Showing papers on "Mobility model published in 2006"

Impact of Human Mobility on the Design of Opportunistic Forwarding Algorithms

Abstract: Studying transfer opportunities between wireless devices carried by humans, we observe that the distribution of the inter-contact time, that is the time gap separating two contacts of the same pair of devices, exhibits a heavy tail such as one of a power law, over a large range of value. This observation is confirmed on six distinct experimental data sets. It is at odds with the exponential decay implied by most mobility models. In this paper, we study how this new characteristic of human mobility impacts a class of previously proposed forwarding algorithms. We use a simplified model based on the renewal theory to study how the parameters of the distribution impact the delay performance of these algorithms. We make recommendation for the design of well founded opportunistic forwarding algorithms, in the context of human carried devices.

Extracting a Mobility Model from Real User Traces

Abstract: Understanding user mobility is critical for simula- tions of mobile devices in a wireless network, but current mobility models often do not reflect real user movements. In this paper, we provide a foundation for such work by exploring mobility characteristics in traces of mobile users. We present a method to estimate the physical location of users from a large trace of mobile devices associating with access points in a wireless network. Using this method, we extracted tracks of always-on Wi-Fi devices from a 13-month trace. We discovered that the speed and pause time each follow a log-normal distribution and that the direction of movements closely reflects the direction of roads and walkways. Based on the extracted mobility characteristics, we developed a mobility model, focusing on movements among popular regions. Our validation shows that synthetic tracks match real tracks with a median relative error of 17%.

Exploiting mobility for energy efficient data collection in wireless sensor networks

Abstract: We analyze an architecture based on mobility to address the problem of energy efficient data collection in a sensor network. Our approach exploits mobile nodes present in the sensor field as forwarding agents. As a mobile node moves in close proximity to sensors, data is transferred to the mobile node for later depositing at the destination. We present an analytical model to understand the key performance metrics such as data transfer, latency to the destination, and power. Parameters for our model include: sensor buffer size, data generation rate, radio characteristics, and mobility patterns of mobile nodes. Through simulation we verify our model and show that our approach can provide substantial savings in energy as compared to the traditional ad-hoc network approach.

An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

Abstract: Vehicular ad hoc networks (VANETs) using WLAN tech-nology have recently received considerable attention. The evaluation of VANET routing protocols often involves simulators since management and operation of a large number of real vehicular nodes is expensive. We study the behavior of routing protocols in VANETs by using mobility information obtained from a microscopic vehicular traffic simulator that is based on the on the real road maps of Switzerland. The performance of AODV and GPSR is significantly in uenced by the choice of mobility model, and we observe a significantly reduced packet delivery ratio when employing the realistic traffic simulator to control mobility of nodes. To address the performance limitations of communication pro-tocols in VANETs, we investigate two improvements that increase the packet delivery ratio and reduce the delay until the first packet arrives. The traces used in this study are available for public download.

Spatial node distribution of the random waypoint mobility model with applications

Abstract: The random waypoint model (RWP) is one of the most widely used mobility models in performance analysis of ad hoc networks. We analyze the stationary spatial distribution of a node moving according to the RWP model in a given convex area. For this, we give an explicit expression, which is in the form of a one-dimensional integral giving the density up to a normalization constant. This result is also generalized to the case where the waypoints have a nonuniform distribution. As a special case, we study a modified RWP model, where the waypoints are on the perimeter. The analytical results are illustrated through numerical examples. Moreover, the analytical results are applied to study certain performance aspects of ad hoc networks, namely, connectivity and traffic load distribution.

A community based mobility model for ad hoc network research

Abstract: Validation of mobile ad hoc network protocols relies almost exclusively on simulation. The value of the validation is, therefore, highly dependent on how realistic the movement models used in the simulations are. Since there is a very limited number of available real traces in the public domain, synthetic models for movement pattern generation must be used. However, most widely used models are currently very simplistic, their focus being ease of implementation rather than soundness of foundation. As a consequence, simulation results of protocols are often based on randomly generated movement patterns and, therefore, may differ considerably from those that can be obtained by deploying the system in real scenarios. Movement is strongly affected by the needs of humans to socialise or cooperate, in one form or another. Fortunately, humans are known to associate in particular ways that can be mathematically modelled and that have been studied in social sciences for years.In this paper we propose a new mobility model founded on social network theory. The model allows collections of hosts to be grouped together in a way that is based on social relationships among the individuals. This grouping is then mapped to a topographical space, with movements influenced by the strength of social ties that may also change in time. We have validated our model with real traces by showing that the synthetic mobility traces are a very good approximation of human movement patterns.

