本文選題：遠(yuǎn)距離無線網(wǎng)絡(luò)　切入點(diǎn)：DCF協(xié)議　出處：《南京航空航天大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：基于載波檢測多點(diǎn)接入/沖突避免機(jī)制(Carrier Sense Multiple Access/Collision Avoidance,CSMA/CA)的信道接入控制(Medium Access Control,MAC)協(xié)議已在短距離無線網(wǎng)絡(luò)中得到廣泛應(yīng)用。其中,最典型的協(xié)議即為無線局域網(wǎng)領(lǐng)域的IEEE 802.11DCF(Distributed Coordination Function)。該協(xié)議通過二進(jìn)制指數(shù)退避的方法避免節(jié)點(diǎn)之間的發(fā)送沖突,并采用RTS/CTS控制幀握手機(jī)制解決隱終端問題,具有靈活、高效、可實(shí)現(xiàn)自組織組網(wǎng)等優(yōu)勢。目前,DCF協(xié)議的基本接入機(jī)制已廣泛應(yīng)用于無線網(wǎng)狀網(wǎng)、無線傳感網(wǎng)等不同的網(wǎng)絡(luò)形式中。近年來,隨著無線網(wǎng)絡(luò)技術(shù)的快速發(fā)展,人們逐漸考慮將基于CSMA/CA機(jī)制的DCF協(xié)議應(yīng)用于遠(yuǎn)距離組網(wǎng)的場景。在民用領(lǐng)域,人們通過DCF協(xié)議,構(gòu)建遠(yuǎn)距離地面WiFi網(wǎng)絡(luò)或空中無人機(jī)WiFi網(wǎng)絡(luò),以低成本的方式為欠發(fā)達(dá)地區(qū)提供因特網(wǎng)接入服務(wù)。在軍用領(lǐng)域,CSMA/CA的接入方式也已用于部分航空數(shù)據(jù)鏈系統(tǒng),例如,以色列預(yù)警機(jī)和戰(zhàn)斗機(jī)之間的高速信息共享數(shù)據(jù)鏈ACR-740。然而,由于DCF協(xié)議本身是為短距離條件應(yīng)用而設(shè)計(jì)的,在遠(yuǎn)距離條件下應(yīng)用存在組網(wǎng)效率低、吞吐量性能差等一系列問題。產(chǎn)生這些問題的根源是什么?以經(jīng)典的DCF協(xié)議為基本框架,如何設(shè)計(jì)遠(yuǎn)距離條件下基于CSMA/CA機(jī)制的信道接入?yún)f(xié)議?本文的研究工作即圍繞上述問題展開,主要工作包括:(1)在近距離條件下,載波檢測接入?yún)f(xié)議中的退避時(shí)隙長度通常設(shè)置為大于信號的最大傳播時(shí)延,從而保證節(jié)點(diǎn)發(fā)送的信號均能被其載波檢測范圍內(nèi)的任一節(jié)點(diǎn)檢測到。然而,在遠(yuǎn)距離條件下,由于信號最大傳播時(shí)延大,如果將每一個(gè)退避時(shí)隙的長度均設(shè)置為信號最大傳播時(shí)延,則節(jié)點(diǎn)發(fā)送前的退避過程將導(dǎo)致網(wǎng)絡(luò)總吞吐量的嚴(yán)重下降。本文通過馬爾科夫鏈建模的方法,揭示了在遠(yuǎn)距離傳輸條件下,節(jié)點(diǎn)退避時(shí)隙長度與網(wǎng)絡(luò)總吞吐量之間的關(guān)系。通過模型求解,分析了在不同網(wǎng)絡(luò)規(guī)模條件下,通過調(diào)整退避時(shí)隙長度優(yōu)化網(wǎng)絡(luò)總吞吐量的策略,為遠(yuǎn)距離條件下載波檢測無線網(wǎng)絡(luò)高效分布式接入?yún)f(xié)議設(shè)計(jì)提供了參考。(2)以上述建模與分析方法為基礎(chǔ),本文提出了一種基于信道競爭節(jié)點(diǎn)感知和競爭窗口優(yōu)化的遠(yuǎn)距離載波檢測接入?yún)f(xié)議(DCWLD)。該協(xié)議采用分布式隨機(jī)競爭的方法產(chǎn)生網(wǎng)絡(luò)中心管理節(jié)點(diǎn)。中心管理節(jié)點(diǎn)周期性的對當(dāng)前競爭信道節(jié)點(diǎn)的數(shù)量進(jìn)行估計(jì),并以廣播的方式告知網(wǎng)絡(luò)中的全部節(jié)點(diǎn)。發(fā)送節(jié)點(diǎn)在當(dāng)前網(wǎng)絡(luò)條件下,以競爭信道節(jié)點(diǎn)數(shù)量為依據(jù),以提高網(wǎng)絡(luò)總平均吞吐量為目標(biāo),采用馬爾科夫鏈建模的方法,確定當(dāng)前競爭退避窗口大小的最優(yōu)取值。不同網(wǎng)絡(luò)條件下的仿真結(jié)果證明,與普通DCF協(xié)議相比,本文提出的DCWLD協(xié)議可以在遠(yuǎn)距離條件下獲得更優(yōu)的網(wǎng)絡(luò)總平均吞吐量性能。
[Abstract]:Carrier Sense Multiple Access/Collision void Control (CSMA / CAA) based on carrier detection multipoint access / collision avoidance mechanism has been widely used in short-range wireless networks. The most typical protocol is IEEE 802.11DCFN distributed Coordination function in the field of WLAN. The protocol avoids the transmission conflict between nodes by binary exponential Backoff, and uses RTS/CTS control frame handshake mechanism to solve the hidden terminal problem, which is flexible and efficient. At present, the basic access mechanism of DCF protocol has been widely used in wireless mesh network, wireless sensor network and other network forms. In recent years, with the rapid development of wireless network technology, People are gradually considering the application of DCF protocol based on CSMA/CA mechanism to remote