Selim Gurun

Energy consumption and conservation in mobile peer-to-peer systems

Todays mobile devices are growing in number and computational resources. Devices capable of storing gigabytes of digital content are becoming ubiquitous, making them an ideal platform for peer-to-peer content delivery and sharing. However, the always on communication patterns of P2P networks is not a natural fit for energy-constrained mobile devices. In this paper, we perform a detailed study of energy consumption of a structured P2P overlay on a PDA device. Using actual energy measurements, we present energy consumption results for different type of operations in P2P overlays. Based on these observations, we implement an approach to improve energy conservation on P2P protocols and show some promising preliminary results.

NWSLite: a light-weight prediction utility for mobile devices

Computation off-loading, i.e., remote execution, has been shown to be effective for extending the computational power and battery life of resource-restricted devices, e.g., hand-held, wearable, and pervasive computers. Remote execution systems must predict the cost of executing both locally and remotely to determine when off-loading will be most beneficial. These costs however, are dependent upon the execution behavior of the task being considered and the highly-variable performance of the underlying resources, e.g., CPU (local and remote), bandwidth, and network latency. As such, remote execution systems must employ sophisticated, prediction techniques that accurately guide computation off-loading. Moreover, these techniques must be efficient, i.e., they cannot consume significant resources, e.g., energy, execution time, etc., since they are performed on the mobile device.In this paper, we present NWSLite, a computationally efficient, highly accurate prediction utility for mobile devices. NWSLite is an extension to the Network Weather Service (NWS), a dynamic forecasting toolkit for adaptive scheduling of high-performance Computational Grid applications. We significantly scaled down the NWS to reduce its resource consumption yet still achieve accuracy that exceeds that of extant remote execution prediction methods. We empirically analyze and compare both the prediction accuracy and the cost of NWSLite and a number of different forecasting methods from existing remote execution systems. We evaluate the efficacy of the different methods using a wide range of mobile applications and resources.

A run-time, feedback-based energy estimation model For embedded devices

We present an adaptive, feedback-based, energy estimation model for battery-powered embedded devices such as sensor network gate-ways and hand-held computers. Our technique maps hardware and software counters to energy consumption values using a set of first order, linear regression equations. Our system is novel in that it combines online and offline techniques to enable runtime power prediction. Our system employs an offline instantiated model that it continuously updates using feedback from a readily available battery monitor within the device. We empirically evaluate our model and detail its robustness, accuracy, and computational cost. We also analyze the stability of the model in the presence of feedback errors. We demonstrate that our approach can achieve an error rate of 1% (extant techniques: 2.6% to 4%) for computationally bound tasks and 6.6% (extant techniques: 11%) for communication bound tasks.

AutoDVS: an automatic, general-purpose, dynamic clock scheduling system for hand-held devices

We present AutoDVS, a dynamic voltage scaling (DVS) system for hand-held computers. Unlike extant DVS systems, AutoDVS distinguishes common, course-grain, program behavior and couples forecasting techniques to make accurate predictions of future behavior. AutoDVS uses these predictions in combination to guide dynamic voltage scaling. AutoDVS estimates periods of user interactivity, user non-interactivity (think time), and computation per-program and system wide to ensure quality of service while reducing energy consumption.We describe our implementation of AutoDVS which consists of a set light-weight, Linux, kernel modules and user library routines for the iPAQ hand-held computer. We evaluate AutoDVS using real user workloads of iPAQ software that consist of interactive and soft-real time tasks executing alone and concurrently. Our results indicate that AutoDVS decreases energy consumption significantly without negatively impacting user perception of system performance.

S 2 DB: a novel simulation-based debugger for sensor network applications

Sensor network computing can be characterized as resource-constrained distributed computing using unreliable, low bandwidth communication. This combination of characteristics poses significant software development and maintenance challenges. Effective and efficient debugging tools for sensor network are thus critical. Existent development tools, such as TOSSIM, EmStar, ATEMU and Avrora, provide useful debugging support, but not with the fidelity, scale and functionality that we believe are sufficient to meet the needs of the next generation of applications.In this paper, we propose a debugger, called S2DB, based on a distributed full system sensor network simulator with high fidelity and scalable performance, DiSenS. By exploiting the potential of DiSenS as a scalable full system simulator, S2DB extends conventional debugging methods by adding novel device level, program source level, group level, and network level debugging abstractions. The performance evaluation shows that all these debugging features introduce overhead that is generally less than 10% into the simulator and thus making S2DB an efficient and effective debugging tool for sensor networks.

NWSLite: A general-purpose, nonparametric prediction utility for embedded systems

Time series-based prediction methods have a wide range of uses in embedded systems. Many OS algorithms and applications require accurate prediction of demand and supply of resources. However, configuring prediction algorithms is not easy, since the dynamics of the underlying data requires continuous observation of the prediction error and dynamic adaptation of the parameters to achieve high accuracy. Current prediction methods are either too costly to implement on resource-constrained devices or their parameterization is static, making them inappropriate and inaccurate for a wide range of datasets. This paper presents NWSLite, a prediction utility that addresses these shortcomings on resource-restricted platforms.

On the Efficacy of Computation Offloading Decision-Making Strategies

We present a framework for making computation offloading decisions in computational grid settings in which schedulers determine when to move parts of a computation to more capable resources to improve performance. Such schedulers must predict when an offloaded computation will outperform one that is local by forecasting the local cost (execution time for computing locally) and remote cost (execution time for computing remotely and transmission time for the input/output of the computation to/from the remote system). Typically, this decision amounts to predicting the bandwidth between the local and remote systems to estimate these costs. Our framework unifies such decision models by formulating the problem as a statistical decision problem that can either be treated “classically” or using a Bayesian approach. Using an implementation of this framework, we evaluate the efficacy of a number of different decision strategies (several of which have been employed by previous systems). Our results indicate that a Bayesian approach employing automatic change-point detection when estimating the prior distribution is the best performing approach.

SimGate: Full-System, Cycle-Close Simulation of the Stargate Sensor Network Intermediate Node

We present SimGate - a full-system simulator for the Stargate intermediate-level, resource-constrained, sensor network device. We empirically evaluate the accuracy and performance of the system in isolation as well as coupled with simulated Mica2 motes. Our system is functionally correct and achieves accurate cycle estimation (i.e. cycle-close). Moreover, the overhead of simulated execution is modest with respect to previously published work

Accurate and scalable simulation of network of heterogeneous sensor devices

A new method was proposed for constructing total variation diminishing (TVD) upwind schemes in conservation forms. Two limiters were used to prevent non-physical oscillations across discontinuity. Both limiters can ensure the nonlinear compact schemes TVD property. Two compact TVD (CTVD) schemes were tested, one is third-order accuracy, and the other is fifth-order. The performance of the numerical algorithms was assessed by one-dimensional complex waves and Riemann problems, as well as a two-dimensional shock-vortex interaction and a shock-boundary flow interaction. Numerical results show their high-order accuracy and high resolution, and low oscillations across discontinuities.更多还原The globed solution for a coupled nonlinear Klein-Gordon system in two-dimensional space was studied. First, a sharp threshold of blowup and global existence for the system was obtained by constructing a type of cross-constrained variational problem and establishing so-called cross-invariant manifolds of the evolution flow. Then the result of how small the initial data for which the solution exists globally was proved by using the scaling argument.Both a real time optical interferometric experiment and a numerical simulation of two-dimension non-steady state model were employed to study the growth process of aqueous sodium chlorate crystals. The parameters such as solution concentration distribution, crystal dimensions, growth rate and velocity field were obtained by both experiment and numerical simulation. The influence of earth gravity during crystal growth process was analyzed. A reasonable theory model corresponding to the present experiment is advanced. The thickness of concentration boundary layer was investigated especially. The results from the experiment and numerical simulation match well.Based on the large deflection dynamic equations of axisymmetric shallow shells of revolution, the nonlinear forced vibration of a corrugated shallow shell under uniform load is investigated. The nonlinear partial differential equations of shallow shell are reduced to the nonlinear integral-differential equations by the method of Green’s function. To solve the integral-differential equations, expansion method is used to obtain Green’s function. Then the integral-differential equations are reduced to the form with degenerate core by expanding Green’s function as series of characteristic function. Therefore, the integral-differential equations become nonlinear ordinary differential equations with regard to time. The amplitude-frequency response under harmonic force is obtained by considering single mode vibration. As a numerical example, forced vibration phenomena of shallow spherical shells with sinusoidal corrugation are studied. The obtained solutions are available for reference to design of corrugated shells更多还原As vibration-based structural damage detection methods are easily affected by environmental noise, a new statistic-based noise analysis method is proposed together with the Monte Carlo technique to investigate the influence of experimental noise of modal data on sensitivity-based damage detection methods. Different from the commonly used random perturbation technique, the proposed technique is deduced directly by Moore-Penrose generalized inverse of the sensitivity matrix, which does not only make the analysis process more efficient but also can analyze the influence of noise on both frequencies and mode shapes for three commonly used sensitivity-based damage detection methods in a similar way. A one-story portal frame is adopted to evaluate the efficiency of the proposed noise analysis technique.更多还原A new class of generalized mixed implicit quasi-equilibrium problems (GMIQEP) with four-functions is introduced and studied. The new class of equilibrium problems includes many known generalized equilibrium problems and generalized mixed implicit quasi-variational inequality problems as many special cases. By employing the auxiliary principle technique, some predictor-corrector iterative algorithms for solving the GMIQEP are suggested and analyzed. The convergence of the suggested algorithm only requires the continuity and the partially relaxed implicit strong monotonicity of the mappings.A nonlinear Galerkin mixed element (NGME) method for the stationary incompressible magnetohydrodynamics equations is presented. And the existence and error estimates of the NGME solution are derived.The Newtonian method is employed to obtain nonlinear mathematical model of motion of a horizontally cantilevered and inflexible pipe conveying fluid. The order magnitudes of relevant physical parameters are analyzed qualitatively to establish a foundation on the further study of the model. The method of multiple scales is used to obtain eigenfunctions of the linear free-vibration modes of the pipe. The boundary conditions yield the characteristic equations from which eigenvalues can be derived. It is found that flow velocity in the pipe may induced the 3:1, 2:1 and 1:1 internal resonances between the first and second modes such that the mechanism of flow-induced internal resonances in the pipe under consideration is explained theoretically. The 3:1 internal resonance first occurs in the system and is, thus, the most important since it corresponds to the minimum critical velocity.更多还原The possible intermittent impacts of a two-stage isolation system with rigid limiters have been investigated. The isolation system is under periodic external excitation disturbed by small stationary Gaussian white noise after shock. The maximal impact Poincare map is proposed based on the multi-body dynamics with unilateral constrains. Then in the period after shock, the zero order approximate stochastic discrete model and the first order approximate stochastic model are developed. The real isolation system of an MTU diesel engine is used to evaluate the established model. After calculating of the numerical example, the effects of noise excitation on the isolation system are discussed. The results show that the property of the system is complicated due to intermittent impact. The difference between zero order model and the first order model may be great. The effect of small noise is obvious. The results may be expected useful to the naval designers.更多还原In a vertically oscillating circular cylindrical container, singular perturbation theory of two-time scale expansions is developed in weakly viscous fluids to investigate the motion of single free surface standing wave by linearizing the Navier-Stokes equation. The fluid field is divided into an outer potential flow region and an inner boundary layer region. The solutions of both two regions are obtained and a linear amplitude equation incorporating damping term and external excitation is derived. The condition to appear stable surface wave is obtained and the critical curve is determined. In addition, an analytical expression of damping coefficient is determined. Finally, the dispersion relation, which has been derived from the inviscid fluid approximation, is modified by adding linear damping. It is found that the modified results are reasonably closer to experimental results than former theory. Result shows that when forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when forcing frequency is high, the surface tension of the fluid is prominent.The reduction approaches are presented for vibration control of symmetric, cyclic periodic and linking structures. The condensation of generalized coordinates, the locations of sensors and actuators, and the relation between system inputs and control forces are assumed to be set in a symmetric way so that the control system posses the same repetition as the structure considered. By employing proper transformations of condensed generalized coordinates and the system inputs, the vibration control of an entire system can be implemented by carrying out the control of a number of sub-structures, and thus the dimension of the control problem can be significantly reduced.A class of Hopfield neural network with time-varying delays and impulsive effects is concerned. By applying the piecewise continuous vector Lyapunov function some sufficient conditions were obtained to ensure the global exponential stability of impulsive delay neural networks. An example and its simulation are given to illustrate the effectiveness of the results.It is demonstrated that when tension leg platform (TLP) moves with finite amplitude in waves, the inertia force, the drag force and the buoyancy acting on the platform are nonlinear functions of the response of TLP. The tensions of the tethers are also nonlinear functions of the displacement of TLP. Then the displacement, the velocity and the acceleration of TLP should be taken into account when loads are calculated. In addition, equations of motions should be set up on the instantaneous position. A theoretical model for analyzing the nonlinear behavior of a TLP with finite displacement is developed, in which multifold nonlinearities are taken into account, i.e., finite displacement, coupling of the six degrees of freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force. Based on the theoretical model, the comprehensive nonlinear differential equations are deduced. Then the nonlinear dynamic analysis of ISSC TLP in regular waves is performed in the time domain. The degenerative linear solution of the proposed nonlinear model is verified with existing published one. Furthermore, numerical results are presented, which illustrate that nonlinearities exert a significant influence on the dynamic responses of the TLP.