Message ferry route design for sparse ad hoc networks with mobile nodes

Abstract: Message ferrying is a networking paradigm where a special node, called a message ferry, facilitates the connectivity in a mobile ad hoc network where the nodes are sparsely deployed. One of the key challenges under this paradigm is the design of ferry routes to achieve certain properties of end-to-end connectivity, such as, delay and message loss among the nodes in the ad hoc network. This is a difficult problem when the nodes in the network move arbitrarily. As we cannot be certain of the location of the nodes, we cannot design a route where the ferry can contact the nodes with certainty. Due to this difficulty, prior work has either considered ferry route design for ad hoc networks where the nodes are stationary, or where the nodes and the ferry move pro-actively in order to meet at certain locations. Such systems either require long-range radio or disrupt nodes' mobility patterns which can be dictated by non-communication tasks. We present a message ferry route design algorithm that we call the Optimized Way-points, or OPWP, that generates a ferry route which assures good performance without requiring any online collaboration between the nodes and the ferry. The OPWP ferry route comprises a set of way-points and waiting times at these way-points, that are chosen carefully based on the node mobility model. Each time that the ferry traverses this route, it contacts each mobile node with a certain minimum probability. The node-ferry contact probability in turn determines the frequency of node-ferry contacts and the properties of end-to-end delay. We show that OPWP consistently outperforms other naive ferry routing approaches.

Evaluating Mobility Pattern Space Routing for DTNs

Abstract: Because a delay tolerant network (DTN) can often be partitioned, routing is a challenge. However, routing benefits considerably if one can take advantage of knowledge concerning node mobility. This paper addresses this problem with a generic algorithm based on the use of a high-dimensional Euclidean space, that we call MobySpace, constructed upon nodes' mobility patterns. We provide here an analysis and a large scale evaluation of this routing scheme in the context of ambient networking by replaying real mobility traces. The specific MobySpace evaluated is based on the frequency of visits of nodes to each possible location. We show that routing based on MobySpace can achieve good performance compared to that of a number of standard algorithms, especially for nodes that are present in the network a large portion of the time. We determine that the degree of homogeneity of node mobility patterns has a high impact on routing. And finally, we study the ability of nodes to learn their own mobility patterns.

Performance analysis of mobility-assisted routing

Abstract: Traditionally, ad hoc networks have been viewed as a connected graph over which end-to-end routing paths had to be established.Mobility was considered a necessary evil that invalidates paths and needs to be overcome in an intelligent way to allow for seamless ommunication between nodes.However, it has recently been recognized that mobility an be turned into a useful ally, by making nodes carry data around the network instead of transmitting them. This model of routing departs from the traditional paradigm and requires new theoretical tools to model its performance. A mobility-assisted protocol forwards data only when appropriate relays encounter each other, and thus the time between such encounters, called hitting or meeting time, is of high importance.In this paper, we derive accurate closed form expressions for the expected encounter time between different nodes, under ommonly used mobility models. We also propose a mobility model that can successfully capture some important real-world mobility haracteristics, often ignored in popular mobility models, and alculate hitting times for this model as well. Finally, we integrate this results with a general theoretical framework that can be used to analyze the performance of mobility-assisted routing schemes. We demonstrate that derivative results oncerning the delay of various routing s hemes are very accurate, under all the mobility models examined. Hence, this work helps in better under-standing the performance of various approaches in different settings, and an facilitate the design of new, improved protocols.

