线型网络VANET传输容量研究

发布时间：2018-08-21 09:51

【摘要】：作为物联网和智能交通系统的重要组成部分之一,车辆自组织网络(VANET)吸引了来自学术界和工业界的广泛关注;IEEE 802.11p及IEEE 1609.x等相关标准的陆续出台,也为未来VANET的研究与发展指引了方向。然而,由于传统VANET相关研究多数直接继承了无线自组织网络的模型和研究框架。因而这一类成果普遍存在两点关键性不足:一是缺乏对更贴近实际的车辆行为和分布的模拟;二是对802.11p MAC层机制的建模不够完善甚至缺失。为了得到与实际车辆通信环境更加贴切的VANET研究成果,本文拟从最基本的线型VANET网络入手,针对以上两点不足之处进行弥补,以期得到更合理的线型VANET网络传输容量上界或表达式。VANET传输容量作为反映车辆自组织网络性能的关键指标之一,其具体表达式或界值的计算推导一直是相关研究领域的热点和难点。本文为推导更真实的传输容量上界与表达式,引入了交通研究领域比较成熟的车辆跟随模型来描述车辆节点分布,同时参考之前相关研究的成果,利用802.11p MAC层EDCA机制中CCA模式的特性,对802.11p MAC层信道接入机制进行建模。从而构建了一套能够模拟出较真实直线道路车辆行驶行为和EDCA信道接入机制的直线型VANET研究模型。在上述模型的基础上,本文首先改进了传荣传输容量上界研究在干扰模型上的缺陷。之后证明在某种同时发送车辆节点极限分布条件下,网络传输容量可以达到上界值。按照该分布推导出传输容量上界的表达式,并通过仿真与之前类似研究进行对比。结果表明本文改进后的上界在高车辆节点密度环境下具有更好的表现,并可以对仿真中出现的瞬时最大传输容量做出准确计算。在得到的改进传输容量上界基础上,又加入了对瑞利衰落(Rayleigh Fading)信道环境的考虑。通过引入收发节点平均距离和中断概率等新参数,最终推导出了瑞利衰落信道下线型VANET传输容量上界的表达式。仿真结果表明,瑞利衰落环境下线型VANET平均传输容量可紧密贴近该上界。基于研究中的模型和理论基础,还在最后尝试推导了线型VANET传输容量的准确表达式,但受限于过高的数学复杂度,该表达式还有待进一步化简。总体而言,本文基于更贴近现实的车辆行为模型和MAC层信道接入机制模拟,得到了线型VANET传输容量在大尺度衰落和瑞利衰落环境下的上界表达式,并通过仿真验证了其合理性。同时尝试推导了传输容量的准确表达式。以上研究将为最终真正得到与真实环境高度吻合的VANET传输容量理论提供一定的借鉴和参考价值。
[Abstract]:As one of the important components of the Internet of things and Intelligent Transportation system, (VANET) has attracted wide attention from academia and industry. The standards of IEEE802.11p and IEEE 1609.x have been published one after another. It also guides the research and development of VANET in the future. However, the traditional VANET research directly inherits the model and research framework of wireless ad hoc networks. Therefore, there are two key shortcomings in this kind of achievement: one is the lack of simulation of vehicle behavior and distribution more closely to the actual situation, the other is that the modeling of 802.11p MAC layer mechanism is not perfect or even lacking. In order to get the research results of VANET which is more appropriate to the actual vehicle communication environment, this paper intends to start with the most basic linear VANET network and make up for the above two deficiencies. In order to obtain a more reasonable upper bound of transmission capacity of linear VANET network or the expression. VANET transmission capacity as one of the key indicators to reflect the performance of the vehicle ad hoc network. The calculation and derivation of its specific expressions or bounds has always been a hot and difficult point in related research fields. In order to derive a more real upper bound and expression of transmission capacity, a more mature vehicle following model is introduced to describe the distribution of vehicle nodes. Using the characteristic of CCA mode in 802.11p MAC layer EDCA mechanism, the channel access mechanism of 802.11p MAC layer is modeled. Thus, a set of linear VANET research models which can simulate the vehicle driving behavior and EDCA channel access mechanism of real linear road are constructed. On the basis of the above model, this paper first improves the defect of the interference model in the study of the upper bound of the transmission capacity. Then it is proved that the transmission capacity of the network can reach the upper bound under the limit distribution condition of some simultaneous transmission vehicle nodes. According to this distribution, the expression of the upper bound of transmission capacity is derived, and the simulation is compared with the previous similar research. The results show that the improved upper bound has better performance in the environment of high vehicle node density and can accurately calculate the instantaneous maximum transmission capacity in simulation. Based on the improved upper bound of transmission capacity, the Rayleigh fading (Rayleigh Fading) channel environment is considered. By introducing new parameters such as average distance of transceiver node and outage probability, the upper bound of transmission capacity of linear VANET in Rayleigh fading channel is derived. The simulation results show that the average transmission capacity of linear VANET in Rayleigh fading environment is close to the upper bound. Based on the model and theoretical basis of the study, an accurate expression of the transmission capacity of linear VANET is derived at last. However, due to the high mathematical complexity, the expression needs to be further simplified. In general, based on the more realistic vehicle behavior model and the simulation of MAC layer channel access mechanism, the upper bound expression of linear VANET transmission capacity in large scale fading and Rayleigh fading environments is obtained, and its rationality is verified by simulation. At the same time, we try to deduce the exact expression of transmission capacity. The above research will provide some reference and reference value for the theory of VANET transport capacity which is highly consistent with the real environment.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.5;U495

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