【作者】 倪旻明；

【导师】 钟章队；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2013， 博士

【摘要】 随着无线通信技术以及移动电话、PDA (Personal Digital Assistant)、笔记本电脑等无线通信设备的不断发展,人类社会已经逐渐进入了泛在通信的新时代。在众多的通信解决方案中,基于分簇结构的移动Ad Hoc网络因其不依赖固定基础设施即可在移动场景中实现动态组网与数据传输的特点在近些年引起了学术界和工业界越来越多的关注。与传统的平面结构相比,分簇结构能够显著地改善资源的利用率、降低路由复杂度、增强网络稳定性。但由于分簇结构的建立与维护不可避免地会依赖于额外的状态信息与控制信息的交互,所以当网络的拓扑结构变化较快并且涉及较多动态节点时,网络中传输的分簇信息则可能出现显著的增长,从而占用大量系统资源,甚至造成网络的瘫痪。因此,如何为移动AdHoc网络设计高效、可靠的分簇组网方案,并进行准确、有效的性能分析就成为推进分簇组网技术继续向前发展的关键。本文首先从分簇组网方案的设计出发,提出了一套基于移动性预测的分簇组网方案(Mobility Prediction Based Clustering, MPBC)以尽可能减少节点的随机移动性对网络拓扑结构所可能产生的影响。与现有面向移动性感知的分簇组网方案相比,MPBC方案采用了基于多普勒频移的相对移动性预测算法获得所需的移动性信息。由于新的预测算法不依赖于外部系统、且无需传输额外的控制信息,MPBC方案体现出了更好的环境适应性。此外,在MPBC方案中,预测得到的移动性信息不仅用于簇头的初步选取、网络结构的初始化,也被用于在分簇保持阶段对网络结构做出适时的调整以尽可能进一步提升簇结构的稳定性。通过理论分析和仿真实验可知：在相同条件下,MPBC方案在链路状态变化率、逻辑链路持续时间、簇头生存时间等一系列稳定性性能指标方面都比现有典型分簇组网方案表现得更为出色。由于分簇组网工作中的信息交互基本都以广播方式完成,因此广播传输的性能会直接影响到分簇组网工作的有效进行。基于这样的考虑,本文在完成分簇方案的设计之后,进而对广播传输的可靠性进行了理论分析。为了准确地描述广播传输过程,本文用Markov链对随机退避计数器的状态变化、节点传输队列中剩余数据包数目的变化分别进行了重新建模,以修正现有文献中所存在的问题与不足。在此基础上,通过模型分析得到的节点平均传输概率被用于推导一般性二维平面场景下移动Ad Hoc网络中基于距离的丢包率、平均丢包率以及平均队列时延这三个可靠性性能指标的闭合表达式。与现有研究成果相比,本文考虑了隐藏终端以及相邻节点选择相同的退避时间对广播传输所产生的影响。此外,本文也对衰落信道在传输可靠性方面所可能产生的负面效应进行了讨论。最后,本文研究了分簇结构对移动Ad Hoc网络容量性能带来的影响以提高分簇组网的有效性。基于描述网络中通信干扰的协议模型(Protocol Model)和由收发节点形成的排斥区域(Exclusive Region),本文首先得到了分簇结构的移动Ad Hoc网络中由簇结构和孤立节点决定的两个理论容量上界,并在此基础上对临界网络面积进行了求解。此后,本文还对不同场景中网络容量下界的可达性进行了分析。研究结果表明,在分簇结构下,移动Ad Hoc网络的网络容量会因网络面积的变化而表现出不同的特征；而临界网络面积这一参量也对“大规模”网络这一概念做出了更为明确地解释。更多还原

【Abstract】 With the recent developments in wireless communication technologies and evolutions in low cost wireless devices such as mobile phones, PDAs, and laptops etc., the human society is entering a ubiquitous communicating era. Among the various possible solutions, cluster-based Mobile Ad Hoc Networks (MANETs) is a proven one for deploying a network without any fixed infrastructure in a mobile scenario. Compared with the traditional flat-structured counterpart, the cluster-based network structure can dramatically improve the channel efficiency, reduce the routing complexity, and enhance the network stability. However, to initialize or maintain a cluster structure in a dynami-cally changing scenario often requires explicit message exchanges between mobile node pairs. When the underlying network topology changes quickly and involves many mo-bile nodes, the clustering-related information exchange increases drastically, which may even block the data transmissions. Therefore, the design of efficient, reliable cluster-ing scheme, and the accurate performance analysis for MANETs are vital for the further development of cluster-based networking technologies.In this dissertation, a Mobility Prediction Based Clustering (MPBC) scheme is firstly proposed to alleviate the effect of random mobility on network topology. Compared with other existing mobility-aware clustering schemes, MPBC adopts a Doppler shift based relative mobility prediction scheme, which works independently from the external system and without extra data interactions, to obtain the required mobility information. Besides its function for initial cluster head selection, the mobility-related information are farther used in the cluster maintaining stage of MPBC. By theoretical analysis and simulation experiments, MPBC outperforms other clustering schemes significantly in association with link status change rate, logic link lifetime, cluster head lifetime, and other stability performance metrics.Due to that most of the control message exchanges for clustering are carried out by broadcast, the broadcast transmission’s reliability plays a key role in clustering schemes’ implementation. To accurately illustrate the broadcast progress, this work models the ran-dom backoff counter’s state transition and the changing pattern of the number of packets waiting in a node’s transmission queue as two Markov chains, respectively. Afterwards, by using the transmission probability derived from the two new Markov models, three different reliability metrics, namely Distance-based Packet Loss Rate (d-PLR), Average Packet Loss Rate (APLR), and Average Queueing Delay (AQD) are analyzed. The deriva-tions for the closed-form of these metrics combine with the features of Poisson Point Process, and take into account both the impact of concurrent transmissions caused by identical backoff interval selection and that of hidden nodes caused by limited sensing range on an observed transmitter. Moreover, a short discussion for the effect of fading channel on broadcast reliability is also given after the part of simulation evaluations.Finally, this work studies the capacity bounds of the clustered MANETs. By making use of the concepts and features of Exclusive Region and Protocol Model, the two theo-retical upper bounds of network capacity induced by clustering and orphan nodes in the network are achieved first. After calculating the critical network area, two constructive lower bounds for network capacity are also obtained. The main result is that the clus-tered network capacity switches behavior at a critical network size, which depends on the cluster size and the density of clusters within the network. Moreover, the clustering parameters of the network allow us to define the meaning of a large network by certain bounds.更多还原