J-Sim: a simulation and emulation environment for wireless sensor networks

Abstract: Wireless sensor networks have gained considerable attention in the past few years. They have found application domains in battlefield communication, homeland security, pollution sensing, and traffic monitoring. As such, there has been an increasing need to define and develop simulation frameworks for carrying out high-fidelity WSN simulation. In this article we present a modeling, simulation, and emulation framework for WSNs in J-Sim - an open source, component-based compositional network simulation environment developed entirely in Java. This framework is built on the autonomous component architecture and extensible internetworking framework of J-Sim, and provides an object-oriented definition of target, sensor, and sink nodes, sensor and wireless communication channels, and physical media such as seismic channels, mobility models, and power models (both energy-producing and energy-consuming components). Application-specific models can be defined by subclassing classes in the simulation framework and customizing their behaviors. We also include in J-Sim a set of classes and mechanisms to realize network emulation. We demonstrate the use of the proposed WSN simulation framework by implementing several well-known localization, geographic routing, and directed diffusion protocols, and perform performance comparisons (in terms of the execution time incurred and memory used) in simulating WSN scenarios in J-Sim and ns-2. The simulation study indicates the WSN framework in J-Sim is much more scalable than ns-2 (especially in memory usage). We also demonstrate the use of the WSN framework in carrying out real-life full-fledged Future Combat System (FCS) simulation and emulation

Capacity Enhancement using Throwboxes in DTNs

Abstract: Disruption Tolerant Networks (DTNs) are designed to overcome limitations in connectivity due to conditions such as mobility, poor infrastructure, and short range radios. DTNs rely on the inherent mobility in the network to deliver packets around frequent and extended network partitions using a store-carry-and-forward paradigm. However, missed contact opportunities decrease throughput and increase delay in the network. We propose the use of throwboxes in mobile DTNs to create a greater number of contact opportunities, consequently improving the performance of the network. Throwboxes are wireless nodes that act as relays, creating additional contact opportunities in the DTN. We propose algorithms to deploy stationary throwboxes in the network that simultaneously consider routing as well as placement. We also present placement algorithms that use more limited knowledge about the network structure. We perform an extensive evaluation of our algorithms by varying both the underlying routing and mobility models. Our results suggest several findings to guide the design and operation of throwbox-augmented DTNs.

Low-field electron mobility in wurtzite InN

Abstract: We report on the low-field electron mobility in bulk wurtzite InN at room temperature and over a wide range of carrier concentration calculated by the ensemble Monte Carlo (MC) method. All relevant phonon scatterings are included in the MC simulation. The scattering with ionized impurities is considered in the basic Brooks-Herring and Conwell-Weisskopf formulations. For the steady-state transport, the drift velocity attains a peak value of ∼5×107cm∕s at an electric field strength of 32kV∕cm. The highest calculated low-field mobility for undoped InN amounts to ∼14000cm2∕Vs at room temperature. We compare our theoretically calculated low-field mobilities with experimental data available in the literature and obtain a quite satisfactory agreement. Finally, an empirical low-field mobility model based on the MC simulation results and experimental mobility data is presented.

