Connectivity Probability of Wireless Ad Hoc Networks: Definition, Evaluation, Comparison

The paper presents a new approach investigating mobile ad hoc network connectivity. It is shown how to define and evaluate the connectivity probability of a mobile network where the position of the nodes and the link quality changes over time. The connectivity probability is a measure that can capture the impact of the node movement on the network connectivity. A number of mobility models is considered ranging from the classical Random Direction model to the Virtual World model based on the mobility measurements of a multi–player game. We introduce an Attractor model as a simple way to model non–homogeneous node distribution by incorporating viscosity regions in the simulation area. Methods of ergodic theory are used to show the correctness of the approach and to reduce the computational time. Simulation results show how the node density distribution affects the network connectivity.     

Connectivity of Mobile Linear Networks with Dynamic Node Population and Delay Constraint

The connectivity properties of a mobile linear network with high speed mobile nodes and strict delay constraint are investigated. A new mobility model is developed to represent the steady state node distribution, and it accurately captures the statistical properties of random node arrival, time-varying node speed, and the distinct behaviors of nodes following different traffic patterns.With the mobility model, the statistical properties of network connectivity are studied and identified. Unlike most previous works that do not consider the impacts of transmission latency, which is critical for real time applications, this paper identifies the quantitative relationship between network connectivity and delay constraint. The results are applicable to both delay constrained networks and delay tolerant networks. The connectivity analysis is performed with a novel geometry-assisted analytical method. Exact connectivity probability expressions are developed by using the volumes of a hypercube intersected by a hyperplane, and a hyperpyramid. The geometry-assisted analytical method significantly simplifies the connectivity analysis.     

A quadratic optimization method for connectivity and coverage control in backbone-based wireless networks

The use of directional wireless communications to form flexible mesh backbone networks, which provide broadband connectivity to capacity-limited wireless networks or hosts, promises to circumvent the scalability limitations of traditional homogeneous wireless networks. The main challenge in the design of directional wireless backbone (DWB) networks is to assure backbone network requirements such as coverage and connectivity in a dynamic wireless environment. This paper considers the use of mobility control, as the dynamic reposition of backbone nodes, to provide assured coverage-connectivity in dynamic environments. This paper presents a novel approach to the joint coverage-connectivity optimization problem by formulating it as a quadratic minimization problem. Quadratic cost functions for network coverage and backbone connectivity are defined in terms of the square distance between neighbor nodes, which are related to the actual energy usage of the network system. Our formulation allows the design of self-organized network systems which autonomously achieve energy minimizing configurations driven by local forces exerted on network nodes. The net force on a backbone node is defined as the negative energy gradient at the location of the backbone node. A completely distributed algorithm is presented that allows backbone nodes to adjust their positions based on information about neighbors’ position only. We present initial simulation results that show the effectiveness of our force-based mobility control algorithm to provide network configurations that optimize both network coverage and backbone connectivity in different scenarios. Our algorithm is shown to be adaptive, scalable and self-organized.     

Network connectivity of one-dimensional MANETs with random waypoint movement

An analysis of network connectivity of one-dimensional mobile ad hoc networks with a particular mobility scheme is presented, focusing on the random waypoint mobility scheme. The numerical results are verified using simulation to show their accuracy under practical network conditions. Observations on RWP properties further lead to approximations and an eventual simple network connectivity formula.     

A Statistical Analysis of the Long-Run Node Spatial Distribution in Mobile Ad Hoc Networks

In this paper, we analyze the node spatial distribution of mobile wireless ad hoc networks. Characterizing this distribution is of fundamental importance in the analysis of many relevant properties of mobile ad hoc networks, such as connectivity, average route length, and network capacity. In particular, we have investigated under what conditions the node spatial distribution resulting after a large number of mobility steps resembles the uniform distribution. This is motivated by the fact that the existing theoretical results concerning mobile ad hoc networks are based on this assumption. In order to test this hypothesis, we performed extensive simulations using two well-known mobility models: the random waypoint model, which resembles intentional movement, and a Brownian-like model, which resembles non-intentional movement. Our analysis has shown that in Brownian-like motion the uniformity assumption does hold, and that the intensity of the concentration of nodes in the center of the deployment region that occurs in the random waypoint model heavily depends on the choice of some mobility parameters. For extreme values of these parameters, the uniformity assumption is impaired.     

