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189
Manet simulation studies: The incredibles
- ACM SIGMOBILE Mobile Computing and Communications Review
, 2005
"... Simulation is the research tool of choice for a majority of the mobile ad hoc network (MANET) community. However, while the use of simulation has increased, the credibility of the simulation results has decreased. To determine the state of MANET simulation studies, we surveyed the 2000-2005 proceedi ..."
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Cited by 164 (0 self)
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Simulation is the research tool of choice for a majority of the mobile ad hoc network (MANET) community. However, while the use of simulation has increased, the credibility of the simulation results has decreased. To determine the state of MANET simulation studies, we surveyed the 2000-2005 proceedings of the ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc). From our survey, we found significant shortfalls. We present the results of our survey in this paper. We then summarize common simulation study pitfalls found in our survey. Finally, we discuss the tools available that aid the development of rigorous simulation studies. We offer these results to the community with the hope of improving the credibility of MANET simulation-based studies. I.
Sound Mobility Models
- in ACM MobiCom
, 2003
"... 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. Unfortunately, the vast majority of mobility models---including all those in which nodal speed and distance ..."
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Cited by 147 (2 self)
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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. Unfortunately, the vast majority of mobility models---including all those in which nodal speed and distance or destination are chosen independently--- su#er from decay ; average speed decreases until converging to some long-term average. Such decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process.
The message delay in mobile ad hoc networks
, 2005
"... A stochastic model is introduced that accurately models the message delay in mobile ad hoc networks where nodes relay messages and the networks are sparsely populated. The model has only two input parameters: the number of nodes and the parameter of an exponential distribution which describes the ti ..."
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Cited by 140 (5 self)
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A stochastic model is introduced that accurately models the message delay in mobile ad hoc networks where nodes relay messages and the networks are sparsely populated. The model has only two input parameters: the number of nodes and the parameter of an exponential distribution which describes the time until two random mobiles come within communication range of one another. Closed-form expressions are obtained for the Laplace–Stieltjes transform of the message delay, defined as the time needed to transfer a message between a source and a destination. From this we derive both a closed-form expression and an asymptotic approximation (as a function of the number of nodes) of the expected message delay. As an additional result, the probability distribution function is obtained for the number of copies of the message at the time the message is delivered. These calculations are carried out for two protocols: the two-hop multicopy and the unrestricted multicopy protocols. It is shown that despite its simplicity, the model accurately predicts the message delay for both relay strategies for a number of mobility models (the random waypoint, random direction and the random walker mobility models).
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 multi-site examples, and provide a ready-to-use 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 ns-2, and it is freely available to download from
Wireless Ad Hoc Podcasting
, 2007
"... Podcasting has become popular for dissemination of streaming contents over the Internet. It is based on software clients that query servers for updates of subscribed content feeds. Podcasting may be used for any media content, but it is most commonly associated with audio streams. It provides a sim ..."
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Cited by 80 (4 self)
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Podcasting has become popular for dissemination of streaming contents over the Internet. It is based on software clients that query servers for updates of subscribed content feeds. Podcasting may be used for any media content, but it is most commonly associated with audio streams. It provides a simple, no-frills broadcasting system for delay tolerant contents. A main limitation with this system is the inflexible separation of downloading to a docked media player and expending of the data when on the move. We herein present how podcast could be supported by our previously proposed delay-tolerant broadcasting system in order to reduce the expected times between updates and to provide a new ad hoc podcasting mode among mobile nodes. Our system substitutes the client-server paradigm inherent in present podcasting by a peer-to-peer paradigm where mobile nodes provide each other with contents. We present the protocol for this, and an evaluation of solicitation and caching strategies that greatly affect the application-level throughput. Our design is aiming at simplicity in order to enable implementation in mobile phones with media players and other devices that communicate over short ranges by means of Bluetooth or wireless LAN.
Spatial Node Distribution of the Random Waypoint Mobility Model with Applications
- IEEE TRANSACTIONS ON MOBILE COMPUTING
, 2006
"... 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 fo ..."
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Cited by 62 (11 self)
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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.
Building realistic mobility models from coarse-grained traces
- in Proc. MobiSys
, 2006
"... 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 ..."
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Cited by 51 (5 self)
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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.
Improving the Accuracy of Random Waypoint Simulations through Steady-State Initialization
, 2004
"... 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 ignor ..."
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Cited by 47 (10 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 "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 not always reliable. If, however, the initial locations and speeds of the nodes are chosen from the stationary distribution, convergence is immediate and no data need be discarded.
Location Privacy in Wireless Networks
- In ACM SIGCOMM Asia Workshop
, 2005
"... Though an increasing number of wireless hotspots and mesh networks are being deployed, the problem of location privacy has been ignored. When a user’s location privacy is compromised, an attacker can determine where the user is, and use this information, for example, to stalk or blackmail the user. ..."
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Cited by 46 (5 self)
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Though an increasing number of wireless hotspots and mesh networks are being deployed, the problem of location privacy has been ignored. When a user’s location privacy is compromised, an attacker can determine where the user is, and use this information, for example, to stalk or blackmail the user. In existing systems, a user’s location can be easily inferred from the signal strengths of packets transmitted from her fixed address. Even if an attacker cannot decode packet contents and addresses, he can correlate different transmissions using a model of the user’s movement. In this paper, we argue that location privacy must be a first-class citizen in the design of a wireless communications system. We build a transaction-based wireless communication system in which transactions (a single request-response exchange between two nodes) are unlinkable; that is, they cannot be correlated. We find that it is even possible to support real-time session-based services such as Voice-over-IP on top of transaction primitives, though with weaker privacy properties. We also identify a number of challenges in providing location privacy in the areas of routing, incentives for multi-hop forwarding, and user- and application-driven tuning of the privacy-performance tradeoff.
Perfect simulations for random trip mobility models
- In Proc. of the 38th Annual Symposium on Simulation
, 2005
"... The random trip model was recently proposed as a generic mobility model that contains many particular mobility models, including the widely-known random waypoint and random walks, and accommodates more realistic scenarios. The probability distribution of the movement of a mobile in all these models ..."
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Cited by 44 (0 self)
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The random trip model was recently proposed as a generic mobility model that contains many particular mobility models, including the widely-known random waypoint and random walks, and accommodates more realistic scenarios. The probability distribution of the movement of a mobile in all these models typically varies with time and converges to a “steady state " distribution (viz. stationary distribution), whenever the last exists. Protocol performance during this transient phase and in steady-state may differ significantly. This justifies the interest in perfect sampling of the initial node mobility state, so that the simulation of the node mobility is perfect, i.e. it is in steady state throughout a simulation. In this work, we describe implementation of the perfect sampling for some random trip models. Our tool produces a perfect sample of the node mobility state, which is then used as input to the widelyused ns-2 network simulator. We further show some simulation results for a particular random trip mobility model, based on a real-world road map. The performance metrics that we consider include various node communication properties and their evolution with time. The results demonstrate difference between transient and steady-state phases and that the transient phase can be long lasting (in the order of a typical simulation duration), if the initial state is drawn from a non steady-state distribution. The results give strong arguments in favor to running perfect simulations. Our perfect sampling tool is available to public at:
