Monday, May 4, 2009

Software development has significantly matured in the last decade. However, one of the critical challenges today is uncertainty inherent to every aspect of software development including requirement specifications, design, coding, and testing. In this paper, we propose a framework for uncertainty management in software engineering. The framework is used to model uncertainty inherent to software development activities and manage their consequences. The framework consists of four main phases: identification and prioritization, modeling and analysis, management and planning, and monitoring and evaluation. Commercial Off-The-Shelf (COTS)-based development is selected as an example to illustrate how the proposed framework is used in a simple but intuitive case study to represent uncertainty and manage its consequences.

Software visualization is to use visual representation to make software more visible. There are a lot of software visualization tools existing for various purposes. Therefore, how to choose the right visualization tool for a specific task becomes an important issue. Although there are a few taxonomies for classifying visualization tools, each has its own defects. This paper proposes a new classification schema based on the widely used Bloom’s cognitive taxonomy. We summarize a set of questions for each level of the Bloom taxonomy using the well defined verbs, to identify if the visualization tool belongs to the individual cognitive level, which in turn can determine the purposes of the tool. We also conduct case studies on five tools to evaluate this new approach. The result demonstrates that the new classification schema can provide good guidance for people to choose a useful visualization tool.

The second-order HF radar ocean cross section is derived for the case of the transmitting and receiving antenna undergoing platform (i.e. barge) motion. The derivation for electromagnetic patch scatter begins with a general expression for the bistatically received second-order electric field. Based on an assumption that the ocean surface can be described as a Fourier series with coefficients being zero-mean Gaussian random variables, the second-order monostatic radar cross section is developed. The derivation for the hydrodynamic patch scatter follows from an earlier first-order analysis. The second-order HF radar cross section is found to consist of Bessel functions, and no singularity exists in the new electromagnetic coupling coefficient. Simulation results depict the effects of barge motion under a variety of sea states.

The Australian Coastal Ocean radar Network (ACORN) is a monitoring network of HF radars which are being installed around Australia under a National Collaborative Research Infrastructure Strategy (NCRIS). It is a five-year project, at the end of which there will be five pairs of radar stations and one triplet installed and operating, enabled by the central pool of funding for the Integrated Marine Observing System (IMOS) which is a part of NCRIS, and augmented by funding from other sources. At each chosen site there is a pair (or triplet) of radar stations, mounted on the shore, which receive radar echoes from the rough sea. Four of the pairs of radar stations are phased array installations and one pair and the triplet are of the amplitude direction finding genre. The NCRIS strategy is to provide easily accessed data, freely available to researchers in quality controlled archives. The IMOS aim is to produce data which will support research into coastal dynamics and exchange between the open ocean and the continental shelf. In addition to research in coastal oceanography, the data are available for algorithm development and evaluation of new applications for HF ocean radar. There is potential for application of the data to management of coastal marine resources, and in marine safety areas. Real-time maps of surface currents and the prospect of short-term forecasting have the potential to reduce search areas in coastal waters and to make pollution/spill mitigation more effective. With the establishment of HF radar monitoring stations like those in ACORN, there is growing opportunity for researchers around the world to access data from well curated archives to carry out basic research on physical oceanography, or applications research without having direct access to the measuring facility. This feature brings the ACORN HF radars into GEOSS for coastal processes and dynamics.

SIFT (Scale Invariant Feature Transform) features are widely used in object recognition. These features are invariant to changes in scale, 2D translation and rotation transformations. To a limited extent they are also robust to 3D projection transformations. SIFT Features however, are of very high dimension and large number of SIFT features are generated from an image. The large computational effort associated with matching all the SIFT features for recognition tasks, limits its application to face recognition problems. In this work we propose a discriminative ranking of SIFT features that can be used to prune the number of SIFT features for face recognition. Our method checks the number of irrelevant features to be matched thereby reducing the computational complexity. In the process it also increases the recognition accuracy. We show that the reduction in the number of computations is more than 4 times and increase in the recognition accuracy is 1% on average. Experimental results confirm that our proposed recognition method is robust to changes in head pose, illumination, facial expression and partial occlusion.

This paper presents a new method for addressing the challenging problem of generating changeable and privacy preserving templates for face based biometric verification systems. The proposed method transforms the extracted face feature vector by a random orthonormal matrix, and the sorted index numbers of the resulting feature vector in the transformed domain is stored as template for verification. A new matching algorithm is introduced for measuring the similarity between the template and the authenticating image. Two different application scenarios, user-independent and user-dependent transformation are discussed. A vector translation technique is introduced to enhance the changeability of the generated templates. Experimental results on a large face data set demonstrate that the proposed method may improve the verification performance, produce strong changeability, and protect the user's privacy.

Wind/hydrogen/diesel cogeneration systems can be quite attractive for the energy supplies of remote communities in terms of economic and environmental factors. For such a weak grid, a power electronics-based dump load controller is usually deployed for frequency regulation to balance the generation and demand. This paper presents a two-leg IGBT-based load controller, which can be operated in low power, medium power, and high power operation modes. A bumpless transfer technique is proposed to smoothly switch between neighboring operation modes. Analysis, simulation, and prototyping test results are presented.

The present paper proposes a software prototype that evaluates and compares economical efficiency of HVDC and AC transmissions. An economic analysis of alternatives is performed to find an appropriate transmission line types during planning construction of transmission lines. This paper proposes a system that automates this process. This software is designed to process financial and technical data of HVDC and AC transmission project and calculate overall cost of them to find an economically efficient transmission lie type. Breakeven analysis and sensitivity analysis are introduced in the software to find an optimum condition of each project. The software calculates power loss from parasite reactance at transmission lines and converts it into financial loss which is added to overall project cost. The software has been tested with sets of virtual project data and test results by using short and medium transmission line are introduced and compared in the present paper.

In this paper, we present signal construction for the future IEEE 40GBASE-T standard. The LDPC assisted coded modulation and demodulation is presented. A code achieving 6dB gain, which is literally high enough to satisfy reliability constraints for data transmission at a rate of 40 Gbps over 50m Cat-7A (class FA) copper cable, is designed and the simulation results are presented. The main objective of the presented work is to extensively reduce the power and implementation complexities of a 40GBASE-T system.

We present formulations and simulation results for infinite-length and finite-length MIMO decision feedback equalization and compare with finite-length SISO equalizer/FEXT canceller for an improved version of Cat-6 cable. Intuitively, far-end crosstalk contains useful information, and instead of being cancelled, could be jointly processed to improve system performance. Conversely, a simpler system could be designed for a given transmission rate. A SISO equalizer/canceller is compared with a MIMO equalizer to investigate possible improvement in decision point SNR and filter lengths. We demonstrate that when FEXT levels are too low, MIMO implementation has no significant benefit in terms of SNR, and possibly has higher complexity.

This paper analyzes technical issues with the installation of a linear generator based offshore wave farm using a Voltage Source Converter (VSC) HVDC connection to the onshore grid. Design issues are introduced by summarizing the current status of VSC HVDC technology and related installations, research in the use of VSC HVDC for offshore wind farms, and characteristics of wave energy converters using linear generators. A DC bus wave farm design using a linear generator model is presented and simulations using time shifted and variable amplitude wave inputs demonstrate the effect of increasing the size of the wave farm on smoothing short-term variations in the power output due to wave oscillations.

The use of hands-on learning experience to teach robotics design techniques is well established. In light of this, a small autonomous underwater vehicle (AUV) for use in the education of undergraduate students has been developed. The system builds on the LEGO NXT Mindstorms kit, maintaining interconnectivity between custom components and the NXT system, to provide an easily reconfigurable platform. The AUV illustrates the design process as well as many of the concepts required in submersible design such as buoyancy, trimming, passive stability, control, seals and propulsion methods. By keeping the cost of the system low, the ability to use the AUV for purely instructional purposes becomes feasible.

