一种高斯-马尔科夫自组网组移动模型

研究了Ad Hoc网络中移动模型问题。针对目前Ad Hoc网络节点通常具有群组移动性的特征,提出了一种新的移动模型—高斯-马尔科夫组移动模型。通过与RWP、CGM移动模型仿真对比得出,该移动模型符合能够有效描述具有群组移动性的Ad Hoc网络,同时也表明,不同的移动模型对Ad Hoc网络路由协议性能具有很大的影响。     

Leader Based Group Routing in Disconnected Mobile Ad Hoc Networks with Group Mobility

When there is disconnection in mobile ad hoc network under group mobility, it falls into the delay-tolerant network (DTN). However, most existing research in DTN targets entity mobility. In this paper, we consider the routing strategy for DTN with group mobility, and propose the leader based group routing (LBGR) by making full use of group structure in group mobility. Three major mechanisms closely related to the group mobility are proposed in LBGR. First, we treat each group as one individual unit during routing execution to substantially reduce the routing overhead and the resource requirement. Second, we consider the resource allocation in each group and propose the leader-dominating routing in LBGR to reduce the impact of the group dynamics on network performance. Third, to make better use of the rare contact opportunities in DTN, we propose the group based packet exchange, in which the contact of any two nodes from two groups will trigger the packet exchange between the two groups. By extensive simulation we show that LBGR outperforms two traditional routing protocols, epidemic routing and DSR, in various network conditions. Especially, we will find that the impact of the group dynamics on LBGR is very limited.     

Spontaneous Group Management in Mobile Ad Hoc Networks

This paper deals with the problem of Location Management in mobile ad hoc networks where users are organized in groups. In the following this type of systems are referred to as Mobile Ad hoc Networks for Group Operations (MANGO). This paper proposes a framework for location management which exploits the trend of mobile users to spontaneously form groups in MANGOs. The management procedures required to support such spontaneous groups, which are by nature dynamic, are introduced as well. The proposed spontaneous group management is based on a hierarchical location database architecture and the concept of Group Leader, which is a terminal responsible for the location update of a group of terminals. Objective of the proposed framework is minimizing the burden on location databases and, at the same time, the signaling issued by terminals. In this paper, distributed operations required to support the whole framework are properly introduced and described. Simulation experiments have been run in order to assess the proposed scheme. Performance results show that the introduced methodology allows reduced signaling and location updating.     

Ad Hoc网络移动模型节点空间分布研究

节点空间分布是Ad Hoc网络移动模型研究的重点,也是对移动模型评价的重要指标.对RW,RD,RWP,GM,SMS移动模型分别在不同条件下处于矩形及圆仿真区域中节点空间分布进行了仿真,并对其进行比较研究,得出了不同速度、速度服从不同分布,暂停时间服从不同分布和不同仿真区域对移动模型节点空间分布的影响,为移动模型的选择、仿真区域的选择及模型中各类参数的设置提供了重要的依据.     

A Power-Aware Multicast Routing Protocol for Mobile Ad Hoc Networks With Mobility Prediction

A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure. Due to the high mobility of nodes, the network topology of MANETs changes very fast, making it more difficult to find the routes that message packets use. Because mobile nodes have limited battery power, it is therefore very important to use energy in a MANET efficiently. In this paper, we propose a power-aware multicast routing protocol (PMRP) with mobility prediction for MANETs. In order to select a subset of paths that provide increased stability and reliability of routes, in routing discovery, each node receives the RREQ packet and uses the power-aware metric to get in advance the power consumption of transmitted data packets. If the node has enough remaining power to transmit data packets, it uses the global positioning system (GPS) to get the location information (i.e., position, velocity and direction) of the mobile nodes and utilizes this information to calculate the link expiration time (LET) between two connected mobile nodes. During route discovery, each destination node selects the routing path with the smallest LET and uses this smallest link expiration time as the route expiration time (RET). Each destination node collects several feasible routes and then selects the path with the longest RET value as the primary routing path. Then the source node uses these routes between the source node and each destination node to create a multicast tree. In the multicast tree, the source node will be the root node and the destination nodes will be the leaf nodes. Simulation results show that the proposed PMRP outperforms MAODV (Royer, E. M. & Perkins, C. E. (1999). In Proceedings of the ACM MOBICOM, pp. 207–218, August 1999.) and RMAODV (Baolin, S. & Layuan, L. (2005). In Proceeding of the 2005 IEEE International symposium on microwave antenna, propagation and EMC technologies for wireless communications, Vol. 2, pp. 1514–1517, August 2005.).     

