机器人自组网的运动控制模型仿真研究

机器人自组网具有较高的军事和民用价值;基于机器人通用运动学模型,对传统自组网的节点运动模型——随机路点和随机方向移动模型进行了修改,为机器人自组网中的节点建立了运动控制模型,并建立了机器人自组网的网络模型,对几种运动模型进行了仿真分析;结果表明,在机器人自组网的仿真场景中网络性能有所恶化;达到了较为真实地仿真机器人自组网的目的,得出的结论对机器人自组网的仿真研究具有一定的参考价值。     

移动Ad Hoc网络中一种多播路由协议算法实现

MANET是一个多跳,节点无中心、自组织、互相通信而不依赖于预先架设的固定基础设施无线移动网络。本文提出了采用按需路由发现策略的移动Ad Hoc多播路由算法。此算法不需要维护全局的路由信息,通过按需路由发现过程,动态更新路由信息和建立多播转发组。多播数据包在转发组成员间进行有限泛洪,能够降低带宽的占用及减少路由更新信息的传播。仿真实验显示多播算法在带宽较低、多播组成员数量变化较大的移动分组无线网环境中,具有较好的可靠性和工作效率。     

基于门限完全分布式密钥管理方案

adhoc网络作为一种无线移动网络正成为网络研究中的热点之一。针对移动adhoc网络的特性和对目前已有的移动adhoe网络密钥管理方案的分析,提出了一种基于信任图和门限密码技术的全分布、自组织的移动adhoc网络密钥管理新方案。该方案允许节点发布公钥证书并且通过证书链实施认证,有效地解决了网络节点之间的信任,同时又阻止恶意节点发布错误公钥证书欺骗认证服务。该方案具有较高的可靠性、扩展性和安全性,适用于大规模移动ad hoc网络。     

基于模糊控制的Ad Hoc网络QoS优先调度算法

无线移动Ad Hoc网络(MANET)作为可移动分布式多跳无线网络,没有预先确定的网络拓扑或网络基础设施以及集中控制.由于移动Ad Hoc网络的动态性和资源的限制,在如此的网络中提供QoS保障是一个挑战性任务.Ad Hoc网络的分组优先级凋度算法将增进网络的性能.提出了一个基于模糊控制的Ad Hoc网络QoS优先调度算法,用于决定Ad Hoc网络中分组的优先级.利用NS2仿真软件对分组的传输率、平均端对端的延迟等做了性能分析,仿真结果表明,该方法高效、可行,可应用于Ad Hoc网络.     

On the lifetime of node-to-node communication in wireless ad hoc networks

Lifetime of node-to-node communication in a wireless ad hoc network is defined as the duration that two nodes can communicate with each other. Failure of the two nodes or failure of the last available route between them ends their communication. In this paper, we analyze the maximum lifetime of node-to-node communication in static ad hoc networks when alternative routes that keep the two nodes connected to each other are node-disjoint. We target ad hoc networks with random topology modeled as a random geometric graph. The analysis is provided for (1) networks that support automatic repeat request (ARQ) at the medium access control level and (2) networks that do not support ARQ. On the basis of this analysis, we propose numerical algorithms to predict at each moment of network operation, the maximum duration that two nodes can still communicate with each other. Then, we derive a closed-form expression for the expected value of maximum node-to-node communication lifetime in the network. As a byproduct of our analysis, we also derive upper and lower bounds on the lifetime of node-disjoint routes in static ad hoc networks. We verify the accuracy of our analysis using extensive simulation studies.     

