Electrical Engineering and Computer Science

An Evolutionary Multi-Objective Crowding Algorithm (EMOCA): Benchmark Test Function Results

Ramesh Rajagopalan et al. — Fri, 08 Mar 2013 08:23:17 PST

A new evolutionary multi-objective crowding algorithm (EMOCA) is evaluated using nine benchmark multiobjective optimization problems, and shown to produce non-dominated solutions with significant diversity, outperforming state-of-the-art multi-objective evolutionary algorithms viz., Non-dominated Sorting Genetic Algorithm – II (NSGA-II), Strength Pareto Evolutionary algorithm II (SPEA-II) and Pareto Archived Evolution Strategy (PAES) on most of the test problems. The key new approach in EMOCA is to use a diversity-emphasizing probabilistic approach in determining whether an offspring individual is considered in the replacement selection phase, along with the use of a non-domination ranking scheme. This approach appears to provide a useful compromise between the two concerns of dominance and diversity in the evolving population.

Enabling Green Networking with a Power Down Approach

Brendan Mumey et al. — Fri, 08 Mar 2013 08:23:16 PST

The most straightforward way to reduce network power consumption is to turn off idle links and nodes (switches/routers), which we call the power down approach. In a wired network, especially in a backbone network, many links are actually “bundles” of multiple physical cables and line cards that can be shut down independently. In this paper, we study the following routing problem for green networking in wired networks: Given a set of end-to-end communication sessions, determine how to route data traffic through the network such that total power consumption is minimized by turning off unused cables in bundled links and nodes, subject to the constraint that the traffic demand of each session is satisfied. We present an integer linear programming to provide optimal solutions. We also present two fast and effective heuristic algorithms to solve the problem in polynomial time. It has been shown by simulation results based on the Abilene network and the NSF network that the proposed heuristic algorithms consistently provide close-tooptimal solutions.

Fusing Heterogeneous Data for Detection Under Non-stationary Dependence

Hao He et al. — Tue, 15 Jan 2013 11:47:02 PST

In this paper, we consider the problem of detection for dependent, non-stationary signals where the non-stationarity is encoded in the dependence structure. We employ copula theory, which allows for a general parametric characterization of the joint distribution of sensor observations and, hence, allows for a more general description of inter-sensor dependence. We design a copula-based detector using the Neyman-Pearson framework. Our approach involves a sample-wise copula selection scheme, which for a simple hypothesis test, is proved to perform better than previously used single copula selection schemes. We demonstrate the utility of our copula-based approach on simulated data, and also for outdoor sensor data collected by the Army Research Laboratory at the US southwest border.

Crowdsourcing to Smartphones: Incentive Mechanism Design for Mobile Phone Sensing

Dejun Yang et al. — Wed, 05 Dec 2012 09:00:26 PST

Mobile phone sensing is a new paradigm which takes advantage of the pervasive smartphones to collect and analyze data beyond the scale of what was previously possible. In a mobile phone sensing system, the platform recruits smartphone users to provide sensing service. Existing mobile phone sensing applications and systems lack good incentive mechanisms that can attract more user participation. To address this issue, we design incentive mechanisms for mobile phone sensing. We consider two system models: the platform-centric model where the platform provides a reward shared by participating users, and the user-centric model where users have more control over the payment they will receive. For the platform-centric model, we design an incentive mechanism using a Stackelberg game, where the platform is the leader while the users are the followers. We show how to compute the unique Stackelberg Equilibrium, at which the utility of the platform is maximized, and none of the users can improve its utility by unilaterally deviating from its current strategy. For the user-centric model, we design an auction-based incentive mechanism, which is computationally efficient, individually rational, profitable, and truthful. Through extensive simulations, we evaluate the performance and validate the theoretical properties of our incentive mechanisms.