In this paper, a fully integrated E-band power amplifier with 17 dB gain, 11.5 dBm saturated output power, and 5 GHz bandwidth was achieved in the 90 nm CMOS technology. The amplifier configuration consists of two cascode stages and a common-source output stage. It exhibits a peak power added-efficiency of 20 % while consuming 50 mW from a 1.5 V power supply.

In this paper a Low power divide-by-two static frequency divider using GDI D flip-flop is proposed which uses only single clock phase. This divider is simulated in a standard 0.18µm CMOS process. Simulation results indicate that the proposed divider consumes, in the worst case, 1.6mW power at 2.5V supply voltage and maximum operating frequency up to 6GHz, and the power consumption is 10.7µW by using of a 1V supply voltage at 1GHz input frequency.

We provide a framework for implementing IPSec security services in a well-structured functional architecture based on a layered functional architecture for network security management [1]. The proposed architecture is modular and allows for the composition of software applications from commercially available products developed by different suppliers to implement the entire security requirements of the IPSec protocol. The proposed architecture supports open standards and interfaces, and implements the security services of IPSec as an integrated solution under a unified security management system.

In order to set up reliable but usable e-commerce web-site, a method is provided to designers and programmers guidance in evaluating an adequate observance of HCI, security, and e-bussines requirements. Previous research works propose a list of primary requirements for HCI, security, and e-commerce. In this paper, we present an outlook of these ba-sic requirements which are subsequently incorporated in a set of metrics. The proposed measurement model is based on the Goal Question Metric technique and complemented with a mathematical formulation. Our proposal is described in a comprehensive framework. We will show the effective-ness of the method by using an illustrative example as a proof-of-concept.

In this paper, we develop a new design for adaptation of linear dispersion code. A new adaptive parameter called space-time symbol rate is applied in our design. We have studied the statistics of signal-to-interference-noise of a linear MMSE receiver over a Rayleigh fading channel. The average BER for a given constellation using the MMSE receiver is calculated numerically. With the statistics as a guideline, two adaptive techniques using constellation and space-time symbol rate are studied, respectively. If constellation and space-time symbol rate are considered jointly, more selection modes can be available. Theoretical analysis demonstrates that the average transmission rate of the joint adaptation can be improved in this case. Simulation results are provided to show the benefits of our new design.

Error-rate evaluation of Space-Time codes using Union bounds sometimes requires very heavy computational loads and so is impractical. In this paper, a Common function shared by different Union bounds is derived and used to develop a modified Union bound (MUB). Results of numerical evaluations and Monte-Carlo simulation on two 2x2 rotation-based S-T codes show that the MUB provides a good compromise between the required computational load and the accuracy for error-rate evaluation.

In this paper we present algorithms for transmitter adaptation in downlink wireless systems based on maximization of the Signal-to-Interference plus Noise-Ratio (SINR). We investigate their fixed-point properties in various scenarios and their relationship with optimal points in dual uplink scenarios.

The aim of our research is to be able to determine the tactile feeling of fabrics, sold over the web, by using inexpensive technologies. A GLCM texture based fractal method is proposed to objectively evaluate the surface roughness of fabric images. The fractal dimension, which has been proved as a descriptor of tactile surface roughness, is calculated from the texture features extracted from GLCMs. The proposed method has been implemented in Matlab and tested by using woven fabric images which are randomly chosen from clothes. Two types of the fractal dimension estimation methods: the box counting method and the power spectrum method are used for roughness evaluation. The power spectrum method is demonstrated to be more robust than the box counting method. The major results of our fabric roughness evaluation show that the GLCM can represent a meaningful descriptive basis of fabric textures and fractal dimension of the GLCM textures have the ability to evaluate the actual fabric surface roughness.

Diagnosis and monitoring of kidney diseases and transplants is supported by microscopic analysis of needle-core biopsy samples. The current methods of analysis allow for inconsistencies, bias, and inaccuracies. We propose image processing methods for automatic segmentation of the effective biopsy area (cortex and medulla) from digital images of renal biopsy samples. The methods include opening-by-reconstruction, a morphological closing operation, and morphological erosion. The results are compared to 100 randomly selected images manually marked by an experienced renal pathologist. Comparative measures indicate that the automatically detected region of interest closely matches the ground truth; the mean distance to the closest point was 5.46 $\pm$ 3.92 $\mu$m (6 $\pm$ 4.31 pixels) and the true-positive fraction was 98.25 $\pm$ 1.77\%.

This research evaluates the performance of the structural similarity index. An increasingly popular image quality metric, the structural similarity index is essentially a measure of the statistical correlation of two images. Its alleged strengths and advantages are widely acclaimed. For an arbitrary set of test images, however, statistical regression reveals a surprisingly high degree of association between the index and the fallible mean squared error, despite claims to the contrary on the part of its designers. This discovery suggests a much closer relationship between these two metrics.

The growth of environmental concerns, and the rapid increase on the electric power demand, increased the interest in renewable energy. Wind energy is a clean, cheap, abundant energy source that could be utilized in rural areas. However, the continuous variation of wind speed results in severe power quality problems, especially in stand-alone networks. This paper proposes a FACTS based dynamic voltage regulator (DVR) controlled by a tri-loop dynamic error-driven PI controller, that could be used to improve the power quality, in a rural load fed from a wind driven separately excited induction generator. This improvement is illustrated via MATLAB simulation.

The incipient faults in underground cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Based on the methodology of wavelet analysis, a method is presented to detect and classify the incipient faults in underground cables at the distribution voltage level. The proposed method is designed to be possibly applied in real systems. Therefore, different fault conditions and system configurations are examined, and other transients caused by permanent fault, capacitor switching, load changing, etc., can also be discriminated.

This paper briefly reviews the synchronization techniques for single-phase converter-interfaced distributed generation (DG) systems. These techniques are compared in terms of their capability in tracking the amplitude and frequency variations, and the phase angle of the grid signal in the presence of low order harmonic. The techniques introduced in this paper are applicable for a wide range of equipment like converter-interfaced distributed generation (DG) units, e.g. wind, photovoltaic, and fuel cells, and also in active power filters and uninterrupted power supplies.

Today's converged networks are mainly characterized by their support of real-time and high priority traffic requiring a certain level of Quality of Service (QoS). In this context, traffic classification and prioritization are key features in providing preferential treatments of the traffic in the core of the network. In this paper, we address the joint problem of path allocation and admission control (JPAC) of new Service Level Agreements (SLA) in a DiffServ Domain. In order to maximize the resources utilization and the number of admitted SLAs in the network, we consider a statistical bandwidth constraints allowing for a certain overbooking over the network's links. SLAs' admissibility decisions are based on solving to optimality an Integer Linear Programming (ILP) model. When tested by simulations, numerical results confirm that the proposed model can be solved to optimality for real-sized instances within acceptable computation times and substantially reduces the SLAs blocking probability, compared to a the Greedy mechanism proposed in the literature.

We study if information entropy of packet traffic passing through selected set of routers may detect anomalous packet traffic (e.g., distributed denial-of-service (DDoS) attacks) in a packet switching network (PSN) model. Given a certain PSN model setup (i.e., topology, routing algorithm, and source load value) a “natural” entropy profile of normal packet traffic monitored at selected routers characterizes normal operation of PSN model. When entropy of packet traffic deviates significantly from this “natural” profile it means that some anomaly in packet traffic emerges. Our simulations of ping DDoS attacks show that after start of attacks the entropy of packet traffics monitored even at small sets of routers may significantly drop and that it is easier to detect these drops if static routing is used instead of dynamic routing. Thus, for detection of DDoS attacks and other anomalous packet traffic information entropy of packet traffic monitored at properly selected routers can be a useful tool.