Ad Hoc Wireless Networks: A Communication-Theoretic Perspective

Abstract: Preface. List of Acronyms. 1 Related Work and Preliminary Considerations. 1.1 Introduction. 1.2 Related Work. 1.3 A New Perspective for the Design of Ad Hoc Wireless Networks. 1.4 Overview of the Underlying Assumptions in the Following Chapters. 1.5 The Main Philosophy Behind the Book. 2 A Communication-Theoretic Framework for Multi-hop Ad Hoc Wireless Networks: Ideal Scenario. 2.1 Introduction. 2.2 Preliminaries. 2.3 Communication-Theoretic Basics. 2.4 BER Performance Analysis. 2.5 Network Behaviour. 2.6 Concluding Remarks. 3 A Communication-Theoretic Framework for Multi-hop Ad Hoc Wireless Networks: Realistic Scenario. 3.1 Introduction. 3.2 Preliminaries. 3.3 Communication-Theoretic Basics. 3.4 Inter-node Interference. 3.5 RESGOMAC Protocol. 3.6 RESLIGOMAC Protocol. 3.7 Network Behavior. 3.8 Conclusions. 4 Connectivity in Ad Hoc Wireless Networks: A Physical Layer Perspective. 4.1 Introduction. 4.2 Quasi-regular Topology. 4.3 Random Topology. 4.4 Concluding Remarks and Discussion. 5 Effective Transport Capacity in Ad Hoc Wireless Networks. 5.1 Introduction. 5.2 Modeland Assumptions. 5.3 Preliminaries. 5.4 Single-Route Effective Transport Capacity. 5.5 Aggregate Effective Transport Capacity. 5.6 Comparison of the RESGO and RESLIGOMAC Protocols. 5.7 Spread-RESGO: Improved RESGOMAC Protocol with Per-route Spreading Codes. 5.8 Discussion. 5.9 Concluding Remarks. 6 Impact of Mobility on the Performance of Multi-hop Ad Hoc Wireless Networks. 6.1 Introduction. 6.2 Preliminaries. 6.3 Switching Models. 6.4 Mobility Models. 6.5 Numerical Results. 6.6 Conclusions. 7 Route Reservation in Ad Hoc Wireless Networks. 7.1 Introduction. 7.2 Related Work. 7.3 Network Models and Assumptions. 7.4 The Two Switching Schemes. 7.5 Analysis of the Two Switching Techniques. 7.6 Results and Discussion. 7.7 Concluding Remarks. 8 Optimal Common Transmit Power for Ad Hoc Wireless Networks. 8.1 Introduction. 8.2 Modeland Assumptions. 8.3 Connectivity. 8.4 BER at the End of a Multi-hop Route. 8.5 Optimal Common Transmit Power. 8.6 Performance Metrics. 8.7 Results and Discussion. 8.8 Related Work. 8.9 Conclusions. 9 Routing Problem in Ad Hoc Wireless Networks: A Cross-Layer Perspective. 9.1 Introduction. 9.2 Experimental Evidence. 9.3 Preliminaries: Analytical Models and Assumptions. 9.4 Route Selection: Simulation Study. 9.5 Network Performance Evaluation. 9.6 Discussion. 9.7 Related Work. 9.8 Conclusions. 10 Concluding Remarks. 10.1 Introduction. 10.2 Extensions of the Theoretical Framework: Open Problems. 10.3 Network Architectures. 10.4 Network Application Architectures. 10.5 Standards. 10.6 Applications. 10.7 Conclusions. Appendix A. Appendix B. Appendix C. Appendix D. Appendix E. References. Index.

Mobility Models for UAV Group Reconnaissance Applications

Abstract: In MANET research the mobility of the nodes is often described using standard synthetic models. Given a particular application, e.g. networks of unmanned aerial vehicles (UAVs) performing a cooperative task, the use of a standard synthetic mobility model can result in incorrect conclusions, as the movement pattern can impact the networking performance of the system. In this paper we present the criteria that characterize desirable mobility properties for the movement of UAVs in a reconnaissance scenario, and provide two mobility models for the scenario. In the first mobility model the UAVs move independently and randomly, and in the second model pheromones guide their movement. The random model is very simple but it achieves mediocre results. The pheromone model has very good scanning properties, but it has problems with respect to network connectivity. The study shows that there in an inherent conflict between the two goals of maximum coverage by frequent rescanning and adequate communication connectivity.

Modeling steady-state and transient behaviors of user mobility: formulation, analysis, and application

Abstract: Recent studies on mobility modeling have focused on characterizing user mobility from real traces of wireless LANs (WLANs)and creating mobility models based on such characterization. However, most of the work does not study how user mobility is correlated in time at different time scales. For example, the future APs with which a user will be associated are predicted without the knowledge of when the association will take place and for how long. In this paper, we build a mathematical model for characterizing both steady state and transient behaviors of user mobility in WLANs. Specifically, we mode user mobility by a semi-Markov process, and obtain the transition probability matrix and the sojourn time distribution from the association history of WLAN users available at Dartmouth college [21]. With the steady-state characterization of user mobility in WLANs, we can estimate the long-term wireless network usage among different access points. By comparing the steady-state distributions of semi-Markov models built based on trace data collected at different time scales, we are able to characterize the degree of correlation in time and location.We also perform a transient behavior analysis of the semi-Markov process (that characterizes user mobility), and devise a timed location prediction algorithm that accurately predicts the future locations of users both the future access points they will associate themselves with and the association duration. We demonstrate the utility of timed location prediction, by showing how it can be utilized to predict the distribution of future user ocations with the time information figured in, and redistributing loads among neighboring APs. An improvement of 80% (in terms of load balance) is observed in a wide spectrum of traffic loads in the simulation.