Survivable Virtual Infrastructure Mapping in Virtualized Data Centers

Jielong Xu et al. — Wed, 05 Dec 2012 09:00:24 PST

In a virtualized data center, survivability can be enhanced by creating redundant VMs as backup for VMs such that after VM or server failures, affected services can be quickly switched over to backup VMs. To enable flexible and efficient resource management, we propose to use a service-aware approach in which multiple correlated Virtual Machines (VMs) and their backups are grouped together to form a Survivable Virtual Infrastructure (SVI) for a service or a tenant. A fundamental problem in such a system is to determine how to map each SVI to a physical data center network such that operational costs are minimized subject to the constraints that each VM’s resource requirements are met and bandwidth demands between VMs can be guaranteed before and after failures. This problem can be naturally divided into two sub-problems: VM Placement (VMP) and Virtual Link Mapping (VLM). We present a general optimization framework for this mapping problem. Then we present an efficient algorithm for the VMP subproblem as well as a polynomial-time algorithm that optimally solves the VLM subproblem, which can be used as subroutines in the framework. We also present an effective heuristic algorithm that jointly solves the two subproblems. It has been shown by extensive simulation results based on the real VM data traces collected from the green data center at Syracuse University that compared with the First Fit Descending (FFD) and single shortest path based baseline algorithm, both our VMP+VLM algorithm and joint algorithm significantly reduce the reserved bandwidth, and yield comparable results in terms of the number of active servers.

A Broadcast Approach for Fading Wiretap Channels

Yingbin Liang et al. — Wed, 05 Dec 2012 09:00:21 PST

A (layered) broadcast approach is studied for the fading wiretap channel without the channel state information (CSI) at the transmitter. Two broadcast schemes, based on superposition coding and embedded coding respectively, are developed to encode information into a number of layers and use stochastic encoding to keep the corresponding information secret from an eavesdropper. The layers that can be successfully and securely transmitted are determined by the channel states to the legitimate receiver and the eavesdropper. The advantage of these broadcast approaches is that the transmitter does not need to know the CSI to the legitimate receiver and the eavesdropper, but the scheme still adapts to the channel states of the legitimate receiver and the eavesdropper. Three scenarios of block fading wiretap channels with a stringent delay constraint are studied, in which either the legitimate receiver’s channel, the eavesdropper’s channel, or both channels are fading. For each scenario, the secrecy rate that can be achieved via the broadcast approach developed in this paper is derived, and the optimal power allocation over the layers (or the conditions on the optimal power allocation) is also characterized. A notion of probabilistic secrecy is also introduced and studied for scenarios when the eavesdropper’s channel is fading, which characterizes the probability that a certain secrecy rate of decoded messages is achieved during one block. Numerical examples are provided to demonstrate the impact of the channel state information at the transmitter and the channel fluctuation of the eavesdropper on the average secrecy rate. These examples also demonstrate the advantage of the proposed broadcast approach over the compound channel approach.

On Exploiting Flow Allocation with Rate Adaptation for Green Networking

Jian Tang et al. — Wed, 07 Nov 2012 09:20:20 PST

Network power consumption can be reduced considerably by adapting link data rates to their offered traffic loads. In this paper, we exploit how to leverage rate adaptation for green networking by studying the following flow allocation problem in wired networks: Given a set of candidate paths for each end-to-end communication session, determine how to allocate flow (data traffic) along these paths such that power consumption is minimized, subject to the constraint that the traffic demand of each session is satisfied. According to recent measurement studies, we consider a discrete step increasing function for link power consumption. We address both the single and multiple communication session cases and formulate them as two optimization problems, namely, the Single-session Flow allocation with Rate Adaptation Problem (SF-RAP), and the Multisession Flow Allocation with Rate Adaptation Problem (MFRAP). We first show that both problems are NP-hard and present a Mixed Integer Linear Programming (MILP) formulation for the MF-RAP to provide optimal solutions. Then we present a 2-approximation algorithm for the SF-RAP, and a general flow allocation framework as well as an LP-based heuristic algorithm for the MF-RAP. Simulation results show that the algorithm proposed for the SF-RAP consistently outperforms a shortest path based baseline solution and the algorithms proposed for the MF-RAP provide close-to-optimal solutions.