In this paper, we are proposing RCUBE (Receiver Window Modified Random Early Detection queues with RECHOKe) which combines the advantages of both Receiver Window Modification (RWM) and RECHOKe schemes. By using the RECHOKe scheme, RCUBE easily identifies malicious flows by using CHOKe hit and CHOKe-RED histories, by requiring only a small amount of information, approximately proportional to the order of magnitude of malicious flows. By using the RWM scheme, we reduce the average TCP queue sizes in the queues and in doing so, not only make it easier to identify malicious flows using RECHOKe but also reduce the queuing delay resulting in significant improvements in one-way end-to-end packet delays, delay jitter, throughput and number of dropped packets for TCP-friendly flows. We analyze xCHOKe, RECHOKe and RCUBE in detail and show that RCUBE using both RWM and RECHOKe easily outperforms RED, either use alone or with RECHOKe, xCHOKe and CHOKE, in identifying, controlling and punishing malicious flows and in protecting TCP-friendly flows. Other proposed schemes either did not perform as well or incur too much overhead.

The operation of switching in selection diversity combining produces transients that increase the system outage. Due to this, the switching rate plays an important role in selection diversity system design. Yet published results on the switching rates of selection diveristy combining are scarce. No published work considers correlated diversity channels. In this paper, the switching rate of a correlated dual branch selection diversity combiner in Rayleigh fading is derived. Balanced and unbalanced correlated Rayleigh fading channels are considered. Numerical results are presented for a space-diversity system with horizontally spaced omnidirectional antennas at a mobile station.

Both cooperative diversity and adaptive modulation provide significant enabling techniques for future generations of wireless communication networks. In this paper, we consider an IRCC (incremental redundancy cooperative coding) based cooperative network, which uses adaptive node transmission. Two cases are considered: (i) adaptive transmission only at relay nodes; (ii) adaptive transmission at source and relay nodes. The performance of these two cases are evaluated in terms of the average bit error rate (ABER) and the average spectral efficiency (ASE) and compared with those of noncooperative scheme without adaptive transmission over Rayleigh fading channels. Simulation results show that the IRCC scheme without adaptive modulation (AM) provides 28% more spectral efficiency compared with that of noncooperative case without AM. However, using AM and selecting the best relay in the IRCC scheme, this improvement increases to 100% at SNR of 1 dB.

Base station cooperation will bring a certain delay due to a series of signaling information exchange, cooperation strategy on base station based on location-aided is proposed in this paper. Future location information is provided by moving speed and direction to predict track of user. Signal strength and adjacent cell load combining with location information will be constraints to selecting cooperative base station. User can advance execute signaling interaction with network before signal strength down to an intolerable to reduce delay to increase satisfaction of users. Meanwhile, Quality of signal in edge of cell is improved due to base station cooperation and handover requests decrease in the process of user mobility. Then unnecessary handover is avoided. Compare with no location-aided, pseudo cooperative request and cooperative setting updating will be reduced. It was shown that adopting base station cooperation based on location-aided can reduce system overhead and increase system capacity.

Energy efficiency in wireless sensor networks is one of the most crucial technologies. In this paper, we propose a simple and feasible synchronous sleep and wake mechanisms for wireless sensor networks in a small scale. Sensor nodes are divided into forwarding nodes and listening nodes. Beacon frame containing sleep command from coordinator can be forwarded to listening nodes by forwarding nodes. The network can enter sleep at about the same time. Through such network synchronization mechanism, we can realize synchronous sleep and wake of the entire network. The proposed mechanisms are implemented in sensor nodes and are evaluated in a test-bed. Through the analysis and evaluation of experimental data, it confirms the proposed energy-saving mechanisms are feasible and effective.

Energy conservation in wireless sensor networks (WSNs) is one of the primary performance parameters. In this paper, an energy-efficient virtual multiple-input multiple-output (MIMO) communication architecture based on distributed source coding (DSC) is proposed for energy-constrained, distributed wireless sensor networks. Low Density Parity Check (LDPC) code is one of the practical codes that can be used for DSC to compress close to Slepian-Wolf limit. Simulation results show that employing DSC by using a LDPC code with length 1000 and compression ratio of R=3/5 in a virtual MIMO-based WSN achieves better energy efficiency compared to that of a virtual MIMO-based communication system without DSC.

Energy conservation in wireless sensor networks (WSNs) is the primary performance parameter, because of their limited energy resources. Thus, some energy saving technologies should be applied. One of these technologies for WSNs is distributed source coding (DSC), related to correlation between sensor outputs. In this paper, we propose to apply multirate distributed source coding to reduce energy consumption for a target BER value. Low Density Parity Check (LDPC) code is one of the practical codes that can be used for DSC to compress close to Slepian-Wolf limit. The simulation results for codes of length 1000 and three different compression ratios show that the proposed multirate approach achieves better energy efficiency rather than a single rate code with similar maximum BER value.

This paper investigates the possibility of implementing a conventional computing architecture that can practically emulate the functionality of a hypothetical quantum computer. The state of the art transistor feature size makes the resource requirement, for emulating quantum computation with a relatively large number of qubits, possible. In this paper we investigate how a programmable logic array can be used to practically emulate quantum computation with entanglement characteristics. We illustrate the concept of our practical quantum computer emulator by examining the steps required to build a HW/SW co-design system that can automatically instantiate HW components that implement a quantum computing processing step.

This paper presents a new approach to meeting communication requirements of on-chip network systems. The method is based on the transaction-oriented protocol employed by on-chip components, and the fact that latency becomes the performance-impacting factor instead of bandwidth. A network-on-chip topology generation and analysis tool is presented which has the primary aim of generating on-chip topologies that will meet a given information throughput. The proposed methodology also incorporates contention estimation into the design phase, thus reducing execution time considerably by eliminating the need for multiple generation iterations. SystemC simulation results for two multimedia applications with differing throughput requirements are presented, and the method provide comparable performance to regular topologies while using, on average, half the resources.

VLSI interconnect capacitance is becoming more significant and also increasingly subject to process variation. A simple technique to extract from layout the sensitivity of interconnect parasitic capacitance to linewidth process variations is proposed based on 2.5D capacitance models and implemented in the Magic VLSI layout editor. The derivative of each extracted capacitance with respect to variation in every level is obtained. Coincident edges in layout result in distinct “shrinking” and “bloating” derivatives. The derivatives form a gradient that may be multiplied by a vector of the variations on each level to give the total expected deviation from nominal capacitance. The gradient allows the process sensitivity of each capacitance to be determined by simply inspecting the netlist.

Many algorithms of memory access scheduling have been studied to attack the well-known memory-wall. However, some of them introduce unfairness problem in Chip-Multi-Processor (CMP) systems. Therefore a new approach called Fair- Priority-Expression-Based (FairPEB) burst scheduling is proposed in this paper to address both performance and unfairness problems. Experiment results show that this method improves data bus utilization of memory system by 15.4% and 31.87% over conventional First-Ready First-Come-First-Service (FR-FCFS) and original burst scheduling. Furthermore it keeps memory accesses of different applications fair.

Chip-multiprocessors (CMs) are emerging as a dominant architectural choice for both high-end (e.g., server machines) and low-power systems (e.g., mobile devices, laptops). The CM system consists of several processors cores connected to their respective multi-level cache memories. Recently, some researchers proposed the concept of “cooperative caching” to make the best use of aggregate cache resources available in the system. However, there are several inter-related issues that need to be investigated in order to get the full benefits of cooperative caching. The issues include the cache coherence at multi-level cache hierarchy, data replication, placement of shared data, and the support for low-power operation, among others. This paper outlines the working of a cache coherence protocol that supports cooperative caching in a power-aware CM system. The paper also presents the framework of an analytical model to evaluate such cooperative caching strategies.

