本文選題：車輛自組織網(wǎng)絡(luò)　切入點(diǎn)：擁塞控制　出處：《西安電子科技大學(xué)》2015年碩士論文

【摘要】：車輛自組織網(wǎng)絡(luò)(Vehicular Ad-hoc Networks, VANETs)是一種特殊的無線自組網(wǎng)(Mobile Ad-hoc Networks, MANETs),它是由車輛之間(Vehicular to Vehicular, V2V)以及車輛和基礎(chǔ)設(shè)施之間(Vehicular to Infrastructure, V2I)組成的無線自組織網(wǎng)絡(luò),車輛可以通過VANETs網(wǎng)絡(luò)向周圍車輛發(fā)送含有車輛速度、位置等基本信息,也可以在交通事故時向周圍車輛發(fā)送警告信息以避免發(fā)生連續(xù)交通事故,同樣也可以提供車載娛樂提高交通出行的趣味性。在車載自組織網(wǎng)絡(luò)中,車輛之間信息的交換扮演著重要的角色,使得車輛之間可以相互感知并且為車輛的安全應(yīng)用或非安全應(yīng)用提供參考信息。因?yàn)檐囕v周期性的發(fā)送消息,當(dāng)車輛過多時,如果不采用擁塞控制策略,信道就會變得擁塞,從而導(dǎo)致干擾增加,接收端信干比下降,嚴(yán)重影響車輛間的通信效率�，F(xiàn)有的擁塞控制方法大都基于調(diào)整發(fā)送功率或發(fā)送速率,忽視了載波監(jiān)聽門限對網(wǎng)絡(luò)擁塞的影響,而通過調(diào)整載波監(jiān)聽門限可以控制網(wǎng)絡(luò)的時延、吞吐量等。本文的主要工作在于：第一,通過分析載波監(jiān)聽門限和競爭窗口對網(wǎng)絡(luò)性能的影響,提出了一種載波監(jiān)聽門限和競爭窗口聯(lián)合控制的算法,在網(wǎng)絡(luò)中,載波監(jiān)聽門限和競爭窗口是兩個很重要的參數(shù),載波監(jiān)聽門限可以決定一個節(jié)點(diǎn)能否進(jìn)行發(fā)送信息。而競爭窗口則決定著當(dāng)節(jié)點(diǎn)偵聽到信道處于忙時的退避時間。通過分析,我們使用一個能反映網(wǎng)絡(luò)狀態(tài)的參數(shù)將網(wǎng)絡(luò)分為三種狀態(tài),并根據(jù)網(wǎng)絡(luò)的不同狀態(tài)設(shè)置不同的載波監(jiān)聽門限值和競爭窗口值,且采取不同的措施來自適應(yīng)的調(diào)整載波監(jiān)聽門限和競爭窗口。通過分析表明,我們提出的載波監(jiān)聽門限與競爭窗口聯(lián)合控制算法可以很好的提高網(wǎng)絡(luò)的吞吐量、降低誤碼率、降低分組時延等。第二,提出了一種基于線性二次型高斯最優(yōu)控制(Linear Quadratic Gaussian, LQG)的車輛網(wǎng)絡(luò)擁塞控制方法。通過分析表明,載波監(jiān)聽門限值對網(wǎng)絡(luò)的吞吐量有著重要的影響,但在實(shí)際中,網(wǎng)絡(luò)的吞吐量往往和預(yù)期值有所偏差,因此我們可以根據(jù)實(shí)際網(wǎng)絡(luò)吞吐量與預(yù)期網(wǎng)絡(luò)吞吐量的差值動態(tài)的調(diào)整載波監(jiān)聽門限,提高網(wǎng)絡(luò)的吞吐量,達(dá)到我們的期望值。我們利用線性二次型最優(yōu)控制的方法來求得所需的載波監(jiān)聽門限。本方法可以分為兩個步驟：(1)利用卡爾曼濾波器來消除獲取載波監(jiān)聽門限時噪聲帶來的影響,以得到精確的網(wǎng)絡(luò)吞吐量。(2)利用線性二次型最優(yōu)控制方法求得最優(yōu)的載波監(jiān)聽門限。求得的最優(yōu)載波監(jiān)聽門限可使網(wǎng)絡(luò)吞吐量達(dá)到預(yù)期值,可確保網(wǎng)絡(luò)不發(fā)生擁塞。仿真表明,本文提出的基于LQG的擁塞控制算法可以有效的提高網(wǎng)絡(luò)吞吐量,使網(wǎng)絡(luò)即使發(fā)生擁塞的情況網(wǎng)絡(luò)吞吐量也能保持在一個合理的水平。
[Abstract]:Vehicular ad hoc networks (Vehicular Ad-hoc, Networks, VANETs) is a kind of wireless ad hoc network special (Mobile Ad-hoc Networks, MANETs), which is composed of the vehicle (Vehicular to Vehicular, V2V) and between vehicles and infrastructure (Vehicular to, Infrastructure, V2I) composed of wireless ad hoc networks, the vehicle can contain the vehicle speed to send around the vehicle through the VANETs network, location and other basic information, also can be in the traffic accident to send warning information around the vehicle to avoid continuous traffic accidents, can also provide car entertainment improve transportation interest. In thevanet, exchange information between vehicles plays an important role, so between the vehicles to provide reference information and mutual awareness for the safety of vehicles or non application security applications can send messages. Because of the vehicle when the vehicle cycle. Over time, if not the congestion control strategy, the channel will become congested, resulting in increased interference, the receiver SNR decreased, seriously affect the efficiency of communication between vehicles. Most of the existing congestion control method to adjust the transmit power or the sending rate based on the effect of listening to the network congestion threshold wave load, and by adjusting carrier sense threshold can control time delay, the throughput of the network. The main work of this paper is: first, through the analysis of the influence of carrier sensing threshold and contention window on the network performance, proposed a carrier monitoring threshold and contention window combined control algorithm, in the network, a carrier sensing threshold and the contention window are two the important parameters of carrier sensing threshold can determine whether a node can send information. And the contention window determines when a node listens to the channel is busy when the backoff time . through the analysis, we use a network can reflect the state parameters of the networks are divided into three kinds of state, and according to different network conditions set different carrier sensing threshold and contention window value, and take different measures to adjust from the carrier sense threshold and competition window. The analysis shows that the carrier sense we propose a threshold and contention window control algorithm can improve network throughput, reduce the error rate, reduce the packet delay. Second, proposed a linear optimal control based on the two Gauss (Linear Quadratic Gaussian, LQG) of the vehicle network congestion control method. The analysis shows that the carrier sense threshold on the throughput of the network have an important impact, but in reality, the network throughput often and the expected value is different, so we can according to the actual network throughput and expected The difference of dynamic adjustment of the network throughput of carrier sensing threshold, improve the network throughput, meet our expectations. We use the method of linear quadratic optimal control in two to obtain the desired carrier sense threshold. This method can be divided into two steps: (1) to eliminate the influence of access threshold noise caused by carrier sense using the Calman filter, in order to get the accurate network throughput. (2) carrier sensing threshold with two linear optimal control method to obtain the optimal threshold is obtained. Optimal carrier sensing can make the network throughput reach the expected value, which can ensure the network congestion. Simulation results show that can effectively improve the network throughput of LQG congestion control algorithm based on this, the network throughput of the network even if congestion occurs can be maintained at a reasonable level.

【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U495;U463.67;TN929.5

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