依据用户妥善安排的多址接入协议在分布式无线网络中的性能研究

本文基于有效竞争预约接入、无冲突轮询传输的思想提出了在多跳分布式无线网络中支持节点移动性和多跳网络结构的依据用户妥善安排的多址接入(UPMA)协议.该协议能够保证发送节点快速接入信道,从而大大提高信道的使用效率.用仿真方法研究了多跳分布式无线网络中采用该协议时的网络性能.结果表明,UPMA协议可以提供较高的通过量、较低的平均分组时延和较小的平均分组丢失率.     

基于粒子群优化的ad hoc网络最小能耗多播路由算法

在无线ad hoc网络中,设备使用电池提供能量,随着多播应用日益广泛,如何构造最小能耗多播树是一个重要问题。针对选择不同的中继节点集对构造最小能耗多播树的影响,提出了一种优化最小能耗多播树构造的离散粒子群算法。为了避免离散粒子群算法早熟收敛,引入惯性权重策略,以平衡算法的全局搜索能力和局部搜索能力。模拟实验结果表明改进后的离散粒子群算法具有较强的优化能力,有效地优化了最小能耗多播树的构造。     

基于L-hop路由策略的无线mesh网络的吞吐量

无线mesh网络是最后一英里宽带互联网的可选技术之一。类似于ad hoe网络。在mesh网络中，每个用户节点既是通信终端又提供路由功能；用户节点以ad hoe多跳方式实现与网关的链接，通过网关可以访问因特网。无线mesh网络的吞吐量受到网关带宽的限制。为了捷高mesh网络网关频带的利用效率，现提出基于节点组织ad hoe通信方式和L-hop路由策略。在新的路由策略下，将给出对mesh网络的吞吐量的研究。     

Energy-Efficient Broadcast and Multicast Trees in Wireless Networks

The wireless networking environment presents formidable challenges to the study of broadcasting and multicasting problems. In this paper we focus on the problem of multicast tree construction, and we introduce and evaluate algorithms for tree construction in infrastructureless, all-wireless applications. The performance metric used to evaluate broadcast and multicast trees is energy-efficiency. We develop the Broadcast Incremental Power (BIP) algorithm, and adapt it to multicast operation by introducing the Multicast Incremental Power (MIP) algorithm. These algorithms exploit the broadcast nature of the wireless communication environment, and address the need for energy-efficient operation. We demonstrate that our algorithms provide better performance than algorithms that have been developed for the link-based, wired environment.     

Minimum-Energy Broadcasting in Static Ad Hoc Wireless Networks

Energy conservation is a critical issue in ad hoc wireless networks for node and network life, as the nodes are powered by batteries only. One major approach for energy conservation is to route a communication session along the route which requires the lowest total energy consumption. This optimization problem is referred to as Minimum-Energy Routing. While the minimum-energy unicast routing problem can be solved in polynomial time by shortest-path algorithms, it remains open whether the minimum-energy broadcast routing problem can be solved in polynomial time, despite the NP-hardness of its general graph version. Recently three greedy heuristics were proposed in [11]: MST (minimum spanning tree), SPT (shortest-path tree), and BIP (broadcasting incremental power). They have been evaluated through simulations in [11], but little is known about their analytical performances. The main contribution of this paper is a quantitative characterization of their performances in terms of approximation ratios. By exploring geometric structures of Euclidean MSTs, we have been able to prove that the approximation ratio of MST is between 6 and 12, and the approximation ratio of BIP is between 13/3 and 12. On the other hand, we show that the approximation ratio of SPT is at least n/2, where n is the number of receiving nodes. To the best of our knowledge, these are the first analytical results for the minimum-energy broadcasting problem.     

新型宽带无线网络技术——无线网状网

无线网状网技术是一种具有良好市场应用前景的新型宽带无线网络技术.本文首先简要介绍了无线网状网的产生和发展,然后针对无线网状网的定义、特点、应用以及影响网络性能的关键因素等最核心的几个问题,进行了初步的探讨和总结.     