Cognitive radio networks use information about their environment and user requirements to achieve specified objectives. There are many radio and network parameters that may be adapted in response to changes in the environment, and these may interact resulting in an emergent state that is not predictable by considering the parameters separately. The cognitive radio network may therefore be considered as a complex adaptive system; further, multiple independent networks form a complex system of systems. Thus, the evaluation of mobile networks operating in congested, heterogeneous environments must consider the high-level objectives rather than those of individual radio and network components. This paper discusses the requirements for the modelling, simulation and evaluation of cognitive radio networks in heterogeneous environments.

Spectrum awareness is a crucial first step of a cognitive radio (CR). This provides information necessary for the CR to adapt to the radio frequency environment, and implies reliable joint signal detection and classification at low signal-to-noise ratios (SNRs), with relaxed a priori information on signal parameters. This paper proposes a joint detection and classification algorithm for single-carrier linearly digitally modulated (SCLD), cyclically prefixed SCLD (CP-SCLD), and orthogonal frequency division multiplexing (OFDM) signals, with the advantage that it does not require estimation of signal and noise powers, symbol timing, and carrier and waveform recovery.

In this paper, a new spectrum sensing structure is introduced which employs several energy detectors in multiple antennas for a cognitive radio system. Performance is evaluated in a Suzuki channel environment by a simulation using several decision criteria to produce a collaborative decision. The performance is described in terms of complementary ROC curves, and compared with that of a conventional energy detector. Additionally, the effect of several parameters such as sensing duration as well as mobile speed is investigated. The simulation results show that the proposed scheme achieves better performance and reliability than the conventional scheme. It is confirmed that the proposed scheme makes sensing most reliable when the mobile speed is assumed to be slow.

Cognitive radio is an enabling technology, which is expected to lead to a more efficient utilization of the available spectral resources due to its flexibility and its ability to sense its spectral environment. Recently, spectrum sensing methods based on exploiting the cyclostationary characteristics of communication signals have been drawing interest. In practice, imperfections in the signal generation or reception may affect the cyclic statistics of a signal of interest, leading to a degradation in the performance of cyclostationarity-exploiting spectrum sensing schemes based on an ideal signal model. A typical source of imperfection is random timing jitter, which can occur at the transmitter side, most notably in the form of pulse timing jitter for digitally modulated signals, or at the receiver side in the form of sampling jitter. In this work, we explore the effect of random timing jitter on the second order cyclostationary statistics of wide sense cyclostationary signals. General analytical expressions are derived for the cyclic statistics of signals in the presence of sampling and pulse timing jitter and specific results are provided for cases of practical interest. Subsequently, the effect of the both jitter types on a cyclostationary-based spectrum sensing algorithm is investigated via simulations.

Cognitive radios are slated to be the next generation of smart transceivers that can dynamically sense and respond to its immediate radio frequency (RF) environment. It is highly likely that the RF environment will vary with time as various interferers come and go out of the range of the target receiver. This leads to the interference at the receiver being impulsive in nature, which if not properly handled can cause irrecoverable damage to the transmitted data. The traditional cognitive radio would, in such a scenario, decide against transmitting when a harmful interferer is present in the vicinity. In this work, we investigate methods to mitigate the effects of such interference through intelligent signal processing at the receiver such that throughput can be greatly enhanced. We introduce receiver structures for the more practical scenario of temporally correlated interference and quantify the achievable gains when simple yet effective interference suppression methods are applied at the receiver.

In this paper, we present an extension of the Colour Edge Co-occurrence Histogram (CECH) object detection scheme for retrieving and tracking colour logos and trademarks in unconstrained image sequences. We introduce more accurate information to the CECH by virtue of incorporating colour edge detection using vector order statistics, producing more accurate representations of edges in images, as compared to the simple colour difference edge classification performed in the CECH. Our proposed method is thus reliant on edge gradient information, thus naming it the Colour Edge Gradient Co-occurrence Histogram (CEGCH). We also use a colour quantization scheme based in the Hue-Saturation-Value (HSV) colour space, for it is more suitable for logo and trademark retrieval, in comparison to the colour quantization scheme used with the CECH. Results illustrate that the CEGCH retrieves and tracks logos and trademarks with greater accuracy in comparison to the CECH.

In this paper, we propose a new non blind robust digital watermarking algorithm for images based on the concept of embedded binary image watermarked by modifying frequency coefficients of the discrete wavelet transform (DWT) except the low-low subband coefficients (LL). The human visual system (HVS) is less sensitive to the small change in edges and textures of an image. From this, the original image is decomposed into three levels using the discrete wavelet transform, and a binary watermark is added on the high-high (HH), lowhigh (LH) and high-low (HL) subbands using a threshold coefficients. The performance of the proposed method is compared with other watermarking method. Simulation results show that our method provide better performance for invisibility and robustness aspects. This method provides good performance against several attacks as: noise addition, histogram equalization, gamma correction, JPEG compression, cropping and randomly line and column removal.

In this paper, we introduce the PCA-whitening CSS affine invariant shape descriptor, which extends the Curvature Scale Space (CSS) shape descriptor to an affine invariant shape descriptor. PCA-whitening is applied to transform the shape contours into their canonical forms. The CSS image maxima are then extracted from those canonical contours as shape descriptors, which can be compared through maxima matching. We tested the descriptors by using them as features in shape based silhouette image retrieval. Experiments on a 1890 silhouette image database show that the proposed descriptor has a promising overall retrieval rate of 91.02%, which is 10.03% more than that of its countparter using traditional affine parameterization.

Fingerprint identification is an important biometric technique for personal identification. Most of the automatic systems of fingerprint recognition are based on matching of fingerprint minutiae. In this paper, we described a method that reduces the complexity of computations and extract the minutiae from binary image with appropriate speed. In this paper a new hardware scheme is presented which is based on pipelined architecture in order to real-time minutiae extraction. Simulations and implementation result shows the operation and accuracy of suggested method.

A method is presented to classify the percent intramuscular fat (\%IMF) for beef cattle using ultrasound imaging. As the images captured tend to include a significant amount of noise a noise reduction algorithm was used. The effectiveness of using filtered images to calculate texture measures for the classification and prediction of the \%IMF is compared to the effectiveness of using unfiltered images.

Power management is an important factor during the design of real-time systems. Dynamic voltage scaling is an effective technology to reduce dynamic power consumption. With the development of processor technology, besides dynamic power consumption, we must take static power consumption into consideration too, which makes power management more complicated. Power shutdown and procrastination method can be used to reduce static power consumption efficiently. We develop a dynamic power consumption algorithm based on these technologies and derive a very good energy performance.

We propose, in this paper, the development of an efficient IGBT model especially designed for simulation and we also present a diode model that can describe the recovery current. Although, the IGBT model can describe the switching mechanism with a good precision, a procedure is presented in order to make this model to better represent the description of real switching losses. The models have the advantage to be configured exclusively from the data-sheet of the manufacturer and they take the form of electrical circuits, which can be realized easily in classical simulators.

A new topology of bridge-type SFCL (Superconducting Fault Current Limiter), which can limit not only the rising speed but also the steady state value of fault current, is proposed in this paper. The new SFCL includes a bridge composed of 4 SCRs and 2 diodes, a superconducting coil and an ordinary bypass reactor. In normal status, the bridge works as a rectifier, the voltage across the coil is zero if the current of the coil keeps greater than the peak value of the load current. when a fault occurs, the fault current is limited in the first cycle by the coil, when the fault is detected, the bridge can be controlled working as two bidirectional switches and the coil is inserted in the ac circuit and the steady fault current can also be limited. By adding the bypass reactor, the cost of the new SFCL can be minimized. Parameter design and simulations are presented. The simulation proves the validity of the new SFCL.

