Computing and Informatics (E-Journal - Institute of Informatics, SAS, Bratislava)
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1506 research outputs found
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An Integrated Software Framework for Localization in Wireless Sensor Network
Get PDFDevices that form a wireless sensor network (WSN) system are usually remotely deployed in large numbers in a sensing field. WSNs have enabled numerous applications, in which location awareness is usually required. Therefore, numerous localization systems are provided to assign geographic coordinates to each node in a network. In this paper, we describe and evaluate an integrated software framework WSNLS (Wireless Sensor Network Localization System) that provides tools for network nodes localization and the environment for tuning and testing various localization schemes. Simulation experiments can be performed on parallel and multi-core computers or computer clusters. The main component of the WSNLS framework is the library of solvers for calculating the geographic coordinates of nodes in a network. Our original solution implemented in WSNLS is the localization system that combines simple geometry of triangles and stochastic optimization to determine the position of nodes with unknown location in the sensing field. We describe and discuss the performance of our system due to the accuracy of location estimation and computation time. Numerical results presented in the paper confirm that our hybrid scheme gives accurate location estimates of network nodes in sensible computing time, and the WSNLS framework can be successfully used for efficient tuning and verification of different localization techniques
Optimization of Layer Selection with Unreliable RI in LTE Systems
Get PDFThis paper investigates the optimization of transmission spatial layer selection with unreliable rank indicator (RI) in downlink LTE systems. Taking the block error rate (BLER) into consideration, we propose an accurate throughput calculation (ATC) algorithm at user equipment (UE) side as well as at evolved NodeB (eNB) side. On the basis of ATC algorithm, we propose an accurate RI selection algorithm to periodically choose the preferred number of transmission spatial layers at UE side. Further based on acknowledgement (ACK)/ negative acknowledgement (NACK) history, channel quality indicator (CQI) is adjusted at eNB side to achieve the throughput optimal target BLER. By substituting the derived BLER into ATC algorithm, the optimal number of transmitted spatial layers in current downlink channel is derived at eNB side. Simulation results show that both the proposed CQI adjustment scheme for spatial layer selection and RI selection algorithm yield up significant throughput improvement for different evaluation scenarios in LTE systems
Autonomous Takeoff and Landing Control for Small Size Unmanned Aerial Vehicles
Get PDFThe aim of the research was to develop an Unmanned Aerial Vehicle (UAV) hardware and software which can control a small size UAV (with 1-10 kg takeoff weight) from takeoff to landing. The research was based on AERObot V5 autopilot, developed and tested previously by us. AERObot can control a chosen aerial vehicle on a predefined route and altitude reliably but requires manual takeoff and landing. The speciality of the new takeoff and landing methods is that they do not need any additional RF guidance transmitter, onboard radio/ultrasonic altimeter or special navigation marker points. Using only the existing onboard sensors (GPS, Inertial Measurement Unit -- IMU, barometric airspeed meter, barometric altimeter) AERObot can safely take off and land the UAV under the specified weather limitations for the aerial vehicle frame
Security and VO Management Capabilities in a Large-Scale Grid Operating System
Get PDFThis paper presents a number of security and VO management capabilities in a large-scale distributed Grid operating system. The capabilities formed the basis of the design and implementation of a number of security and VO management services in the system. The main aim of the paper is to provide some idea of the various functionality cases that need to be considered when designing similar large-scale systems in the future
Quantitative Assessment of Safety Integrity Level of Message Transmission Between Safety-Related Equipment
Get PDFThis paper describes and analyses the possibilities of a quantitative assessment of message transmission between safety-related equipment for control and communication systems with a guarantee of a higher safety integrity level (SIL). The theoretical methods and standards recommended for industrial safety-related control, information and communication systems with SIL3 are described. The main part of the contribution covers theoretical methods and practical procedures used within a safety analysis of safety-related message transmission with the requirement of SIL4 for the area of railway interlocking systems. The theoretical analysis of these methods is compared with the knowledge and experience, the authors gained within several safety verifications of such systems in practice in Slovakia as well as abroad. Also, based on a case study in the mentioned application area, the authors proposed their own quantitative mathematical model for assessing the safety integrity level of message transmission within a closed transmission system with the failure tree analysis (FTA) and Markov's analysis (MA). The designed model, which evaluates the effect of electromagnetic interferences (EMI) and random hardware failures of a safety-related communication system (SRComS) to its safety, was realised and verified. The verification in available conditions confirmed the contribution of the model to the process of objectification of the safety assessment of message transmission via SRComS
