A novel mobility model based on semi-random circular movement in mobile ad hoc networks

When simulating a mobile ad hoc network (MANET), it is important to use a realistic mobility model to reflect the actual performance of a mobile system. The spatial distribution of node locations in a mobile model plays a key role when investigating the characteristics of a MANET. However, most existing mobility models with random and simple straight line movement lead to unrealistic scenarios and non-uniform distributions, and can not describe the actual movement of Unmanned Aerial Vehicles (UAVs) connected via a MANET. To address this issue, a novel mobility model based on semi-random circular movement (SRCM) is presented. The approximate node distribution function in SRCM is derived within a 2D disk region. The relationship between application performance and node distribution is investigated for a UAV MANET, with focus on scan coverage and network connectivity. A simulation using the NS2 tool is conducted. It is shown that the presented model with a uniform distribution performs better than the popular Random Waypoint mobility model. The SRCM model with the NS2 simulator provides a realistic way for simulation and performance evaluation of UAV MANETs.     

多状态实体随机移动模型建模与仿真

移动模型是移动Ad Hoc网络协议设计和性能评估的基础。根据实体随机移动模型建模的要求,提出一种能够较好地反映现实节点运动规律、参数独立可控性强、适用性广的多状态实体随机移动模型,通过调整模型的若干参数可以产生多种现有常用的移动模型,具有一定的灵活性和通用性,给移动Ad Hoc网络模拟仿真场景的产生带来极大的方便。     

An environment-aware mobility model for wireless ad hoc network

Simulation is a cost effective, fast and flexible alternative to test-beds or practical deployment for evaluating the characteristics and potential of mobile ad hoc networks. Since environmental context and mobility have a great impact on the accuracy and efficacy of performance measurement, it is of paramount importance how closely the mobility of a node resembles its movement pattern in a real-world scenario. The existing mobility models mostly assume either free space for deployment and random node movement or the movement pattern does not emulate real-world situation properly in the presence of obstacles because of their generation of restricted paths. This demands for the development of a node movement pattern with accurately representing any obstacle and existing path in a complex and realistic deployment scenario. In this paper, we propose a general mobility model capable of creating a more realistic node movement pattern by exploiting the concept of flexible positioning of anchors. Since the model places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, it is capable of representing any terrain realistically. Furthermore, obstacles of arbitrary shapes with or without doorways and any existing pathways in full or part of the terrain can be incorporated which makes the simulation environment more realistic. A detailed computational complexity has been analyzed and the characteristics of the proposed mobility model in the presence of obstacles in a university campus map with and without signal attenuation are presented which illustrates its significant impact on performance evaluation of wireless ad hoc networks.     

基于极端学习机的MANET移动性预测模型

针对移动自组织网络移动性在管理无线网络带宽资源可用性方面的重要性,为了更好地规划连续服务可用性和有效能源管理以提升网络的整体服务质量,提出了一种基于极端学习机的MANET移动性预测模型。利用ELM对MANET中的任意节点进行建模;假设已知每个移动节点当前的移动性信息（位置、速度和运动方向角度）,以这种方式预测节点未来的位置和相邻节点之间未来的距离;基于几个标准移动性模型,产生更加真实、精确的移动性预测,从而更好地捕捉任意节点直角坐标系之间现有交互/相关性。使用标准移动性模型的仿真结果验证了所提模型的有效性,实验结果表明,提出的预测模型明显改进了传统基于多层感知器的模型,此外,当预测相邻节点之间未来距离时,避免了当前算法对预测精度的限制。     

一种平滑高斯半马尔可夫传感器网络移动模型

在总结现有实体随机移动模型优、缺点的基础上,提出一种能够较好地反映现实节点运动规律的参数独立可控性比较强的平滑高斯-半马尔可夫实体随机移动模型(smooth Gauss-semi-Markov mobility model,简称SGM),并利用马尔可夫过程及更新过程理论证明了该模型具有平均速率时间平稳和点空间分布均匀的特性,适用于移动无线传感器网络的模拟仿真研究.     

