一种跨层协助的Ad hoc无线网络广播策略

在Ad hoc无线网络中，对全网范围进行广播有着广泛的应用。而Ad hoc网络节点资源、网络资源严重受限，广播引起的广播风暴问题加剧了资源的消耗。本文提出一种跨层协助的广播策略，该策略利用一跳邻节点的信息和物理层、数据链路层的信息统一在MAC设置退避时间，并根据发送节点密度自适应调整退避的时间，减少转播冗余、冲突发生的概率和延迟，确保了广播的可达性。仿真结果也表明提高了广播的效率。     

无冲突的无线传感器网络广播算法

无线传感器网络的节点众多,各种资源严重受限,广播引起的冗余转播加剧了资源的消耗,因而慎重选择转播节点非常关键.提出了一种无冲突的广播策略,该策略利用邻节点能量和度等信息构建最小连通树,减少了转播节点的数量,同时对最小连通树中的节点的转播进行调度,避免冲突的发生.该策略减少网络中节点的能量消费、延长了网络寿命,同时确保了广播的可达性.仿真结果表明该算法提高了广播的效率.     

一种节能的Ad hoc网络路由协议

针对Ad hoc网络中移动节点能量有限的问题,综合考虑节点剩余能量和节点能量消耗速率两方因素,提出一种基于节点生存时间的路由算法MRL（Maximum Routing Life）。通过估算节点使用寿命,选择生存时间最长的路由,均衡移动网络中各节点的能量。引入NS能量模型,与Ad hoc网络中典型路由协议进行比较;仿真结果表明,与传统路由协议相比,新的路由协议有效地提高了Ad hoc网络性能。     

一种基于博弈论模型的Ad Hoc网络功率控制算法

在Ad hoc网络中,采用控制数据报文向相邻节点的发射功率的方法来提高能量的使用效率是一种常用的方法.但是采用功率控制也会对网络连通性、延迟和容量带了负面影响.文中对Ad hoc网络中能量控制机制进行了讨论,给出了Ad hoc网络基于非合作博弈的功率控制问题模型.提出了一种以满足网络连通性、容量最大化、网络半径最小为目标的分布式非合作功率控制博弈算法,并给出了对该算法纳什均衡的存在性和唯一性的证明.实验表明该算法具有较好的综合性能.     

Ad Hoc网络中基于惩罚机制的激励合作转发模型

由于Ad hoc网络中的节点受到自身处理能力、存储空间和电池能量等各种资源的限制,节点为了节省自身的宝贵资源经常会表现出自私性,因此激励自私节点之间合作转发成为Ad hoe网络重要的研究内容.为此,结合重复博弈理论的思想,首先建立邻居节点之间的单阶段博弈模型,得到对应的支付策略,并对该模型进行延伸,建立了无限重复博弈模...     

基于能量有效的移动Ad Hoc网络路由算法

由于移动Ad hoc网络中节点通常采用电池供电,一旦电源耗尽,节点就会被迫退出网络,因此降低节点的能量消耗对保证节点间链路稳定至关重要。给出了节点剩余能量的计算公式,基于节点剩余能量提出了一种能量有效的移动Ad Hoc网络路由算法MTMR,该算法能够延长网络的生命周期,并给出了该路由算法的寻径示例。     

基于功率退避的MAC协议优化算法

针对多跳稠密的移动Ad hoc网络面临的网络生存时间、无线资源利用效率以及时延要求等问题,提出一种新的功率控制MAC协议,该协议在功率退避基础上结合改进的时间退避机制,采用较灵活的竞争窗口调节方法有效地缓解冲突。仿真结果表明,该协议可以减少移动节点消耗的功率,提高节点的能量利用效率和系统的吞吐量性能。     

移动自组网络信任激励机制研究

该文结合移动 Ad hoc 网络的特点分析了移动 Ad hoc 网络面临的安全信任问题。旨在构建一种基于信誉激励的机制,来发现并处理 Ad hoc 网络系统中节点对于资源的非法使用．从而推动 Ad hoc 网络健康发展。     