Analytical model for connectivity of vehicular ad hoc networks in the presence of channel randomness

A vehicular ad hoc network (VANET) is a highly mobile wireless ad hoc network formed by vehicles equipped with communication facilities. Developing multihop communication in VANETs is a challenging problem because of rapidly changing network topology and frequent network disconnections. This paper investigates the network connectivity probability of one‐dimensional VANET in the presence of channel randomness. Network connectivity is one of the most important issues in VANETs, because the dissemination of time‐critical information requires, as a preliminary condition, the network to be fully connected. We present an analytical procedure for the computation of network connectivity probability, taking into account the underlying wireless channel. Three different fading models are considered for the connectivity analysis: Rayleigh, Rician, and Weibull. A distance‐dependent power law model is employed for the pathloss in a vehicle‐to‐vehicle channel. Furthermore, the speed of each vehicle on the highway is assumed to be a Gaussian distributed random variable. The analysis provides a general framework for investigating the dependence of various parameters such as vehicle arrival rate, vehicle density, vehicle speed, highway length, and various physical layer parameters such as transmit power, receive signal‐to‐noise ratio threshold, path loss exponent, and fading factors (Rician and Weibull) on VANET connectivity. Copyright © 2011 John Wiley & Sons, Ltd.     

Human-mobility enabled networks in urban environments: Is there any (mobile wireless) small world out there?

In the last 10 years, new paradigms for wireless networks based on human mobility have gained the attention of the research community. These paradigms, usually referred to as Pocket Switched Networks or Delay Tolerant Networks, jointly exploit human mobility and store-and-forward communications to improve the connectivity in sparse or isolated networks. Clearly, understanding the human mobility patterns is a key challenge for the design of routing protocols based on such paradigms. To this aim, we anonymously collected the positions of almost two thousand mobile phone users, spread over a metropolitan area greater than 200 km² for roughly one month. Then, with a multi-disciplinary approach, we estimated the mobility patterns from the collected data and, assuming Wi-Fi connectivity, we inferred the contact events among the devices to evaluate the connectivity properties of a human mobility-enabled wireless network. In a nutshell, the contribution of the paper is threefold: (i) it confirms some of the results obtained in smaller environments, such as the power-law distribution for contact and inter-contact times, allowing us to estimate the distribution parameters with high statistical significance; (ii) it addresses the feasibility of the transmission opportunities provided by human mobility to build a city-wide connected network for different forwarding strategies classes; (iii) it shows uncovered characteristics of the connectivity properties of human mobility, such as the presence of the small world phenomenon in wide-scale experiments.     

Impact of Interference on the Wireless Ad-Hoc Networks Capacity and Topology

It is wide spread belief that wireless mobile ad-hoc networks will be a further evolutionary step towards ubiquitous communication and computing. Due to the mobility of the network nodes, the strongly varying radio propagation conditions and the varying data traffic load these networks constitute a very dynamic environment. One essential step in evaluating the true benefit of this new technology consists of estimates and constraints concerning the scalability and performance of such networks. Using a simple model we discuss analytically the effect of interference on the link quality and connectivity of large networks. It turns out that the outage probability rapidly increases with increasing traffic load. Furthermore, we investigate the connectivity of the network under varying traffic load and find a percolation phase transition at a particular value of the traffic load. We discuss the dependence of these effects on parameters characterizing the receiver and the radio propagation conditions.     

Nonlinearities compensator based on SORBFNN in ultra-long-haul high-capacity CO-OFDM systems

The ultraviolet (UV) scattering communication can be applied in military networked on-the-move and unattended ground sensor networks. This paper focuses on the connectivity properties of unmanned aerial vehicles (UAVs) network based on UV communication that ensures the secret communications between UAVs. UAVs network is consisting of a group of UAVs, each of which moving according to a particular mobility model. We discuss random waypoint (RWP) mobility model and circle movement based model (CMBM), which can describe the actual movement of UAVs, respectively. In this paper, the approximations of the probability that the network is k-connected are provided with consideration of transmission using on–off keying and pulse position modulation. More precisely, we evaluate the effects of node density, transmission power, and data rate on k-connectivity. The numerical examples show that the mobility degrades the connectivity probability. When the numbers of nodes \(n=500\) and data rate \(R_b =10\,\hbox {kbps}\), the required transmission power for nodes moving according to RWP is lower than CMBM in order to achieve 2-connectivity of the UAVs network, but it is about twice that for uniformly distributed nodes.     