具有多出入口区域的节点移动和分布研究

在Ad Hoc网络的仿真研究中,节点移动模型的选择会严重影响到网络的拓扑结构和通信协议的性能.然而,现有移动模型大多是为理想环境设计的,不能适用于真实环境.在理想移动模型RWP(Random Waypoint)的基础上,提出了具有多出入口区域的RWP节点移动模型(RWP with entrances,RWPWE).在该模型中,区域出入口是节点进出区域的必经之地,节点在区域内的移动符合RWP节点移动模型,通过引入域内停留概率来完成节点在区域内外移动的转移,并从节点移动速度、移动时间、移动路程和空间分布概率等几个方面研究了区域出入口的影响.理论分析和实验仿真的结果表明,由于出入口的存在,与RWP模型相比节点的移动更加复杂,节点的空间分布也显著不同,这些差别将会影响到网络的拓扑性能和对网络协议的评价.     

Impact of mobility on the performance of relaying in ad hoc networks – Extended version

We consider a mobile ad hoc network consisting of three types of nodes: source, destination, and relay nodes. All the nodes are moving over a bounded region with possibly different mobility patterns. We introduce and study the notion of relay throughput, i.e. the maximum rate at which a node can relay data from the source to the destination. Our findings include the results that (a) the relay throughput depends on the node mobility pattern only via its (stationary) node position distribution, and (b) that a node mobility pattern that results in a uniform steady-state distribution for all nodes achieves the lowest relay throughput. Random waypoint and random direction mobility models in both one and in two dimensions are studied and approximate simple expressions for the relay throughput are provided. Finally, the behavior of the relay buffer occupancy is examined for the random walk and random direction mobility models. For both models, the explicit form of the mean buffer is provided in the heavy-traffic case.     

On a moving direction pattern based MAP selection model for HMIPv6 networks

In a large-scale mobile IPv6 network, usually there are several coexisting mobility anchor points (MAPs) for networking robustness and traffic sharing. Therefore, it is a challenging issue for an arriving mobile node to choose the most appropriate MAP to bind. This task must be carried out by considering the issues of load balancing, binding update and packet delivery cost minimization. This paper proposes a novel MAP selection scheme for hierarchical mobile IPv6 networks to allow a mobile node to discover the most appropriate MAP when there are multiple coexisting MAPs. This scheme is an enhancement to the adaptive MAP selection scheme. The proposed scheme improve the overall performance due to the consideration of the movement (direction) pattern of mobile nodes. Simulation results show that this scheme outperforms the existing cost models in terms of total binding update and packet delivery costs, ensuring a level of load balance similar to adaptive MAP selection scheme.     

Mobility prediction in mobile wireless networks

In realistic mobile ad-hoc network scenarios, the hosts usually travel to the pre-specified destinations, and often exhibit non-random motion behaviors. In such mobility patterns, the future motion behavior of the mobile is correlated with its past and current mobility characteristics. Therefore, the memoryless mobility models are not capable of realistically emulating such a mobility behavior. In this paper, an adaptive learning automata-based mobility prediction method is proposed in which the prediction is made based on the Gauss–Markov random process, and exploiting the correlation of the mobility parameters over time. In this prediction method, using a continuous-valued reinforcement scheme, the proposed algorithm learns how to predict the future mobility behaviors relying only on the mobility history. Therefore, it requires no a prior knowledge of the distribution parameters of the mobility characteristics. Furthermore, since in realistic mobile ad hoc networks the mobiles move with a wide variety of the mobility models, the proposed algorithm can be tuned for duplicating a wide spectrum of the mobility patterns with various randomness degrees. Since the proposed method predicts the basic mobility characteristics of the host (i.e., speed, direction and randomness degree), it can be also used to estimate the various ad-hoc network parameters like link availability time, path reliability, route duration and so on. In this paper, the convergence properties of the proposed algorithm are also studied and a strong convergence theorem is presented to show the convergence of the algorithm to the actual characteristics of the mobility model. The simulation results conform to the theoretically expected convergence results and show that the proposed algorithm precisely estimates the motion behaviors.     