Stochastic Properties of Mobility Models in Mobile Ad Hoc Networks

The stochastic model assumed to govern the mobility of nodes in a mobile ad hoc network has been shown to significantly affect the network's coverage, maximum throughput, and achievable throughput-delay trade-offs. In this paper, we compare several mobility models, including the random walk, random waypoint, and Manhattan models on the basis of the number of states visited in a fixed time, the time to visit every state in a region, and the effect of the number of wandering nodes on the time to first enter a set of states. These metrics for a mobility model are useful for assessing the achievable event detection rates in surveillance applications where wireless-sensor-equipped vehicles are used to detect events of interest in a city. We also consider mobility models based on Correlated Random Walks, which can account for time dependency, geographical restrictions, and nonzero drift. We demonstrate that these models are analytically tractable by using a matrix-analytic approach to derive new, closed-form results in both the time and transform-domains for the probability that a node is at any location at any time for both semi-infinite and finite 1D lattices. We also derive first entrance time distributions for these walks. We find that a correlated random walk 1) covers more ground in a given amount of time and takes a smaller amount of time to cover an area completely than a random walk with the same average transition rate, 2) has a smaller first entrance time to small sets of states than the random waypoint and random walk models, and 3) leads to a uniform distribution of nodes (except at the boundaries) in steady state.     

Rate Control Algorithm Considering Mobility in Mobile Ad Hoc Networks

For reducing the loss of data packet due to network congestion and mobility, rate control algorithm is effective means for ensuring the fair allocation of network resource among communication flows and alleviating network congestion. The Transport Control Protocol (TCP) was originally designed for wire-line networks, where the links are assumed to be reliable and with fixed capacities. However, the performance of TCP becomes very poor when it is directly used in ad hoc networks. Some optimization-based congestion control schemes have been proposed to improve TCP performance in ad hoc networks, but the mobility of hosts and route change frequently are not considered for designing rate control algorithm. In this paper, we propose rate control algorithms in a more practical way by taking into account link congestion and node movement. Numerical results show that the rate control algorithms can approach the globally optimal value and show the effect of the node mobility on the algorithms.     

一种基于迁移可测度的移动自组织网路由模型

 本文利用链路状态有效估测端到端路径的可达性。路由模型给出最近时间内,任意两点分组传输的迁移可测度;节点根据其邻节点的迁移可测度制定组合策略,计算组合迁移可测度,选取最优中继组合完成分组传输。仿真实验表明,该路由模型既可有效控制分组副本数目,又可获得较高的分组到达率。     

Explicit Multicasting for Mobile Ad Hoc Networks

In this paper we propose an explicit multicast routing protocol for mobile ad hoc networks (MANETs). Explicit multicasting differs from common approaches by listing destination addresses in data packet headers. Using the explicit destination information, the multicast routing protocol can avoid the overhead of employing its own route construction and maintenance mechanisms by taking advantage of unicast routing table. Our protocol – termed Differential Destination Multicast (DDM) – is an explicit multicast routing protocol specifically designed for MANET environment. Unlike other MANET multicasting protocols, instead of distributing membership control throughout the network, DDM concentrates this authority at the data sources (i.e. senders) thereby giving sources knowledge of group membership. In addition, differentially-encoded, variable-length destination headers are inserted in data packets which are used in combination with unicast routing tables to forward multicast packets towards multicast receivers. Instead of requiring that multicast forwarding state to be stored in all participating nodes, this approach also provides the option of stateless multicasting. Each node independently has the choice of caching forwarding state or having its upstream neighbor to insert this state into self-routed data packets, or some combination thereof. The protocol is best suited for use with small multicast groups operating in dynamic MANET environment.     

