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147
Stationary Distributions for the Random Waypoint Mobility Model
 IEEE Transactions on Mobile Computing
, 2003
"... In simulations of mobile ad hoc networks, the probability distribution governing the movement of the nodes typically varies over time, and converges to a "steadystate" distribution, known in the probability literature as the stationary distribution. Some published simulation results ig ..."
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Cited by 188 (7 self)
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In simulations of mobile ad hoc networks, the probability distribution governing the movement of the nodes typically varies over time, and converges to a "steadystate" 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.
Extracting a mobility model from real user traces
 In Proceedings of IEEE INFOCOM
, 2006
"... Abstract — Understanding user mobility is critical for simulations 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 p ..."
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Cited by 167 (1 self)
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Abstract — Understanding user mobility is critical for simulations 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 alwayson WiFi devices from a 13month trace. We discovered that the speed and pause time each follow a lognormal 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%. I.
Access and Mobility of Wireless PDA Users
"... In this paper, we analyze the mobility patterns of users of wireless handheld PDAs in a campus wireless network using an 11 week trace of wireless network activity. Our study has three goals. First, we characterize the highlevel mobility and access patterns of handheld PDA users and compare these c ..."
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Cited by 142 (4 self)
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In this paper, we analyze the mobility patterns of users of wireless handheld PDAs in a campus wireless network using an 11 week trace of wireless network activity. Our study has three goals. First, we characterize the highlevel mobility and access patterns of handheld PDA users and compare these characteristics to previous workload mobility studies focused on laptop users. Second, we develop two wireless network topology models for use in wireless mobility studies: an evolutionary topology model based on user proximity and a campus waypoint model that serves as a tracebased complement to the random waypoint model. Finally, we use our wireless network topology models as a case study to evaluate adhoc routing algorithms on the network topologies created by the access and mobility patterns of users of modern wireless PDAs.
Perfect Simulation and Stationarity of a Class of Mobility Models
 in IEEE Infocom
, 2005
"... Abstract — We define “random trip", a generic mobility model for independent mobiles that contains as special cases: the random waypoint on convex or non convex domains, random walk with reflection or wrapping, city section, space graph and other models. We use Palm calculus to study the model ..."
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Cited by 106 (3 self)
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Abstract — We define “random trip", a generic mobility model for independent mobiles that contains as special cases: the random waypoint on convex or non convex domains, random walk with reflection or wrapping, city section, space graph and other models. We use Palm calculus to study the model and give a necessary and sufficient condition for a stationary regime to exist. When this condition is satisfied, we compute the stationary regime and give an algorithm to start a simulation in steady state (perfect simulation). The algorithm does not require the knowledge of geometric constants. For the special case of random waypoint, we provide for the first time a proof and a sufficient and necessary condition of the existence of a stationary regime. Further, we extend its applicability to a broad class of non convex and multisite examples, and provide a readytouse algorithm for perfect simulation. For the special case of random walks with reflection or wrapping, we show that, in the stationary regime, the mobile location is uniformly distributed and is independent of the speed vector, and that there is no speed decay. Our framework provides a rich set of well understood models that can be used to simulate mobile networks with independent node movements. Our perfect sampling is implemented to use with ns2, and it is freely available to download from
Towards Mobility as a Network Control Primitive
 In MobiHoc ’04: Proceedings of the 5th ACM international symposium on Mobile ad hoc networking and computing
, 2004
"... In the near future, the advent of largescale networks of mobile agents autonomously performing longterm sensing and communication tasks will be upon us. However, using controlled node mobility to improve communication performance is a capability that the mobile networking community has not yet inv ..."
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Cited by 106 (1 self)
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In the near future, the advent of largescale networks of mobile agents autonomously performing longterm sensing and communication tasks will be upon us. However, using controlled node mobility to improve communication performance is a capability that the mobile networking community has not yet investigated. In this paper, we study mobility as a network control primitive. More specifically, we present the first mobility control scheme for improving communication performance in such networks. Our scheme is completely distributed, requiring each node to possess only local information. Our scheme is selfadaptive, being able to transparently encompass several modes of operation, each respectively improving power efficiency for one unicast flow, multiple unicast flows, and manytoone concast flows. We provide extensive evaluations on the feasibility of mobility control, showing that controlled mobility can improve network performance in many scenarios. This work constitutes a novel application of distributed control to networking in which underlying network communication serves as input to local control rules that guide the system toward a global objective.
MOCA: Mobile certificate authority for wireless ad hoc networks
 In Proceedings of the 2nd Annual PKI Research Workshop (PKI 03
, 2003
"... An authentication service is one of the the most fundamental building blocks for providing communication security. In this paper, we present the MOCA (MObile Certificate Authority) key management framework designed to provide authentication service for ad hoc wireless networks. MOCA is a distributed ..."