During the late 1990’s, a lot of research focused on the area of remote operations for far reaching applications in commercial appliances such as routers, mobile telecommunication devices, and web servers. The field of power generation is still in its initial phases, including hard wiring the control system directly to a machine, allowing the installation of the machine’s control firmware from a far-off location. Existing internet based controller modules and remote installation methodologies like updating router firmware for routers and remotely updating web server firmware were investigated. The performance of each method was compared with the others, and based on this, a novel cost effective system was designed which is capable of controlling, monitoring and installing inverter firmware from a remote location with the use of internet.

This paper introduces a new multilevel converter topology. Its modular construction allows it to be scalable to different voltage and power levels. It can integrate power from both its dc, ac terminals and from external energy storage units as well. The converter is developed starting from the well-known cascaded H-bridge topology. A simulation case study is presented to demonstrate the underlying concept.

In the current body of knowledge, planarity is necessary in order to recover from routing holes using left- or right-hand rule (LHR). This is often referred to as face-routing. In this paper we introduce the Prohibitive-link Detection and Routing Protocol (PDRP). PDRP is a position-based wireless protocol that, when faced with a routing hole, can recover using left-hand rule in a non-planar environment. As the name implies, the protocol detects and circumvents the prohibitive links that hamper LHR. The goal of PDRP is to provide the same levels of service as GPSR-like protocols, while avoiding the prohibitive transmissions of cooperative protocols such as CLDP. Initial results are promising, revealing the same level of service as face-routing protocols despite preserving most intersecting links in the network.

Crossbar switches are fundamental building blocks of digital networks such as the Internet. An Input-Queued (IQ) crossbar switch includes a set of queues at the input side of the switch, combined with an unbuffered switching matrix with NxN crosspoints. A Crosspoint-Queued (XQ) crossbar switch contains a FIFO queue at each of the NxN crosspoints of the switching matrix. Switches with combined IQs and XQs, denoted CIXQ, have been the subject of considerable research over the last decade. The use of crosspoint queues simplifies the scheduling of traffic through the switch, at the cost of adding O(NxN) FIFO queues to the switching matrix. In this paper, a power analysis of IQ and CIXQ switches is presented, assuming an FPGA implementation. The basic switch design consists of a demultiplexer network associated with each row of the switching matrix, and a multiplexer network associated with each column of the matrix. An accurate power analysis for these switches in an FPGA environment is presented. Analysis indicates that the internal FIFO queues in a CIXQ switch roughly triple the power required in an FPGA implementation. To minimize power, the FIFO queues at each crosspoint should be small or eliminated completely. The use ofan analytic power models allows for a rapid design space exploration for power minimization.

We propose a new way of designing a Protected Working Capacity Envelope (PWCE) in survivable WDM networks by using pre-configured protection structures with unrestricted shapes (arbitrary shape patterns). The pre-configured cycle (p-cycle) structure is the only building block that has been used so far in the design of PWCE. In this article, we do not impose any condition on the shape of the protection structures, and search for the structures that favor the protection efficiency (reliability, redundancy), and recovery speed (local protection). In order to cope with the large solution space, we use an efficient large scale optimization modeling that relies on Column Generation (CG) where only promising (i.e., value added structures) p-structures are enumerated on the fly during the optimization process. We compare the performance of our PWCE design to the p-cycle based one on the basis of the capacity efficiency, the reliability, and the length of the backup paths. The results show that a design based on unrestricted p-structure patterns is ~10% less capacity redundant, ~15% more reliable, and allow recovery along shorter backup paths compared to the p-cycle based scheme.

OBS networks are quite apart traditional networking, at least due to their bufferless packet oriented nature. Indeed, they disclose particular characteristics in the core network. For instance, the transparency assumption increases the responsibility of the access nodes, since the emission process completely defines the traffic profile in the core. Advanced signaling protocols such as JET allow OBS to perform end-to-end all optical transfers. In this paper, we will discuss several issues regarding the burst emission process and its impact on the traffic observed in the core. This preliminary study motivates the discussion for a hybrid architecture that features burst re-aggregation in some intermediate nodes. Simulations performed on EONET network shows significant loss rate improvement. We also discuss in depth the delay issue based on the numerical results.

In this paper, we evaluate the effect of different queueing disciplines and different codecs on a voice over IP (VoIP) network with video (also known as videoconferencing). A real network topology is implemented using Cisco equipment. Experimental results show that LLQ and AutoQoS can provide significant improvements over FIFO in terms of delay, jitter and reserved bandwidth for a VoIP call with video. As far as codecs are concerned, they are suitable for different scenarios. It's for certain that G.729 helps when low bandwidth is a must but, without any QoS parameters in place, codecs do not make a good enough difference for acceptable call quality on a congested network.

Transients generated by the switching in selection diversity combining cause receiver ``dead time'' and therefore increase the system outage. For this reason, the switching rate is an important parameter in selection diversity system design. Yet, there are few published results regarding the switching rates of selection diversity combining. All published work considers noiseless diversity systems; no results for switching rates of selection diversity in systems with noise exist. The switching rates of dual selection diversity combining in Rayleigh and Rician fading are examined in a noisy environment. Analytical expressions are derived for independent and identically distributed (i.i.d.) and independent and non-identically distributed (i.n.d.) fading channels. The switching rates in the presence of noise are compared to those in noise-free cases. It is seen that, in the presence of noise, the receiver filtering can greatly influence the switching rate.

This paper presents a capacity analysis of a decode-and-forward (DF) cooperative network under adaptive source transmission. Three different adaptive techniques are considered: (i) optimal simultaneous power and rate adaptation (OPRA); (ii) constant power with optimal rate adaptation (ORA); (iii) truncated channel inversion with fixed rate (TIFR). Closed form capacity expressions are derived for non-identical and independently distributed (non-i.i.d.) Nakagami-m fading wireless environments. These expressions are validated by simulation results obtained through Monte Carlo simulation. It is observed that OPRA and ORA provide roughly the same capacity, while TIFR yields slightly less capacity relative to the other two.

User cooperative communication can bring spatial diversity, and improve cell boundary uplink quality. This paper gives a kind of convolutional codes suitable for user cooperation with lower complexity than Turbo codes and LDPC codes, and can guarantee good inter-user communication quality when cooperation succeeds, and also good uplink communication quality when cooperation defeats. Simulation results show that when we use 50% cooperation, under the condition that the two users have similar uplink quality and perfect inter-user channel, at BER=10−3 , this kind of coded cooperation can provide almost 11 dB performance gains, compared with non-cooperation. Moreover, performance of user cooperation using this kind of convolutional codes is better than that using rate compatible punctured convolutional codes.

This paper presents our research results on the Digital Television (DTV) signals, measured in the mobile receive diversity channels. The measurements were conducted in the TV frequency band of 788-794 MHz in different types of environments. The mobile receiver was equipped with two antennas sepparated by 6 wavelengths. The presented results include the signal envelope crosscorrelation, evaluatedwith a globalmean and a localmean; the level crossing rate and the average fade duration, evaluated with and without the receive diversity; and the diversity gain achieved when three combining techniques, i.e. diversity selection, equal gain and maximal ratio combining, are in used.

