Search

This paper addresses the secrecy performance of the downlink of a non-orthogonal multiple access network in the presence of multiple randomly located eavesdroppers. The network consists of a base station and a near receiver that are located inside a protected zone, free of eavesdroppers, while a far user is located outside. Herein, it is considered that the source transmits a superposed jamming signal to enhance the secrecy performance. In this sense, imperfections on the removal of the jamming signal by the legitimate receivers are also investigated. Integral-form exact and closed-form approximate expressions for the secrecy outage probability are derived by employing stochastic geometry tools. The expressions are corroborated via Monte Carlo simulations.

GeO 2 -PbO glasses demonstrated to be adequate hosts for incorporation of rare-earth ions and nucleation of metallic nanoparticles. However, Ag nanoclusters were not explored in GeO 2 -PbO glasses. The luminescence of Ag nanoclusters in glasses has several applications such as UV-driven flexible color monitors, mercury-free white light generation under UV pumping, tunable light sources/lasers, and solar cells. The present investigation shows white light generation by Ag nanocluster in Tm3+/Yb3+ doped GeO 2 -PbO glasses. Moreover, we also demonstrate tunable visible emission provided by Ag nanoclusters. Glasses were produced by melt-quenching technique followed by annealing to reduce internal stress. Different emission colors ranging from the blue to the green-yellowish were obtained for GeO 2 -PbO glasses doped only with AgNO3, under different excitation wavelengths. Doping GeO 2 -PbO glasses with AgNO 3 and Yb3+/Tm3+ ions resulted in a blue emission for excitation at 405nm, whereas white light generation was observed for excitation with a commercial 365 nm UV lamp. The photoluminescence (PL) was attributed to the combination of emission bands, from Tm3+ ions and Ag nanoclusters. The results reported herein show the potential of GeO 2 -PbO glasses for white light emitting devices such as light phosphors for UV light driven W-LEDs.

This paper addresses the modeling and control of a novel Forward dc-dc converter with multiplexer for active voltage cell balancing of a bank of Lithium-Ion batteries. The modeling of the converter is developed using a state-space averaging model. The control system is based on a cascade feedback linearization approach for the forward converter and an event-driven control based on the voltage of the cells. Simulation results in time-domain allow to evaluate the performance of the proposed voltage balancing system control.

This paper presents a fuzzy clusterwise regression method aiming to provide linear regression models that are based on homogeneous clusters of observations with respect to the explanatory variables and that are well fitted with respect to the response variable. To achieve this aim, this method combines Fuzzy C-Regression Models and Fuzzy C-Means with automatic computation of relevance weights to the explanatory variables. Because it learns simultaneously a prototype and a linear regression model for each cluster it is able to provide an appropriated regression model for unknown observations based on their description by the explanatory variables. We also discussed both, a heuristic procedure to automatically tune one of the hyperparameters of the proposed method in order to obtain more useful (explanation) models in a prediction task, and a way of making a fuzzy combination of each intra-cluster fitted model as a more natural and appropriate response to the problem of choosing the best regression model for a prediction task. Experiments with synthetic and real datasets corroborate the usefulness of the proposed method.

This paper presents an indoor navigation system built in a wearable device. The system allows visually impaired users to perform guided audio navigation safe, fast and has a low computational complexity. The methodological approach chosen divides the process into two phases: offline and online. In offline phase, the indoor mapping is done by data fusing of radio frequency and visual markers, constructing a unique and consistent representation. In the online phase navigation and recognition of each of the internal positions are performed through the fusion representation or only by the wi-fi or visual signals when one of the sensors is strongly affected by noises or other interferences. The results showed that the recognition levels of wi-fi, visual and fusion markers were 87.59%, 90.92%, and 92.03%, respectively. The error margin after the data fusion application was 0.8 m, with an average time of 0.62 ms.