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Cited by 94 (4 self)
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An authentication service is one of the the most fundamental building blocks for providing communication security. In this paper, we present the MOCA (MObile Certificate Authority) key management framework designed to provide authentication service for ad hoc wireless networks. MOCA is a distributed certificate authority (CA) based on threshold cryptography. We present a set of guidelines for a secure configuration of threshold cryptography to maintain strong security. MOCA utilizes a carefully selected set of mobile nodes to function as a collective certificate authority while the MOCA nodes are kept anonymous. Equipped with a novel routing protocol designed to support the unique communication pattern for certification traffic, MOCA achieves high availability without sacrificing security. Both the security of the framework and the operational performance is evaluated with rigorous analysis and extensive simulation study. 1
Modeling media access in embedded twoflow topologies of multihop wireless networks
 In Proceedings of ACM MobiCom ’05
, 2005
"... In this paper, we decompose a large or smallscale multihop wireless network into embedded subgraphs, each consisting of four nodes and two flow pairs. We systematically study all twelve possible topologies that arise according to whether the different nodes are in radio range of each other. We sh ..."
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Cited by 73 (14 self)
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In this paper, we decompose a large or smallscale multihop wireless network into embedded subgraphs, each consisting of four nodes and two flow pairs. We systematically study all twelve possible topologies that arise according to whether the different nodes are in radio range of each other. We show that under both a random spatial distribution of nodes and random waypoint mobility with shortestpath routing, a critical and highly probable scenario is a class in which the channel state shared by the two flows is not only incomplete (i.e., the graph is not fully connected), but there is also asymmetry in the state between the two flows. We develop an accurate analytical model validated by simulations to characterize the longterm unfairness that naturally arises when CSMA with twoor fourway handshake is employed as a random access protocol. Moreover, we show that another key class of topologies consists of incomplete but symmetric shared state. We show via modeling and simulations that in this case, the system achieves longterm fairness, yet endures significant durations in which one flow dominates channel access with many repeated transmissions before relinquishing the channel. The model predicts the timescales of this unfairness as a function of system parameters such as the maximum retransmission limit.
Logical Neighborhoods: A programming abstraction for wireless sensor networks
 In Proc. of the the 2 st Int. Conf. on Distributed Computing on Sensor Systems (DCOSS
, 2006
"... Abstract. Wireless sensor networks (WSNs) typically exploit a single base station for collecting data and coordinating activities. However, decentralized architectures are rapidly emerging, as witnessed by wireless sensor and actuator networks (WSANs), and in general by solutions involving multiple ..."
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Cited by 63 (19 self)
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Abstract. Wireless sensor networks (WSNs) typically exploit a single base station for collecting data and coordinating activities. However, decentralized architectures are rapidly emerging, as witnessed by wireless sensor and actuator networks (WSANs), and in general by solutions involving multiple data sinks, heterogeneous nodes, and innetwork coordination. These settings demand new programming abstractions to tame complexity without sacrificing efficiency. In this work we introduce the notion of logical neighborhood, which replaces the physical neighborhood provided by wireless broadcast with a higherlevel, applicationdefined notion of proximity. The span of a logical neighborhood is specified declaratively based on the characteristics of nodes, along with requirements about communication costs. This paper presents the SPIDEY programming language for defining logical neighborhoods, and a routing strategy that efficiently supports the communication enabled by its programming constructs. 1
Building realistic mobility models from coarsegrained traces
 in Proc. MobiSys
, 2006
"... In this paper we present a tracedriven framework capable of building realistic mobility models for the simulation studies of mobile systems. With the goal of realism, this framework combines coarsegrained wireless traces, i.e., association data between WiFi users and access points, with an actual ..."
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Cited by 51 (5 self)
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In this paper we present a tracedriven framework capable of building realistic mobility models for the simulation studies of mobile systems. With the goal of realism, this framework combines coarsegrained 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.
The critical transmitting range for connectivity in mobile ad hoc networks
 IEEE Transactions on Mobile Computing
, 2005
"... this paper, we study the critical transmitting range (CTR) for connectivity in mobile ad hoc networks. We prove that ln n rM c n for some constant c 1, where rM is the CTR in the presence of Mlike node mobility and n is the number of network nodes. Our result holds for an arbitrary mobility model ..."
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Cited by 48 (3 self)
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this paper, we study the critical transmitting range (CTR) for connectivity in mobile ad hoc networks. We prove that ln n rM c n for some constant c 1, where rM is the CTR in the presence of Mlike node mobility and n is the number of network nodes. Our result holds for an arbitrary mobility model M such that: 1) M is obstacle free and 2) nodes are allowed to move only within a certain bounded area. We also investigate in detail the case of random waypoint mobility, which is the most common mobility model used in the simulation of ad hoc networks. Denoting with rw p the CTR with random waypoint mobility when the pause time is set to p and node velocity is set to v, we prove that rw qffiffiffiffiffi pþ0:521405 v ln n p p n if p>0 and that rw qffiffiffiffiffi ln n 0 n. The results of our simulations also suggest that if n is large enough (n 50), rw r 0 is well approximated by 4 ln n, where r is the critical range in case of uniformly distributed nodes. The results presented in this paper provide a better understanding of the behavior of a fundamental network parameter in the presence of mobility and can be used to improve the accuracy of mobile ad hoc network simulations. Index Terms—Critical transmitting range, connectivity, random waypoint model, mobility modeling, ad hoc networks. æ 1