In this paper, a new family of Linear Dispersion Codes (LDCs) that can be decoded using a fast Sphere Decoding (SD) algorithm in MIMO systems is proposed. The basic principle of this structure is to make the LDC to have as many as possible the rows orthogonal in the dispersion matrices. Monte Carlo simulation results show that the optimum LDCs with this orthogonal structure have nearly identical bit-error-rate (BER) performances as other optimal LDCs. We develop a simplified Sphere Decoding (SD) algorithm that can significantly reduce the decoding complexity in decoding the new LDCs with proposed orthogonal structure. Simulation results show that the complexity reduction is more significant for MIMO system transmitting higher level modulation. For 2×4 MIMO systems transmitting 4 64QAM and 256QAM symbols in a block length of 4, the reductions are about 71-83% and 76-88%, respectively.

We present a new analytical model of MAC layer for wireless ad hoc networks that takes into account frame retry limits for four-way handshaking mechanism. This model offers flexibility to address key design issues such as the effects of traffic parameters and possible improvements for wireless ad hoc networks. It effectively captures the important network performance characteristics such as throughput, channel utilization, delay and average energy. Under this analytical framework, we evaluate the effect of RTS (Request-to-Send) state on unsuccessful transmission probability and its effect on the performance specially when either the traffic is heavy, or the data frame length is very large. By using our proposed model, we show that the probability of collision can be reduced when using RTS/CTS mechanism. Thus, the throughput increases and, at the same time, the delay and the average energy to transmit the frame is reduced.

Sensor array beamforming performance using independently mobile antennas connected through a wireless sensor network is analyzed where a performance metric is proposed enabling mitigation of the perturbation of array factor formation caused by dynamic node positions. Wireless networking has expanded array design possibilities to include wirelessly connected elements; however, static positioning of elements remains central to determination and application of weights necessary for coherent array beam formation. Wireless networks allow for participant mobility, but applied weights must be reformed for each position update in order to maintain target focus. While deterministic motion allows easy weight translation, random element motion requires significant network energy to reform weights through position updates. The relationship between array factor and stochastic element motion is analyzed. A relationship is developed between motion and array factor magnitude probability towards the intended target vector. The relationship proposed is shown to be assessable and useful for reducing network traffic and processing overhead and while producing operationally acceptable gain towards the target. The result compares favorably against a constant position updating model in terms of sensor energy usage across the network.

Power consumption, latency, and complexity are considered to be a bench mark for comparing Medium Access Control (MAC) protocols in Wireless Sensor Networks (WSN). However, the importance of these elements varies according to the application. In this paper, three MAC protocols are proposed for forest fire detection. Basically, two of these protocols are based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol with some modification to suit the forest fire detection application. These protocols are called Persistent CSMA (P-CSMA) and Per Hope Synchronization CSMA (PHS-CSMA). The third one is a Time Division Multiple Access (TDMA)-based protocol, called Sensor TDMA (S-TDMA). These three protocols are investigated and analyzed by simulation. Results show that there is no superior protocol which outperforms other protocols in terms of power consumption, delay and complexity. However, a trade-off does exist. In terms of power consumption, S-TDMA outperforms other protocols but it has the worst performance in terms of delay time. On the other hand, considering the design complexity, S-TDMA is the most complex as it needs time synchronization over the entire cluster while PCSMA and PHS-CSMA don’t require time synchronization between nodes is needed.

The LEACH algorithm for selecting cluster heads is a probabilistic method which produces clusters with a large variation of link distances and uneven energy consumption during the data transmission phase. To address this issue, a RF signal strength algorithm based on link quality is presented. Using a competitive distributed algorithm, nodes attempt to reduce the overall energy required for transmission in addition to forming favourable clusters based on Received Signal Strength Indication (RSSI) density and quality. Cluster heads form in areas of high node density leading to a significant reduction in transmission link length, a reduced variance in link length distribution and greater opportunity for energy savings through data aggregation. Simulations show that cluster heads selected by this algorithm form clusters with a lower average link length and have less link distance variability. This produces a lower and more evenly distributed energy cost per node in the network.

Abstract- It has always been a technical challenge for operations service team to expand wireless network reception inside reactor buildings (RB) and their service wings (SW). This is driven by the volume of metal equipment inside the Reactor Buildings (RB) that blocks and somehow shields the signal throughout the link. In this study, to improve wireless reception inside the Reactor Building (RB), an experimental model using indoor localization mesh based on IEEE 802.15 is developed to implement a wireless sensor network. This experimental model estimates the distance between different nodes by measuring the received signal strength indication (RSSI).Then by using triangulation and RSSI measurement, the validity of the estimation techniques is verified to simulate the physical environmental obstacles, which block the signal transmission.

Application of a vision system and a remote control car to an elective fourth year design project in electrical engineering is discussed. The design project invovles learning and application of various sensors, actuators, control theories. The end product of the design project is an intelligent vehicle that is able to follow an emulated highway automatically. A camera with embedded color tracking capabilities is included in the project. A remote control car is used as a mobile robot to build the intelligent vehicle. The objective for building the intelligent vehicle is to design an intelligent controller for path tracking tasks. Experimental results have demonstrated that the developed intelligent vehicle is able to achieve the tasks. Fourth year electrical engineering students are trained through the design project. They are able to apply their knowledge in digital electronics, analogue electronics, sensors, motors, microcontrollers, and mechatronics to complete the project.

This paper describes the ROV Pontus, built by the Eastern Edge Robotics Team for the 2008 MATE International ROV Competition. The process of building the ROV and traveling to the MATE Competition cost approximately $60,000, including the value of donated materials. Two pontoons connected by High Density Polyethylene (HDPE) frames are the basis of the chassis, which also has four 24 V thrusters and a stereoscopic camera. The chassis has two latches to hold and lift an Ocean Bottom Seismometer (OBS) platform, and a thermistor to record temperature of a venting fluid. The control system was programmed in C# and runs using seven threads that sample data continuously. The ROV has an onboard electronics system that is inside polycarbonate housing connected to the surface using a custom-built tether. The topsides electronics consists of a joystick and a control unit.

This paper describes Quanser's Mobile Robot Control Framework (QMRCF) for an educational robot called Qbot. The QMRCF accelerates the development of mobile robot control algorithms and hardware-in-the-loop (HIL) testing using model-basd design techniques of MATLAB Simulink. This paper also validates the performance of QMRCF using several experiments in various research fields of mobile robots, e.g., teleoperation with force-feedback, map and vision based navigation, obstacle avoidance, and mapping.

This paper describes the evolution and components of a program designed to enhance the teaching opportunities and expertise of graduate teaching assistants in the Faculty of Engineering and Applied Science at Memorial University of Newfoundland. Teaching Opportunities for Graduate Assistants (TOGA) was adopted by the Faculty of Engineering and Applied Science as a pilot program in 2005. TOGA was initiated by the School of Graduate Studies and its implementation was the responsibility of the Instructional Development Office. Professional development for graduate teaching assistants related to teaching and learning is the main focus of TOGA. While professional development was, and is, targeted mostly to graduate teaching assistants at Memorial who are involved in regularly scheduled direct teaching interactions, the Faculty of Engineering and Applied Science provides a professional development program for graduate teaching assistants at four different levels.

Cognitive radio (CR) systems make efficient use of the frequency spectrum by opportunistically exploiting unoccupied or under-utilized frequency bands. However, the frequency bands used by CR systems are expected to suffer from various forms of noise and interference with non-Gaussian distributions, such as narrowband and co-channel interference caused by the primary user and other CRs, respectively, and man-made impulsive noise. To mitigate the harmful effects of non-Gaussian noise and interference, we propose a robust Lp-norm metric for CR systems that employ the popular combination of bit-interleaved coded modulation (BICM) and orthogonal frequency division multiplexing (OFDM). For the considered CR system we provide an approximate upper bound and an asymptotic closed-form approximation for the bit error rate (BER). Our results show that the proposed Lp-norm metric can achieve large performance gains compared to the conventional L2-norm metric in non-Gaussian noise and interference.

