Results 1  10
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159
User mobility modeling and characterization of mobility patterns
 IEEE Journal on Selected Areas in Communications
, 1997
"... Abstract—A mathematical formulation is developed for systematic tracking of the random movement of a mobile station in a cellular environment. It incorporates mobility parameters under the most generalized conditions, so that the model can be tailored to be applicable in most cellular environments. ..."
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Cited by 140 (0 self)
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Abstract—A mathematical formulation is developed for systematic tracking of the random movement of a mobile station in a cellular environment. It incorporates mobility parameters under the most generalized conditions, so that the model can be tailored to be applicable in most cellular environments. This mobility model is used to characterize different mobilityrelated traffic parameters in cellular systems. These include the distribution of the cell residence time of both new and handover calls, channel holding time, and the average number of handovers. It is shown that the cell resistance time can be described by the generalized gamma distribution. It is also shown that the negative exponential distribution is a good approximation for describing the channel holding time. Index Terms—Mobile communication. I.
Population Dynamics of Spiking Neurons: Fast Transients, Asynchronous States, and Locking
 NEURAL COMPUTATION
, 2000
"... An integral equation describing the time evolution of the population activity in a homogeneous pool of spiking neurons of the integrateandfire type is discussed. It is analytically shown that transients from a state of incoherent firing can be immediate. The stability of incoherent firing is analy ..."
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Cited by 134 (25 self)
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An integral equation describing the time evolution of the population activity in a homogeneous pool of spiking neurons of the integrateandfire type is discussed. It is analytically shown that transients from a state of incoherent firing can be immediate. The stability of incoherent firing is analyzed in terms of the noise level and transmission delay and a bifurcation diagram is derived. The response of a population of noisy integrateandfire neurons to an input current of small amplitude is calculated and characterized by a linear filter L. The stability of perfectly synchronized `locked' solutions is analyzed.
Neuronal spike trains and stochastic point processes. II. Simultaneous spike trains
 Biophys. J
, 1967
"... AsTRAcT The statistical analysis oftwo simultaneously observed trainsofneuronal spikes is described, using as a conceptual framework the theory of stochastic point processes. The first statistical question that arises is whether the observed trains are independent; statistical techniques for testing ..."
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Cited by 115 (1 self)
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AsTRAcT The statistical analysis oftwo simultaneously observed trainsofneuronal spikes is described, using as a conceptual framework the theory of stochastic point processes. The first statistical question that arises is whether the observed trains are independent; statistical techniques for testing independence are developed around the notion that, under the null hypothesis, the times of spike occurrence in one train represent random instants in time with respect to the other. Ifthe null hypothesis is rejectedif dependence is attributed to the trainsthe problem then becomes that of characterizing the nature and source of the observed dependencies. Statistical signs of various classes of dependencies, including direct interaction and shared input, are discussed and illustrated through computer simulations of interacting neurons. The effects ofnonstationarities on the statistical measures for simultaneous spike trains are also discussed. For twotrain comparisons of irregularly discharging nerve cells, moderate nonstationarities areshown tohave little effecton the detection of interactions. Combining repetitive stimulation and simultaneous recording of spike trains from two (or more) neurons yields additional clues as to possible modes of interaction among the monitored neurons; the theory presented is illustrated by an application to experimentally obtained data from auditory neurons. Acompanion paper covers the analysis ofsingle spike trains.
High timeresolution measurement and analysis of LAN traffic: Implications for LAN interconnection
, 1991
"... The interconnection of local area networks is increasingly important, but little data are available on the characteristics of the aggregate traffic that LANs will be submitting to the interconnection media. In order to understand the interactions between LANs and the proposed interconnection network ..."
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Cited by 99 (1 self)
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The interconnection of local area networks is increasingly important, but little data are available on the characteristics of the aggregate traffic that LANs will be submitting to the interconnection media. In order to understand the interactions between LANs and the proposed interconnection networks (MANs, WANs, and BISDN networks), it is necessary to study the behavior of this external LAN traffic over many time scales – from milliseconds to hundreds of seconds. We present a high timeresolution hardware monitor for Ethernet LANs that avoids the shortcomings of previous monitoring tools, such as traffic burst clipping and timestamp jitter. Using data recorded by our monitor for several hundred million Ethernet packets, we present an overview of the shortrange time correlations in external LAN traffic. Our analysis shows that LAN traffic is extremely bursty across time domains spanning six orders of magnitude. We compare this behavior with simple formal traffic models and employ the data in a tracedriven simulation of the LANBISDN interface proposed for the SMDS SM service. Our results suggest that the pronounced shortterm traffic correlations, together with the extensive time regime of traffic burstiness, strongly influence the patterns of loss and delay induced by LAN interconnection. 1.
Local Area Network Traffic Characteristics, with Implications for Broadband Network Congestion Management
"... This paper examines the phenomenon of congestion in order to better understand the congestion management techniques that will be needed in highspeed, cellbased networks. The first step of this study is to use high timeresolution local area network (LAN) traffic data to explore the nature of LAN t ..."
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Cited by 92 (0 self)
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This paper examines the phenomenon of congestion in order to better understand the congestion management techniques that will be needed in highspeed, cellbased networks. The first step of this study is to use high timeresolution local area network (LAN) traffic data to explore the nature of LAN traffic variability. Then, we use the data for a tracedriven simulation of a connectionless service that provides LAN interconnection. The simulation allows us to characterize what congestion might look like in a highspeed, cellbased network. The most
Is finding security holes a good idea
 IEEE Security & Privacy
, 2005
"... Alarge amount of effort is expended every year on finding and patching security holes. The underlying rationale for this activity is that it increases welfare by decreasing the number of vulnerabilities available for discovery and exploitation by bad guys, thus reducing the total cost of intrusions. ..."
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Cited by 55 (0 self)
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Alarge amount of effort is expended every year on finding and patching security holes. The underlying rationale for this activity is that it increases welfare by decreasing the number of vulnerabilities available for discovery and exploitation by bad guys, thus reducing the total cost of intrusions. Given the amount of effort expended, we would expect to see noticeable results in terms of improved software quality. However, our investigation provides a mixed answer: the data does not allow us to exclude the possibility that the rate of vulnerability finding in any given piece of software is constant over long periods of time. Ifthere islittle or no quality improvement, then we have no reason to believe that that the disclosure of vulnerabilities reduces the overall cost of intrusions. 1
Point Process Approaches for Modeling and Analysis of SelfSimilar Traffic: Part II  Applications
, 1997
"... In previous work [24], Fractal Point Processes (FPPs) have been proposed as novel tools for understanding, modeling and analyzing diverse types of selfsimilar traffic behavior. We apply the FPP models in the context of network traffic modeling and performance analysis. Two qualitatively different f ..."
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Cited by 50 (8 self)
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In previous work [24], Fractal Point Processes (FPPs) have been proposed as novel tools for understanding, modeling and analyzing diverse types of selfsimilar traffic behavior. We apply the FPP models in the context of network traffic modeling and performance analysis. Two qualitatively different fractal data sets (Bellcore Ethernet traces) are characterized by FPP models. Comparison of modeldriven and tracedriven queueing simulation results show that the matched models yield close agreement with the traces over a wide range of system parameters. We also show that under suitable conditions, the FPP models yield Gaussian processes. Queueing simulation shows that the FPP models can be computationally efficient alternatives for generating fractional Gaussian noise processes. Finally, we divide fractal traffic into two types, applicationlevel fractal traffic and networklevel fractal traffic, and argue that each type has radically different implications for the design and control of fut...
A Study of the Reliability of Internet Sites
, 1991
"... Modeling &e reliability of distributed systems requires a good understanding of the reliability of the components'. Careful modeling allows highly faulttolerant distributed data applications to be constructed at the least cost. Failure and repair ..."
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Cited by 48 (6 self)
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Modeling &e reliability of distributed systems requires a good understanding of the reliability of the components'. Careful modeling allows highly faulttolerant distributed data applications to be constructed at the least cost. Failure and repair
Ip covert timing channels: design and detection
 In CCS ’04: Proceedings of the 11th ACM conference on Computer and communications security
, 2004
"... A network covert channel is a mechanism that can be used to leak information across a network in violation of a security policy and in a manner that can be difficult to detect. In this paper, we describe our implementation of a covert network timing channel, discuss the subtle issues that arose in i ..."
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Cited by 45 (1 self)
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A network covert channel is a mechanism that can be used to leak information across a network in violation of a security policy and in a manner that can be difficult to detect. In this paper, we describe our implementation of a covert network timing channel, discuss the subtle issues that arose in its design, and present performance data for the channel. We then use our implementation as the basis for our experiments in its detection. We show that the regularity of a timing channel can be used to differentiate it from other traffic and present two methods of doing so and measures of their efficiency. We also investigate mechanisms that attackers might use to disrupt the regularity of the timing channel, and demonstrate methods of detection that are effective against them.
Noise in IntegrateandFire Neurons: From Stochastic Input to Escape Rates
 TO APPEAR IN NEURAL COMPUTATION.
, 1999
"... We analyze the effect of noise in integrateandfire neurons driven by timedependent input, and compare the diffusion approximation for the membrane potential to escape noise. It is shown that for timedependent subthreshold input, diffusive noise can be replaced by escape noise with a hazard funct ..."
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Cited by 41 (6 self)
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We analyze the effect of noise in integrateandfire neurons driven by timedependent input, and compare the diffusion approximation for the membrane potential to escape noise. It is shown that for timedependent subthreshold input, diffusive noise can be replaced by escape noise with a hazard function that has a Gaussian dependence upon the distance between the (noisefree) membrane voltage and threshold. The approximation is improved if we add to the hazard function a probability current proportional to the derivative of the voltage. Stochastic resonance in response to periodic input occurs in both noise models and exhibits similar characteristics.