REV Journal on Electronics and Communications
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VANET Modelling and Statistical Properties of Connectivity in Urban Environment
Get PDFThis paper proposes a new approach for modelling Vehicular Ad Hoc Networks (VANETs) based on stochastic geometry and point processes, where road systems are modelled as random lines process and vehicle’s locations on a road are linear Poisson point processes. We derive some functions, which show the connectivity properties of VANETs under the impact of fading and path loss, that can be used for large vehicular networks analysis
Blind Identification for Communication Signals: An Approach Exploiting Sampling Phase Diversity
Get PDFThis paper presents a second-order blind channel estimation algorithm for digital communication signals under natural asynchronous conditions where no synchronization exists between transmitting and receiving antennas. The approach exploits sampling phase diversity provided by the cyclostationary nature of the received signals as an advantageous means of constructing multiple sets of distinct autocorrelation matrices evaluated at equals time lags. Channel estimation is then performed via joint diagonalization of a set of differential autocorrelation target matrices, avoiding the need of noise power or statistical distribution estimation. A broad set of simulation experiments is presented in distinctive signal contexts as a means of supporting and evidencing the potential of the proposed estimation method
NetFPGA Based OpenFlow Switch Extension for Energy Saving in Data Centers
Get PDFThe increasing demand for data centers in both scale and size has led to huge energy consumption. The cost and environmental impact of data centers increases due to large amounts of carbon emissions. One solution to this problem is to intelligently control the power consumption of switches used in data centers. This paper proposes an extension to OpenFlow switches to support different power saving modes. The extension includes defining new messages in the OpenFlow protocol stack and designing an OpenFlow Switch Controller (OSC) that is able to turn on/off switches and disable/enable ports. To prove the soundness of the proposed extension, the functions of an OSC has been integrated in a NetFPGA based OpenFlow switch used in the ECODANE framework. The results presented in this paper can also be used by the OpenFlow compliant switches manufacturer or by power aware research community
A Comprehensive Model for Performance Analysis of APD-based FSO Systems using M-PPM Signaling in Atmospheric Turbulence
Get PDFIn this paper, a model of Gaussian pulse propagation over atmospheric turbulence channel is used to comprehensively analyze the performance of APD-based free-space optical communication (FSO) systems using M-PPM signaling. This model is able to simultaneously take into account all effects of atmospheric turbulence including attenuation, intensity fluctuation, and pulse broadening, which has not been considered in previous works. In addition, the impacts of APD shot noise, background noise, and thermal noise are included in our analysis. The numerical results show that the main factor that limits the system performance is intensity fluctuation. However, when M is large enough, optical pulse is so short that the effect of pulse broadening becomes dominant. By using APD receiver, bit-error rate is improved significantly. Finally, based on channel capacity, we are able to determine the maximum transmission length of the system
Single-machine Scheduling with Splitable Jobs and Availability Constraints
Get PDFThis paper deals with a single machine scheduling problem with availability constraints. The jobs are splitable and lower bound on the size of each sub-job is imposed. The objective is to find a feasible schedule that minimizes the makespan. The proposed scheduling problem is proved to be NP-hard in the strong sense. Some effective heuristic algorithms are then proposed. Additionally, computational results show that the proposed heuristic performs well
Solving the Traveling Salesman Problem with Ant Colony Optimization: A Revisit and New Efficient Algorithms
Get PDFAnt colony optimization (ACO) techniques are known to be efficient for combinatorial optimization. The traveling salesman problem (TSP) is the benchmark used for testing new combinatoric optimization algorithms. This paper revisits the application of ACO techniques to the TSP and discuss some general aspects of ACO that have been previously overlooked. In fact, it is observed that the solution length does not reflect exactly the quality of a particular edge belong to the solution, but it is only used for relatively evaluating whether the edge is good or bad in the process of reinforcement learning. Based on this observation, we propose two algorithms– Smoothed Max-Min Ant System and Three-Level Ant System– which not only can be easily implemented but also provide better performance, as compared to the well-known Max-Min Ant System. The performance is evaluated by numerical simulation using benchmark datasets
A New Decoding Algorithm based on Equivalent Parity Check Matrix for LDPC Codes
Get PDFThe article introduces a new LDPC decoding algorithm based on Equivalent Parity Check Matrix. Simulation results show that the new LDPC decoding algorithm can improve LDPC decoding performance. Compared to some other improvements, the new LDPC decoding algorithm, which is simpler, can detect errors and be applied to LDPC codes for great-length LDPC codes
3D Reconstruction using Kinect Sensor and Parallel Processing on 3D Graphics Processing Unit
Get PDFOne of depth cameras such as the Microsoft Kinect is much cheaper than conventional 3D scanning devices, thus it can be acquired for everyday users easily. However, the depth data captured by Kinect over a certain distance is of low quality. In this work, we implement a set of algorithms allowing users to capture 3D surfaces by using the handheld Kinect. As a classic alignment algorithm such as the Iterative Closest Point (ICP) does not show efficacy in aligning point clouds that have limited overlapped regions, another coarse alignment using the Sample Consensus Initial Alignment (SAC-IA) is incorporated in to the registration process in order to ameliorate 3D point clouds’ fitness. Two robust reconstruction methods namely the Alpha Shapes and the Grid Projection are also implemented to reconstruct 3D surface from registered point clouds. The experimental results have shown the efficiency and applicability of of our blueprint. The constructed system obtains acceptable results in a few minutes with a low price device, thus it may practically be an useful approach for avatar generations or online shoppings