Building realistic mobility models from coarse-grained traces

Abstract: In this paper we present a trace-driven framework capable of building realistic mobility models for the simulation studies of mobile systems. With the goal of realism, this framework combines coarse-grained wireless traces, i.e., association data between WiFi users and access points, with an actual map of the space over which the traces were collected. Through a sequence of data processing steps, including filtering the data trace and converting the map to a graph representation, this framework generates a probabilistic mobility model that produces user movement patterns that are representative of real movement. This is done by adopting a set of heuristics that help us infer the paths users take between access points. We describe our experience applying this approach to a college campus, and study a number of properties of the trace data using our framework.

Sink mobility protocols for data collection in wireless sensor networks

Abstract: In wireless sensor networks data propagation is usually performed by sensors transmitting data towards a static control center (sink). Inspired by important applications (mostly related to ambient intelligence) and as a first step towards introducing mobility, we propose the idea of having a sink moving in the network area and collecting data from sensors. We propose four characteristic mobility patterns for the sink along with different data collection strategies. Through a detailed simulation study, we evaluate several important performance properties of each protocol. Our findings demonstrate that by taking advantage of the sink's mobility, we can significantly reduce the energy spent in relaying traffic and thus greatly extend the lifetime of the network.

A review of mobility support paradigms for the internet

Abstract: With the development of mobile communication and Internet technology, there is a strong need to provide connectivity for roaming devices to communicate to other communication end point in the Internet at any time and anywhere. The key issue of this vision is how to support mobility in TCP/IP networks. In this paper, we review the TCP/IP protocol stack and analyze the problems associated with it in a mobile environment. We then investigate the mobility support techniques and existing solutions to provide mobility support in the Internet. We classify the proposed solutions based on the protocol layers and present examples for each category. We also provide a comparison of the different solutions belonging to different categories and in the same category, including their advantages and disadvantages, and conclude that there is no single solution perfectly addresses mobility support for the Internet. We conclude this survey with a recommendation of features that need to be satisfied in Internet mobility support.

Island Hopping: Efficient Mobility-Assisted Forwarding in Partitioned Networks

Abstract: Mobile wireless ad hoc and sensor networks can be permanently partitioned in many interesting scenarios. This implies that instantaneous end-to-end routes do not exist. Nevertheless, when nodes are mobile, it is possible to forward messages to their destinations through mobility. We observe that in many practical settings, spatial node distributions are very heterogeneous and possess concentration points of high node density. The locations of these concentration points and the flow of nodes between them tend to be stable over time. This motivates a novel mobility model, where nodes move randomly between stable islands of connectivity, where they are likely to encounter other nodes, while connectivity is very limited outside these islands. Our goal is to exploit such a stable topology of concentration points by developing algorithms that allow nodes to collaborate to discover this topology and to use it for efficient mobility forwarding. We achieve this without any external signals to nodes, such as geographic positions or fixed beacons; instead, we rely only on the evolution of the set of neighbors of each node. We propose an algorithm for this collaborative graph discovery problem and show that the inferred topology can greatly improve the efficiency of mobility forwarding. Using both synthetic and data-driven mobility models we show through simulations that our approach achieves end-to-end delays comparable to those of epidemic approaches, while requiring a significantly lower transmission overhead

The Global In-Flight Internet

Abstract: In this paper, the concept of a new form of mobile network formed in the sky is introduced, where the mobile routers are simply the commercial aircraft. This implementation aims to eliminate two main problems arising from the current in-flight broadband implementation. The first problem is the resource management issue that may arise from the rapid increase of in-flight broadband Internet use in the near future. This could consequently limit current satellite resources, and bandwidth. The other issue is the inherent problem associated with Internet use over satellite, such as the degraded performance of delay sensitive applications due to the long propagation delay of a satellite link. A system model for data access, stable clustering of aircraft, and efficient routing schemes are introduced, which are suitable for the aeronautical mobility model. Link stability is predicted by a novel approach using Doppler shift subjected to control packets to dynamically form stable clustering and routing protocols. Another aim of this paper is to show that relative velocity between nodes is adequate as a stability metric, dominating relative distance, and this becomes evident in the simulations presented. An outline of how the new system could potentially interact with the traditional Internet using Mobile IP is also briefly discussed

A Comparative Study of Random Waypoint and Gauss-Markov Mobility Models in the Performance Evaluation of MANET

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.

