The random waypoint mobility model with uniform node spatial distribution

In this paper, we tackle the problem of designing a random mobility model generating a target node spatial distribution. More specifically, we solve a long standing open problem by presenting two versions of the well-known random waypoint (RWP) mobility model in bounded regions generating a uniform steady-state node spatial distribution. In the first version, named temporal-RWP, we exploit the temporal dimension of node mobility and achieve uniformity by continuously changing the speed of a mobile node as a function of its location and of the density function of trajectories in the movement region R. In the second version, named spatial-RWP, we instead exploit the spatial dimension and achieve uniformity by selecting waypoints according to a suitably defined mix of probability density functions. Both proposed models can be easily incorporated in wireless network simulators, and are thus of practical use. The RWP models presented in this paper allow for the first time completely removing the well-known border effect causing possible inaccuracies in mobile network simulation, thus completing the picture of a “perfect” simulation methodology drawn in existing literature.     

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.     

Detecting Hot Road Mobility of Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) can provide value-added services to both drivers and passengers with on-board vehicular communication systems. Node mobility and volatile wireless connection in VANETs affect inter-contact time (T _I ) between mobile nodes, which greatly degrades the performance of vehicular applications. Nevertheless, the node spatial distribution in VANETs is another important factor especially in real applications. It positively affects the inter-contact time of vehicular nodes. By leveraging it, we can significantly improve the performance of data transmissions and inter-vehicle communication. To this end, we investigate the data collected from around 4,000 taxisin Shanghai and propose in this paper an efficient hot road mobility model. We find that most taxis distribute on some hot roads, which makes the node spatial distribution follow the power law. Based on this observation, we propose the concepts of indirect contact and heterogeneous inter-contact time (T _H ) to reveal how hot roads can change the distribution of inter-contact time. We find that the tail distribution of T _H also appears the power law, and both node spatial distribution and T _H distribution decay at least as the power law. We further propose a model for detecting vehicle mobility in hot roads, which can generates synthetic traces that captures both spatial and temporal features of nodes in VANETs.     

Capacity Scaling in Ad Hoc Networks With Heterogeneous Mobile Nodes: The Super-Critical Regime

We analyze the capacity scaling laws of mobile ad hoc networks comprising heterogeneous nodes and spatial inhomogeneities. Most of previous work relies on the assumption that nodes are identical and uniformly visit the entire network space. Experimental data, however, show that the mobility pattern of individual nodes is usually restricted over the area, while the overall node density is often largely inhomogeneous due to the presence of node concentration points. In this paper we introduce a general class of mobile networks which incorporates both restricted mobility and inhomogeneous node density, and describe a methodology to compute the asymptotic throughput achievable in these networks by the store-carry-forward communication paradigm. We show how the analysis can be mapped, under mild assumptions, into a Maximum Concurrent Flow (MCF) problem over an associated Generalized Random Geometric Graph (GRGG). Moreover, we propose an asymptotically optimal scheduling and routing scheme that achieves the maximum network capacity.     

Gamma random waypoint mobility model for wireless ad hoc networks

Random waypoint (RWP) mobility model is widely used in ad hoc network simulation. The model suffers from speed decay as the simulation progresses and may not reach the steady state in terms of instantaneous average node speed. Furthermore, the convergence of the average speed to its steady state value is delayed. This usually leads to inaccurate results in protocol validation of mobile ad hoc networks modeling. Moreover, the probability distributions of speed vary over the simulation time, such that the node speed distribution at the initial state is different from the corresponding distribution at the end of the simulation. In order to overcome these problems, this paper proposes a modified RWP mobility model with a more precise distribution of the nodes' speed. In the modified model, the speeds of nodes are sampled from gamma distribution. The results obtained from both analysis and simulation experiments of the average speed and the density of nodes' speed indicate that the proposed gamma random waypoint mobility model outperforms the existing RWP mobility models. It is shown that a significant performance improvement in achieving higher steady state speed values that closely model the pre‐assumed average speeds are possible with the proposed model. Additionally, the model allows faster convergence to the steady state, and probability distribution of speed is steady over the simulation time. Copyright © 2012 John Wiley & Sons, Ltd.     

Modeling epidemic data diffusion for wireless mobile networks

Data/content dissemination among the mobile devices is the fundamental building block for all the applications in wireless mobile collaborative computing, known as mobile peer‐to‐peer. Different parameters such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in a mobile peer‐to‐peer environment. In this paper, we develop analytical models for object diffusion time/delay in a wireless mobile network to apprehend the complex interrelationship among these different parameters. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in the wireless mobile network considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in the wireless mobile network. Copyright © 2012 John Wiley & Sons, Ltd.     