In this paper we continue our studies on dynamic spectrum trading framework recently proposed. The focus is set on on the overload probabilities of single operators and on a per-network view while reallocating resources between mobile operators. The hierarchic model aims at maintaining a reliable allocation of resources in every time instant as well as it enables dynamic adaptations on a short-term basis. In this paper we study the traffic model with respect to overload probabilities and present numerical results. The outcomes show, that by dynamically adjusting the allocation on a short-term basis to current demands, per-operator and system-wide overload probabilities can be significantly reduced at given offered traffic.

Digital signal processing (DSP) has enabled the exponential sine sweep (ESS) method of measuring the acoustical parameters of a concert hall to be increasingly efficient. Part of this is due to the implementation of software modules that perform specific tasks such as filtering and equalization. In using a measurement loudspeaker source for the sine sweep process, it is necessary to: first, derive a loudspeaker prefilter to ensure that the resulting output sweep possesses a frequency response that is reasonably uniform; and second, to derive a transducer inverse filter in order to remove the effects of the loudspeakers and microphones from the measured impulse response of the hall. In the present work, by measuring the acoustical impulse response function (AIRF) of three different halls, using a high-frequency horn-loaded loudspeaker system as a reference source, it is shown that the effects of the transducers may be effectively filtered and removed from the AIRF.

The ETSI “Aurora” is a digit-based standard developed for distributed speech recognition (DSR) over telephone communication channels. This paper introduces a digit- based text-independent distributed speaker identification (DSID) system over telephone channels within the DSR framework. In this DSID system, the hypothesized speaker model is derived by GMM-UBM model training using Aurora2 connected digit training speech data and maximum a posteriori (MAP) adaptation. The UBM technique for speaker models is incorporated into this DSID system to reduce the computational complexities significantly. Experiments on the Aurora2 speech recognition corpus show that GMM-UBM yields excellent performance for speaker recognition over telephone channels. Compared to the baseline system, we got 100% recognition accuracy for this proposed DSID within the ETSI DSR framework.

A fast search procedure to reduce the search complexity required to locate the codevectors during the encoding process in multistage tree-structured vector quantization (MTVQ) is proposed. Quantization of line spectral frequency (LSF) parameters at different rates is used to provide experimental results, which are compared to the multipath sequential search or M-L search (MSS) and the multipath sequential tree-assisted search (MSTS). The Federal standard MELP coder is modified by replacing the original LSF quantizer with an MTVQ using the proposed fast search procedure, and an evaluation of the produced speech quality is given.

Recently, Modeling and detection of different boundary properties is becoming and essential tool in many applications such as drug delivery and modeling of capillary walls. In this paper, we propose computationally efficient framework for estimating the boundary properties using stochastic differential equations. The main advantage of this technique lies in the fact that it accounts for random effects such as Brownian motion which are not accounted for in commonly used classical techniques based on Fick’s law of diffusion. We model the dispersion of particles in the presence of absorbing/reflecting boundaries using Fokker-Planck equation. We then derive the inverse model for the estimation of the absorbing region. We demonstrate the applicability of our results using numerical examples.

Renewable energy sources have the ability to provide power in rural areas when available. Although cheap, clean and abundant, the variation of output power with the variation of wind speed can cause significant power quality issues, especially in case of standalone generation. This paper studies a network presenting a rural load, such as a small village, fed from a wind farm. The effect of wind speed on the power quality is illustrated via simulation. The introduction of the Modulated Power Filter- Compensator (MPFC) to the network established a significant improvement to power quality, while being cheap and robust.

This work presents a reliability analysis of the Power Conditioning System (PCS) for both the Permanent Magnet Generator (PMG) and Wound Rotor Induction Generator (WRIG)-based small wind turbine generation systems. The PCS for grid connection of the PMG-based system requires a rectifier, boost converter and a grid-tie inverter, while the WRIG-based system employs a rectifier, a chopper and an external resistor in the rotor side with the stator directly connected to the grid. Reliability of the PCS is analyzed for the worst case scenario of maximum conversion losses at a predetermined wind speed. The analysis reveals that the Mean Time Between Failures (MTBF) of the PCS of a WRIG-based small wind turbine is much higher than the MTBF of the PCS of a PMG-based small wind turbine. The investigation is extended to identify the least reliable component within the PCS for both systems. It is shown that the inverter has the dominant effect on the system reliability for the PMG-based system, while the rectifier is the least reliable for the WRIG-based system. This research indicates that the WRIG-based small wind turbine with a simple PCS is a much better option for small wind energy conversion system.

In this paper, a novel PI-based predictive voltage controller with a feed-forward voltage compensator is developed for a single phase Uninterruptible Power Supply (UPS) inverter of a stand-alone wind turbine system in order to obtain high system performance with both linear loads and nonlinear loads. Space vector pulse width modulation (SVPWM) and pulse based dead-time compensation are introduced in this paper to implement the control technique. Simulation and experimental results based on a 1 kVA single phase inverter prototype are included to show the effectiveness and the performance of this proposed controller.

This paper is mainly focusing on the dynamic authentication data management for the heterogeneous interworking authentication among WiMAX and 3GPP. First, the 3GPP AAA server in 3GPP home domain takes charge of AAA function for the 3GPP/WiMAX UE. Specifically, 3GPP AAA server will obtain authentication vectors (AV) from the HSS, and consume one AV for each mutual authentication. In addition, after the departure of the 3GPP/WiMAX UE from the previous HPLMN or VPLMN to new VPLMN, the first registered 3GPP AAA server also performs the authentication process, with retrieving new AVs array. However, the unused AVs for the previous PLMN can be reserved for a time interval, which is called the threshold periodic interval (TPI). If the UE returns the previous PLMN within the period of TPI, the stored AVs will still be used for mutual authentication instead of retrieving new AVs. It should be pointed out that a long TPI period results in fewer accesses to the HSS, so as to reduce the authentication signaling cost. In this paper, we present an analytic model to investigate the impact of TPI period on the system performance. From the numeric simulations, it is desirable to conclude that only through adjusting the TPI period dynamically in accordance with the system parameters, the system can achieve the best performance.

This research project was conducted at TRLabs and at the sensor network testbed (SENETBED) at the University of Manitoba, for an international sponsor, Vansco/Parker Inc. The project aimed to determine the impact of electromagnetic noise on the communications performance of a ZigBee sensor network, which was embedded within a large industrial excavator. The project consisted of four phases. Phase 1 of the project [7] determined the requirements and chose a wireless technology to replace the wireline technology in the deployment of a sensor control system for industrial machinery; modeled broadband electromagnetic noise using contemporary fractal theory; and designed a novel emulation environment for testing the noise performance. Phase 2 of the project [8] addressed an improved experimental setup, and provided preliminary Packet Error Rate (PER) vs. Signal-to-Noise Ratio (SNR) results, showing the impact of fractal generated noise on ZigBee communications. Phase 3 of the project [12] analyzed the process of modulating a monofractal, and found that the modulated monofractal changed character to a multifractal; however, the modulated signal was approximately monofractal in a small frequency range. Phase 4 of the project [10] captured starter motor noise emanated from a large industrial tractor; performed fractal measurements on the data; and found that the noise exhibited fractal and multifractal characteristics, verifying that fractal theory is indeed a good model of broadband electromagnetic noise. This paper summarizes the first four phases of this research project, to provide continuity and readability. The results and contributions of Phase 5, the final installment of this project, include: (1) the SNR was measured more accurately, through a written c-program, which programmatically captured the signal and noise power readings from a spectrum analyzer, and calculated the signal and noise powers directly from the amplitudes. The improved method for calculating the SNR allowed more accurate PER vs. SNR results, which are reported here; (2) The SNR measurements were also improved by changing the location of the actual measurements. The SNR measured at the receiver was used to obtain PER vs. SNR data, while the SNR measured at the transmitter SNR was used to obtained maximum node separation data; and (3) noise emulation was improved by injecting the noise into the channel at the receiver. In this Phase 5, we found that a better assumption of noise injection was to assume that the noise was uniformly and equally distributed in space, so that the incremental impacts of the noise throughout the channel could be modeled by injecting the noise at the final destination, i.e., at the receiver.