Delay of intrusion detection in wireless sensor networks

Abstract: In this paper we consider sensor networks for intrusion detection, such that node deployment, node failures and node behavior result in coverage gaps and a fraction of disconnected nodes in an otherwise dense and well-connected network We focus on the time delay for a mobile intruder to be detected by a sensor with a connected path to the sink, in contrast to existing results for the detection time by a sensor with arbitrary connectivity We model our network using a supercritical percolation model on the plane, implying the existence of a unique unbounded connected component, and we assume that the sink belongs to this component We analyze the distribution of the distance traveled by a moving target until it comes within sensing range of a node in the giant component, providing analytical bounds for linear intruder mobility and thorough simulation results for other mobility models We show that the probability that the intruder proceeds undetected exhibits non-memoryless behavior over shorter distances and an exponentially decreasing tail We also show that the time of contact with the giant component incurs considerably more delay than the time of first contact with any node, in networks with less than 10% of nodes without a path to the sink, which means that even a small percentage of node failures may have a drastic impact on the performance of intrusion detection by a wireless sensor networ

Field-effect mobility temperature modeling of 4H-SiC metal-oxide-semiconductor transistors

Abstract: Here a physically based channel mobility model has been developed to investigate the temperature dependence of the field-effect mobility of 4H-SiC metal-oxide-semiconductor (MOS) transistors with thermally oxidized gate insulators. This model has been designed so that it accounts for the high density of traps at the MOS interface. This temperature dependence is a key issue for silicon carbide electronics, as its basic material properties make it the foremost semiconductor for high power/high temperature electronic devices in applications such as spacecraft, aircraft, automobile, and energy distribution. Our modeling suggests that the high density of charged acceptor interface traps, encountered in thermally grown gate oxides, modulates the channel mobility due to the Coulomb scattering of free carriers in the inversion layer. When the temperature increases, the field-effect mobility of these devices also increases, due to an increase in inversion charge and a reduction of the trapped charge. Experimental ...

Delay-tolerant broadcasting

Abstract: There are many asynchronous communication situations for which the prevalent continuous connectivity paradigm is not needed. Communication with a fair delay tolerance may instead be provided by intermittent store-and-forwarding between nodes. This paper proposes a design for an open, receiver-driven broadcasting system that relies on delay-tolerant forwarding of data chunks through mobility of wireless nodes. The system provides public broadcast channels, which can be openly used for both transmission and reception. We show by simulation under benchmark mobility models that a delay-tolerant broadcast channel has both a sufficiently high throughput and reach to be interesting as a competitive alternative to the regulated wireless broadcast channel. We also present the design of, and experiences with, a proof-of-concept prototype.

Analyzing the impact of mobility in ad hoc networks

Abstract: The impact of mobility on the link and route lifetimes in ad hoc networks is of major importance for the design of efficient MAC and network layer protocols. Up to now, no real-life measurements were used to study the effect of node mobility on link and route lifetime distributions. In this paper, we present data gathered from a real network of 20 test users and analyze it with regard to link and route lifetime distributions. Besides link breakage due to node mobility, links might also break due to diverse sources of interference or packet collisions. We develop a statistical framework to distinguish between the mobility and interference or collision errors. With this framework, we are able to determine and analyze the lifetime distributions for both error types separately. We use this framework together with our measurements to validate two commonly used stochastic mobility models including the random waypoint and the random reference group mobility model. The results show that the distributions of the two stochastic mobility models match very closely the empirical link lifetime distribution.

