| The development of wireless network WLAN, have brought to people high speed andconvenience, the wireless communication technology of the wireless local area network is stillon the development and improvement. The electronic electrical engineers associationannounced the original the wireless local area network sta ndard802.11. In recent years, moreand more accidents happen everyday, traffic environment caused a series of new demand ofwireless network communication standard, the high-speed mobile vehicles lead to thetopology of the network structure changing rapidly, cars on the road communicate with othervehicles, can not tolerate long link confirm delay, the same, as the travel time of vehiclewithin range of the base station is limited, the application and the interactive communicationalso need better way. In order to solve the problems, people hope that through wireless mobilecommunication technology will improve the driving safety and improve the transportationsystem congestion, VANET technology provide rapid access network for high-speed mobilevehicles can, in order to realize the data communication, safe driving, charge management, etc.The goal of VANET technology is to build a wireless vehicles communication platform, slowdown the city traffic to worsen in the countries all over the world, employing cutting-edgecommunication technology to strengthen the management of the Transportation system, andimprove the development of Intelligent Transportation system (Intelligent TransportationSystems, ITS). ITS will make full use of roads and facilities, in a larger sense, can save energy,curb environmental pollution and increase economic benefits. Car road cooperativetechnology have developed rapidly in All countries， The United States、 Japan、 theEuropeanand and other developed countries have defined basic co llaborative scenecompletely，Related technology is still in research and experiment stage, can not use in alarge-scale promotion，the development need government support，the active participate ofresearch units，widespread concern of industrial enterprise.IEEE802.11p draft standard is the ground floor of network protocol specially design for thewireless network communication, which provides a more exact goals and methods for theresearch and development of VANET, this paper, according to802.11p draft standards forphysical media access and control and the layer of standardization, from the analysis ofnetwork protocol, use the NS2simulation method for inspection of network agreement theperformance changed. This paper studies the characteristics of the wireless transmissionbetween cars, put emphasis on802.11p physical layer channel technology, frame format ofthe MAC layer management and application of the timer. In NS simulation tools, according to 802.11p standards, OFDM technology set different way of channel coding modulationtransmission and bit rate, re-structuring MAC layer management frame field, as applicable tothe WAVE mode of transmission timer function has made the relevant adjust. As the vehicledriving speed, network topology structure result in great changes in a short time, it will maketime delay tolerance of WAVE mode communication be very low,802.11MAC layer accessmethod cannot guarantee the safety of the WAVE mode information transmission, so802.11pstandard MAC agreement should simplify the process of channel access, make sure thevehicles communicate with each other in the quickest way. The simulation experiment use theNS which is a open source simulation tools, add the improved protocols of wireless networkMAC layer into the mac folder, configuration NS, make the simulation tools support NS802.11p, and write tcl scripts for network scene arrangement and configuration parameters.Then run the simulation program and compared with the traditional network environment802.11standard, through the experimental results, in terms of package lose rate and averagedelay,802.11p standard is better than802.11. In the whole simulation experiments,Referencestandard agreement，Improved the performance of this agreement,And reference other highquality related papers of802.11p protocol emulation. the basic data of the experimentalresults can meet the requirements of the standards of IEEE802.11p draft. the achievements ofimprovement in this simulation test Is gradually to802.11p standard guidelines direction. |
PDF Full Text Request