Generation of a Wide-Band Response Using Early-Time and Middle-Frequency Data Throught the Use of Orthogonal Fuctions

Woojin Lee et al. — Wed, 07 Nov 2012 09:20:17 PST

Abstract|Generation of a wide-band response using partial information from the time domain (TD) data and frequency domain (FD) data has been accomplished in this paper through the use of three different orthogonal functions, such as the continuous Laguerre functions, the Bessel-Chebyshev functions, and the associate Hermite functions. In this hybrid approach, one can generate the early-time response using the method of marching-on-in-time (MOT) and use the method of moment (MOM) to generate the middle-frequency response, as the low-frequency data may be unstable. Since the early-time and the middle-frequency data are mutually complimentary, they can provide the missing low- and high-frequency response and the late- time response, respectively. Even though obtaining middle-frequency response from an object needs more computation time than the low- frequency response, this approach has better performance for the interpolation and extrapolation of a wide-band response.

Comprehensive Solution to Scattering by Bianisotropic Objects of Arbitrary Shape

Chong Mei et al. — Wed, 07 Nov 2012 09:20:15 PST

This paper presents a method of moments (MoM) solution for the problems of electromagnetic scattering by inhomogeneous three- dimensional bianisotropic scatterers of any shape. The electromagnetic response of bianisotropy has been described by the constitutive relations of the most general form composed of four 3 X 3 matrices or tensors. The volume equivalence principle is used to obtain a set of mixed potential formulations for a proper description of the original scattering problem. Here, the total fields are separated into the incident fields and the scattered fields. The scattered fields are related to the electric and magnetic potentials which are excited by electric and magnetic bound charges and polarization currents. The body of the scatterer is meshed through the use of tetrahedral cells with face-based functions used to expand unknown quantities. At last, the Galerkin test method is applied to create a method of moments (MoM) matrix from which the numerical solution is obtained. Implemented in a MATLAB program, the numerical formulation is evaluated and verified for various types of scatterers. The results are compared with those of previous work, and a good agreement is observed. Finally, a scattering from a two-layered dispersive chiroferrite sphere is presented as the most general example.

On Noise-Enhanced Distributed Inference in the Presence of Byzantines

Mukul Gagrani et al. — Wed, 07 Nov 2012 09:20:12 PST

This paper considers the noise-enhanced distributed detection problem in the presence of Byzantine (malicious) nodes by suitably adding stochastic resonance (SR) noise. We consider two metrics - the minimum number of Byzantines (alpha_blind) needed to blind the fusion center as a security metric and the Kullback- Leibler divergence (DKL) as a detection performance metric. We show that alpha_blind increases when SR noise is added at the honest nodes. When Byzantines also start adding SR noise to their observations, we see no gain in terms of alpha_blind . However, the detection performance of the network does improve with SR. We also consider a game theoretic formulation where this problem of distributed detection in the presence of Byzantines is modeled as a minimax game between the Byzantines and the inference network, and numerically find Nash equilibria. The case when SR noise is added to the signals received at the fusion center (FC) from the sensors is also considered. Our numerical results indicate that while there is no gain in terms of , the network-wide performance measured in terms of alpha_blind the deflection coefficient does improve in this case

Fusing Dependent Decisions for Hypothesis Testing with Heterogeneous Sensors

Satish Giridhar Iyengar et al. — Wed, 07 Nov 2012 09:20:10 PST

In this paper, we consider a binary decentralized detection problem where the local sensor observations are quantized before their transmission to the fusion center. Sensor observations, and hence their quantized versions, may be heterogeneous as well as statistically dependent. A composite binary hypothesis testing problem is formulated, and a copula-based generalized likelihood ratio test (GLRT) based fusion rule is derived given that the local sensors are uniform multi-level quantizers. An alternative computationally efficient fusion rule is also designed which involves injecting a deliberate random disturbance to the local sensor decisions before fusion. Although the introduction of external noise causes a reduction in the received signal to noise ratio, it is shown that the proposed approach can result in a detection performance comparable to the GLRT detector without external noise, especially when the number of quantization levels is large