Ad Hoc网络节点毁坏的拟生灭模型

在Ad hoc网络中由于节点通信是分布式的,网络中的节点毁坏会影响通信链路的中断甚至导致某些节点不可达。为此,基于 M/M/C排队系统,通过合理假设,建立一个Ad hoc网络中节点毁坏及处理过程的拟生灭模型。运用矩阵分析法,在给定参数下,求得稳态概率、毁坏节点的平均队长、毁坏节点到达时无需等待的概率等。该模型能够在保证系统正常工作的情况下,提高Ad hoc网络节点维护效率,为制定维护策略提供参考。     

大规模Ad hoc网络中一种高效的组密钥协商协议*

移动Ad hoc网络自身的特点决定了该网络中节点资源的有限性,所以在移动Ad hoc网络中构建组密钥协商协议时,应尽量减少节点的资源开销。为了解决这个问题,提出了一种基于分簇-K叉树组模型结构的组密钥协商协议——CKT-ECC协议。该协议在分簇-K叉树组模型结构上,采用椭圆曲线密码体制实施密钥协商和分配,使得节点在密钥协商过程中具有低计算开销和低通信开销的优势。与GDH、TGDH组密钥协商协议相比,本协议有效地降低了节点在密钥协商过程中的计算开销和通信开销,适用于大规模移动Ad hoc网络。     

节点度估计和静态博弈转发策略的Ad Hoc网络路由协议

针对Ad Hoc网络路由发现过程中广播路由请求分组导致的广播风暴问题，提出了一种基于节点度估计和静态博弈转发策略的Ad Hoc网络路由协议NGRP.NGRP考虑边界影响，采用分段函数的思想将网络场景分为中心、边和角区域，分别估算网络中节点在不同区域的节点度，避免了周期性广播Hello消息获取节点度导致的开销；NGRP路由请求分组的转发采用静态博弈转发策略，利用节点度估算参与转发路由请求分组的节点数量，将转发和不转发作为策略集合，设计效益函数，通过纳什均衡获得节点转发路由请求分组的转发概率，从而减少了路由请求分组广播过程中产生的大量的冗余、竞争和冲突，提高了路由发现过程中路由请求分组的广播效率.运用NS-2对协议的性能进行大量的仿真，结果表明：NGRP的分组投递率、路由开销、MAC层路由开销和吞吐率这4项指标明显优于AODV+FDG，AODV with Hello和AODV without Hello协议.     

Energy-Efficient Wireless Network Design

A crucial issue in wireless networks is to support efficiently communication patterns that are typical in traditional (wired) networks. These include broadcasting, multicasting, and gossiping (all-to-all communication). In this work we study such problems in static ad hoc networks. Since, in ad hoc networks, energy is a scarce resource, the important engineering question to be solved is to guarantee a desired communication pattern minimizing the total energy consumption. Motivated by this question, we study a series of wireless network design problems and present new approximation algorithms and inapproximability results.     

The role of congestion in probabilistic broadcasting for ubiquitous wireless multi-hop networks through mediation analysis

Broadcast schemes play an important role in the performance of mobile ad hoc networks, which are a clear example of ubiquitous wireless multi-hop networks where nodes collaborate in a distributed way. They are widely used as a dissemination mechanism and as a part of the discovery phase of routing protocols. The simple flooding algorithm is the usual mechanism employed in mobile ad hoc networks, but its inefficiency has been demonstrated in congested scenarios due to the high number of collisions and contentions. However, these problems can be partially alleviated by using a probabilistic broadcast approach in which every node forwards the incoming packets according to a certain forwarding probability. In this paper, we use a simple probabilistic broadcast protocol to evaluate the effects of congestion on the performance of broadcasting in ad hoc networks through a mediation analysis. We hypothesize that the congestion mediates in the relationship between the forwarding probability (independent variable) and the output metric (dependent variable). We consider several output metrics according to the application of the broadcasting protocol such as reachability, broadcasting delay, packet delivery fraction and end to end delay. The simulation results show the existence of the mediating effects and how such effects may be counterbalanced depending on the target use of the probabilistic broadcast scheme.     