The automation of computational systems is currently presenting itself as a facilitator in several segments of society, among them is the agricultural sector. As far as irrigation methods are concerned, information technology, especially in embedded systems, can be applied to a large extent on crops and rural properties, offering alternatives to meet the needs of the farmer, such as adequate water supply for the plantations and the dosage of nutrients. The objective of this work is to automate the greenhouse irrigation through the Arduino platform in order to control the flow of water to reduce financial costs. As a result, we obtained a prototype of an automated greenhouse irrigation system that was tested for efficiency and performance. From the results of the tests, it was $^{verified}$that the developed system met the operating needs for irrigation of the greenhouse and was characterized as a good alternative for the cultivation of the plantations.

The prediction of adverse events in patient health has attracted researchers' attention for many years. Sensors in or on the body allow the continuous monitoring of patient's vital signs and their accurate analysis, supporting the generation of medical alerts. Exploring adverse event prediction only makes sense if medical alerts can be promptly transmitted to a hospital emergency response team. However, promptly transmitting them through heterogeneous wireless networks is still a challenge because of wireless communication features, i.e., interferences and collisions, and the current medium access control (MAC) protocol design, that still produces competition between medical alerts, and video, voice and other types of data. Differently from current mechanisms that either are separately concerned to the prediction of adverse events or to give priority to different type of data transmission, this work presents SANTE, a System for Anticipated identificatioN and Transmission of mEdical alerts on wireless networks. Based on trends about the imminence of adverse events on patient health, the system generates medical alerts and promptly transmit them. It presents a novel proposal to medium access control for medical alerts, reducing contention window and Arbitration Inter-Frame Spacing (AIFS) time for them. Simulation results show a reduction of 39% in the average latency for alert transmissions and 8% in losses.

This paper reports on the performance of a sub-THz liquid sensor tool coupled to a microfluidic platform. Non-invasive, non-destructive and on-line measurements are demonstrated for the determination of ethanol concentration and for controlling bymicromixer device. We have developed a label-free chemical sensing methodology coupling a sub-terahertz sensor technology in microfluidic devices fabricated on glass and polydimethylsiloxane. The concept of sensor in micromixer applications operating at 60 GHz for known ethanol concentration ranging 0% to 100%, with a corresponding dynamic range of 2.79dB. The sensor allowed establishing the correlation between the mass flow rate and the ethanol concentration in the microfluidic system, where two-stream lines form the mixture in laminar flows, with Reynolds number 25700. We demonstrated on-line sensing and linear control of ethanol concentration on demand with a small variation of 0.32% (v/v) between measured and required ethanol concentration.

Intellectually disabled students have difficulty in tasks that require attention, memorization and comprehension of concepts. Assistive technologies in education, e.g. games, allow the creation of new effective alternatives for helping the learning. The main objective of this work is to evaluate the potential of an educational memory game as an assistive technology for students with intellectual disability. It was developed a game composed by a computer and a wood box in trapezoidal shape with four pushbuttons with different colors. It is presented to the volunteer, a sequence of colored images that can be yellow, blue, green or red. After the presentation, the participant should select the pushbutton with the corresponding color to the sequence presented, and the selection is presented on the screen. If the player selects correctly, it will be showed a motivational message. If the sequence is wrong, it will be showed an activity to be done by the participants. It has been done a preliminary test, to evaluate the performance of intellectually disabled students and it was possible to observe a reduction of errors along the sessions. Thus, the proposed memory game can be used as a potential assistive technology in education of intellectually disabled students.

Ultra broadband mobile communication is a key requirement of fifth generation (5G) wireless cellular networks. To fulfill this requirement much larger bandwidth is needed which can be delivered in millimeter band from 30 to 300 GHz. Beam formed transmission over a massive MIMO (m-MIMO) structure is an essential element of a millimeter wave (mmwave) system to compensate the large air propagation loss. This however requires new air interface design to overcome hardware limitations tied to m-MIMO and mmwave, particularly for higher frequencies above 40 GHz. In this paper a block-wise single carrier (BWSC) waveform with low peak-to-average ratio (PAPR) is proposed to lower the cost of massive number of RF components needed to realize an m-MIMO structure for mmwave. Same as OFDM, data-based cyclic prefix (CP) is attached to every BWSC block to enable frequency domain equalization (FDE). Evaluations have been conducted to demonstrate the advantage of data-CP BWSC over orthogonal division multiplexing (OFDM) and null-CP single carrier waveform in terms of some key performance measures such as system efficiency, adjacent channel leakage ratio (ACLR), inter-symbol inference (ISI) and PAPR.