Database Security System for Applying Sophisticated Access Control via Database Firewall Server
Get PDFDatabase security, privacy, access control, database firewall, data break masking
Recently, information leakage incidents have occurred due to database security vulnerabilities. The administrators in the traditional database access control methods grant simple permissions to users for accessing database objects. Even though they tried to apply more strict permissions in recent database systems, it was difficult to properly adopt sophisticated access control policies to commercial databases due to performance degradations. This paper proposes a database security system including a database firewall server as an enhanced database access control system which can efficiently enforce sophisticated security policies to provide database with confidentiality using a data masking technique for diverse conditions such as the date, time, SQL string, and table columns to database systems
Implementation of a RANLUX Based Pseudo-Random Number Generator in FPGA Using VHDL and Impulse C
Get PDFMonte Carlo simulations are widely used e.g. in the field of physics and molecular modelling. The main role played in these is by the high performance random number generators, such as RANLUX or MERSSENE TWISTER. In this paper the authors introduce the world's first implementation of the RANLUX algorithm on an FPGA platform for high performance computing purposes. A significant speed-up of one generator instance over 60 times, compared with a graphic card based solution, can be noticed. Comparisons with concurrent solutions were made and are also presented. The proposed solution has an extremely low power demand, consuming less than 2.5 Watts per RANLUX core, which makes it perfect for use in environment friendly and energy-efficient supercomputing solutions and embedded systems
Multiobjective Algorithms with Resampling for Portfolio Optimization
Get PDFConstrained financial portfolio optimization is a challenging domain where the use of multiobjective evolutionary algorithms has been thriving over the last few years. One of the major issues related to this problem is the dependence of the results on a set of parameters. Given the nature of financial prediction, these figures are often inaccurate, which results in unreliable estimates for the efficient frontier. In this paper we introduce a resampling mechanism that deals with uncertainty in the parameters and results in efficient frontiers that are more robust. We test this idea on real data using four multiobjective optimization algorithms (NSGA-II, GDE3, SMPSO and SPEA2). The results show that resampling significantly increases the reliability of the resulting portfolios
Network Firewall using Artificial Neural Networks
Get PDFToday's most common firewalls are mostly rule-based. Their knowledge consists of a set of rules upon which they process received packets. They cannot do anything they have not been explicitly configured to do. This makes the system more straightforward to set up, but less flexible and less adaptive to changing circumstances. We will investigate a network firewall whose rule-base we will try to model using an artificial neural network, more specifically using a multi-layer perceptron (MLP) trained by the back-propagation algorithm. The training data are acquired from the network and we consider two possible scenarios. In Scenario 1, the user has no firewall available and the policy is deduced from the existing traffic in the network which is considered to be legitimate. In Scenario 2, the learning module is placed behind the existing firewall (or firewalls) in order to learn their behavior. In both cases, all traffic, which is recorded, contains only positive examples; however, a direct training of a MLP from a set of positive examples is impossible. We solved this problem using a synthetic generation of negative examples which led to successful learning
Dynamic Optimal Training for Competitive Neural Networks
Get PDFThis paper introduces an unsupervised learning algorithm for optimal training of competitive neural networks. The learning rule of this algorithm is rived from the minimization of a new objective criterion using the gradient descent technique. Its learning rate and competition difficulty are dynamically adjusted throughout iterations. Numerical results that illustrate the performance of this algorithm in unsupervised pattern classification and image compression are also presented, discussed, and compared to those provided by other well-known algorithms for several examples of real test data