Analytical Model for Connectivity in Vehicular Ad Hoc Networks

We investigate connectivity in the ad hoc network formed between vehicles that move on a typical highway. We use a common model in vehicular traffic theory in which a fixed point on the highway sees cars passing it that are separated by times with an exponentially distributed duration. We obtain the distribution of the distances between the cars, which allows us to use techniques from queuing theory to study connectivity. We obtain the Laplace transform of the probability distribution of the connectivity distance, explicit expressions for the expected connectivity distance, and the probability distribution and expectation of the number of cars in a platoon. Then, we conduct extensive simulation studies to evaluate the obtained results. The analytical model that we present is able to describe the effects of various system parameters, including road traffic parameters (i.e., speed distribution and traffic flow) and the transmission range of vehicles, on the connectivity. To more precisely study the effect of speed on connectivity, we provide bounds obtained using stochastic ordering techniques. Our approach is based on the work of Miorandi and Altman, which transformed the problem of connectivity distance distribution into that of the distribution of the busy period of an equivalent infinite server queue. We use our analytical results, along with common road traffic statistical data, to understand connectivity in vehicular ad hoc networks.      

A mobility-based upper bound on route length in MANETs

In mobile ad-hoc networks (MANETs) routes are usually found by means of discovery packets that are injected to the network by sender nodes. Once the intended destination is reached by a discovery packet, it replies back to the sender using the same route. Upon reception of the reply message, data transfer from sender to destination can initiate. Node mobility, however, negatively affects route duration time since position changes may lead to connectivity disruptions. Furthermore, the whole process of route discovery breaks down when, due to position changes, the route followed by a discovery packet is useless by the time it reaches the destination. In this paper the conditions leading to this effect are studied and it is shown that they impose a practical limit on how long a route can be. The paper introduces a model to compute an upper bound on route length in MANETs, which is derived from the combination of a route duration model and an access delay model for multi-hop routes. The model was validated by simulations with different network settings. From this model, it was found that the node transmission range, node mobility and total per-hop delays actually define the maximum feasible number of hops in a route. To the best of the authors’ knowledge, this is a fundamental scaling problem of mobile ad-hoc networks that has not been analyzed before from a mobility-delay perspective.     

Mobile multi-user ATM platforms: architectures, design issues, andchallenges

Rapid growth in use of the Internet at and away from the workplace has spurred tremendous interest in the provision of anytime-anywhere network connectivity to mobile users. Commonly studied mobility scenarios involve users equipped with portable data terminals roaming around at slow to moderate speeds within a coverage area. Mobile IP and wireless ATM are examples of protocols designed for providing network connectivity to such mobiles in IP and ATM networks. A different application involving mobile multi-user platforms (MMUP) equipped with onboard private ATM networks is discussed in this article. Examples of such mobile platforms include airplanes, trains, and ships. The presence of an onboard network, multiple users, and potentially high speed of travel presents unique challenges in provision of internetwork connectivity to these MMUPs. Specific characteristics of MMUPs, architectural issues in design of the underlying cellular network, subnetwork mobility within ATM internetworks, location management of MMUPs, and multi-user connection handoffs on MMUP moves are the main issues addressed in the article. Network architectures and protocols developed for terminal mobility scenarios are evaluated for applicability in the present context, and new solutions are presented for problems unique to the MMUP application scenario     

Estimation method of airspace connectivity probability in military AANET

Connectivity is the premise and foundation of networking and routing. For the probabilistic flight path of military aircraft resulting in the difficulty of Aeronautical Ad hoc NETwork （AANET） research, an estimation method of connectivity probability is proposed. The method takes airspace as the research object, starts with actual flight characteristics, and applies conclusions of random waypoint mobility model. Building a connectivity model by establishing Airspace Unit Circle （AUC） from the perspective of circle-circle coverage, the method obtains a theory of airspace network connectivity. Experiment demonstrates its correctness. Finally, ac- cording to the actual condition simulation, relationship between the number of aircraft, commu- nication radius, and the flight area under connectivity probabilities is achieved, results provide reference for creating a network that under certain aerial combat condition.     

AAA authentication for network mobility

Network mobility (NEMO) is a protocol proposed for the mobility management of a whole network.It offers seamless Internet connectivity to the mobile end users.However,the NEMO protocol has not been wid...     