Receiver algorithms which combine belief propagation (BP) with the mean field (MF) approximation are well-suited for inference of both continuous and discrete random variables. In wireless scenarios involving detection of multiple signals, the standard construction of the combined BP-MF framework includes the equalization or multi-user detection functions within the MF subgraph. However, the MF approximation is not particularly effective for multi-signal detection. For this reason, we propose a new factor graph construction for application of the BP-MF framework to problems involving the detection of multiple signals. We also developed a low-complexity variation to the proposed construction in which Gaussian BP is applied to detection and expectation propagation links the discrete BP and Gaussian BP subgraphs. The result is a probabilistic receiver architecture with strong theoretical justification which can be applied to multi-signal detection and, in general, detection in the presence of interference.

A new social conscience is created, which will be used by an net society, at local and global levels, crossing both informatics and education contexts. In this sense, several fields of science use Stewart platforms (SP) in order to manipulate objects in 3D environments. The Ilizarov Hexapod System, which correct bone deformities, is also one of SP's contributions. However, teaching IHS operation to orthopedic doctors, who are the key stakeholders in this field, is hindered due to IHS's three-dimensional characteristic. With the support of the Scrum framework, researchers conducted the development of four 3D Learning Objects. These 3DLOs were used in class with eight orthopedic doctors and eleven residents in orthopedics, and evaluated by means of a questionnaire. This study's results reflect on the support framework used and on the effectiveness of 3DLOs to teach the principles of the IHS. Finally, this paper presents the contributions of Scrum framework to the construction of 3DLOs and the effectiveness of this type of learning objects as an instructional mechanism in orthopedics. For that purpose, given the characteristics of the study, the research methodology was based of grounded theory and empirical-descriptive.

Degenerative disc disease is the most common cause of low back pain, affecting 70–85% of the general population at some time in life. Considering this fact, it is essential to characterize the behavior of the intervertebral disc and its degeneration mechanisms. To study this problem, numerical modeling presents itself as an advantageous approach, being extensively used by researchers to understand the human spine complex. A lumbar partial motion segment model and respective finite element formulation are briefly described. The model's geometric sensitivity is analyzed by varying its wedge angle and average height, and simulating its biomechanical behavior under different incremental loads, using a homemade finite element solver. The results prove that both wedge angle and average height variations have significant influence in the intervertebral discs' behavior under loading.

This work presents a radiation hardening controller for a DC-DC converter. Radiation hardening circuits are used typically in space applications. An overview of the radiation effects on bulk CMOS integrated circuits, as well as, the design techniques required for radiation tolerance are presented. Power converter constraints and trade-offs are discussed and the state-of-the-art radiation tolerant current mode controller for switch mode power supplies implemented is described. The controller was integrated in AMS 0.35μm CMOS technology and uses ELT MOS transistors for radiation hardening. The fabricated IC was tested proving its functionality.

This paper presents a comparative analysis of eigenvector-based signal detection algorithms and a new eigenvector-based modulation classifier for multiple antenna cognitive radio applications. The signal detection algorithms considered in this work are: Feature Template Matching (FTM), Multiple Feature Matching (MFM) and Principal Components (PC)-based detection. A software-defined radio (SDR) platform is used to experimentally evaluate the detection performance of these algorithms. It is observed that MFM, which uses four signal features extracted across space, time and phase dimensions, provides the best performance among the considered algorithms. This paper also presents a new idea on the use of eigenvectors for signal classification in multiple antenna systems. Using computer simulations, it is shown that eigenvectors corresponding to different modulation schemes allow for reliable signal identification even at very low SNR values (on the order of −20 dB), therefore they can be used effectively for signal classification in cognitive radio applications.