移动ad hoc网络安全综述

移动ad hoc网络是由移动节点自组织形成的网络,由于其动态拓扑、无线通信的特点,容易遭受各种安全威胁.该文介绍了移动ad hoc网络安全研究的最新研究进展.首先从传输信道、移动节点、动态拓扑、安全机制、路由协议几方面,分析了移动ad hoc网络的安全弱点,然后将移动ad hoc网络安全方面的研究分为三个方向:密钥分配与管理、入侵检测、增强合作.对每个方向内一些典型安全方案也进行了分类论述,同时分析了各种方案的优点和缺点,并进行了综合比较.文中阐明了目前协议存在的一些问题并提出了相应的改进方法,最后指出了下一步研究方向.     

Internet Connectivity for Ad Hoc Mobile Networks

The growing deployment rate of wireless LANs indicates that wireless networking is rapidly becoming a prevalent form of communication. As users become more accustomed to the use of mobile devices, they increasingly want the additional benefit of roaming. The Mobile IP protocol has been developed as a solution for allowing users to roam outside of their home networks while still retaining network connectivity. The problem with this solution, however, is that the deployment of foreign agents is expensive because their coverage areas are limited due to fading and interference. To reduce the number of foreign agents needed while still maintaining the same coverage, ad hoc network functionality can cooperate with Mobile IP such that multihop routes between mobile nodes and foreign agents can be utilized. In this work, we present a method for enabling the cooperation of Mobile IP and the Ad hoc On-Demand Distance Vector (AODV) routing protocol, such that mobile nodes that are not within direct transmission range of a foreign agent can still obtain Internet connectivity. In addition, we describe how duplicate address detection can be used in these networks to obtain a unique co-located care-of address when a foreign agent is not available.     

A Mutual Exclusion Algorithm for Ad Hoc Mobile Networks

A fault-tolerant distributed mutual exclusion algorithm that adjusts to node mobility is presented, along with proof of correctness and simulation results. The algorithm requires nodes to communicate with only their current neighbors, making it well-suited to the ad hoc environment. Experimental results indicate that adaptation to mobility can improve performance over that of similar non-adaptive algorithms when nodes are mobile.     

Associativity-Based Routing for Ad Hoc Mobile Networks

This paper presents a new, simple and bandwidth-efficient distributed routing protocol to support mobile computing in a conference size ad-hoc mobile network environment. Unlike the conventional approaches such as link-state and distance-vector distributed routing algorithms, our protocol does not attempt to consistently maintain routing information in every node. In an ad-hoc mobile network where mobile hosts (MHs) are acting as routers and where routes are made inconsistent by MHs' movement, we employ an associativity-based routing scheme where a route is selected based on nodes having associativity states that imply periods of stability. In this manner, the routes selected are likely to be long-lived and hence there is no need to restart frequently, resulting in higher attainable throughput. Route requests are broadcast on a per need basis. The association property also allows the integration of ad-hoc routing into a BS-oriented Wireless LAN (WLAN) environment, providing the fault tolerance in times of base stations (BSs) failures. To discover shorter routes and to shorten the route recovery time when the association property is violated, the localised-query and quick-abort mechanisms are respectively incorporated into the protocol. To further increase cell capacity and lower transmission power requirements, a dynamic cell size adjustment scheme is introduced. The protocol is free from loops, deadlock and packet duplicates and has scalable memory requirements. Simulation results obtained reveal that shorter and better routes can be discovered during route re-constructions.     

