车载自组织网络中信标消息传输机制研究

发布时间：2017-12-27 11:09

本文关键词：车载自组织网络中信标消息传输机制研究　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：车载自组织网络作为无线通信技术在交通领域中的最新应用,受到了学术界和工业界的广泛关注。在智能交通系统中,车载自组织网络技术被认为是实现交通安全保障、提高交通效率、解决能源和污染问题的关键技术之一。车载自组织网络中的一种最基本、最重要的消息类型被称为信标消息。信标消息承载了节点的行驶状态和通信状态,所有车辆节点和路边设备节点通过周期性的信标消息传输建立彼此之间的联系,形成车载自组织网络。由于车载自组织网络具有节点密度变化大、网络拓扑变化快、无线信道质量变化多样等特点,导致实时可靠的信标消息传输难以得到保证,直接影响了车载自组织网络的整体服务质量。针对这一问题,研究者们进行了广泛的研究,通过寻找合适的优化依据和优化方法,努力提高信标消息传输性能。然而已有的关于信标消息传输机制研究,往往仅针对车辆与车辆通信这种单一情况,很少考虑车辆分簇或者有路边设备参与等网络环境。此外,如何优化信标传输机制以快速响应车辆密度的大幅度变化,如何优化路边设备的信标消息传输能效,以及如何改善已有信标消息传输机制优化方法的滞后性等,也是目前亟待解决的问题。本文针对上述内容,对车载自组织网络中信标消息传输机制进行了深入的研究,主要内容及创新点包括:1.在分簇车载自组织网络环境中,对信标消息传输机制的优化依据进行研究,设计了一种簇成员数量快速评估方法,实现对簇成员数量是否低于阈值的快速判断。认识到已有的数量评估方法是通过查询簇成员列表实现的,这种方法耗时较长且不适用于车辆密度较高的环境,无法满足信标消息传输机制优化的需求。本文提出了一种基于竞争的时隙占用方法,有效提高簇成员数量评估效率。具体而言:1)介绍了通过时隙占用方法实现节点数量评估的基本原理和特点,给出了时隙占用方法的参数选择过程,并分析了所提方法的有效性和准确性,参数选择结果验证了所提方法的高效性;2)在所提方法的基础上进一步提出了一种改进的簇成员数量快速评估方法,通过适时进行评估过程中断,实现评估效率的再次提升;3)分析了信道状态对所提两种数量评估方法的影响,证明了在非理想信道条件下,通过合理的参数选择,所提方法依然能够保证其有效性、准确性和高效性。2.在有路边设备的车载自组织网络环境中,对信标消息传输机制的优化方法进行研究,设计了一种考虑能效的路边设备信标消息传输机制优化方案。传统的信标消息传输机制要求路边设备周期性的广播信标消息,然而当车辆密度较低时,周期性的广播往往因为没有车辆接收而意味着能量的浪费。在实际道路上,车辆的到达是服从一定规律的,如何优化信标消息发送间隔,平衡能量消耗与得到一次有效消息传输机会所需时间之间的关系,成为一个值得研究的课题。具体研究包括:1)利用最大似然法实现车辆到达规律的马尔科夫模型建模,并基于中心极限定理分析了观测样本数量与模型建立准确度之间的关系:2)利用所得模型分析了信标消息发送间隔与获得一次有效消息传输机会所需时间之间的关系,给出了不同初始状态下信标消息发送间隔的优化方法:3)基于Sigmoid函数设计了路边设备的满意度函数,分析了系统参数对满意度函数的影响,综合考虑各指标的满意度,实现了最优信标消息发送间隔的求解。3.在车载自组织网络中,对信标消息传输机制的优化依据和优化方法进行研究,设计了一种基于短期交通状态预测的信标消息传输机制优化方案。认识到现有优化方案通常是根据已有数据来对未来的信标消息传输机制进行优化。对于拓扑结构快速变化的车载自组织网络,这种优化方案是相对滞后的。本文提出了一种基于短期交通状态预测的自适应信标消息传输机制,有效改善了信标消息传输性能。方案设计过程中充分考虑了车辆节点对信道资源利用的公平性。具体而言:1)设计了一种新的平均邻居节点数量的估算方法,给出了信标消息传输机制的优化发起条件;2)根据自回归移动平均模型,利用历史交通数据建立不同的交通流模式,通过模式匹配实现短期交通状态参数的一步预测;3)以参数预测结果为优化依据,提出了一种信标消息传输机制联合优化方法,通过对信标消息生成频率和传输功率的联合优化控制,实现信标消息传输性能的优化。
[Abstract]:As the latest application of wireless communication technology in the field of traffic, vehicular ad hoc networks have received extensive attention from academia and industry. In intelligent transportation system, vehicular ad hoc network technology is considered to be one of the key technologies to achieve traffic safety, improve traffic efficiency, solve energy and pollution problems. One of the most basic and important message types in vehicular ad hoc networks is called beacon messages. Beacon message carries the running state and communication state of nodes, and all vehicle nodes and roadside device nodes establish the connection between each other by periodic beacon message transmission, and form vehicular ad hoc network. Because the vehicular ad hoc network has the characteristics of large node density, fast network topology and diverse quality of wireless channel, the real-time reliable beacon message transmission is difficult to be guaranteed, which directly affects the overall quality of service of vehicular ad hoc network. In order to solve this problem, researchers have carried out a wide range of research, and strive to improve the performance of beacon message transmission by looking for appropriate optimization basis and optimization methods. However, the existing researches on beacon message transmission mechanism usually aim at the single situation of vehicle and vehicle communication, and rarely consider vehicle clustering or roadside device participation. In addition, how to optimize the beacon transmission mechanism to respond to the rapid change of vehicle density, how to optimize the beacon message transmission energy efficiency of roadside devices, and how to improve the lagging of the existing beacon message transmission mechanism optimization methods, is also an urgent problem to solve now. According to the content of vehicular ad hoc network beacon message transmission mechanism is studied, the main contents and innovations include: 1. in the cluster of vehicular ad hoc network environment, the paper studies the optimal basis of beacon message transmission mechanism, design a rapid assessment method the number of cluster members, achieve rapid judgment the number of cluster members is lower than the threshold. It is recognized that the existing quantitative evaluation method is implemented through querying cluster member list. This method takes a long time and is not suitable for