Performance of ad hoc networks with two-hop relay routing and limited packet lifetime (extended version)

We consider a mobile ad hoc network consisting of three types of nodes (source, destination and relay nodes) and using the two-hop relay routing. This type of routing takes advantage of the mobility and the storage capacity of the nodes, called the relay nodes, in order to route packets between a source and a destination. Packets at relay nodes are assumed to have a limited lifetime in the network. Nodes are moving inside a bounded region according to some random mobility model. Closed-form expressions and asymptotic results when the number of nodes is large are provided for the packet delivery delay and for the energy needed to transmit a packet from the source to its destination. We also introduce and evaluate a variant of the two-hop relay protocol that limits the number of generated copies in the network. Our model is validated through simulations for two mobility models (random waypoint and random direction mobility models), and the performance of the two-hop routing and of the epidemic routing protocols are compared.     

High dynamic adaptive mobility network model and performance analysis

Since mobile networks are not currently deployed on a large scale, research in this area is mostly by simulation. Among other simulation parameters, the mobility model plays a very important role in determining the protocol performance in MANET. Based on random direction mobility model, a high dynamic adaptive mobility network model is proposed in the paper. The algorithms and modeling are mainly studied and explained in detail. The technique keystone is that normal distribution is combined with uniform distribution and inertial feedback control is combined with kinematics, through the adaptive control on nodes speed and prediction tracking on nodes routes, an adaptive model is designed, which can be used in simulations to produce realistic and dynamic network scenarios. It is the adaptability that nodes mobile parameters can be adjusted randomly in threedimensional space. As a whole, colony mobility can show some rules. Such random movement processes as varied speed and dwells are simulated realistically. Such problems as sharp turns and urgent stops are smoothed well. The model can be adapted to not only common dynamic scenarios, but also high dynamic scenarios. Finally, the mobility model performance is analyzed and validated based on random dynamic scenarios simulations.     

基于圆周运动的自组网移动模型研究

自组网仿真研究大多基于特定的移动模型,而移动模型中节点空间概率分布是研究和评价自组网性能的理论基础.然而,现有的自组网移动模型存在诸多缺陷(如不现实的移动场景、节点的非均匀分布等).在分析和比较现有移动模型的基础上,提出一种基于圆周运动的移动模型,推导出移动节点的二维概率密度函数公式.理论分析和仿真实验表明,该模型能够克服现有移动模型的这些缺陷,为仿真和评估自组网的性能提供了精确的理论模型.     

The message delay in mobile ad hoc networks

A stochastic model is introduced that accurately models the message delay in mobile ad hoc networks where nodes relay messages and the networks are sparsely populated. The model has only two input parameters: the number of nodes and the parameter of an exponential distribution which describes the time until two random mobiles come within communication range of one another. Closed-form expressions are obtained for the Laplace–Stieltjes transform of the message delay, defined as the time needed to transfer a message between a source and a destination. From this we derive both a closed-form expression and an asymptotic approximation (as a function of the number of nodes) of the expected message delay. As an additional result, the probability distribution function is obtained for the number of copies of the message at the time the message is delivered. These calculations are carried out for two protocols: the two-hop multicopy and the unrestricted multicopy protocols. It is shown that despite its simplicity, the model accurately predicts the message delay for both relay strategies for a number of mobility models (the random waypoint, random direction and the random walker mobility models).     

Ad Hoc网络移动模型研究

无线移动AdHoc网络是一种不依赖任何固定设施的移动无线多跳网络。如何选择最贴近实际、最易于实现的移动模型是研究的基础,也是成功的关键。论文研究了几个典型的用于AdHoc网络中的移动模型。分析各种移动模型的关联和差异,给出了各自适用的范围及选择的依据条件,有利于AdHoc网络协议的研究和评价。     

Ad Hoc网络链路持续时间计算模型

链路持续时间是衡量Ad Hoc网络动态性的重要参数,对网络的路由协议性能和网络性能有直接影响。链路持续时间的计算为设计Ad Hoc网络路由协议、评价网络性能及描述网络动态性提供了理论依据,是计算路径持续时间的基础,目前尚无链路持续时间的准确计算方法。基于统计原理,该文提出适用多种Ad Hoc网络移动模型的链路持续时间计算模型,推导出链路持续时间概率分布的精确公式,得到链路持续时间和移动模型参数的关系和相关的动态性参数(平均链路持续时间、链路变化率)的计算公式。通过ns-2仿真实验验证了公式的正确性。     

