Ad Hoc网络路径选择中泛洪消息冲突问题研究

发布时间：2018-06-28 05:57

本文选题：Ad + Hoc网路　；参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：随着无线网络的快速发展,网络环境也日渐复杂,Ad Hoc网络能够在无基础设施的场合或既设通信设施无法覆盖的区域,为地理上相邻但散布区域超过单个节点无线传输范围的一组节点提供节点之间的通信服务,得到了众多学者的重视与研究。本文对Ad Hoc网络路径选择中泛洪消息冲突问题做出研究,改进了传统重发策略算法,提高了广播消息重传效率。首先根据Ad Hoc网络的应用环境及特点,提出了一种改进型的信道建模方法用以替代Ad Hoc网络仿真中常用的自由空间传播模型及两径模型,同时应用AODV协议及802.11 MAC协议实现路由查找及数据收发功能。通过计算机仿真,我们发现Ad Hoc网络的性能与所使用的信道模型紧密相关,不同信道模型会导致系统性能产生较大差异。本文中所提出的改进型信道模型可以充分考虑信号传播过程中的损耗、建筑物产生的阴影效应及信号传输过程中相位、幅度的小尺度衰减,不同信道模型将会影响Ad Hoc网络仿真时的性能参数。其次对Ad Hoc网络路径选择中泛洪消息问题做出了详细的研究。首先分析了在Ad Hoc网络场景下,利用概率论思想与随机过程,建立泛洪方式下广播包平均接收个数的闭式解,该闭式解能够根据网络性能得出广播消息后能够被接收端解调的数据包的个数,并进行真实网络场景模拟验证,通过仿真验证了该闭式解的符合Ad Hoc网络泛洪消息模型,理论值与仿真值基本相一致。最后改进了传统广播重发策略算法,该算法通过调整节点重发数据包的功率值进行重新选择接入信道时隙发送,由于接收端是靠检测广播包功率值进行判决接收的,因此该算法降低了冲突数据包的丢包率。通过与原有的重发算法进行比较,改进后的算法减少了广播重发次数,并通过仿真验证了改进算法能够减少广播消息的重传次数。因此本文所提出的无线信道模型以及改进的泛洪消息重发算法均可以应用的Ad Hoc网络性能仿真中。
[Abstract]:With the rapid development of wireless networks, the network environment is becoming more and more complex. Many scholars have paid much attention to providing communication services for a group of nodes that are geographically adjacent but whose scattered areas exceed the wireless transmission range of a single node. In this paper, the problem of flooding message conflict in Ad Hoc network path selection is studied, the traditional retransmission strategy algorithm is improved, and the broadcast message retransmission efficiency is improved. Firstly, according to the application environment and characteristics of Ad Hoc network, an improved channel modeling method is proposed to replace the free space propagation model and two-path model commonly used in Ad Hoc network simulation. At the same time, AODV protocol and 802.11 MAC protocol are used to realize routing lookup and data transceiver. By computer simulation, we find that the performance of Ad Hoc networks is closely related to the channel models used, and different channel models will lead to great differences in system performance. The improved channel model proposed in this paper can fully take into account the loss in the signal propagation process, the shadow effect produced by the building, the phase in the signal transmission process and the small scale attenuation of the amplitude. Different channel models will affect the performance parameters of Ad Hoc network simulation. Secondly, the flooding message problem in Ad Hoc network path selection is studied in detail. Firstly, the closed-form solution of the average number of broadcast packets in flooding mode is established by using probability theory and stochastic process in Ad Hoc network scenario. According to the network performance, the closed solution can get the number of packets that can be demodulated by the receiver after broadcast message, and verify the real network scene simulation. The simulation results show that the closed solution accords with the flooding message model of Ad Hoc network. The theoretical value is basically consistent with the simulation value. Finally, the traditional broadcast retransmission strategy algorithm is improved. The algorithm reselects the time slot of access channel by adjusting the power value of the retransmission packet, because the receiver receives it by detecting the power value of the broadcast packet. Therefore, the algorithm reduces the packet loss rate of collision packets. Compared with the original retransmission algorithm, the improved algorithm reduces the number of broadcast retransmissions, and the simulation results show that the improved algorithm can reduce the number of retransmissions of broadcast messages. Therefore, the proposed wireless channel model and the improved flooding message retransmission algorithm can be used in the performance simulation of Ad Hoc networks.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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