This article proposes to create and evaluate a software prototype that uses the idea of telemedicine to send an electronic medical record along with the patient's ECG, using tablets with Android as operating system and a 3G network, helping the specialist on his decisions on the emergency procedures, treatment and transport of the patient. This scenario sets the use of new technologies as an ally to help diagnosis at a distance.

In 2001, the Federal Communications Commission made available a large block of spectrum known as the 60 GHz band. The 60 GHz band is attractive because it provides the opportunity of multi-Gbps data rates with unlicensed commercial use. One of the main challenges facing the use of this band is poor propagation characteristics including high path loss and strong attenuation due to oxygen absorption. Antenna arrays have been proposed as a means of combating these effects. In this paper we study the feasibility of outdoor communication in the 60 GHz band. Because arrays are required for antenna gain and adaptability, we explore the use of arrays as a form of equalization in the presence of channel-induced intersymbol interference. A site-specific study is conducted using ray tracing to model an outdoor environment on the Virginia Tech campus. The performance of outdoor links is evaluated through simulation of the bit error probability.

We present a signal detection algorithm for digital amplitude-phase modulated signals in frequency-selective fading channels with non-Gaussian noise. We consider an asynchronous scenario in which the timing (symbol transition epochs) is unknown and a symbol rate offset is present due to clock drift. A Gibbs sampling-based algorithm is proposed to estimate the unknown parameters and signal detection is performed using a maximum-likelihood procedure. The additive noise is modeled by a Gaussian mixture distribution, a well-known model for man-made and natural noise. Numerical results are presented to characterize the performance of the proposed algorithm.

In recent years Network Virtualization has gained considerable attention from the scientific community once it provides mechanisms to overcome the ossification problem of the current Internet architecture. One of the main problems regarding Network Virtualization is the Network Embedding Problem, since it is a NP-Hard problem. In this work we present a new embedding algorithm based on the Tabu Search Metaheuristic and propose a VN selection policy based on the Bidimensional Knapsack Problem.

The performance of the double THz photometers system is presented. It is the first detection device conceived to observed solar flare THz emissions on board of stratospheric balloons. The system, named SOLAR-T, has been built, integrated to data acquisition and telemetry modules developed for this application, and tested. It utilizes two Golay cell detectors preceded by low-pass filters, 3 and 7 THz band-pass filters, and choppers. SOLAR-T photometers can detect relative temperature variations smaller than 1 K with sub second time resolution. It is intended to determine the still unrevealed spectral shape of the mysterious THz solar flares emissions. The experiment is planned to fly on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014-2016.

A 263 GHz gyrotron dedicated to Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy has been designed by EPFL and manufactured by Thales. With this device, we have demonstrated an output power up to 160 W in continuous wave. Design and main experimental results are discussed in this paper.

This paper presents a discussion of the classification of digital communication signals given incomplete knowledge of the channel. Through a maximum-likelihood framework, modulation classifiers are presented which assume no or limited a priori knowledge of the fading experienced by the signal (including time offset, phase shift, and amplitude) and/or the distribution of the noise added in the channel. A recently published asynchronous classifier for digitally modulated signals, which uses a new channel estimator that is blind to the modulation scheme of the received signal, is introduced and analyzed. In addition, results are presented of our recent work on the classification of digitally modulated signals in flat fading non-Gaussian channels.

A direct arterial pressure monitoring system for post EVAR procedure based on inductive-coupling is presented which avoids the need for more complex biomedical imaging systems. Post stent-graft implantation complications, such as endoleaks, can be detected with capacitive pressure sensors placed in the stent-graft and monitored externally after the measurement of the oscillation frequency of a LC resonant circuit created by sensors and inductive coupling. Several measurements were performed in order to characterize the system and compare the results with the expected values based on theoretical models. Different measurements were carried-out with the purpose of evaluating the system's frequency detection accuracy throughout the working bandwidth and varying distances between the reader and the sensors. Both air and a phantom with electrical characteristics similar to the human body were used between the reader and the sensors antennas in order to evaluate the influence of the transmission medium. It is shown that in both cases the system is capable of detecting the oscillation frequencies, even in the case a cluster of sensors is used.