Optimal Control of Vehicular Formations With Nearest Neighbor Interactions

Fu Lin et al. — Wed, 07 Nov 2012 09:20:07 PST

We consider the design of optimal localized feedback gains for one-dimensional formations in which vehicles only use information from their immediate neighbors. The control objective is to enhance coherence of the formation by making it behave like a rigid lattice. For the single-integrator model with symmetric gains, we establish convexity, implying that the globally optimal controller can be computed efficiently. We also identify a class of convex problems for double-integrators by restricting the controller to symmetric position and uniform diagonal velocity gains. To obtain the optimal non-symmetric gains for both the single- and the double-integrator models, we solve a parameterized family of optimal control problems ranging from an easily solvable problem to the problem of interest as the underlying parameter increases. When this parameter is kept small, we employ perturbation analysis to decouple the matrix equations that result from the optimality conditions, thereby rendering the unique optimal feedback gain. This solution is used to initialize a homotopy-based Newton’s method to find the optimal localized gain. To investigate the performance of localized controllers, we examine how the coherence of large-scale stochastically forced formations scales with the number of vehicles. We establish several explicit scaling relationships and show that the best performance is achieved by a localized controller that is both non-symmetric and spatially-varying.

A New Framework For Distributed Detection with Conditionally Dependent Observations

Hao Chen et al. — Fri, 05 Oct 2012 09:48:26 PDT

Distributed detection with conditionally dependent observations is known to be a challenging problem in decentralized inference. This paper attempts to make progress on this problem by proposing a new framework for distributed detection that builds on a hierarchical conditional independence model. Through the introduction of a hidden variable that induces conditional independence among the sensor observations, the proposed model unifies distributed detection with dependent or independent observations. This new framework allows us to identify several classes of distributed detection problems with dependent observations whose optimal decision rules resemble the ones for the independent case. The new framework induces a decoupling effect on the forms of the optimal local decision rules for these problems, much in the same way as the conditionally independent case. This is in sharp contrast to the general dependent case where the coupling of the forms of local sensor decision rules often renders the problem intractable. Such decoupling enables the use of, for example, the person-by-person optimization approach to find optimal local decision rules. Two classical examples in distributed detection with dependent observations are reexamined under this new framework: detection of a deterministic signal in dependent noises and detection of a random signal in independent noises.

Performance of Permutation Trellis Codes in Cognitive Radio Networks

Raghed El Bardan et al. — Thu, 04 Oct 2012 08:48:29 PDT

In this paper, we investigate the error correction performance of Permutation Trellis Codes (PTC) combined with M -ary Frequency Shift Keying (M -FSK) modulation in Cognitive Radio Networks (CRNs). Using this modulation technique, a secondary user (SU) can improve its data rate by increasing its transmission bandwidth while operating at low power and without creating destructive interference to the primary users (PUs). Given an active PU, we first derive the bit error rate (BER) of the PTC based M-FSK system for a given SU link. For different PTCs, we compare the analytical BER with the corresponding simulation results. For the same transmitting power, bandwidth availability and transmission time, simulation results show that for a SU link, M-FSK scheme using PTC provides better protection against the interference caused by the PU than M-FSK schemes employing conventional error correction coding such as convolutional and low density parity check (LDPC) codes.

