【摘要】：Vehicular Ad Hoc Network (VANET) is an application of Mobile Ad Hoc (MANET) for road traffic. VANET has the characteristics of high moving speed, frequent changing topology, and different node densities. In this dissertation, according to the characteristics of VANET, it is aimed to improve the performance of MAC layer and provide reliable and real-time communications between vehicles. Modeling and analysis of periodic broadcast, modeling and analysis of broadcast in control channel, dynamic contention window scheme, MAC delay based clustering algorithm and cluster based time division multiple access are studied in detail.The main research contributions are as follows.(1) Modeling of periodic broadcast and dynamic contention window scheme in VANETA 1-D Markov model is proposed to analyze the performance of periodic broadcast in VANET. In this model, a new idle state is introduced under non-saturated condition when there is no message to send in the buffer of a node. The freezing of backoff time counter in backoff process is also considered in this model and a discrete time D/M/l queue is established to model the buffer of each node. Theoretical analysis show when vehicle density increases the performance of periodic broadcast decreases accordingly. Dynamic contention window scheme is proposed according to the changing of node density. Simulation results show the collision probability of DCW scheme is lower than that of fixed-contention window broadcast in IEEE 802.11 p. Simulation results also verify the accuracy of the Markov model.(2) Modeling of priority access to control channel in VANETAccording to the characteristics of messages with different priorities accessing to control channel, discrete time queue D/M/1 and M/M/1 are proposed to model periodic messages and emergent messages, respectively. Priority analysis is added to this model which is based on the previous 1-D Markov model. Packet collision probability, access delay of periodic message and emergent message and performance of DCW scheme in control channel are analyzed. Simulation results show DCW scheme could reduce the collision probability, which is suitable for control channel with different priority messages.(3) MAC delay based clustering algorithmThe performance of MAC protocol decreases in high vehicle density scenario. A MAC delay based adaptive (MDBA) clustering algorithm is proposed. Under the restriction of MAC delay, speed, acceleration, position and destination are considered in cluster head election algorithm. Cluster maintenance algorithm adaptively adjusts cluster according to changes of network topology. Traffic simulation software VISSIM is used to verify the proposed algorithm, and simulation results show that MDBA clustering algorithm performs better than classic clustering algorithms in wireless sensor network and mobile Ad Hoc network, which is more suitable for VANET.(4) Cluster based time division multiple access in VANETIn dense vehicle scenario, time slots are not available for all nodes in TDMA based access scheme. To solve this problem, a cluster based time division multiple access method is proposed. In this method, position based segment time slot allocation is employed. Cluster members are divided into two teams and allocated to two time segments. Moreover, slot reservation scheme is proposed to reduce collision and transmit emergent messages as soon as possible which lowers the access delay of emergent messages. Simulation results show the proposed method could reduce the collision probability and access delay of emergent messages in small traffic flow, compared with traditional TDMA scheme in VANET.
【圖文】：

也給道路交通帶來了挑戰(zhàn)，城市交通擁堵、道路交通事故Ｗ及惡劣天氣下道路交逡逑通安全成了亟待解決的問題。根據(jù)統(tǒng)計數(shù)據(jù)顯示Ｗ，近年來我國交通事故次數(shù)２５萬次逡逑左右，死亡人數(shù)為５萬人左右，直接經(jīng)濟損失在１０億元左右，如圖１．１所示。而根據(jù)逡逑世界衛(wèi)生組織公布的數(shù)據(jù)，我國交通事故的致死率為２７．３％，居世界首位，美國作為一逡逑個被世界公認(rèn)為＂車輪上行走的國家＂，交通事故的致死率僅為１．３％，曰本只有０．９％。逡逑可見，近年來隨著我國汽車數(shù)量的不斷增加，關(guān)系到廣大人民群眾生命財產(chǎn)安全的道路逡逑交通安全管理的工作非常嚴(yán)峻。逡逑３５ｒｔ邐邐邐邐邐：逡逑３０邋＾ｒ￣ｎ邐；逡逑Ｉ口巧灥次數(shù)（方次）逡逑—Ｕ；邐—邐＼＿＿邋｜＿邐＾＿＿邐＿＿邐—邐＿＿＾畫死亡人數(shù)（方人）逡逑巧＇ｒ邋＾邐｜￣邋—－邋一邐；邋——￣＾邐□巧巧人數(shù)（乃人）逡逑ｉ0Ｔ三１—邋Ｌ邐Ｔ邐Ｔ邐￣邋ｎ邋■邋Ｉ□經(jīng)濟損失（億元）逡逑Ｐ邋ｍ邋ＩＨ１１邋□邋１１Ｄ１１０逡逑２００８邐２００９邐２０１０邐２０１１逡逑圖１．１近年來我國交通事故數(shù)據(jù)統(tǒng)計逡逑作為智能交通系統(tǒng)（Ｉｎｔｅｌｌｉｇｅｎｔ邋Ｔｒａｎｓｐｏｒｔａｔｉｏｎ邋Ｓｙｓｔｅｍ，邋ＩＴＳ）邋口－Ｓ］重要組成部分的車逡逑輛自組織網(wǎng)絡(luò)（Ｖｅｈｉｃｕｌａｒ邋Ａｄ邋Ｈｏｃ邋Ｎｅｔｗｏｒｋ，ＶＡＮＥＴ）就是在此背景下提出的，成為保逡逑障行車安全和提高交通效率的關(guān)鍵技術(shù)。ＶＡＮＥＴ是將無線通信技術(shù)應(yīng)用于車輛間通信逡逑的自組織網(wǎng)絡(luò)，車輛與車輛之間通過無線通信實現(xiàn)消息的傳遞。車輛在獲取本車行駛數(shù)逡逑據(jù)（車輛位置、速度、加速度、行駛方向等）后可Ｗ將自己的行駛信息發(fā)送給周圍的其逡逑他車輛

個用多重數(shù)組（矩陣）表示的信息描述模型。根據(jù)這個理論模型比較容易得到網(wǎng)絡(luò)的拓逡逑撲結(jié)構(gòu)進(jìn)而研究其體系結(jié)構(gòu)。例如，若＆，７取設(shè)備所在位置的經(jīng)、韓度，并將其按照大逡逑小順序在圖２．１中排列時，通過適當(dāng)?shù)倪\算即可得到一張兩維的所有車輛位置圖；如果逡逑考慮到車輛的移動（速度和方向等）Ｗ及道路狀況，可Ｗ通過改變及Ｊ數(shù)紀(jì)的類型和數(shù)逡逑值，把圖２．１映射為狀態(tài)和狀態(tài)轉(zhuǎn)移，從而得到狀態(tài)圖和狀態(tài)轉(zhuǎn)移圖；同理可＾＾＾將通信逡逑模式（包括通信設(shè)備特征、所屬子網(wǎng)等）、聯(lián)網(wǎng)狀態(tài)（包括車輛間通信狀態(tài)、車輛內(nèi)設(shè)逡逑備協(xié)同工作狀態(tài)、與外部網(wǎng)絡(luò)的連接情況等）、優(yōu)先等級、緊急情況標(biāo)識、節(jié)點切換方逡逑法等等，，用這種多重數(shù)組表征，從而進(jìn)行定量的分析。逡逑用所提出的多維多層的理論模型進(jìn)行ＶＡＮＥＴ體系結(jié)構(gòu)的研究能夠提供高度的可擴逡逑展性，同時做到靈活、方便，使得組網(wǎng)變得容易。逡逑ＶＡＮＥＴ的網(wǎng)絡(luò)架構(gòu)主要分為兩大部分：一是車輛間的通信，二是車輛與固定設(shè)施逡逑（即路邊節(jié)點）之間的通信，如圖２．２所示。逡逑Ｉｎｔｅｒｎｅｔ邋網(wǎng)絡(luò)逡逑Ｊ邐＾邋ｒｒ逡逑ｆ邐Ｉ邋信息發(fā)布逡逑１＾邋／邋Ｉ邋＼一逡逑＼0／＾４ｗｉＳ？＾￣。邐Ｉ路邊單兀［路邊單凡逡逑Ｉ邐邐Ｉ邋Ｌ邋」邐Ｌ邋ｊｓ己邋Ｊ逡逑Ｉ削平心型Ｌ逡逑Ｉ邐＼邐巧逡逑Ｉ車輛狀態(tài)參數(shù)采集邐輸入輸出設(shè)備Ｉ邐＾巾元服Ｕ｜逡逑圖２．２邋ＶＡＮＥＴ基本架構(gòu)逡逑圖中，車輛上裝載有車載單元（化ＢｒｏａｄＵｎｉｔ，ＯＢＵ），車輛通過車載單元ＯＢＵ與外逡逑界通信；固定設(shè)施主要是指在道路邊緣設(shè)置的路邊單元（Ｒｏａｄ邋Ｓｉｄｅ邋Ｕｎｉｔ
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TN929.5;U495

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 江昊;陳立家;晏蒲柳;;VANET信道規(guī)律探討與建模[J];武漢大學(xué)學(xué)報(理學(xué)版);2008年01期

2 常促宇;向勇;史美林;;車載自組網(wǎng)的現(xiàn)狀與發(fā)展[J];通信學(xué)報;2007年11期

3 陳立家;江昊;吳靜;郭成城;徐武平;晏蒲柳;;車用自組織網(wǎng)絡(luò)傳輸控制研究[J];軟件學(xué)報;2007年06期

本文編號：2587546