This paper presents a CMOS pixel motion detector based on a current-mode APS (Active Pixel Sensor) topology with wireless capability using an Impulse Radio - Ultra Wide Band (IR-UWB) in standard 0.35μm CMOS technology for applications in image sensor networks. A pixel was designed with a transmission gate to control one copier cell in order to compare different integration times. The pixel output is a digital signal proportional to the difference between the two currents. The proposed IR-UWB has a simple architecture, without inductors and carrier modulators. It is based on parallel pulse generator blocks that produce Gaussian pulses, and a pulse shaping stage which adjusts the pulse amplitude, below the FCC -41.3dBm floor. The transmitter exhibits as main characteristics: output pulse of 408ps wide at 4.90GHz, and voltage amplitude of 144mVpp, an average power is only of 7.15μW/pulse at 170MHz PRF (Pulse Repetition Frequency). The whole circuit has been simulated using LTSpice and the results demonstrate the circuit capability to operate as a motion detector. The complete circuit pixel occupies a very small area of 120μm × 115μm.

In this paper, we propose a distributed power control scheme which can take into account the end-to-end performance of users in a multihop cellular network. Bottleneck links in a multihop wireless network limit the maximum rate achieved by users along their routes. Under the proposed scheme a link dynamically switches between different power adaptation algorithms based on whether it is a bottleneck or a non-bottleneck link. Specifically, non-bottleneck links iteratively reduce their transmit powers whereas the bottleneck links use power control to exploit the corresponding interference reduction and further increase their signal-to-noise-and-interference ratios (SINRs). We show substantial system throughput performance gain under our scheme and for which, under certain scenarios, we derive a closed-form expression of the converged transmit power levels regardless of their initial values.

Due to the lack of sufficient channel state information, modulation classification in frequency-selective fading channels is a challenging task. This is mainly because the complexity of the pre-processing stage, where the required channel state information for (optimal) likelihood-based classification is estimated, can be relatively high. For this reason, we propose in this paper a low-complexity cumulant-based channel estimation algorithm that enables the reliable classification of digital amplitude-phase modulated signals in frequency-selective fading channels. Numerical results are presented which show that the proposed algorithm outperforms a commonly used channel estimation algorithm for modulation classification, especially at low signal-to-noise ratio values. Using the proposed algorithm, it is also shown that the performance of a practical modulation classification method can approach that of a clairvoyant classifier assumed to have perfect channel knowledge.

New monitoring methods of dengue vector and evaluation of public policies on dengue control are major concerns for several tropical countries. Drawback on monitoring methods base on oviposition surveys are the counting process of mosquito eggs, information store and analysis. Here we present a new automated egg counting system for remote Aedes aegypti population survey. The system is base on an optical scanning platform, a man-machine interface, and a software for mosquitoes eggs counting. Acquired information are sent over the internet and remotely analyzed. Prototypes of the device were installed and implement in two different cities.

Ink-jet printing is a novel method to promote electrical circuit by printing metal nanoparticles onto flexible substrates. This novel method allows to develop sensor that can be used to measure deformation, and also to measure the life cycle of a material. The conductive ink printed directely onto flexible surface allows to evaluate the behaviour of the substrate material under mechanical solicitation. The present work aims to evaluate electro-mechanically the conductive trace obtained by silver nano-particles. The trace consists of a line of 25 mm equivalent to one grid of a printed strain gauge. The amount of layer and the width of the trace was evaluated in order to selected the best set-up, in which is the sample that have low level of roughness and satisfactory reproducibility of the electrical resistance. Cyclic bending fatigue test were carried out on selected samples with two different displacement applied. Ag printed trace submitted to 4 of mm displacement presented life cycle 50% less than displacement of 2 mm.