一种面向无线Ad Hoc网络的新型分布式哈希表

为了在无线ad hoc网络上构建各种应用系统，有必要提供一种高效的数据共享机制，使得网络中各节点之间能够方便地进行协同和交互。该文将分布式哈希表(DHT)的基本思想与无线ad hoc网络中的基于地理位置的路由技术结合起来，提出了一种新型的面向无线ad hoc网络的数据共享方案——基于位置的DHT(LDHT)。与传统的DHT方案相比，LDHT不是通过逻辑上的覆盖网络来实现，而是直接基于网络的物理拓扑结构来构建，有效地消除了传统DHT方案的拓扑结构不匹配问题，提高了在无线ad hoc网络中进行数据共享的效率。     

Energy-efficient topology control in wireless ad hoc networks with selfish nodes

In wireless ad hoc networks there is no fixed infrastructure or centralized controller to enforce cooperation between nodes. Therefore, nodes may act selfishly in running network protocols for conserving their own energy resources. In this paper, we consider the “topology control (TC) game” as the problem of creating an energy-efficient topology in wireless ad hoc networks in the presence of selfish nodes. We define a new TC game in which nodes are able to dynamically adjust their transmission power in a per-packet manner, and try to minimize their energy usage through considering both traffic load and transmission power parameters. After analyzing the problem, we propose several algorithms to find stable topologies in an environment composed of selfish nodes, using two types of global and local connectivity information. Finally, we evaluate the performance of the proposed algorithms by simulations. Our simulation results show that using appropriate local information can interestingly result in more efficient topologies than global information.     

Robust self-keying mobile ad hoc networks

Pairwise key establishment in mobile ad hoc networks allows any pair of nodes to agree upon a shared key. This is an important security service needed to secure routing protocols, and in general to facilitate secure communication among the nodes of the network.We present two self-keying mechanisms for pairwise key establishment in mobile ad hoc networks which do not require any centralized support. The mechanisms are built using the well-known technique of threshold secret sharing, and are robust and secure against a collusion of up to a certain number of nodes. We evaluate and compare the performance of both the mechanisms in terms of the node admission and pairwise key establishment.     

Robust self-stabilizing weight-based clustering algorithm

Ad hoc networks consist of wireless hosts that communicate with each other in the absence of a fixed infrastructure. Such networks cannot rely on centralized and organized network management. The clustering problem consists of partitioning network nodes into non-overlapping groups called clusters. Clusters give a hierarchical organization to the network that facilitates network management and that increases its scalability.In a weight-based clustering algorithm, the clusterheads are selected according to their weight (a node’s parameter). The higher the weight of a node, the more suitable this node is for the role of clusterhead. In ad hoc networks, the amount of bandwidth, memory space or battery power of a node could be used to determine weight values.A self-stabilizing algorithm, regardless of the initial system configuration, converges to legitimate configurations without external intervention. Due to this property, self-stabilizing algorithms tolerate transient faults and they are adaptive to any topology change.In this paper, we present a robust self-stabilizing weight-based clustering algorithm for ad hoc networks. The robustness property guarantees that, starting from an arbitrary configuration, after one asynchronous round, the network is partitioned into clusters. After that, the network stays partitioned during the convergence phase toward a legitimate configuration where the clusters verify the “ad hoc clustering properties”.     

Toward secure and scalable time synchronization in ad hoc networks

Time synchronization is crucial in ad hoc networks. Due to the infrastructure-less and dynamic nature, time synchronization in such environments is vulnerable to various attacks. Moreover, time synchronization protocols such as IEEE 802.11 TSF (Timing Synchronization Function) often suffer from scalability problem.In this paper, we address the security and the scalability problems of time synchronization protocols in ad hoc networks. We propose a novel suite of time synchronization mechanisms for ad hoc networks based on symmetric cryptography. For single-hop ad hoc networks, we propose SSTSP, a scalable and secure time synchronization procedure based on one-way Hash chain, a lightweight mechanism to ensure the authenticity and the integrity of synchronization beacons. The “clock drift check” is proposed to counter replay/delay attacks. We then extend our efforts to the multi-hop case. We propose MSTSP, a secure and scalable time synchronization mechanism based on SSTSP for multi-hop ad hoc networks. In MSTSP, the multi-hop network is automatically divided into single-hop clusters. The secure intra-cluster synchronization is achieved by SSTSP and the secure inter-cluster synchronization is achieved by exchanging synchronization beacons among cluster reference nodes via bridge nodes.The proposed synchronization mechanisms are fully distributed without a global synchronization leader. We further perform analytical studies and simulations on the proposed approaches. The results show that SSTSP can synchronize single-hop networks with the maximum synchronization error under 20 μs and MSTSP 55–85 μs for multi-hop networks, which are, to the best of our knowledge, among the best results of currently proposed solutions for single-hop and multi-hop ad hoc networks. Meanwhile, our approaches can maintain the network synchronized even in hostile environments.     

