本文選題：車聯(lián)網(wǎng) + 網(wǎng)絡(luò)斷開�。� 參考：《天津科技大學(xué)》2014年碩士論文

【摘要】：到現(xiàn)在為止,大多數(shù)的車載自組網(wǎng)研究一直專注在高密度網(wǎng)絡(luò)拓撲結(jié)構(gòu)下的廣播風暴問題的協(xié)議,這些研究都是基于過于簡單的VANET網(wǎng)絡(luò)連接良好的情形下進行的。然而,網(wǎng)絡(luò)斷開問題是VANET中普遍存在的問題,因此需要開發(fā)一個可靠高效的廣播協(xié)議,用以支持多樣化網(wǎng)絡(luò)拓撲結(jié)構(gòu)。 本文通過對SCF(Store-Carry-Forward)、SCB(Store-Carry-Broadcast)機制流程進行分析,由于它們是單純借助反方向行駛的車輛實現(xiàn)斷開連接的車-車通訊,無法保證簇尾車輛遇到反方向轉(zhuǎn)發(fā)者的等待時間,因此消息傳播的時延就可能會很長。在此基礎(chǔ)上,利用固定設(shè)施RSU(roadside unit),提出旨在縮短節(jié)點間的重新愈合時間的廣播協(xié)議。論文中涉及到的主要問題有： 首先,基于路邊設(shè)施的廣播協(xié)議模型：當研究VANET中的數(shù)據(jù)包傳送問題時,根據(jù)需要不同區(qū)分開以下2種情形是很重要的：第1種源車輛檢測到事故可以產(chǎn)生一個警告信息,并將其傳播給后方車輛,在后方車輛到達潛在危險區(qū)之前能夠得到此警告信息；當目標遠離源車輛(即幾公里至幾十公里遠的發(fā)送者)就會發(fā)生第2種情況—需要將消息發(fā)送到遠方的特定節(jié)點。 其次,基于消息時間戳的退避時延τ計算：該算法主要思想是源節(jié)點在發(fā)送消息中加入發(fā)送時間戳,每個節(jié)點在接收到消息之后,計算相應(yīng)的退避時延τ,并在等待τ時間后,對此消息進行確認和下一步廣播；如果在τ時間內(nèi),節(jié)點收到了其他節(jié)點的確認,則放棄再次廣播。消息的確認機制用于在廣播前抑制中間其他節(jié)點的廣播。 最后,重新愈合時間(re-healing time,簡稱tr)的計算：重新愈合時間是兩個相鄰簇間傳遞消息的時間。 通過QualNet進行仿真實驗,與SCB、SCF機制進行對比。結(jié)果表明應(yīng)用RSU之后重新愈合時間大大的減少,提高了廣播的實時性和可靠性。
[Abstract]:Up to now, most of the studies of vehicle-mounted ad hoc networks have focused on the broadcast storm protocols under the topology of high-density networks. These studies are based on the case that the VANET network is too simple and well connected. However, the problem of network disconnection is a common problem in VANET, so it is necessary to develop a reliable and efficient broadcast protocol to support diverse network topologies. In this paper, the flow of SCF (Store-Carry-Forward) SCB (Store-Carry-broadcast) mechanism is analyzed. Because they are simply disconnected vehicle-vehicle communication with the aid of vehicles driving in the opposite direction, it is impossible to guarantee the waiting time for the vehicles with cluster tails to meet the reverse direction repeater. Therefore, the delay of message propagation can be very long. On this basis, a broadcast protocol designed to shorten the time of rehealing between nodes is proposed by using the fixed facility RSU (roadside unit),. The main problems involved in this paper are as follows: first, the broadcast protocol model based on roadside facilities: when the packet transmission problem in VANET is studied, It is important to distinguish between the following two situations depending on the need: the first source vehicle detects an accident that generates a warning message and disseminates it to the rear vehicle. This warning message can be obtained before the rear vehicle reaches the potential danger area; a second situation occurs when the target is far from the source vehicle (i.e. the sender several to several kilometers away)-messages need to be sent to a specific node in the distance. Secondly, the Backoff delay 蟿 calculation based on message timestamp: the main idea of this algorithm is that the source node adds the sending time stamp to the sending message. After receiving the message, each node calculates the corresponding Backoff delay 蟿, and after the waiting time 蟿, This message is confirmed and broadcast next. If the node receives confirmation from other nodes within 蟿 time, it will give up broadcasting again. The message confirmation mechanism is used to suppress the broadcast of other intermediate nodes before broadcast. Finally, the calculation of re-healing time (tr): the time of recuperation is the time of passing messages between two adjacent clusters. The simulation experiment is carried out by QualNet and compared with the SCB / SCF mechanism. The results show that the time of re-healing after RSU is greatly reduced, and the real-time and reliability of broadcast is improved.
【學(xué)位授予單位】：天津科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U495;TN915.04

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