This paper presents a novel combination of 8-QAM trellis codes with multi-carrier code division multiple access (MC-CDMA) and controlled equalization for multiuser downlink Rayleigh fading channel. In literature, minimum mean square error (MMSE) is known to be the optimal single user detection (SUD) technique. We show that the proposed system, with 16-state encoder and full system load, outperforms an equivalent system that uses MMSE as the equalization technique by almost 3dB. Moreover, as the number of active users increase (from single user load to a fully loaded system), error performance of the proposed system surpasses an equivalent system using MMSE. This suggests that the proposed system is more robust to multiple access interference (MAI) as compared to that with MMSE.

This paper performs a comparative analysis of several different types of SMS text classifiers: weight enhanced Multinomial naive Bayes, Poisson naive Bayes, and L2-loss Support Vector Machine. The effects of preprocessing and incorporating addition features on the classifiers were examined. The preliminary experimental results show that the use of preprocessing and incorporating addition features produced no significant gain or loss in classification efficiency. However the feature space used by the classification methods decreased, which could be beneficial for resource limited environments. In addition the solutions to the SMS text classification may be applied to other problems, like the classification of English sentences. Our collection of text messages may not be statistically significant, because of very limited sources for text messages.

This paper studies video streaming system over a wireless medium. The major challenge is to provide a robust link along the transmission/ transport path and most importantly through noisy channels that could add or drop bytes by unforeseeable factors. As a remedy for this phenomenon, we combine the Forward Error Correction, Blind Compensation and Traffic Shaping to improve the over all performance. We report on the experiments on this unique performance improvement method. Our study finds application in WiMax and AVCP.

A proposed fractional Fourier domain communication system (FrFDCS) using transform domain processing is demonstrated as having enhanced interference avoidance capability under adverse environmental conditions. The basic idea for this system is to synthesize an intelligent adaptive waveform in the fractional Fourier domain at both the transmitter and receiver to avoid spectral crowded regions. This approach offers better bit error performance in contrast to other conventional interference mitigation techniques that process the signal at the receiver only. Moreover, since this smart waveform is able to search “spectrum hole” and adapt to electromagnetic environment, it could be a potential candidate in cognitive radio technology. The proposed FrFDCS and its response to interferences are modeled and simulation results are obtained. Compared to similar systems such as the transform domain communication system (TDCS).The results indicate that the proposed FrFDCS is a viable option for interference avoidance communications.

In this paper, a new backoff algorithm based on sliding the backoff interval is proposed to maximize the channel throughput and improve the fairness of random access channels. In the sliding backoff interval (SB) algorithm, every node that experiences packet collisions increase its SB range by a forward sliding factor (FSF) and in case of successful transmission decrease its SB range by a backward sliding factor (BSF). Forward and backward sliding factor (SF) is controlled according to the channel offered traffic using fuzzy controller to maximize the channel throughput. Furthermore, the operation of the proposed backoff algorithm does not depend on the knowledge of the number of active nodes. A computer simulation is developed using MATLAB to evaluate the performance of the proposed backoff algorithm and compare it with the binary exponential backoff (BEB) scheme which is widely used due to its high channel throughput while its fairness is relatively poor. It is shown that the proposed backoff algorithm achieves nearly the ideal performance of fairness at Bmin=2 and the ideal performance of fairness for all other values of Bmin. So, it significantly out-performs the BEB scheme in terms of improving the performance of fairness, while achieving high channel throughput.

A subchip multipath search method for DSSS system based on fractional fourier transform (FrFT) is proposed. Chirp signal is used as pilot signal, the multipath chirps are processed by FrFT at receiver, then the relative delays between multipath chirps can be calculated after detecting peak positions in FrFT domain according to the linear relationship between the relative delay in time domain and difference between peak positions of multipath chirps in FrFT domain. The search resolution is equal to reciprocal of the bandwidth of chirp signal, so the chirp signal with bandwidth larger than that of DSSS signal should be used to resolve subchip multipath. Simulation results show that the proposed method can calculate the relative delay of subchip multipath effectively.

In this paper, we study the empirical performance of GPS for relative location discovery in wireless sensor networks. Various sensor deployment scenarios are used that are representative of the real operational conditions of wireless sensor network applications. A GPS handheld is used to measure the sensor node locations, and the MDS technique is used to estimate the ground truth sensor node locations by measuring the internode distances between the sensors. The analysis is based on the approach of Procrustes analysis. An optimal rigid transformation is obtained using a least squares method, which is used to align the ground truth to the GPS measurements. Based on the results, conclusions and discussions are made about the suitability of GPS as a localization tool in wireless sensor networks.

Mobile sensor network (WSN) is a kind of sensor networks in which nodes can move under their own control or under the control of the environment. The mobile nodes could be used to physically collect and transport data or to recharge, repair and replace the static nodes in the network. In this paper we develop a new mobile sensor node that supports IPv6 technology, which enables WSN to easily connect to Internet. Furthermore, we propose a dynamic path planing for mobile node's moving and mobility control mechanism. Mobile node can dynamically adjust its moving direction according to wireless signal strengths between sensor nodes till it arrives at the destination location. Finally, we set up a test-bed with our developed mobile sensor network and illustrate network operation procedures.

Intuitively, many wireless and sensing applications benefit from knowledge of network boundaries. Many virtual coordinate constructions rely on the furthest set of nodes as beacons. Network edges may also bound routing holes in the network, regions of failure due to environmental effects, or indicate the need for additional deployment. In this paper we explore the potential to solve the edge detection problem using a geometric structure called the alpha-shape ($\alpha$-shape). For a disc of radius $1/\alpha$, the $\alpha$-shape consists of nodes (and joining edges) that sit on the boundary of the discs that contain no other nodes in the network. In addition to geometry-related fields of study such as graphics and computational geometry, $\alpha$-shapes have been used in the disciplines of molecular biology, particle physics, and others. We explore the relationship between the $\alpha$ parameter and radio communication range and show that, by setting the $\alpha$ parameter appropriately, it is possible to compute the network $\alpha$-shape locally.

In this paper, the dynamic spectrum access problem for cognitive radio (CR) networks is formulated as maximizing the sum channel capacity while satisfying the power budgets of individual secondary users radios as well as the SINR constraints on both the secondary and primary users. By applying the Karush-Kuhn-Tucker theorem, we derive a water-filling soluton. An iterative water-filling algorithm is proposed for implementing joint channel and power allocation in a dynamically changing set of available channels. The proposed algorithm has a complexity that increases linearly with both the numbers of channels and the number of users.

This paper investigates a novel narrowband interference (NBI) suppression method in Cognitive Ultra-wide Band (CUWB) Radio system. UWB signals and NBI are separated by Fractional Fourier Transform (FRFT) domain filters, and therefore an estimation of NBI can be obtained by utilizing inverse FRFT. The simulation results show that the UWB pulse waveform designed by Semi-definite Programming (SDP), which is a weighted sum of chirp functions, meets the emission mask established by the Federal Communications Commission (FCC), and the use of chirp function ensures that the FRFT domain duration of UWB pulse waveform is very short. Therefore the NBI parameters (e.g. center frequency, bandwidth, energy) are more convenient to be obtained by the estimated NBI. The UWB signal will not have a detrimental effect on the performance of the narrowband system by suppressing the UWB signal in the NBI band.