environments with high vehicle density, which can not satisfy the requirement of beacon message transmission mechanism optimization. In this paper, a competition based time slot occupancy method is proposed to effectively improve the efficiency of cluster membership evaluation. Specifically: 1) introduced the method through the slot of the realization of the basic occupation principle and characteristics of the number of node evaluation, selection of process parameters is presented. The slot occupancy method, and analyze the effectiveness of the proposed method and the accuracy of parameter selection, results show that the proposed method; 2) based on the proposed method. Put forward a fast assessment method improved the number of cluster members, through the timely implementation of the evaluation process is interrupted, to evaluate the efficiency of the upgrade again; 3) analyzes the channel status of the two assessment methods, and proved that the non ideal channel conditions, through the reasonable choice of parameters, the proposed method is still to ensure the effectiveness, accuracy and efficiency. 2., in the vehicular ad hoc network with roadside devices, we study the optimization method of beacon message transmission mechanism, and design an optimization scheme of the beacon message transmission mechanism considering the energy efficiency. Traditional beacon message transmission mechanism requires periodic broadcast beacon messages on roadside devices. However, when vehicle density is low, periodic broadcasting often means energy waste because there is no vehicle reception. On the real road, the arrival of vehicles is subject to certain rules. How to optimize the relationship between beacon message sending interval, balancing energy consumption and obtaining the time of effective message transmission opportunity has become a worthy research topic. Specific studies include: 1) Markoff model to realize vehicle arrival pattern using maximum likelihood method, and based on the central limit theorem of the number of observation samples and models the relationship between accuracy of the analysis: 2) the beacon interval of message transmission and get an effective message transmission opportunity for relations between the time by using the above model. Gives the optimization method under different initial conditions the beacon message transmission interval: 3) based on the Sigmoid function design the satisfaction function of roadside equipment, analyzes the influence of system parameters on the satisfaction function, considering each index satisfaction, achieve optimal beacon message transmission interval. 3., in vehicle self-organizing network, we studied the optimization basis and optimization method of beacon message transmission mechanism, and designed an optimization scheme of beacon message transmission mechanism based on short-term traffic state prediction. It is recognized that the existing optimization scheme is usually based on the existing data to optimize the future beacon message transmission mechanism. This optimization scheme is relatively lagged for the fast changing topology of the vehicular self organizing network. In this paper, an adaptive beacon message transmission mechanism based on short-term traffic state prediction is proposed, which effectively improves the performance of beacon message transmission. In the process of design, the fairness of vehicle node to channel resource utilization is fully considered. Specifically: 1) design a method for estimating the average number of new neighbor nodes, gives the optimal beacon message transmission mechanism of the launch conditions; 2) based on the autoregressive moving average model, using historical traffic data to build traffic flow patterns, the pattern matching step to predict short-term traffic parameters; 3 the prediction results for the optimization of parameters) basis, put forward the optimization method of a beacon message transmission mechanism, controlled by the joint optimization of the beacon message generation frequency and transmission power, optimize the transmission performance of beacon message.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN929.5;U495

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