Background and Objective: Today, Wi-Fi technology is practically being used as a default connectivity solution for many new technologies and concepts like Internet of Things (IoT) and Smart City. The design of Wi-Fi network is a complex problem, where it is necessary to decide about the location and number of access points in given indoor or outdoor environment. Method and Results: In this paper, the measurement results of Wi-Fi signal in the indoor-to-outdoor building environment are investigated and possible sources of signal loss in the examined Wi-Fi channel are pointed out and discussed. The influence of human hand signal absorption is examined by comparison of the measurements performed by professional equipment with the ones obtained by a smartphone. We considered different receiver positions as well as the change of transmitter antenna gain with respect to the receiver height. Conclusion: The gain correction was estimated, and results showed a good agreement between the calculated and measured power levels at the receiver. Keywords: Building surrounding, channel loss, human hand signal absorption, line of sight propagation, outdoor radio propagation, indoor radio propagation, radio measurements, spectrum analyzer, Wi-Fi signal.
Uncertainties regarding wireless propagation environments pose challenges for spectrum management in general and specifically hinder the implementation of dynamic spectrum sharing systems. Without the ability to reliably evaluate interference risks, spectrum sharing policies specify spectrum access behaviors such as exclusion zones and maximum transmit powers based on risk thresholds applied to statistical results from propagation models and measurements. Because the models can contain significant levels of uncertainty, establishing behavior limits for low interference risk necessarily results in significant spectrum access inefficiencies. It is only by reducing the degree of uncertainty that risk thresholds can be maintained while increasing spectrum access efficiency. Probabilistic reasoning applied to dynamic spectrum sharing systems provides potential to increase spectrum sharing by reducing situational uncertainty. Further, probabilistic reasoning approaches enable risk-constrained spectrum access, a concept in which regulators and spectrum users establish spectrum access rules defining acceptable levels of interference and spectrum access risks. This paper develops the concepts and underlying theory of probabilistic reasoning and risk-constrained spectrum access for spectrum sharing. It further presents simulation results showing that situation-specific probabilistic reasoning combined with risk-constrained spectrum access potentially enables greater spectrum sharing. Specifically, probabilistic reasoning with real-time spectrum sensing is shown to greatly reduce situational uncertainty, which then results in better interference prevention and more effective spectrum sharing as measured by user capacity and overall network density.
Background: Owing to rapid development of hardware components and reduction in prices, Unmanned Ariel Vehicles (UAVs) are becoming ubiquitous including application to airborne ad-hoc communication relay stations. Quadcopters are one class of UAVs, which have particularity seen rapid growth due to their versatility. Since quadcopters are inherently unstable and hard to stabilize by human operator, they need automated attitude stabilization. However, altitude stabilization around desired height is often overlooked, while it has an important role in optimal location for airborne communication relay. Objective: The paper addresses the issue by developing controllers for UAV hovering. The proposed approach can then be extended to arbitrary height (possibly with different sensor setup). Method: For the development of control schemes, two approaches were used: PID and Neural network (NN) based one. For the development of NN (i.e. learning phase) Gazebo simulation environment was used essentially modeling the human driver. Developed approaches were tested both in simulation and in real-world scenario on AR.Drone 1.0 and AR.Drone 2.0 UAVs. Results: Obtained indoor results demonstrated PID accuracy of 1 cm with overshoot of 2.7% and settling time of 3.75 s, while NN demonstrated 2.1 cm, 1%, and 8.4 s, respectively. Outdoor testing was also performed with similar result trends. Conclusion: Both developed controllers demonstrated good results (indoor and outdoor) and could be used in real world scenario, but NN due to its favorable characteristics (i.e. human driver modelling) and straightforward development phase (as compared to PID which involves lot of trial-and-error) is preferred. Keywords: Altitude control, communication relay, neural network, PID, stabilization, UAV, simulation.
History: The battle for achieving the Sustainable Development Goals (SDGs) of United Nations Agenda 2030, will be won at the city level. All countries are addressing the SGDs at the city level by implementing smart city initiatives. Smart cities take advantage of ICT systems for improving city’ system performance and optimize its resources. Objective: The ultimate objective is to improve the citizen quality of the life while the sustainability at social, economic and environmental level is guaranteed. For leading with the complexity of the urban problems ICT-enable systems such as massive data analysis in real time can be used as an instrument for supporting the decision-making process. Method: In that sense, this paper proposes a tool, which helps decision makers, to design and implement smart city initiatives. The tool is an online platform capable of doing three-dimensional data analysis of a repository of smart city initiatives. Results: The platform makes use of the OLAP technology to produce the 3D analysis and it showed to be a very powerful tool for decision-makers which want to know more about smart cities projects and learn from past experiences to make always the best decisions based on evidence based information. Keywords: Smart cities, ICTs, business Intelligence, OLAP, open source, architecture scheme.
Recent advancement in data transfer and networking techniques has put forward a considerable threat for secure data transfer. It is the sensitive information that flows via network fuels the engine of global economy. One of the main concerns in data communication is the ability to exchange information in a secured fashion and embed the information of interest in any multimedia carrier like audio, video and an image. The proposed work is an ideal modernistic novel approach for secured sensitive information communication over an encrypted color host image carrying exceptionally confidential data. Distortion less retrieval of both payload and host signal information from marked image is an appealing feature in scenarios like medical, Military and satellite applications. Reversibility not only assures zero error retrieval of sensitive information hidden and also perfect reconstruction of host medium information contents while safeguarding the confidentiality of secret information. Most popular and widely in use Advanced Encryption Standard(AES) stream cipher in Counter mode is used for encrypting the cover image content, by performing XOR operation over cover image information bits with key dependent pseudorandom bits. Signal Processing over the encrypted domain is one of the most demanding features for most of the privacy preserving applications like cloud computing and remote sensing. High Embedding capability is achieved through Lempel-Ziv-Welch (LZW) compression technique. High performance reversible data hiding technique is assured via public key modulation scheme. Two of the most powerful image classifiers Support Vector Machine (SVM) and KNearest neighbor (KNN) algorithms are used at the decoder end to distinguish between encrypted and non encrypted image blocks. Performance evaluation of image classifiers is done, considering their ability to accurately categorize image patches as encrypted and unencrypted using feature vectors. Features used for ca tegorizing encrypted and unencrypted image blocks are variation of pixel intensity in all four directions, entropy, standard deviation and histogram plot of segmented image blocks. Proposed algorithm comes with a unique feature of simultaneous retrieval of both host image and payload information in an error free fashion with zero distortion. Proposed algorithm is proven more secured considering several security attacks as evaluation parameters. Few of Cryptanalysis and Steganalysis techniques considered to verify the security feature of proposed algorithm are Sample pair analysis (SPA), Number of changing pixel rate (NPCR), Unified averaged changed intensity (UACI) and Chisquare attack.
Background: Present study inspects the profiles of electric Dipole Moment (DPM) and polarizability (αp) of impurity doped GaAs Quantum Dots (QDs) in the presence of noise. Objective: Noise term maintains a Gaussian white character and it has been introduced to the system via two different pathways; additive and multiplicative. In view of a comprehensive analysis, modulation of DPM and αp has been scrutinized along with the variations of several relevant quantities such as electric field, magnetic field, confinement potential, dopant location, dopant potential, noise strength and aluminium concentration (only for AlxGa1-xAs QD). Methods: Application of noise almost invariably reduced the magnitude of αp and DPM from that of noisefree condition. However, the extent to which the said properties are altered depends on the noise strength domain and the pathway through which noise is applied. It can therefore be inferred that introduction of noise diminished the asymmetric nature of the system to a noticeable extent. Research: Moreover, the extent of drop in the asymmetric character of the system was found to be more with multiplicative noise than its additive analogue. Thus, the mode of application of noise also appears important in harnessing the polarizability and dipole moment of the system. Conclusion: The outcomes of the study delineate viable routes to tune the dipole moment and polarizability of doped QD system, particularly in presence of noise. Keywords: Quantum dot, impurity, electric field, dipole moment, polarizability, Gaussian white noise.
The aim is to compute the time delay between the set of measurements in each of two or more Spectrum Analyzers using a linear relation between two dimensions (power and time). This method of time measurement implies to input in each Spectrum Analyzer two identical and synchronized Amplitude Shift Keying signals, each one modulated by a square wave of duty cycle of 50%. It is also valid with Direct Current. Instead of an input of an Amplitude Shift Keying signal (Radio Frequency /Microwaves) it is input a square wave and the power is measured with a Direct Current power meter with trigger. Keyword: Amplitude Shift Keying (ASK), Direct Current, Power Meter, trigger by software, trigger by hardware, Spectrum Analyzer (SA), Spectrum Occupancy, Fusion
Background: As it is known that the access network is very sensitive to the cost, and the number of remote nodes (RNs) is large in metro-access network. RN cost occupies the main part of the whole network cost. Keywords: Broadcasting services, dual-fiber ring, high reliability, large-scale access network, low-cost, remote node, wavelength division multiplexing.
Aims: Software Test Suite Optimization (TSO) is a common approach for generating efficient test data in lesser time. This paper presents an efficient methodology for automatic generation of independent paths and TSO with the help of Artificial Bee Colony (ABC) investigating technique. Keywords: Investigating technique, software under test, ant colony, software testing, artificial bee colony, optimization, genetic algorithm, test data generation.
Objectives: The paper presents performance analysis of centralised and decentralised architecture of IoT sensor networks. Two most popular security mechanisms for Sensor Networks based on their energy consumption, which may lead to poor performance of the IoT system, are also evaluated. The Internet of Things (IoT) technology aims to improve easy access to the information needed using devices. Keywords: Internet of things, Cooja, XTEA, RC5, architecture, security.
Background: Predicting attacker’s behavior plays an important role in network security assessment. Attack graphs systematically classify the possible intrusion paths against a system. For our purpose, we assume the attack graph structure comprised of states and transitions between them. Each state represents an attack phase (or adversarial action) and each transition indicates a possible action of attacker. Keywords: Computer networks, information systems, security, quantitative evaluation, attack graph, workstations.