Comprehensive Solution to Scattering by Bianisotropic Objects of Arbitrary Shape

Chong Mei et al. — Thu, 04 Oct 2012 08:34:38 PDT

This paper presents a method of moments (MoM) solution for the problems of electromagnetic scattering by inhomogeneous three- dimensional bianisotropic scatterers of any shape. The electromagnetic response of bianisotropy has been described by the constitutive relations of the most general form composed of four 3 £ 3 matrices or tensors. The volume equivalence principle is used to obtain a set of mixed potential formulations for a proper description of the original scattering problem. Here, the total ¯elds are separated into the incident ¯elds and the scattered ¯elds. The scattered ¯elds are related to the electric and magnetic potentials which are excited by electric and magnetic bound charges and polarization currents. The body of the scatterer is meshed through the use of tetrahedral cells with face-based functions used to expand unknown quantities. At last, the Galerkin test method is applied to create a method of moments (MoM) matrix from which the numerical solution is obtained. Implemented in a MATLAB program, the numerical formulation is evaluated and veri¯ed for various types of scatterers. The results are compared with those of previous work, and a good agreement is observed. Finally, a scattering from a two-layered dispersive chiroferrite sphere is presented as the most general example.

Fault Coverage Measurement Technique for Analog Circuits

E. Paul Ratazzi — Fri, 21 Sep 2012 12:22:06 PDT

This report describes an effort to develop a technique for measuring the amount of fault detection coverage that an analog test pattern has for a particular analog device. The technique is based on a software tool which statistically analyzes data from a circuit simulator. One example of a fault simulation experiment is presented, and some of the results are discussed. Finally, some ideas for future work in this area are given.

Near-Real-Time Cloud Auditing for Rapid Response

Joon S. Park et al. — Fri, 21 Sep 2012 12:22:05 PDT

Due to the rapid emergence of Information Technology, cloud computing provides assorted advantages to service providers, developers, organizations, and customers with respect to scalability, flexibility, cost-effectiveness, and availability. However, it also introduces new challenges and concerns, especially in terms of security and privacy. One of the major security obstacles to widespread adoption of cloud computing is the lack of near-real-time auditability. In particular, near-real-time cloud auditing, which provides timely evaluation results and rapid response, is the key to assuring the cloud. In this paper, we discuss security and privacy concerns in cloud computing and the current status of cloud auditing efforts. Next, we address the strategies for reliable cloud auditing and analyze the deficiencies of current approaches. We then discuss the summary of our case study with Amazon CloudWatch, which is one of the most developed cloud-monitoring APIs.

A New Framework For Distributed Detection with Conditionally Dependent Observations

Hao Chen et al. — Fri, 21 Sep 2012 12:18:19 PDT

Social Network Based Reputation Computation and Document Classification

Joo Young Lee et al. — Fri, 06 Jul 2012 09:33:43 PDT

We develop two social network based algorithms that automatically compute author reputation from a collection of textual documents.We first extract keyword reference behaviors of the authors to construct a social network, which represents relationships among the authors in terms of information reference behavior. With this network, we apply the two algorithms: the first computes each author’s reputation value considering only direct reference and the second utilizes indirect reference recursively. We compare the reputation values computed by the two algorithms and reputation ratings given by a human domain expert. We further evaluate the algorithms in email categorization tasks by comparing them with machine learning techniques. Finally, we analyse the social network through a community detection algorithm and other analysis techniques. We observed several interesting phenomena including the network being scale-free and having a negative assortativity.

Comparison of Silicon-on-Insulator and Body-on-Insulator FinFET Based Digital Circuits with Consideration on Self-Heating Effects

Peijie Feng et al. — Tue, 01 May 2012 08:44:06 PDT

In summary, we have compared SOI and BOI FinFET device characteristics and the performance of digital circuits designed with those devices. For low voltage supply, SHE is modest in both devices and during digital circuit operations. SOI FinFET CMOS inverter and SRAM cell characteristics are very similar to BOI ones. Considering the lesser fabrication complexity, SOI FinFET thus would be more preferable than BOI FinFET for the design of low voltage digital circuits.