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Christian Bettstetter - One of the best experts on this subject based on the ideXlab platform.

  • Stochastic properties of the random waypoint Mobility Model
    Wireless Networks, 2004
    Co-Authors: Christian Bettstetter, Hannes Hartenstein, Xavier Pérez-costa
    Abstract:

    The random waypoint Model is a commonly used Mobility Model for simulations of wireless communication networks. By giving a formal description of this Model in terms of a discrete-time stochastic process, we investigate some of its fundamental stochastic properties with respect to: (a) the transition length and time of a mobile node between two waypoints, (b) the spatial distribution of nodes, (c) the direction angle at the beginning of a movement transition, and (d) the cell change rate if the Model is used in a cellular-structured system area. The results of this paper are of practical value for performance analysis of mobile networks and give a deeper understanding of the behavior of this Mobility Model. Such understanding is necessary to avoid misinterpretation of simulation results. The movement duration and the cell change rate enable us to make a statement about the "degree of Mobility" of a certain simulation scenario. Knowledge of the spatial node distribution is essential for all investigations in which the relative location of the mobile nodes is important. Finally, the direction distribution explains in an analytical manner the effect that nodes tend to move back to the middle of the system area.

  • the node distribution of the random waypoint Mobility Model for wireless ad hoc networks
    IEEE Transactions on Mobile Computing, 2003
    Co-Authors: Christian Bettstetter, Giovanni Resta, Paolo Santi
    Abstract:

    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.

  • stochastic properties of the random waypoint Mobility Model epoch length direction distribution and cell change rate
    Modeling Analysis and Simulation of Wireless and Mobile Systems, 2002
    Co-Authors: Christian Bettstetter, Hannes Hartenstein, Xavier Perezcosta
    Abstract:

    The random waypoint Model is a commonly used Mobility Model for simulations of wireless communication networks. In this paper, we present analytical derivations of some fundamental stochastic properties of this Model with respect to: (a) the length and duration of a movement epoch, (b) the chosen direction angle at the beginning of a movement epoch, and (c) the cell change rate of the random waypoint Mobility Model when used within the context of cellular networks. Our results and methods can be used to compare the random waypoint Model with other Mobility Models. The results on the movement epoch duration as well as on the cell change rate enable us to make a statement about the 'degree of Mobility' of a certain simulation scenario. The direction distribution explains in an analytical manner the effect that nodes tend to move back to the middle of the system area.

  • the spatial node distribution of the random waypoint Mobility Model
    Mobile Ad-Hoc Netzwerke 1. deutscher Workshop über Mobile Ad-Hoc Netzwerke WMAN 2002, 2002
    Co-Authors: Christian Bettstetter, Christian Wagner
    Abstract:

    The random waypoint Model is a frequently used Mobility Model for simulation–based studies of wireless ad hoc networks. This paper investigates the spatial node distribution that results from using this Model. We show and interpret simulation results on a square and circular system area, derive an analytical expression of the expected node distribution in one dimension, and give an approximation for the two–dimensional case. Finally, the concept of attraction areas and a modified random waypoint Model, the random borderpoint Model, is analyzed by simulation.

  • smooth is better than sharp a random Mobility Model for simulation of wireless networks
    Modeling Analysis and Simulation of Wireless and Mobile Systems, 2001
    Co-Authors: Christian Bettstetter
    Abstract:

    This paper presents an enhanced random Mobility Model for simulation-based studies of wireless networks. Our approach makes the movement trace of individual mobile stations more realistic than common approaches for random movement. After giving a survey of Mobility Models found in the literature, we give a detailed mathematical formulation of our Model and outline its advantages. The movement concept is based on random processes for speed and direction control in which the new values are correlated to previous ones. Upon a speed change event, a new target speed is chosen, and an acceleration is set to achieve this target speed. The principles for a direction change are similar. Moreover, we propose two extensions for Modeling typical movement patterns of vehicles. Finally, we consider strategies for the nodes' border behavior (i.e., what happens when nodes move out of the simulation area) and point out a pitfall that occurs when using a bounded simulation area.

Paolo Santi - One of the best experts on this subject based on the ideXlab platform.

  • the node distribution of the random waypoint Mobility Model for wireless ad hoc networks
    IEEE Transactions on Mobile Computing, 2003
    Co-Authors: Christian Bettstetter, Giovanni Resta, Paolo Santi
    Abstract:

    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.