A mobility-based framework for adaptive clustering in wireless adhoc networks

This paper presents a novel framework for dynamically organizing mobile nodes in wireless ad hoc networks into clusters in which the probability of path availability can be bounded. The purpose of the (α, t) cluster is to help minimize the far-reaching effects of topological changes while balancing the need to support more optimal routing. A mobility model for ad hoc networks is developed and is used to derive expressions for the probability of path availability as a function of time. It is shown how this model provides the basis for dynamically grouping nodes into clusters using an efficient distributed clustering algorithm. Since the criteria for cluster organization depends directly upon path availability, the structure of the cluster topology is adaptive with respect to node mobility. Consequently, this framework supports an adaptive hybrid routing architecture that can be more responsive and effective when mobility rates are low and more efficient when mobility rates are high     

The node distribution of the random waypoint mobility model for wireless ad hoc networks

The random waypoint model is a commonly used mobility model in the simulation of ad hoc networks. It is known that the spatial distribution of network nodes moving according to this model is, in general, nonuniform. However, a closed-form expression of this distribution and an in-depth investigation is still missing. This fact impairs the accuracy of the current simulation methodology of ad hoc networks and makes it impossible to relate simulation-based performance results to corresponding analytical results. To overcome these problems, we present a detailed analytical study of the spatial node distribution generated by random waypoint mobility. More specifically, we consider a generalization of the model in which the pause time of the mobile nodes is chosen arbitrarily in each waypoint and a fraction of nodes may remain static for the entire simulation time. We show that the structure of the resulting distribution is the weighted sum of three independent components: the static, pause, and mobility component. This division enables us to understand how the model's parameters influence the distribution. We derive an exact equation of the asymptotically stationary distribution for movement on a line segment and an accurate approximation for a square area. The good quality of this approximation is validated through simulations using various settings of the mobility parameters. In summary, this article gives a fundamental understanding of the behavior of the random waypoint model.     

A myopic mobile sink migration strategy for maximizing lifetime of wireless sensor networks

Network lifetime maximization is challenging particularly for large-scale wireless sensor networks. The sensor nodes near the sink node tend to suffer high energy consumption due to heavy traffic relay operations, becoming vulnerable to energy depletion. The rationale of the sink mobility approach is that as the sink node moves around, such risk of energy depletion at some nodes can be alleviated. In this paper, we first obtain the optimal mobile sink sojourning pattern by solving a linear programming model and then we mathematically analyze why the optimal solution exhibits such sojourning pattern. We use the insights from this analysis to design a simple practical heuristic algorithm for sink mobility, which utilizes only local information. Our heuristic is very different from the existing algorithms which often use the traffic volume as the main decision factor, in that we consider the variance of residual energy of neighboring sensor nodes. The simulation results show that our scheme achieves near-optimal network lifetime even with the relatively low moving speed of the mobile sink.     

A multi‐anchoring approach in mobile IP networks

Many recent mobility solutions, including derivatives of the well‐known Mobile IP as well as emerging protocols employed by future Internet architectures, propose to realize mobility management by distributing anchoring nodes (Home Agents or other indirection agents) over the Internet. One of their main goals is to address triangle routing by optimizing routes between mobile nodes and correspondent nodes. Thus, a key component of such proposals is the algorithm to select proper mobility anchoring nodes for mobile nodes. However, most current solutions adopt a single‐anchoring approach, which means each mobile node attaches to a sole mobility anchor at one time. In this paper, “we argue that the single‐anchoring approach has drawbacks when facing various mobility scenarios. Then, we offer a novel multi‐anchoring approach that allows each mobile node to select an independent mobility anchor for each correspondent node. We show that in most cases our proposal gains more performance benefits with an acceptable additional cost by evaluation based on real network topologies. For the cases that lead to potential high cost, we also provide a lightweight version of our solution which aims to preserve most performance benefits while keeping a lower cost. At last, we demonstrate how our proposal can be integrated into current Mobile IP networks. Copyright © 2017 John Wiley & Sons, Ltd.     

Utilizing detours for energy conservation in mobile wireless networks

Autonomous robotic systems have been gaining the attention of research community in mobile ad hoc network since the past few years. While motion cost and communications cost constitute the primary energy consumers, each of them is investigated independently. By taking into account the power consumption of both entities, the overall energy efficiency of a system can be further improved. In this paper, the energy optimization problem of radio communication and motion is examined. We consider a hybrid wireless network in two scenarios: first, a single autonomous mobile node communicating with multiple static relays through single hop, and secondly, a single mobile node communicating with a static base station via a mobile relay. The mobile node interacts with the relays within its vicinity by continuously transmitting high-bandwidth data, e.g. triggered by a multimedia application like video surveillance. The goal is to find the best paths such that the energy consumption for both mobility and communications is minimized for all mobile nodes. We introduce Radio-Energy-Aware (REA) path computation strategy by utilizing node mobility. Given the starting point, the target point and the position of the relays, our simulation results show that the proposed strategy improves the energy efficiency of mobile node compared to Motion-Energy-Aware (MEA) path constructed based only on the mobility cost.     