This paper presents a performance analysis of an ultra wideband (UWB) communication system based on Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the presence of narrowband interference. Although OFDM-based systems are known to be capable of withstanding some level of narrowband interference, mitigation techniques may have to be used when interference levels are high. Furthermore, as typical UWB systems employ low resolution analog-to-digital converters, the effect of narrowband interference may be exacerbated in the process of analog-to-digital conversion. In order to improve the performance of MB-OFDM UWB systems in the presence of narrowband interference, we consider the use of analog notch filters. This paper proposes an analytical model and formulation that allows for the evaluation of the probability of symbol error of an MB-OFDM UWB system when an analog notch filter is used for narrowband interference mitigation. It is shown that using an analog notch filter can significantly improve the performance of MB-OFDM UWB systems in high-interference scenarios.

This paper presents novel single-source localization techniques for a sensor network that is capable of obtaining both direction and range estimates by considering an optimization approach. Specifically, linear programming and non-linear programming techniques are developed and compared to a classic linear least squares technique. It is shown that the proposed techniques achieve superior results to the least squares approach in most cases.

The majority of prior work in signal-to-noise ratio estimation makes fairly strong assumptions concerning a priori knowledge of the channel state and signal. For instance, many of these estimators assume knowledge of the modulation scheme of the signal, or even complete knowledge of the transmitted set of modulated data symbols (typically through the use of training sequences). Even more universally, perfect time synchronization between the transmitter and receiver is assumed. The purpose of this paper is to remove some of these commonly stated assumptions through the presentation of a novel asynchronous, noncoherent, and non-data-aided method-of-moments based signal-to-noise ratio estimator for PSK/QAM modulated signals in flat-fading channels. This estimator requires no a priori knowledge of the channel gain, phase, and delay, nor the specific modulation scheme (PSK or QAM) and modulation order used.

VHTR (Very High Temperature Reactor) and LS-VHTR (Liquid Salted - Very High Temperature Reactor) reactors were analyzed and compared from the viewpoint of the neutronic parameters. The multiplication coefficient (k inf ), the fuel and the moderator temperature coefficients (α TF and α TM , respectively) and the hardening spectrum (oF/oT, fast flux/total flux) parameters were analyzed focusing to understanding better the VHTR and LS-VHTR neutronic behaviors. The experience obtained performing this work will be used in the future to study and to simulate the possibility of such systems for fuel reprocessing and recycling always analyzing how the process can affect the hydrogen production efficiency. The preliminary analyses have demonstrated that the VHTR reactor has a safer behavior in comparison with to the LS-VHTR one considering the evolution of the safety parameters along the burnup using WIMSD simulations.

The frequency assignment is a very important task in the planning of the GSM networks, and it still continues to be a critical task for current (and future) mobile communication operators. In this work we present a hybrid differential evolution (DE) algorithm to solve a real-world instance of the frequency assignment problem. We present a detailed explanation about the hybridization method applied to DE in order to make it more efficient. The results that are shown use accurate interference information. That information was also adopted by other researchers and it represents a real GSM network, granting, therefore, an extremely important applicability. Furthermore, we have analyzed and compared our approach with other algorithms, obtaining good results.

Channel frequency response is one of the banner performance specifications for discrete Fourier transform (DFT) based spectrum analysers. Digital techniques have emerged as most attractive approaches to correct the linear distortion introduced in the microwave and immediate frequency (IF) analogue signal paths. This paper presents a novel technique for correcting the channel frequency response (flattening amplitude and linearizing phase) on microwave spectrum analysers. By combining factory calibration data of the amplitude and phase response and run-time IF alignment, we can accomplish significant improvement in vector measurement performance. In contrast, traditional equalization of channel frequency response is only performed at a fixed IF frequency and the channel response variation over RF frequencies is mostly ignored. A cost-effective calibration solution can also be realized using an arbitrary waveform generator (AWG) and an off the shelf mixer to generate calibration signal.