Distributed Mobility Management for Target Tracking in Mobile Sensor Networks

Mobility management is a major challenge in mobile ad hoc networks (MANETs) due in part to the dynamically changing network topologies. For mobile sensor networks that are deployed for surveillance applications, it is important to use a mobility management scheme that can empower nodes to make better decisions regarding their positions such that strategic tasks such as target tracking can benefit from node movement. In this paper, we describe a distributed mobility management scheme for mobile sensor networks. The proposed scheme considers node movement decisions as part of a distributed optimization problem which integrates mobility-enhanced improvement in the quality of target tracking data with the associated negative consequences of increased energy consumption due to locomotion, potential loss of network connectivity, and loss of sensing coverage.     

Connectivity Analysis of Vehicular Ad Hoc Networks from a Physical Layer Perspective

This paper investigates the network connectivity properties of a vehicular ad hoc network (VANET) from a physical layer perspective. Specifically, we investigate the minimum transmit power used by all vehicles, sufficient to guarantee network connectivity. As opposed to the conventional graph-theoretic approach, in this paper, the network connectivity problem is analyzed according to a physical layer-based quality of service constraint. Under this approach, a multi-hop path joining a pair of vehicles in a VANET is said to be connected if and only if the average route BER meets a target requirement. We derive closed form analytical expression for the minimum transmit power sufficient to ensure network connectivity. We also derive analytical expression for the maximum number of hops, a packet can traverse satisfying the route BER constraint, for a given transmit power. The validity of our theoretical analysis is verified by extensive simulation studies. The analysis provides a framework for investigating the impact of traffic dependent parameters such as vehicle arrival rate, vehicle density, mean and standard deviation of vehicle speed, highway length and physical layer-based parameters such as path loss exponent, fading factor, Doppler spread, and data rate on VANET connectivity characteristics.     

Connectivity analysis for dynamic movement of vehicular ad hoc networks

Speed variation is one of the main challenges in deriving the connectivity related predictions in mobile ad-hoc networks, especially in vehicular ad hoc networks (VANETs). In such a dynamic network, a piece of information can be rapidly propagated through dedicated short-range communication, or can be carried by vehicles when multihop connectivity is unavailable. This paper proposes a novel analytical model that carefully computes the connectivity distance for a single direction of a free-flow highway. The proposed model adopts a time-varying vehicular speed assumption and mathematically models the mobility of vehicles inside connectivity. According to the dynamic movability scenario, a novel and accurate closed form formula is proposed for probability density function of connectivity. Moreover, using vehicular spatial distribution, joint Poisson distribution of vehicles in a multilane highway and tail probability of the expected number of vehicles inside single lane in a multilane highway are mathematically investigated. The accuracy of analytical results is verified by simulation. The concluded results provide helpful insights towards designing new applications and improving performance of existing applications on VANETs.     

无线通信网干扰有效性准则初探

网络干扰已经成为当今解决战场无线通信网对抗问题的一种最现实的方式。从网络连通性和业务吞吐量角度,建立了战场无线通信网络模型,提出了评价网络干扰有效性的基本准则。通过实例说明了该准则的有效性。该准则对网络干扰有效性分析具有重要的指导意义。     

组移动模型中基于模型特点的数据收集分簇算法

如今移动传感器网络在各个领域已起到重要作用。目前,移动传感器网络在军事、民用、科研等领域的应用价值都很高。而数据收集问题一直是这方面科研中必须被突破的难题。组移动模型是移动传感网络中的一个重要的移动模型,在本领域内都起到重要作用,然而有关移动传感器网络组模型的数据收集算法却屈指可数。提出了一种组移动模型中基于模型特点的数据收集分簇算法——MCBC算法。该算法根据节点的速度和角度之间的关系确定两节点是否同组,再从中选择簇头,有效地利用了组移动模型中节点的移动特征。仿真结果表明,在组移动模型中,该算法能取得较好的性能。     

DTN 网络环境下动态随机网络编码方法简

容迟容断网络的移动性、间歇连通性和动态拓扑等动态特性使得当前应用于静态网络拓扑和固定多播容量的静态随机网络编码难以适应DTN网络环境的网络编码传输,为此提出了一种DTN网络环境下动态随机网络编码传输方法。该方法以马尔科夫信道模型为基础,根据节点的数据状态动态监测信道速率,在信源节点构造了带信道容量的网络流图,并计算和预测当前网络多播容量,最后根据多播容量的变化动态扩展和裁剪随机网络编码方案,实现DTN网络环境下数据的动态网络编码传输。仿真结果表明,相比传统的固定多播率编码方法,动态随机网络编码方法降低了数据的平均传递延迟,提高了数据投递率。