基于邻居节点的拓扑控制算法研究与仿真

拓扑控制是移动自组织网络提高网络能量利用率和网络容量的一种重要机制。针对移动自组织网络拓扑易变、带宽和能量有限等特点,简要介绍了一种节约节点能耗,有效提高整个网络寿命的拓扑控制算法;通过对基于邻居个数的拓扑控制协议K-Neigh算法的仿真,研究了不同k值的选择下拓扑控制对节点功耗和网络性能(包括吞吐量、丢包率和时延等)的影响。其结果表明选择合适的k值可以取得节点功耗和网络性能的平衡,而且经过K-Neigh拓扑控制后的网络具有很好的鲁棒性。     

VANET中利用空闲TDMA时隙协助发送数据的方法

车载自组网中的分布式TDMA方法没有利用节点的空闲TDMA时隙,未能充分利用无线信道资源,基于此,提出了一种利用空闲TDMA时隙的MAC层数据重发方法,当节点发送数据失败时,附近节点利用空闲的TDMA时隙重新发送传输失败的数据。理论分析和仿真结果表明,所提方法显著提高了分布式TDMA方法的数据发送成功概率和网络吞吐量。此外,通过仿真比较所提方法与IEEE802.11p的性能,结果表明,由于以确定的方式访问信道,所提方法能够及时稳定地传输车载自组网中的实时安全信息。     

Energy Consumption of TCP in Ad Hoc Networks

In this paper we study the energy cost (protocol processing and communication cost) and goodput of different flavors of TCP (Transmission Control Protocol) in ad hoc networks. We implemented a testbed and measured the actual energy cost as well as goodput of running TCP Reno, Newreno, SACK (Selective ACKnowledgement) and a version that combines Explicit Link Failure Notification (ELFN) [7] and Explicit Congestion Notification (ECN) [5] in Newreno. We see that the use of ECN & ELFN does yield higher goodput in most cases with a corresponding lower total energy cost. We see an energy savings of between 20% and 500% depending on the network conditions.     

Ad hoc网络中一种生命周期约束的自适应退避算法

在IEEE 802.11标准定义的BEB退避算法基础上,提出一种生命周期约束的自适应退避算法LCAB,以生命周期代替最大重传次数作为分组丢弃的依据,并根据网络忙闲程度自适应地调整节点执行退避过程的权限,以最大化系统归一化有效吞吐量,适合于ad hoc网络中有严格时延要求的VoIP等实时性业务.构建Markov链模型分析LCAB算法性能,得到系统归一化有效吞吐量表达式.仿真结果表明,理论分析与仿真结果一致,且LCAB算法的归一化有效吞吐量优于BEB算法.     

无线自组织网络极限信道容量增长规律研究

 为了分析和提高无线自组织网络的吞吐能力,提出了无线自组织网络的极限信道容量增长规律(capacity scaling laws)的一般表达式,研究发现单个节点的策略决定了整个无线自组织网络的吞吐能力,证明了使得整个网络吞吐能力最大化的最优策略的存在性。进一步通过应用博弈论,推导得出最优策略,并验证其满足纳什均衡且是演化稳定策略。     

Algorithms for Energy-Efficient Multicasting in Static Ad Hoc Wireless Networks

In this paper we address the problem of multicasting in ad hoc wireless networks from the viewpoint of energy efficiency. We discuss the impact of the wireless medium on the multicasting problem and the fundamental trade-offs that arise. We propose and evaluate several algorithms for defining multicast trees for session (or connection-oriented) traffic when transceiver resources are limited. The algorithms select the relay nodes and the corresponding transmission power levels, and achieve different degrees of scalability and performance. We demonstrate that the incorporation of energy considerations into multicast algorithms can, indeed, result in improved energy efficiency.