远距离载波检测无线网络分布式接入协议设计与建模优化

发布时间：2018-03-13 21:05

  本文选题：远距离无线网络　切入点：DCF协议　出处：《南京航空航天大学》2014年硕士论文　论文类型：学位论文

【摘要】：基于载波检测多点接入/冲突避免机制(Carrier Sense Multiple Access/Collision Avoidance,CSMA/CA)的信道接入控制(Medium Access Control,MAC)协议已在短距离无线网络中得到广泛应用。其中,最典型的协议即为无线局域网领域的IEEE 802.11DCF(Distributed Coordination Function)。该协议通过二进制指数退避的方法避免节点之间的发送冲突,并采用RTS/CTS控制帧握手机制解决隐终端问题,具有灵活、高效、可实现自组织组网等优势。目前,DCF协议的基本接入机制已广泛应用于无线网状网、无线传感网等不同的网络形式中。近年来,随着无线网络技术的快速发展,人们逐渐考虑将基于CSMA/CA机制的DCF协议应用于远距离组网的场景。在民用领域,人们通过DCF协议,构建远距离地面WiFi网络或空中无人机WiFi网络,以低成本的方式为欠发达地区提供因特网接入服务。在军用领域,CSMA/CA的接入方式也已用于部分航空数据链系统,例如,以色列预警机和战斗机之间的高速信息共享数据链ACR-740。然而,由于DCF协议本身是为短距离条件应用而设计的,在远距离条件下应用存在组网效率低、吞吐量性能差等一系列问题。产生这些问题的根源是什么?以经典的DCF协议为基本框架,如何设计远距离条件下基于CSMA/CA机制的信道接入协议?本文的研究工作即围绕上述问题展开,主要工作包括:(1)在近距离条件下,载波检测接入协议中的退避时隙长度通常设置为大于信号的最大传播时延,从而保证节点发送的信号均能被其载波检测范围内的任一节点检测到。然而,在远距离条件下,由于信号最大传播时延大,如果将每一个退避时隙的长度均设置为信号最大传播时延,则节点发送前的退避过程将导致网络总吞吐量的严重下降。本文通过马尔科夫链建模的方法,揭示了在远距离传输条件下,节点退避时隙长度与网络总吞吐量之间的关系。通过模型求解,分析了在不同网络规模条件下,通过调整退避时隙长度优化网络总吞吐量的策略,为远距离条件下载波检测无线网络高效分布式接入协议设计提供了参考。(2)以上述建模与分析方法为基础,本文提出了一种基于信道竞争节点感知和竞争窗口优化的远距离载波检测接入协议(DCWLD)。该协议采用分布式随机竞争的方法产生网络中心管理节点。中心管理节点周期性的对当前竞争信道节点的数量进行估计,并以广播的方式告知网络中的全部节点。发送节点在当前网络条件下,以竞争信道节点数量为依据,以提高网络总平均吞吐量为目标,采用马尔科夫链建模的方法,确定当前竞争退避窗口大小的最优取值。不同网络条件下的仿真结果证明,与普通DCF协议相比,本文提出的DCWLD协议可以在远距离条件下获得更优的网络总平均吞吐量性能。
[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.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN92
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本文编号：1608113