一种实用的适用于移动自组织网络的认证协议

与传统网络相比，自组织网络本身存在许多系统脆弱性．使得传统网络安全机制不再适用于自组织网络。文章对传统PKI作必要改进，定义了适用于自组织网络的的公钥基础设施AH-PKI．并设计了一种基于AH-PKI的认证协议。     

移动Ad hoc网络中的密钥管理

首先阐述了移动adhoc网络中密钥管理的重要性,接着探讨了几种密钥管理的方法,包括局部分布式认证授权中心、完全分布式认证授权中心、自发证书、安全Pebblenets、指示性标志、基于口令验证的密钥交换等,并对这些方法进行了较完整的概括总结和深入的比较分析,最后提出了一些研究移动adhoc网络中密钥管理方法所必须注意的问题。     

Quantifying Impact of Mobility on Data Availability in Mobile Ad Hoc Networks

In mobile ad hoc networks, there are many applications in which mobile users share information, e.g., collaborative rescue operations at a disaster site and exchange of word-of-mouth information in a shopping mall. For such applications, improving data availability is a significant issue and various studies have been conducted with this aim. However, each of these conventional works assumed a particular mobility model and did not fully investigate the influence of the mobility on the proposed approach. In this paper, we aim to quantify the influences of mobility on data availability from various perspectives. We assume neither specific applications nor specific protocols but we propose and quantify several metrics that affect data availability. We also report results of some experiments that measure the proposed metrics assuming several typical mobility models.     

Modeling Mobility in Cooperative Ad Hoc Networks

This paper addresses issues concerned with design and managing of mobile ad hoc networks. We focus on self-organizing, cooperative and coherent networks that enable a continuous communication with a central decision unit and adopt to changes in an unknown environment to achieve a given goal. In general, it is very difficult to model a motion of nodes of a real-life ad hoc network. However, mobility modeling is a critical element that has great influence on the performance characteristics of a cooperative system. In this paper we investigate a novel approach to cooperative and fully connected networks design. We present an algorithm for efficient calculating of motion trajectories of wireless devices. Our computing scheme adopts two techniques, the concept of an artificial potential field and the concept of a particle-based mobility. The utility and efficiency of the proposed approach has been justified through simulation experiments. The results of presented case studies show a wide range of applications of our method starting from simple to more complex ad hoc networks.     

A Generalized Random Mobility Model for Wireless Ad Hoc Networks and Its Analysis: One-Dimensional Case

In wireless ad hoc networks, the ability to analytically characterize the spatial distribution of terminals plays a key role in understanding fundamental network QoS measures such as throughput per source to destination pair, probability of successful transmission, and connectivity. Consequently, mobility models that are general enough to capture the major characteristics of a realistic movement profile, and yet are simple enough to formulate its long-run behavior, are highly desirable. We propose a generalized random mobility model capable of capturing several mobility scenarios and give a mathematical framework for its exact analysis over one-dimensional mobility terrains. The model provides the flexibility to capture hotspots where mobiles accumulate with higher probability and spend more time. The selection process of hotspots is random and correlations between the consecutive hotspot decisions are successfully modeled. Furthermore, the times spent at the destinations can be dependent on the location of destination point, the speed of movement can be a function of distance that is being traveled, and the acceleration characteristics of vehicles can be incorporated into the model. Our solution framework formulates the model as a semi-Markov process using a special discretization technique. We provide long-run location and speed distributions by closed-form expressions for one-dimensional regions (e.g., a highway).     

移动Ad Hoc网络中的安全问题

移动自组网(Mobile Ad HoC Network)是一种无基础设施的无线网络由于它具有开放的媒质、分布式的合作、动态的拓扑结构和受限的网络能力等特点,所以特别容易受到攻击.为此文章结合移动Ad Hoc网络的特点分析了移动Ad Hoc网络面临的安全威胁,并对移动Ad Hoc网络的安全路由和安全报文传送问题进行了详细讨论.