Frequency assignment is a very important real-world problem, specially in GSM networks. These networks are very used in the telecommunication area (by mid 2006 GSM services were used by more than 1.8 billion subscribers across 210 countries, representing approximately 77% of the world's cellular market). In this paper we solve a real-world instance of this problem, using a differential evolution (DE) algorithm hybridized with a local search method. We also analyze the performance of the several configuration parameters, because the performance of optimization algorithms is highly dependent on the specific properties of the problem to be solved. Several experiments were carried out to find the best set of parameters for the DE algorithm implemented in this work. The final results obtained by DE are very good.

In recent years, cognitive radio (CR) has been introduced as a new paradigm for enabling much higher spectrum utilization by dynamically accessing and sharing the spectrum with incumbent radio devices. This paper proposes an innovative and practical spectrum-sharing approach and evaluates its performance. The goal is to minimize CR's harmful interference to incumbent primary users and to maximize the utility of spectrum-sharing networks by exploiting the proposed radio environment map (REM). REM-enabled CR adaptation algorithms are developed for various operational environments, namely, the open area and the dense urban area. This paper also compares the performance gain when using the Global REM and the Local REM, respectively. The impact of imperfect REM information due to node mobility and REM dissemination delay is simulated. By exploiting the REM information, CR can make situation-aware adaptations in transmit power, transmit timing, routing protocol, and topology, thereby reducing interference to primary users. More importantly, the painful hidden node or hidden receiver problem can be mitigated with the help of the Global REM. REM-enabled CR could be a cost-efficient and reliable approach to "waterfilling" underutilized spectrum in both space and time domains.

Mobile computing applications are required to operate in environments in which the availability for resources and services may change significantly during system operation. Thus, mobile computing applications need to be capable of adapting to these changes to offer the best possible level of service to their users. However, traditional middleware is limited in its capability of adapting to the environment changes and different users requirements. Aspect Oriented Programming has been used in the design and implementation of adaptive middleware architectures. In this paper, we propose an adaptive middleware architecture which can be used to develop adaptive mobile applications. Such architecture is compared to a component-based architecture from a quantitative perspective. The results suggest that middleware based on this model can be used to build mobile adaptive applications that require only a very small overhead in terms of running time as well as memory footprint while producing code that is more ease to comprehend and modify.

A special switched reluctance motor for a fractional horsepower and high speed hand tool is studied in order to improve its torque characteristic. This task is accomplished by optimizing some rotor geometrical parameters with the aid of a numerical approach based on the application of simulated annealing and Kriging method. Finite element simulations are used to evaluate the approximation points for the Kriging model. The numerical results are compared to tests on a prototype.

Modular exponentiation is an essential operation for various applications, such as cryptography. The performance of this operation has a tremendous impact on the efficiency of the whole application. Therefore, many researchers devoted special interest to providing smart methods and efficient implementation for modular exponentiation. One this method is the sliding-window method, which pre-processes the exponent into zero and non-zero partitions so that the number of modular multiplications required computing the modular power is reduced. In this paper, we devise a novel hardware for computing modular exponentiation using the sliding-window method. The implementation is efficient when compared against existing hardware implementations of the modular exponentiation

In this paper it is presented and researched the possibility of using the differential evolution (DE) algorithm to solve the frequency assignment problem (FAP). This problem involves a free assignment of a number of available frequencies to a set of requesters, subject to a set of specified constraints given by an interference matrix. Hence, it is a very important problem in the telecommunications area (especially in GSM networks -global system for mobile). In this work, by the first time, the performance of DE is evaluated using for the results seven well-known benchmark problems on the MS-FAP (minimum span frequency assignment problem). Furthermore, we also compare the influence of each configuration parameter of the DE, presenting the most important conclusions.