Logarithmic Store-Carry-Forward Routing in Mobile Ad Hoc Networks

Two schools of thought exist in terms of handling mobility in mobile ad hoc networks (MANETs). One is the traditional connection-based model, which views node mobility as undesirable and tries to either remove (through recovery schemes) or mask (through tolerant schemes) the effect of mobility. The other is the mobility-assisted model, which considers mobility as a desirable feature, where routing is based on the store-carry-forward paradigm with random or controlled movement of mobile nodes (called ferries). It is well known that mobility increases the capacity of MANETs by reducing the number of relays in routing. Surprisingly, only two models, diameter hop count in the connection-based model and constant hop count in the mobility-assisted model, which correspond to two extremes of the spectrum, have been systematically studied. In this paper, we propose a new routing model that deals with message routing, as well as trajectory planning, of the ferries that carry the message. A logarithmic number of relays are enforced to achieve a good balance among several contradictory goals, including increasing network capacity, increasing ferry sharing, and reducing moving distance. The model considers the dynamic control of ferries in terms of the number of ferries, trajectory planning of ferries, and node communication and synchronization. The effectiveness of the proposed model is evaluated analytically, as well as through simulation     

移动传感器网络路由协议的多跳数据传输及能耗性能分析

为了研究无线传感器网络路由协议性能与网络节点移动性之间的关系,基于网络模拟器NS-2构建了无线传感器网络的11种静止模型和16种移动模型,基于模型设计了不同的仿真实验,并对AODV和DSR协议的性能进行了评估。在评估过程中引入了一种全新的可以精确计算网络能耗的层次型能耗评价方法ECOB。实验结果表明,在节点静止及低移动速度的环境中,无线传感器网络路由协议性能受节点移动速度及网络规模的影响不大;然而,随着越来越多的移动节点参与多跳数据传输,受节点移动速度提高的影响,AODV和DSR的多跳数据传输性能下降幅度增大;与DSR相比,AODV更适合高移动性的大规模移动场景。     

Ad hoc node connectivity improvement analysis – Why not through mesh clients?

A mobile ad-hoc network (MANET) is a complex distributed system with unpredictable node movements, which results in frequent node disconnectivity. In a MANET, each node works independently, using the resources based on individual need. The main problem with this arises during the movement of the nodes and random utilization of network resources. This work attempts to solve the mobility maintenance issues using three mesh structures; (i) mesh tree (M_T), (ii) mesh backbone (M_B) and (iii) mesh cluster (M_C). The mobility maintenance architectures are formed based on a localized connectivity analysis and the node degree as a key parameter for network construction. The performance of the proposed work is analysed through mathematical models and simulation results.     

Energy Optimization under Informed Mobility

Energy optimization is important in wireless ad hoc networks, where node battery power is usually limited. Research results show that such a network can exploit controlled node mobility to reduce communication-related energy consumption. However, node movement itself usually consumes energy. In this paper we study the energy optimization problem that accounts for energy costs associated with both communication and physical node movement. We refer to this model as informed mobility. We first review the theoretical foundations on how to reduce total communication energy consumption, as well as increase system lifetime, by combining node movement and transmission power adaptation. Next, we describe and analyze the informed mobility optimization problem. Based on this analysis, we introduce localized algorithms and protocols for informed mobility. We propose iMobif, a flow-based informed mobility framework that collects network information for mobility decision making. We demonstrate how to use iMobif to minimize total communication energy consumption as well as to maximize system lifetime. We compare the performance of iMobif to that of systems with no mobility or only cost-unaware mobility. Simulation results show iMobif is effective in reducing energy consumption relative to such systems.     

Clone wars: Distributed detection of clone attacks in mobile WSNs

Among security challenges raised by mobile Wireless Sensor Networks, clone attack is particularly dreadful since it makes an adversary able to subvert the behavior of a network just leveraging a few replicas of some previously compromised sensors. In this work, we provide several contributions: first, we introduce two novel realistic adversary models, the vanishing and the persistent adversary, characterized by different compromising capability. We then propose two distributed, efficient, and cooperative protocols to detect replicas: History Information-exchange Protocol (HIP) and its optimized version (HOP). Both HIP and HOP leverage just local (one-hop) communications and node mobility, and differ for the amount of computation required. We study their behavior against the introduced types of attacker, considering two different mobility models and comparing our solutions against the state of the art. Both analysis and simulation results show that our solutions are effective and efficient, providing high detection rate, while incurring limited overhead.