Deterministic broadcasting in ad hoc radio networks

We consider the problem of distributed deterministic broadcasting in radio networks of unknown topology and size. The network is synchronous. If a node u can be reached from two nodes which send messages in the same round, none of the messages is received by u. Such messages block each other and node u either hears the noise of interference of messages, enabling it to detect a collision, or does not hear anything at all, depending on the model. We assume that nodes know neither the topology nor the size of the network, nor even their immediate neighborhood. The initial knowledge of every node is limited to its own label. Such networks are called ad hoc multi-hop networks. We study the time of deterministic broadcasting under this scenario. For the model without collision detection, we develop a linear-time broadcasting algorithm for symmetric graphs, which is optimal, and an algorithm for arbitrary n-node graphs, working in time . Next we show that broadcasting with acknowledgement is not possible in this model at all. For the model with collision detection, we develop efficient algorithms for broadcasting and for acknowledged broadcasting in strongly connected graphs. Received: January 2000 / Accepted: June 2001     

Revisiting relative neighborhood graph-based broadcasting algorithms for multimedia ad hoc wireless networks

Multimedia broadcasting is a popular application in an ad hoc wireless network, itself composed of battery-operated nodes. Hence, energy conservation and avoidance of frequent re-construction of broadcast paths are crucial to ensure robust and uninterrupted service of multimedia broadcasting applications. This paper introduces a class of distributed broadcast algorithms based on variations of Relative Neighborhood Graphs (RNG). In contrast to the original RNG-based algorithms, the proposed algorithms consider the remaining battery energy of nodes and the distance between nodes as criteria for determining the relative neighborhood of a node. This approach is intended to boost the resiliency of the broadcast path by avoiding the choice of nodes with low remaining battery capacity as rebroadcast nodes. Extensive simulations are conducted, demonstrating that the proposed algorithms improve over the original RNG in several aspects, including the reduction of broadcast storms, longer path lifetime, and shorter broadcast latency.     

一个新的分布式最小连通支配集近似算法

在计算机网络中广泛使用广播来解决一些网络问题,设计有效的广播算法是一项重要的课题。文中提出一种分布地计算网络最小连通支配集的近似算法并给出了它的正确性证明。它只需要网络节点具有局部的网络状态信息,可伸缩性强。通过此算法可以在网络中自动形成一个虚拟骨干网,从而可为网络中的广播和路由操作提供一个有效的通信基础。模拟结果表明,文中提出的算法求得的连通支配集小,能较好地应用于一般网络以及移动自组网络中。     

Network trust management in emergency situations

We study the unique trust management, and more precisely reputation management and revocation of malicious nodes in the context of ad hoc networks used for emergency communications.Unlike in centralized systems, reputation management and revocation in ad hoc networks is non-trivial. This difficulty is due to the fact that the nodes have to collaboratively calculate the reputation value of a particular node and then revoke the node if the reputation value goes below a threshold. A major challenge in this scheme is to prevent a malicious node from discrediting other genuine nodes. The decision to revoke a node has to be communicated to all the nodes of the network. In traditional ad hoc networks the overhead of broadcasting the message throughout the network may be very high. We solve the problem of reputation management and node revocation in ad hoc networks of cell phones by using a threshold cryptography based scheme. Each node of the network would have a set of anonymous referees, which would store the reputation information of the node and issue reputation certificates to the node with timestamps. The misbehavior of a particular cell phone is reported to its anonymous referees, who issue certificates which reflect the positive and negative recommendations.     

Dynamic probabilistic broadcasting in MANETs

In mobile ad hoc networks (MANETs), the efficiency of broadcasting protocol can dramatically affect the performance of the entire network. Appropriate use of a probabilistic method can reduce the number of rebroadcasting, therefore reduce the chance of contention and collision among neighboring nodes. A good probabilistic broadcast protocol can achieve higher throughput and lower energy consumption, without sacrificing the reachability or having any significant degradation. In this paper, we propose a probabilistic approach that dynamically adjusts the rebroadcasting probability as per the node distribution and node movement. This is done based on locally available information and without requiring any assistance of distance measurements or exact location determination devices. We evaluate the performance of our approach by comparing it with the AODV protocol (which is based on simple flooding) as well as a fixed probabilistic approach. Simulation results show our approach performs better than both simple flooding and fixed probabilistic schemes.