【作者】 王勇；

【导师】 袁东风；

【作者基本信息】 山东大学 ， 通信与信息系统， 2008， 博士

【摘要】 无线Ad hoc网络是由一组带有无线收发装置的移动终端组成的一个多跳临时性自治系统,移动终端具有路由功能,可以通过无线连接构成任意的网络拓扑,这种网络可以独立工作,也可以与Internet或蜂窝无线网络连接。无线Ad hoc网络中,每个移动终端兼备路由器和主机两种功能:作为主机,终端需要运行面向用户的应用程序;作为路由器,终端需要运行相应的路由协议,根据路由策略和路由表参与分组转发和路由维护工作。在无线Ad hoc网络中,节点间的路由通常由多个网段(跳)组成,由于终端的无线传输范围有限,两个无法直接通信的终端节点往往要通过多个中间节点的转发来实现通信。所以,它又被称为多跳无线网、自组织网络、无固定设施的网络或对等网络。Ad hoc网络同时具备移动通信和计算机网络的特点,可以看作是一种特殊类型的移动计算机通信网络。本文对无线Ad Hoc网络功率控制和跨层协议交互、控制流调度方案的改进、簇头的筛选和控制、QoS拓扑控制进行了研究,主要工作和创新点如下:1、介绍了功率控制技术在无线自组织网络中所起的作用,分析了功率控制对网络层、媒体访问控制(MAC)层和物理层性能的影响,在此基础上提出一种以提高网络能量效率为目的,同时能够减小物理层信号间的干扰、保障网络层网络的连通性、减少MAC层数据包竞争冲突率的跨层功率控制机制。以应用层恒定比特率(CBR)协议为例,进行了应用层到网络层、网络层到应用层的跨层交互通信机理分析。仿真实验结果表明,经过跨层,减少了UDP传输层的处理流程,在延时和抖动变化不大的情况下,极大地提高了网络吞吐量和成功接收应用层分组的数量,降低了丢包率,在自组织网络中能明显地改善多媒体传输的性能。2、进行了无线自组织网络中控制流的性能分析与改进方案研究。在性能分析方面,基于网络控制信令的相关行为和特点,分析和比较了无线自组织网络中各种传统性能评估和提升方法的优缺点,并针对自组织网络自身的特点分析了隐藏节点问题,分析和验证了自组织网络中控制流的不稳定性、不公平性和吞吐量性能不佳的现象。在性能提升方面,给出了结合跨层设计和拓扑控制改进网络控制流工作机制的方法。基于两种的典型的无线自组织网络拓扑结构(双带状型结构与双直线型拓扑)分析和比较了不同控制流数量和不同可允许跳数条件下的相关网络性能,并通过仿真实验验证了这种算法针对路由协议改进的有效性。3、分析了在网络节点随机接入的环境下,基于跨层设计的思想选取适当的上层参数,并服务于网络簇头的选取。通过两种方法来分析拓扑控制问题,第一种方法是先假设网络节点的无线覆盖半径为固定值,然后通过节点位置的空间约束来求干扰的最小值。这种方法对信息分发有较大的负面影响。假设无线自组织网络所包含的网络节点皆通过普通广播信道进行通信,且网络节点所使用的天线皆为相同覆盖半径的全向天线。第二种方法是通过网络生成树法,研究了基于跨层设计的无线自组织网络簇头选择方案和簇头控制方法。在其他层的参数的协助下,选择出最优的簇头,网络生成树对网络拓扑和簇头选择的影响作为限制条件,将标识信息与网络属性相结合的方法来构建无线自组织网络簇头集合的标识信息,对网络拓扑控制方法加以研究。仿真结果表明,通过将新的方案作用于DSR-TC和AODV-TC协议而构造出基于簇头筛选和控制的DSR-TCCL和AODV-TCCL协议对不同拓扑结构的影响各不相同,但都可以不同程度的提高网络的吞吐量性能。4、分析了无线Ad Hoc网络跨层QoS路由设计,给出了新的QoS拓扑控制方案。通过分析链路层、网络层拓扑属性及物理层的整体网络属性,提出一种新的跨层QoS拓扑控制算法,通过网络节点识别信息寻求保证QoS的最佳网络拓扑结构控制方法。基于系统QoS系数分层模型对拓扑控制方法进行了分析,讨论和比较了QoS相关约束条件,然后将QoS路由问题以及算法相结合,给出了新的QoS拓扑控制方案。由于在新算法中添加了尽可能少的网络链路信息以保证QoS需求,所以该算法在最小化网络节点功率消耗和最优化拓扑方面皆有良好的表现。更多还原

【Abstract】 A wireless Ad Hoc network is a multi-hop self-organized communication network cosists of wireless mobile transmitters and receivers, compared with traditional radio communication networks, the terminals using the routing protocols of infrastructure networks. The wireless Ad Hoc network is an important part of the future wireless communication networks and needs no fixed network infrastructure. It shows many features such as flexible networking, anti-destroy and so on. The developments and applications of this kind of networks are very promising not only in military but also in commercial areas.Considering the dynamical of the topology, limitation of the transmitting band and the unidirectional links, the conventional routing protocols can not be used immediately. The topology of the wireless Ad Hoc network will be changed rapidly along with the moving of the nodes, so the existing routing protocols of infrastructure networks can not give the topology information of the networks in time. To distribute the control information will waste much band which maintains the topology to the network.This thesis research on the the performance of wireless Ad Hoc network based on the lacation information of the nodes and the performance of topological control and to seek the the optimized network topology construction scheme and take the research on QoS within the topology analysis. This thesis modified the routing protocols in wireless Ad Hoc networks based on the power control and cross layer design and improved the network performance in special scenarios with the aid of the intergration of routing protocols and location information of nodes. The analysis on the stability of the cotroling stream flow and the peer-to-peer problem such as routing connectivity, maximum of frame, unsymmetry and stability in wireless Ad Hoc network can improve the TCP stability of wireless Ad Hoc networks based on location information. The topology which can not only realize the network connectivity but also minimize the power consume and interference should be computed by the research on the information distribution and the usability of different topologies. This thesis take a research on the above problems and give the main contributions shown below:1. Discusses the function of power control technology in wireless sensor network, and analyzes how the power control technology affects the performance of network layer, Media Access Control (MAC) layer and Physical Layer (PHY). Based on these discussions, a cross-layer power control mechanism for energy efficiency is proposed, which is able to decrease the interference between signals of PHY, keep the connectivity of network and reduce the contention collision probability of MAC.2. The analysis for TCP controlling stream stability of wireless Ad Hoc networks in this thesis shown that the stability of TCP is worse than other networks because of the characters of this kind of networks. The thesis gave a new method to improve the stability of TCP based on the location information.3. This thesis analyzed the performance of the hybrid network based on the theory of the topological spaces and attributes. Two topological scheme are considered: linear topology and dual strip topology. New schemes for DSR and AODV algorithm, called DSR-TCCL and AODV-TCCL algorithm, are given. Because of each parameter for nodes and TCP flows are all represented and recurrence optimization is used, the new schemes can improve the performances of wireless Ad Hoc networks such as throughput, and reduce the packet loss rate, so the reliability and the efficiency of the network will be improved.4. This thesis analyzed the QoS routing with optimized cross layer design by using the attributes of the networks, and give a new QoS topology control algorithm. Discussed the QoS problem in layered model and analyzed QoS topology control algorithm. To meet the demand of QoS routing, as less as network link information is added in the new algorithm, so the power efficiency and topology optimization are improved.更多还原