A general framework to construct stationary mobility models for the simulation of mobile networks

Abstract: Simulation has become an indispensable tool in the design and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. In this paper, we show that a large class of mobility models - including all those in which nodal speed and distance or destination are chosen independently - have a transient period in which the average node speed decreases until converging to some long-term average. This speed decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process. In this paper, we derive a general framework for describing this decay and apply it to a number of cases. Furthermore, this framework allows us to transform a given mobility model into a stationary one by initializing the simulation using the steady-state speed distribution and using the original speed distribution subsequently. This transformation completely eliminates the transient period and the decay in average node speed and, thus, provides sound models for the simulation of mobile systems.

Mobility models for vehicular ad hoc network simulations

Abstract: Considerable amount of research has been going on in the area of Vehicular Ad-Hoc networks (VANETS), where vehicles moving along streets in an urban city establish a network among themselves. There has been an increasing commercial and research interest in the development and deployment of such networks and the routing protocols used in these networks. Unfortunately the current state of the art mobility models for VANET simulations do not reproduce the characteristic movement of vehicles on the urban streets. They do not take into consideration the constrained movement of vehicles subject to street boundaries, stop signs, traffic lights and obstacles like buildings.Simulation is a very important tool for performance evaluation of ad-hoc networks. It enables us to conduct repeatable experiments under a controlled environment by isolating different parameters and varying them to study their affect on network performance. This would be highly costly and infeasible to accomplish in the real world. For close to accurate prediction of results, it is desirable that real world behavior is closely replicated while carrying out the simulations. The evaluation results need to be good predictors of protocol performance in the real world. The movement pattern of the nodes in the ad hoc networks is a factor that has a considerable impact on network performance. Mobility pattern is important in the sense that the position of nodes at any point of time, impacts the network connectivity which is central to the performance of the network. In this context, the mobility pattern of vehicles would play a crucial role in the performance evaluation of any VANET protocol done using simulations.Through this work, methods to capture the realistic mobility characteristics of vehicles on urban streets are proposed. These characteristics can then be used for carrying out more accurate simulations for VANETS. Two new simple mobility models that account for constrained movement patterns of vehicles on real world urban street maps are introduced. These two models incorporate the Stop Signs, Traffic Lights on the streets and interdependent motion of vehicles on same street. Also these traffic control mechanisms are enforced on real street maps available from US bureau database [2]. The mobility files generated by these models can be used by the network simulator ns2 [1] to carry out realistic simulations.

SIMPS: Using Sociology for Personal Mobility

Abstract: Assessing mobility in a thorough fashion is a crucial step toward more efficient mobile network design. Recent research on mobility has focused on two main points: analyzing models and studying their impact on data transport. These works investigate the consequences of mobility. In this paper, instead, we focus on the causes of mobility. Starting from established research in sociology, we propose SIMPS, a mobility model of human crowd motion. This model defines two complimentary behaviors, namely socialize and isolate, that regulate an individual with regard to her/his own sociability level. SIMPS leads to results that agree with scaling laws observed both in small-scale and large-scale human motion. Although our model defines only two simple individual behaviors, we observe many emerging collective behaviors (group formation/splitting, path formation, and evolution). To our knowledge, SIMPS is the first model in the networking community that tackles the roots governing mobility.

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

Abstract: 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.

A Survey of Research in Inter-Vehicle Communications

Abstract: As a component of the intelligent transportation system (ITS) and one of the concrete applications of mobile ad hoc networks, inter-vehicle communication (IVC) has attracted research attention from both academia and industry of, notably, US, EU, and Japan. The most important feature of IVC is its ability to extend the horizon of drivers and on-board devices (e.g., radar or sensors) and, thus, to improve road traffic safety and efficiency. This chapter surveys IVC with respect to key enabling technologies ranging from physical radio frequency to group communication primitives and security issues. The mobility models used to evaluate the feasibility of these technologies are also briefly described. We focus on the discussion of various MAC protocols that seem to be indispensable components in the network protocol stack of IVC. By analyzing the application requirements and the protocols built upon the MAC layer to meet these requirements, we also advocate our perspective that ad hoc routing protocols and group communication primitives migrated from wired networks might not be an efficient way to support the envisioned applications, and that new coordination algorithms directly based on MAC should be designed for this purpose.