DECADE: Distributed Emergent Cooperation through ADaptive Evolution in mobile ad hoc networks

The scarce resources of a mobile ad hoc network (MANET) should not be wasted attending selfish nodes (those nodes that use resources from other nodes to send their own packets, without offering their own resources to forward other nodes’ packets). Thus, rational nodes (those nodes willing to cooperate if deemed worthy) must detect and isolate selfish nodes in order to cooperate only among themselves. To achieve this purpose, in this paper we present a new game theoretic trust model called DECADE (Distributed Emergent Cooperation through ADaptive Evolution). The design of DECADE is shown by first, analyzing a simple case of packet forwarding between two nodes, and then the results are extended to bigger networks. In DECADE, each node seeks individually to maximize its chance to deliver successfully their own packets, so that the cooperation among rational nodes and the isolation of selfish nodes appear as an emergent collective behavior. This behavior emerges as long as there is a highly dynamic interaction among nodes. So, for those cases where the mobility alone does not suffice to provide this interaction, DECADE includes a sociability parameter that encourages nodes to interact among them for faster learning and adaptability. Additionally, DECADE introduces very low overhead on computational and communication resources, achieving close to optimal cooperation levels among rational nodes and almost complete isolation of selfish nodes.     

Performance of dead reckoning‐based location service for mobile ad hoc networks

A predictive model‐based mobility tracking method, called dead reckoning, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use ‘distance effect’, where distant nodes maintain less accurate tracking information to save overheads. The dead reckoning‐based location service mechanism is evaluated against three known location dissemination service protocols: simple, distance routing effect algorithm for mobility (DREAM) and geographic region summary service (GRSS). The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low‐control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, that affects its predictive ability. Copyright © 2004 John Wiley & Sons, Ltd.     

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...     

Relaying in mobile ad hoc networks: The Brownian motion mobility model

Mobile ad hoc networks are characterized by a lack of a fixed infrastructure and by node mobility. In these networks data transfer can be improved by using mobile nodes as relay nodes. As a result, transmission power and the movement pattern of the nodes have a key impact on the performance. In this work we focus on the impact of node mobility through the analysis of a simple one-dimensional ad hoc network topology. Nodes move in adjacent segments with reflecting boundaries according to Brownian motions. Communications (or relays) between nodes can occur only when they are within transmission range of each other. We determine the expected time to relay a message and compute the probability density function of relaying locations. We also provide an approximation formula for the expected relay time between any pair of mobiles.     

Purposeful mobility for relaying and surveillance in mobile ad hoc sensor networks

We consider a mobile ad hoc sensor network. The mobility of the sensor nodes is designed with the cost of communication and mobility in mind along with consideration of the possible scanning tasks of the nodes. Our mobility algorithm is developed in the context of a distributed system where, for any single mobile node, only local information about associated energy costs is known. We use a distributed simulated annealing framework to govern the motion of the nodes and prove that, in a limiting sense, a global objective function comprising mobility and communication energy costs are minimized. This paper concludes with a simulation study focusing on mobile sensors with dual roles of scanning and relaying higher priority tracking traffic from tracking nodes.     

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.     

Superdiffusive Behavior of Mobile Nodes and Its Impact on Routing Protocol Performance

Mobility is the most important component in mobile ad hoc networks (MANETs) and delay-tolerant networks (DTNs). In this paper, we first investigate numerous GPS mobility traces of human mobile nodes and observe superdiffusive behavior in all GPS traces, which is characterized by a “faster-than-linear” growth rate of the mean square displacement (MSD) of a mobile node. We then investigate a large amount of access point (AP) based traces, and develop a theoretical framework built upon continuous time random walk (CTRW) formalism, in which one can identify the degree of diffusive behavior of mobile nodes even under possibly heavy-tailed pause time distribution, as in the case of reality. We study existing synthetic models and trace-based models in terms of the capability of producing various degrees of diffusive behavior, and use a set of Lévy walk models due to its simplicity and flexibility. In addition, we show that diffusive properties make a huge impact on contact-based metrics and the performance of routing protocols in various scenarios, and that existing models such as random waypoint, random direction model, or Brownian motion lead to overly optimistic or pessimistic results when diffusive properties are not properly captured. Our work in this paper, thus, suggests that the diffusive behavior of mobile nodes should be correctly captured and taken into account for the design and comparison study of network protocols.     

A tree-based mobility management using message aggregation based on a skewed wait time assignment in infrastructure based MANETs

For the effective mobility management of mobile nodes in Infrastructure-based Mobile Ad Hoc Networks, every mobile node is obliged to send a registration message to the Internet Gateway (IG) periodically. Not only do the registration messages and the additional control messages to establish paths from mobile nodes to the IG to send the registration messages incur a considerable amount of control overhead, but also they impose high traffic congestion on the mobile nodes in the vicinity of the IG which is referred to as the “funneling effect.” The control overhead and the funneling effect make it hard to handle mobility management with little impact on the performance of a routing protocol. Therefore, in this paper we propose a tree-based mobility management approach using a message aggregation technique that employs a novel timing model suitable for tree topology, referred to as a skewed wait time assignment technique, in order to maximize message aggregation. Despite its superior performance, this wait time assignment technique differs from the other techniques in that it does not require clock synchronization over nodes. By resorting to simulations, we show that the proposed approach can significantly alleviate the funneling effect as well as improve the performance of mobility management compared with the Tree-based and Quasi-tree based mobility management schemes.