  • an analysis of the node spatial distribution of the random waypoint Mobility Model for ad hoc networks
    Proceedings of the second ACM international workshop on Principles of mobile computing, 2002
    Co-Authors: Giovanni Resta, Paolo Santi
    Abstract:

    In this paper we analyze the node spatial distribution generated by nodes moving according to the random waypoint Model, which is widely used in the simulation of mobile ad hoc networks. We extend an existing analysis for the case in which nodes are continuously moving (i.e., the pause time is 0) to the more general case in which nodes have arbitrary pause times between movements. We also generalize the Mobility Model, allowing the nodes to remain stationary for the entire simulation time with a given probabilit . Our analysis shows that the structure of the resulting as asymptotic spatial density is composed by three distinct components: the initial, the pause and the mobilit component. The relative values of these components depend on the mobilit parameters. We derive an explicit formula of the one-dimensional node spatial density, and an approximated formula for the two-dimensional case.The quality of this approximation is verified through experimentation, which shows that the accuracy heavily depends on the choice of the mobilit parameters.

Tracy Camp - One of the best experts on this subject based on the ideXlab platform.

  • stationary distributions for the random waypoint Mobility Model
    IEEE Transactions on Mobile Computing, 2004
    Co-Authors: William Navidi, Tracy Camp
    Abstract:

    In simulations of mobile ad hoc networks, the probability distribution governing the movement of the nodes typically varies over time and converges to a "steady-state" distribution, known in the probability literature as the stationary distribution. Some published simulation results ignore this initialization discrepancy. For those results that attempt to account for this discrepancy, the practice is to discard an initial sequence of observations from a simulation in the hope that the remaining values will closely represent the stationary distribution. This approach is inefficient and not always reliable. However, if the initial locations and speeds of the nodes are chosen from the stationary distribution, convergence is immediate and no data need be discarded. We derive the stationary distributions for location, speed, and pause time for the random waypoint Mobility Model. We then show how to implement the random waypoint Mobility Model in order to construct more efficient and reliable simulations for mobile ad hoc networks. Simulation results, which verify the correctness of our method, are included. In addition, implementation of our method for the NS-2 simulator is available.

  • a survey of Mobility Models for ad hoc network research
    Communications and Mobile Computing, 2002
    Co-Authors: Tracy Camp, Jeff Boleng, Vanessa Davies
    Abstract:

    In the performance evaluation of a protocol for an ad hoc network, the protocol should be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer space for the storage of messages, representative data traffic Models, and realistic movements of the mobile users (i.e., a Mobility Model). This paper is a survey of Mobility Models that are used in the simulations of ad hoc networks. We describe several Mobility Models that represent mobile nodes whose movements are independent of each other (i.e., entity Mobility Models) and several Mobility Models that represent mobile nodes whose movements are dependent on each other (i.e., group Mobility Models). The goal of this paper is to present a number of Mobility Models in order to offer researchers more informed choices when they are deciding upon a Mobility Model to use in their performance evaluations. Lastly, we present simulation results that illustrate the importance of choosing a Mobility Model in the simulation of an ad hoc network protocol. Specifically, we illustrate how the performance results of an ad hoc network protocol drastically change as a result of changing the Mobility Model simulated.

C Sathitwiriyawong - One of the best experts on this subject based on the ideXlab platform.

  • a comparative study of random waypoint and gauss markov Mobility Models in the performance evaluation of manet
    International Symposium on Communications and Information Technologies, 2006
    Co-Authors: J Ariyakhajorn, P Wannawilai, C Sathitwiriyawong
    Abstract:

    A mobile ad hoc network (MANET) is a network consisting of a set of wireless mobile nodes that communicate with each other without centralized control or established infrastructure. The Mobility Model represents the moving behavior of each mobile node (MN) in the MANET that should be realistic. It is a crucial part in the performance evaluation of MANET. Random Waypoint Mobility Model is the only Mobility Model that has been widely used in the simulation study of MANET despite some unrealistic movement behaviors such as sudden stop and sharp turn. Whilst Gauss-Markov Mobility Model has been proved that it can solve both of these problems. This paper presents a comparative simulation study of Random Waypoint and Gauss-Markov Mobility Models on the performance study of MANET that uses Ad-hoc On-Demand Distance Vector (AODV) as the routing protocol. The results show that both Mobility Models are not different in case each MN is moving at human running speed. Therefore, it is suggested to use Random Waypoint Mobility Model because of its less computational overhead comparing to Gauss-Markov Mobility Model. When the speed of MNs is as high as fast automobiles, the performance result using Random Waypoint Mobility Model is significant different from Gauss-Markov Mobility Model. Therefore, Gauss-Markov Mobility Model should be used instead. Moreover, different levels of randomness setting have no effect on the accuracy of throughput and end-to-end delay.

Jin Jang - One of the best experts on this subject based on the ideXlab platform.

  • field effect Mobility Model in organic thin film transistor
    Applied Physics Letters, 2011
    Co-Authors: Kwansoo Chung, Jin Jang
    Abstract:

    An analytical Model is presented here for the field effect Mobility in organic thin-film transistors. It is developed rigorously using the variable range hopping theory, the Gaussian density of states distribution function and the transistor Model. Based on the proposed Model, a variety of temperature and gate voltage dependencies of the field effect Mobility can be well described. Good agreement between the calculation and recent experimental data is also observed.