vehicle density is more, delay becomes equal to LVADD.
H-VADD has advantage of both D-VADD and LVADD. The packet can be forwarded through multiple paths but that path should be chosen which is going to take minimum tolerable delay. Therefore, at every intersection data packets are transferred to RSU and RSU forwards this packet to the vehicle which is moving to the optimal road to the destination with minimum delay. In this protocol, the packet is transmitted from source to destination using the intermediate node. The vehicle needs two types of transmission.