A survey of secure wireless ad hoc routing

Ad hoc networks use mobile nodes to enable communication outside wireless transmission range. Attacks on ad hoc network routing protocols disrupt network performance and reliability. The article reviews attacks on ad hoc networks and discusses current approaches for establishing cryptographic keys in ad hoc networks. We describe the state of research in secure ad hoc routing protocols and its research challenges.     

Performance evaluation of a mesh-evolving quality-of-service-aware multicast routing protocol for mobile ad hoc networks

The tremendous amount of multimedia applications running across the wireless communication medium makes quality of service (QoS) a fundamental requirement for mobile ad hoc networks. However, it is not easy to incorporate QoS into these networks. Moreover, the growing number of group-oriented applications also necessitates the efficient utilisation of network resources. The multicast model is a promising technique which can achieve this efficiency by facilitating the inherent broadcast capability of the wireless medium. The mesh-evolving ad hoc QoS multicast (MAQM) routing protocol is developed to address the resource efficiency and QoS problems with one, integrated solution. MAQM achieves multicast efficiency by tracking the availability of resources for each node within its neighbourhood. The QoS status is monitored continuously and announced periodically to the extent of QoS provision. Using these features, MAQM nodes can make their decisions on joining a new multicast session based on the sustainability of their perceived QoS. MAQM also evolves the initial multicast tree into a mesh during the course of an ongoing session to achieve a more robust network topology. Thus, MAQM integrates the concept of QoS-awareness into multicast routing in mobile ad hoc networks. Since ad hoc networks require the protocol control overhead to be as small as possible, we analyse the multicast session establishment process of MAQM to see its impact on the protocol performance in terms of system control overhead. We also evaluate the performance of MAQM through computer simulations using various qualitative and quantitative criteria. The simulation results validate our mathematical analysis of the control overhead and show that MAQM significantly improves multicast efficiency through its QoS-aware admission and routing decisions with an acceptably small overhead. Thus, MAQM shows that QoS is not only essential for, but also applicable to mobile ad hoc networks.     

A cost matrix agent for shortest path routing in ad hoc networks

Wireless ad hoc networks do not rely on an existing infrastructure. They are organized as a network with nodes that act as hosts and routers to treat packets. With their frequent changes in topology, ad hoc networks do not rely on the same routing methods as for pre-established wired networks; they require routing methods for mobile wireless networks. To select a path from a source to a destination in dynamic ad hoc networks, an efficient and reliable routing method is very important. In this paper, we introduce a cost-matrix-based routing algorithm. An agent node creates topology information in the form of the adjacency-cost matrix which shows link costs of the network.Based on the adjacency-cost matrix, the minimum-cost matrix and the next-node matrices can be calculated. Based on the minimum-cost matrix and the next-node matrices, the minimum cost between source and destination nodes and between intermediate nodes on the minimum-cost paths can be calculated.The matrices are periodically distributed by the agent to the other nodes. Based on the minimum-cost matrix and the next-node matrices, each node decides the minimum-cost path to its destination. Because none of the nodes except the agent needs to gather network topology information, the control overhead of the proposed method is small compared with those of the general table-driven routing protocols.     

