Researches On Warning Message Propagation And Maintenance Mechanism In VANETs

Since the end of last century,with the Ad hoc technical depth study carried out in the field of commercial and civilian subject to a wide range of growing concern,and the field of mobile communications is rapidly becoming a public hotspot.VANETs(Vehicle Ad hoc Network) is an upsurge in this research produced, as a new type of MANET,is which the Ad hoc technology in road traffic and industrial areas of vehicle applications.Currently has VANETs research institutions around the world and the close attention of researchers,but also have a great deal of scientific research.VANETs in ensuring the smooth conduct of transportation activities,as well as traffic incident early warning research of great practical significance,in which the dissemination of the warning message with the maintenance of common concern has been a hot research.Several domestic and foreign scholars have put forth a mechanism for information dissemination in VANETs different algorithm.The current research on VANETs is still in its early stages,the intelligent traffic systems,electronic and communications,automobile manufacturing and the Ad hoc network for researchers,is a major technological breakthrough opportunities,but also a very challenging task.On the one hand the difficulties of research VANETs for Ad hoc technical restrictions on the development stage, and on the other nodes from its systems in road traffic has the characteristics of the traffic flow,such as carrier-phase high-speed movement at any time make changes to network topology instability,a single channel,and even set the length of an antenna installed and the metal surface will cause difficulties in communication VANETs.Not only that,because of cost,space and other constraints,VANETs can not expertise with the physical construction and testing methods system.Therefore,the major work of this paper is divided into two aspects:First, the use of OMNET++ simulation tool for traffic flow simulation and Ad hoc network simulation,to achieve a reasonable simulation model available VANETs;Then, in the model built for VANETs warning message dissemination and maintenance of the design,and final simulation.Before the use of OMNET + + simulator for VANETs simulation design,we must work on the environment in which this article to a basic set.The following three basic principles:1) Respect for the basic traffic flow theory perspective,VANETs node movement to follow the basic principles of traffic flow;2) Design of network industry to follow generally accepted standards of the Ad hoc communications,in strict accordance with the IEEE802.11 international standards,as this article VANETs the MAC protocol;3) According to this article needs works,the environment is set to follow the basic principles on the basis of a reasonable simplification to highlight the key points,in favor of the realization of the objectives of this article.For VANETs attributes of the traffic flow as well as the focus of this paper, we have taken the road transport system in the concept of simulation modeling, and its transport network in the macro basis,the individual vehicles Add a macro analysis of traffic flow,making traffic flow simulation only VANETs system as an important feature of the realization of the main purpose is to give a warning after the dissemination of information and maintaining the design and testing of algorithms to provide the conditions.In OMNET++ for VANETs simulation modeling,this article has taken a number of simplifying the processing and similar processing.On road transport system design,acquisition of only a few basic parameters for their data,vehicle and road interaction is controlled entirely through the controller,not aseparate module to establish a simple road.Event simulation in the design of traffic will be designed for a simple module to make it a fixed life cycle in the road, the vehicle sensing node similar to the incident to deal with the incident to carry out small-scale broadcast a warning message.The core of this paper is to design a proper warning message viable method of communication and to maintain.First of all,the depth analysis of this paper, Carnegie-Mellon University Ozan Tonguz,Nawaporn Wisitpongphan and others General Motors Corp.and the United States co-sponsored laboratory ECI sub-transport system Broadcast VANETs,Boston University,TDC Little and A. Agarwal in proposed in 2005 a sub-cluster information dissemination strategy VANETs,as well as an associate professor YU Oiangyuan of Jilin University,the Netherlands University of Twente,Professor Geert Heijenk completed in 2008 a continuous warning message propagation.The main work is to Geert Heijenk and Professor Yu Qiangyuan in the application of the algorithm for further promotion.First of all,the original algorithm as the basis for this article,the main way of using radio,the development of network parameters,radio,the calculation cycle,safety line and the effect line delineated by reference to the original algorithm are the calculation of the test results.Secondly,the paper work on the traffic environment settings,is the original algorithm by a section of straight road to the intersection of the expanded OMNET++ simulation,traffic generation mechanism by a line(both directions) to the two cross-line(four direction) to expand,and to judge by the controller module random node movement towards the junction.Third,the original algorithm used the structure in the warning message by adding Sender-information,as a basis for making the node received a message around the traffic information to determine,due to broadcast and receive messages of the CPU time occupied by very few,and even that is an instant completed,so this article nodes taken regularly updated information on its environmental program.At the same time,this change to change the original algorithm are required to calculate each node WaitTime design,making a node can be grouped with a simple to use storage space in exchange for an increase in the cost of the average running time algorithm for savings.Fourth,the study shows that the traffic density on the exchange of information in VANETs have a significant impact on the quality,Ozan Tonguz and others refer to the sub-transport system to the broadcasting strategy,this article can be regularly updated in the node table,based on the regional traffic density can be calculated,traffic conditions at different take on the news of the deal.Finally,this paper tests the use of digital simulation technology OMNET++ simulator on a single-event algorithm,multi-events,with the sub-cluster and the amortization of the original algorithm efficiency,as well as a simple imitation of traffic in major cities in the sub-priority Experimental implementation of algorithm level,an analysis of relevant data extracted in this paper that the OMNET++ simulator VANETs simulation model established,the algorithm is feasible and has good stability,in the complexity of the analysis also followed the industry to generally accepted principles of space for time, similar work has a certain reference value.Certainly,this paper carried out the work of VANETs simulation experiments, many parameters have been greatly simplified,and the actual traffic flow and the Ad hoe communication networks there is a great gap,so in the future studies need to be further in-depth study and exploration.Have been completed to improve the OMNET++ traffic flow simulation model concept to include more practical factors;traffic flowhas obvious spatial and temporal characteristics of the future need to predict the mobility of vehicles to conduct in-depth exploration of the work.