Healthcare IT applications (e.g., real-time location systems (RTLS)) are increasingly dependent on positional data. Such systems typically combine unique identifiers, metadata, and optional sensor data with position-derived data. Position can be an absolute or relative location. Real-time and historical change of position over the time leads to data such as speed, velocity, directional acceleration, and dwell time at a particular location. Technology such as global positioning system (GPS), radio frequency identification (RFID), near field communication (NFC), wireless local area network (WLAN) triangulation, mobile phone tower tracking, distributed sensor networks (DSN), and distributed readers (e.g., RFID, bar code) generate this data. IT systems and big data they generate track objects and people, and are beginning to develop behavioral models. These in turn can be used to influence processes and people through layered applications such as real time personalized advertising, security, and autonomous mobility. This paper organizes and analyzes recent patent advances combining sensors, short range wireless, unique identifiers, and IT for position-based healthcare applications along with the future of Smart Wearables and internet of things (IoT), for healthcare applications. Keywords: Global positioning system, healthcare applications, healthcare information systems, internet of things, position and motion data, real-time location.
Background: Embedded systems are small computing devices which are designed to perform a specific task with real-time computing and resource constraints. To meet the demands of industries and real-time applications, embedded systems are networked delivering the real-time results to required entities and make itself available to server entities. Due to the connectivity nature of embedded systems, they are placed in remote environments where embedded systems use third party service tool to connect to the external world. The connectivity and resource constraints make embedded systems susceptible to various attacks like Denial of Service (DOS) attack, Joint Test Action Group (JTAG) attacks, spoofing attack and many more while updating or retrieving data from embedded systems. Keywords: Cryptographic algorithms, firmware update networked embedded systems, security, XCP.
Aims: Network security commonly uses internet protocol (IP) filtering solutions. Anonymous proxies (anonymizers) act as a gateway to the resource, meaning that filters will be bypassed, another feature of anonymizers is that they will not give out the user’s IP address or any other detail about the user, the network will see the request come from the anonymizer service. Keywords: Anonymous proxies, security, tor, onion routing, IP filtering, hacking.
Background: Routing in opportunistic networks is subject to attacks such as blackhole and grayhole attacks. A blackhole attack is a type of attack where the malicious node called blackhole node attracts all the data packets by using a forged route to falsely claim that it has a shortest route to the destination, then drops all the data packets that it receives. On the other hand, a greyhole attack is a kind of denial of service attack where a malicious node in the network acts as a normal node, causing eaves dropping and selective forwarding. Blackhole and greyhole attacks in opportunistic networks have been extensively studied in the literature and several defence mechanisms against those attacks have been proposed. This paper adds a novel contribution to this problem by proposing a novel secured protocol (so-called SHBPR) against such attacks. Keywords: Blackhole attack, delay tolerant networks (DTNs), greyhole attack, opportunistic network simulator (ONE), opportunistic networks (Oppnets), secure routing.
El Editor Cientifico y Editor Tecnico de Maderas, Ciencia y Tecnologia agradecen a los revisores por su asistencia como arbitros en los procesos de revision por pares de la revista. La calidad de los contenidos cientificos de Maderas, Ciencia y Tecnologia depende del trabajo a conciencia de los colaboradores. Apreciamos su esfuerzo en la revision de los manuscritos y valoramos enormemente su disponibilidad para compartir su tiempo y experiencia con la Revista Maderas, Ciencia y Tecnologia. Apreciamos su evaluacion cuidadosa de los manuscritos recibidos durante 2014-2015.
History: The countries of the European Union have faced one of the worst financial and economic crises of the recent history. The crisis impacts several social – economic indicators with multiple effects on societies and market sectors such as the Information and Communication Sector (ICT), which has been identified as a key factor for social and economic growth. Keywords: Broadband, broadband policy, economic crisis, electronic communications, financial crisis, ICT, ICT policy.
Background: While smart objects are present in our cities everywhere, the real aim of the Internet of Things is not turned into reality yet. Each smart object is still designated to a specific task and requires proprietary procedures for interaction. Thus, it becomes more necessary to have a connection platform for abstracting the complexity of smart objects and to present their data to the end-users through a simpler interaction procedure. Keywords: Human Computer Interface, IoT, middleware, smart city, NVE, VEoT, virtual reality, WebGL.
There has been a rapid increase in wind turbine connection to distribution and transmission networks in recent years. With individual wind turbines approaching the multi - MW and the wind plants, as a result, approaching the output rating of conventional power plants, a deeper understanding of their potential impacts on interactions with the bulk electric power system is needed. The increased penetration makes the power network more dependent on, and susceptible to, the wind energy production. As the wind power penetration into the grid increases rapidly, the influence of wind turbines on the power quality and voltage stability is becoming more important. The main objective of this study is to analyze the voltage stability of the Egyptian Electrical Network with large scale wind power under normal operation and under single contingency (N-1). The single contingency is defined as the loss of any transmission line, transformer, or generator. In addition, the paper determines the size of reactive power compensation devices (capacitors or STATCOM) that should be installed at weak buses to prevent the voltage collapse. Keywords: PV analysis, QV analysis, reactive compensation, voltage sensitivity, voltage stability, wind energy.