Secure communications for cluster-based ad hoc networks using node identities

Ad hoc networks are self-configurable networks with dynamic topologies. All involved nodes in the network share the responsibility for routing, access, and communications. The mobile ad hoc network can be considered as a short-lived collection of mobile nodes communicating with each other. Such networks are more vulnerable to security threats than traditional wireless networks because of the absence of the fixed infrastructure. For providing secure communications in such networks, lots of mechanisms have been proposed since the early 1990s, which also have to deal with the limitations of the mobile ad hoc networks, including high power saving and low bandwidth. Besides, public key infrastructure (PKI) is a well-known method for providing confidential communications in mobile ad hoc networks. In 2004, Varadharajan et al. proposed a secure communication scheme for cluster-based ad hoc networks based on PKI. Since the computation overheads of the PKI cryptosystem are heavy for each involved communicating node in the cluster, we propose an ID-based version for providing secure communications in ad hoc networks. Without adopting PKI cryptosystems, computation overheads of involved nodes in our scheme can be reduced by 25% at least.     

移动Ad Hoc网络中带路由机制的密钥管理

移动Ad Hoc网络是一种无中心自组织的多跳无线网络,有效的密钥管理是网络安全的关键。因此,本文提出了一个能够快速响应的密钥管理框架。这个框架通过应用可验证的秘密共享方案来建立PKI,并通过引入路由机制构造了一个快速响应的服务器组。服务器组可以对组内结点的私钥分量更新和所有结点的证书更新提供快速响应。为了验证框架的
的性能,本文通过仿真给出了实验结果。     

基于自适应波束天线的局部优化拓扑控制算法

拓扑控制有助于提高ad hoc网络的性能,采用定向天线的自组网拓扑控制比全向天线网络更为复杂。基于自适应波束定向天线模型提出一种局部区域优化的拓扑控制算法。该算法利用分簇的思想将网络划分为可重叠的多个区域,区域内节点采用最小生成树（MST）的思想确定邻居关系,通过调整节点发射功率,改变天线波束的朝向、宽度和增益来构建拓扑。算法减小了节点的平均度数,降低了节点的发射功率,从而降低节点能耗,减少了节点间干扰,提高了网络吞吐量,仿真结果表明,算法显著提高了网络性能。     

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.     

一种移动Ad Hoc网络中身份认证与地址分配方案

现有ad hoc网络协议都是假设节点进入网络时已经分配了IP地址，而且在节点进入网络时假设节点之间无条件信任，这种缺乏对安全性的考虑是无法在实际战场环境下使用的。该文提出一种新的安全的解决方案，它由建立路由前的节点间的相互身份认证和安全地址分配(公钥散列产生节点地址)两个部分组成。方案可以有效地防止各种相关的攻击，最后还进行了方案的效率分析。     

A rule-based adaptive routing protocol for continuous data dissemination in WSNs

Wireless sensor networks (WSNs) are a subclass of ad hoc networks with severe resource constraints. These constraints preclude the use of traditional ad hoc protocols, and demand optimizations that incur in solutions specific to a class of applications. This work presents PROC, a protocol designed for continuous data dissemination networks that interacts with the application to establish routes. This mechanism allows the application to reconfigure PROC on runtime. PROC also provides fault-tolerance mechanisms to ensure reliable routes. A performance evaluation in topologies varying from 50 to 200 nodes showed that PROC increases network lifetime around 7% to 12%, and has a higher throughput than both energy-aware data-centric routing (EAD) and a simplified version of TinyOS Beaconing. Furthermore, PROC presents a graceful performance degradation when the number of nodes in the network increases.     

Energy saving and capacity improvement potential of power control in multi-hop wireless networks

This study investigates the potential of using transmission power control in wireless packet networks with differing number of hops between source and destination nodes. Here we exploit the benefits of power control in the context of multi-hop wireless ad hoc type networks with a distributed media access control. For our investigations we choose several general ad hoc network topologies and study the effects of power control with respect to energy consumption and network capacity. We show that power control largely improves the network capacity and energy savings in all investigated scenarios, and that utilizing a greater number of intermediate hops between source and destination nodes improves the energy savings though may cause a tradeoff in capacity, depending on the network topology considered.