network scenarios. In the civilian field, people construct long-distance ground WiFi network or aerial UAV WiFi network through DCF protocol. Providing Internet access to underdeveloped regions in a low-cost manner. In the military sphere, CSMA / CA access has also been used in some aviation data link systems, such as the high-speed information sharing data link ACR-740between Israeli early warning aircraft and fighter jets. However, Because the DCF protocol is designed for short-range conditional applications, there are a series of problems such as low network efficiency and poor throughput in long-distance applications. What are the root causes of these problems? Taking the classical DCF protocol as the basic framework, how to design the channel access protocol based on the CSMA/CA mechanism under the condition of long distance? The research work in this paper is focused on the above problems. The main work includes: 1) under the condition of close distance, the Backoff time slot length in the carrier detection access protocol is usually set to the maximum propagation delay greater than the signal. So as to ensure that the signal transmitted by the node can be detected by any node in the range of carrier detection. However, under the condition of long distance, the maximum propagation delay of the signal is large, If the length of each Backoff slot is set to the maximum propagation delay of the signal, the Backoff process before the node sends will lead to a serious decrease in the total throughput of the network. The relationship between the node Backoff slot length and the total throughput of the network is revealed under the condition of long-distance transmission. By solving the model, the strategy of optimizing the total throughput of the network by adjusting the length of the Backoff slot under different network scales is analyzed. This paper provides a reference for the design of efficient distributed access protocol for carrier detection wireless network under the condition of long distance) based on the above modeling and analysis methods. In this paper, a remote carrier detection access protocol based on channel competitive node awareness and contention window optimization is proposed. The protocol uses distributed random competition to generate network central management nodes and central management node cycle. A periodic estimate of the current number of competing channel nodes, All nodes in the network are informed by broadcast. Under the current network conditions, the transmitting node is based on the number of competing channel nodes, and the goal is to improve the total average throughput of the network, and the Markov chain modeling method is adopted. The simulation results under different network conditions show that the proposed DCWLD protocol can achieve better overall average throughput performance than the conventional DCF protocol over long distances.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN92
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本文編號：1608113