Ad Hoc与无线网络的扩展性研究

Ad Hoc作为无线网络的具有高抗毁性和灵活性的扩展网络,日益引人关注。本文首先从环绕网的理念入手,介绍Ad Hoc作为现有无线网络扩展的意义和优势,然后重点分析并提出融合策略以及需要思考的问题。     

Performance of PKI-based security mechanisms in mobile ad hoc networks

Security for ad hoc network environments has received a lot of attention as of today. Previous work has mainly been focussing on secure routing, fairness issues, and malicious node detection. However, the issue of introducing and conserving trust relationships has received considerably less attention. In this article, we present a scalable method for the use of public key certificates and their revocation in mobile ad hoc networks (MANETs). With the LKN-ad hoc security framework (LKN-ASF) a certificate management protocol has been introduced, bringing PKI technology to MANETs. In addition a performance analysis of two different revocation approaches for MANETs will be presented.     

DSR的一种自适应路由自动缩短机制

动态源路由协议是无线自组织网络众多路由协议中被广泛关注的一种按需路由协议，目前，关于该协议的优化措施有很多。本文先分析了动态源路由协议的一种优化机制——路由自动缩短，该机制能动态缩短处于工作状态路由的跳数，但不保证缩短路由的质量，在此基础上，提出一种自适应路由自动缩短机制，新机制既可缩短路由．又能保证缩短路由质量．理论分析及仿真结果表明，自适应路由缩短机制的各项性能优于原路由缩短机制。     

无线Ad hoc 网络及其研究难点

无线Ad hoc网络作为没有基础设施的网络，在军事和民用方面具有广阔的应用前景，是目前网络研究中的热点问题。本文对无线Ad hoc网络进行了详细的论述，指出了目前研究中存在的一些难点。     

Process and technology challenges in swift-starting virtual teams

Virtual teams often face tight schedules and a need to start quickly and perform instantly. The goal of our study was to enhance understanding of the challenges faced by such teams. We used time–interaction–performance theory as the framework for following the processes and functions within virtual teams working on a systems development task. Our study provided a detailed examination of the group process, applied to virtual teams working under time pressure. The challenges faced by virtual teams in such settings showed that teams must work to enhance their effectiveness in multiple dimensions.     

Performance analysis of IEEE 802.11 ad hoc networks in the presence of exposed terminals

The paper evaluates the performance effects of exposed terminals in IEEE 802.11 ad hoc networks in finite load conditions. It derives analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions with and without exposed terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly accurate.     

无线网状网技术与应用

无线网状网(WMNs)由网状路由器节点和客户机节点组成,其中的网状路由器节点组成了无线网状网的网络骨干,其移动性很小。他们一起为无线网状网和其他常规无线网络的客户机节点提供网络的无线接入。WMNs技术结合了中心式控制的蜂窝网与分布式控制的无线自组织网的优点,可有效克服这两种技术的缺陷并显著提高无线网络的性能,已经成为下一代无线通信网络的研究热点之一。WMNs可为无线个域网、局域网、校园网、城域网的一系列应用提供高速无线宽带接入服务。虽然目前WMNs技术发展很快,但其协议栈各层仍存在许多有待研究的课题。首先简要介绍了无线网状网的结构与特点;随后重点分析了其主要的几个应用领域;最后探讨了WMNs各协议层的研究现状与关键技术,并分析了该技术存在的问题及未来的研究方向。     

On the Fundamental Limits of Topology Control in Ad Hoc Networks

We prove two results that provide new fundamental limits for topology control in large ad hoc and sensor networks. First, we show that it remains true under very general conditions that the maximum expected node degree must grow to infinity at least logarithmically if we want to maintain asymptotic connectivity. This has been known so far only for much more special models than ours. Building on this result, we prove a new fundamental limit regarding link dynamics, which means the worst case length ratio of the longest and shortest link adjacent to the same node. We prove that if link dynamics remains bounded, then no topology control algorithm can keep a large network connected with high probability. Moreover, bounded link dynamics prevents connectivity in the limit without any a priori assumption on node degrees or transmission ranges. Our results hold in a model that is much more general than the frequently used assumption of uniformly distributed nodes in a regularly shaped planar domain. Our more abstract setting also aims at finding (hopefully) more robust and elegant proofs that have less dependence on the special geometry. Since link dynamics is expected to be bounded in practice, the results strenghten the theoretical basis for the argument that a very large ad hoc or sensor network is unable to maintain connectivity if it has a flat, random organization without additional structure. Supported in part by NSF Grants ANI-0220001 and CCF-0634848.     

一种AODV跨层优化方法及仿真测试分析

针对Ad Hoc网络中传统AODV协议不支持QoS的缺陷,提出了一种多约束QoS AODV跨层优化方法MQ-AODV（Multi-Constrained QoS AODV）。该方法采用跨层设计的思想,除以传统AODV协议的转发跳数作为路由选择判据之外,而且加入应用层的QoS需求信息和MAC层的多种QoS指标作为路由选择判据,并通过改进AODV路由表结构和路由查找算法,提高AODV路由协议性能。仿真测试结果表明MQ-AODV协议缩短了传输时延,增强了路由协议的适应性和鲁棒性。     

基于Ad Hoc网络的SMR优化算法的研究

SMR是一种基于DSR算法的多路径路由算法,这种算法的本身具有明显的局限性。第一,它可能在存在多条不相关多路径路由的情况下选择两条相关多路径路由作为最后的主路由与备份路由;第二,它在目的节点只收到一个RREQ分组的情况下只生成一条主路由,而实际可能存在多条传输线路。针对SMR算法的局限性,本文提出一种改进的SMR算法—ISMR,该算法保证了两条路由的形成,保证了在存在多条不相关多路径路由情况下,一定会生成两条不相关多路径路由。