The Smart Antenna has been proposed as an enabling technology for beam steering in Software Defined Radio (SDR) equipments and can be used to increase the quality in wireless communications link. This paper presents a possible architecture for testing smart antenna algorithms for SDR. The Software Defined Radio Group of University of Brasilia (SDR-UnB) has implemented a small prototype of SDR architecture, which should be able to estimate the Direction of Arrival (DOA) of a signal. The present study deals with the reconfigurability and selectivity of the SDR antennas using a linear uniform array of four antenna elements to estimate the DOA of a signal and the Universal Software Radio Peripheral (USRP) as RF front-end. With the proposal architecture it is possible to evaluate the effects of mutual coupling among the antenna elements caused by the wideband or multiband RF structures used in SDR smart antennas taking into account the co-channel interference. The validation of DOA algorithms can be done in a more realistic way using the prototype.

This paper describes a system able to acquire, process and eliminate noise in continuous streams of data in real-time. The signal processing algorithms were based on the discrete wavelet transform and employ a new approach to deal with border problems, allowing the data to be continuously processed while they are acquired. The system was implemented using a DSP coupled to a digitizer through its external memory bus to guarantee deterministic behavior while maintaining some degree of flexibility on its configuration. The achieved performance and potential applications are discussed at the end of the text.

Two new algorithms to compute the direct and the inverse discrete wavelet transform of continuous streams of data are discussed in this paper. The algorithms are optimized to be used in uniprocessor systems, presenting as one of their main features the ability to compute over the borders of the data segments without relying on any techniques that are traditionally used for thus task, like zero padding. A modified version of the recursive pyramid algorithm was used to compute the direct transform, keeping just the features to minimize data storage but eliminating its dependency on extension techniques. The inverse transform is computed by an algorithm inspired in the RPA, the quadrature mirror filter bank and the overlap-save method for filter convolutions. To evaluate the performance the algorithms were implemented on a DSP coupled to a digitizer through its external memory bus, what allowed deterministic behavior. After a stage of optimization an analysis of data storage and computation load were made. These results and the potential applications are discussed at the end of the paper.

Documents written on both sides on translucent paper make visible the ink from one side on the other. This artifact is called "back-to-front interference" or "bleeding". The direct binarization of documents with such interference yields unreadable documents. The literature presents several algorithms for suitably removing such artifact. This paper presents a quantitative method to assess algorithms to remove back-to-front interference.

Java is a platform independent, portable, robust and distributed programming language suitable for the development of Internet applications. Performance is its strongest limitation. This paper analyses the quality of service provided by the session initiation protocol (SIP) for Voice on IP implemented in Java. Delay, jitter and packet losses are tested.

We make a comparative analysis of two proposals for setting up a facilities-based metropolitan network to serve the education and research community in the city of Belem do Para in Brazil, using the "do-it-yourself" (DIY) model of building infrastructure, and benefiting around a dozen research and education institutions. The first alternative is to build a fiber optic network, using Gigabit Ethernet technology. The second one uses a metropolitan wireless network, based on the IEEE 802.16 standard, studying the feasibility of the use of this technology in a context with the particular characteristics of the Amazon region. In both cases, we show that the capital cost for each institution is feasible, and that the total cost in the medium term is lower than the recurrent costs of maintaining the traditional model based on telecommunications provider services

The paper aims at quantifying the uplink soft-handover (SHO) gain for a W-CDMA network from measurements in the field. SHO gains measured in the field are heavily dependent on the power control algorithms implemented at the user equipment (UE). Two different UE uplink power control implementations were used in the measurement campaign. The first approach uses uplink power control with TPC combining, i.e., combining transmit power control (TPC) bits from all the cells in the active set. The second approach does not perform TPC combining, i.e., it selects the TPC from the best server (i.e., the best CPICH Ec/Io). The uplink soft handover gains measured in static conditions for both uplink power control algorithms are presented, and the advantages and disadvantages of each power control implementation are discussed.

This paper introduces a new control technique for power factor correction in ac-dc converters. It combines the advantages of conventional hysteresis control strategy and the prominent characteristics of constant switching frequency. This is possible because the hysteresis bandwidth can be adjusted to provide fixed switching frequency. The operating principles, theoretical analysis and results on a single-phase boost converter are presented to validate the proposal.