ALBERT

Description: A range of techniques have emerged in recent years for the conduct of environmental programming. Such programming techniques are meant to facilitate the systematic application of environment-behavior research to the design process. However, despite the efforts of both researchers and practitioners, the success of environmental programming in bringing about effective research application remains quite limited. This article reviews several reasons for these difficulties in research application, and concludes that the problem is rooted in quite basic conceptions of the nature and goals of behavioral research. An alternative "action research" approach to the conduct of environment-behavior studies is then presented. Some of the benefits of viewing environmental research and programming as interrelated phases within a larger "action" framework are considered.

Description: Good behavior for the altitude estimation has been validated in terms of accuracy using instrumented GPS targets, as well as opportunistic ones (coherence of the altitude history with respect to the speed indicator). In most cases, this altitude estimation satisfied our objectives, even though they were quite ambitious objectives. A system such as this one should clearly distinguish the different altitudes of different flight patterns, and the difference between the two altitudes was equal to 330 m. This multistatic DVB-T SFN tracker is exploiting detections based on a 2D planar DVB-T receiving array: the parameters estimated are the bistatic range and Doppler, as well as the azimuth and elevation measurements. Some opportunistic targets have also been analyzed for validation of the 3D localization capacities, especially for low speed targets at very low altitude.

Description: A novel method enabling single-site localization of wireless emitters in a rich multipath environment is presented. The localization is based on a novel fingerprinting technique exploiting the spatial-temporal characteristics of the multipath signals received by the base station antenna array. The fingerprint is based on a lower dimensional signal subspace of the spatial-temporal covariance matrix, capturing the dominant multipath signals. The performance is validated with both simulated and real data, demonstrating localization accuracy of about 1 m in typical indoor environments.

Description: A quasi-optical interferometric technique capable of measuring antenna phase patterns without the need for a heterodyne receiver is presented. It is particularly suited to the characterization of terahertz antennas feeding power detectors or mixers employing quasi-optical local oscillator injection. Examples of recorded antenna phase patterns at frequencies of 1.4 and 2.5 THz using homodyne detectors are presented. To our knowledge, these are the highest frequency antenna phase patterns ever recovered. Knowledge of both the amplitude and phase patterns in the far field enable a Gauss–Hermite or Gauss–Laguerre beam-mode analysis to be carried out for the antenna, of importance in performance optimization calculations, such as antenna gain and beam efficiency parameters at the design and prototype stage of antenna development. A full description of the beam would also be required if the antenna is to be used to feed a quasi-optical system in the near-field to far-field transition region. This situation could often arise when the device is fitted directly at the back of telescopes in flying observatories. A further benefit of the proposed technique is simplicity for characterizing systems in situ, an advantage of considerable importance as in many situations, the components may not be removable for further characterization once assembled. The proposed methodology is generic and should be useful across the wider sensing community, e.g., in single detector acoustic imaging or in adaptive imaging array applications. Furthermore, it is applicable across other frequencies of the EM spectrum, provided adequate spatial and temporal phase stability of the source can be maintained throughout the measurement process. Phase information retrieval is also of importance to emergent research areas, such as band-gap structure characterization, meta-materials research, electromagnetic cloaking, slow light, super-lens design as well as near-field and virtual imaging app- ications.

Description: Direction of arrival (DOA) estimation is a classical problem in signal processing with many practical applications. Its research has recently been advanced owing to the development of methods based on sparse signal reconstruction. While these methods have shown advantages over conventional ones, there are still difficulties in practical situations where true DOAs are not on the discretized sampling grid. To deal with such an off-grid DOA estimation problem, this paper studies an off-grid model that takes into account effects of the off-grid DOAs and has a smaller modeling error. An iterative algorithm is developed based on the off-grid model from a Bayesian perspective while joint sparsity among different snapshots is exploited by assuming a Laplace prior for signals at all snapshots. The new approach applies to both single snapshot and multi-snapshot cases. Numerical simulations show that the proposed algorithm has improved accuracy in terms of mean squared estimation error. The algorithm can maintain high estimation accuracy even under a very coarse sampling grid.

Description: This paper investigates reliable and covert transmission strategies in a multiple-input multiple-output (MIMO) wiretap channel with a transmitter, receiver and an adversarial wiretapper, each equipped with multiple antennas. In a departure from existing work, the wiretapper possesses a novel capability to act either as a passive eavesdropper or as an active jammer, under a half-duplex constraint. The transmitter therefore faces a choice between allocating all of its power for data, or broadcasting artificial interference along with the information signal in an attempt to jam the eavesdropper (assuming its instantaneous channel state is unknown). To examine the resulting trade-offs for the legitimate transmitter and the adversary, we model their interactions as a two-person zero-sum game with the ergodic MIMO secrecy rate as the payoff function. We first examine conditions for the existence of pure-strategy Nash equilibria (NE) and the structure of mixed-strategy NE for the strategic form of the game. We then derive equilibrium strategies for the extensive form of the game where players move sequentially under scenarios of perfect and imperfect information. Finally, numerical simulations are presented to examine the equilibrium outcomes of the various scenarios considered.

Description: We propose a sparsity-based space-time adaptive processing (STAP) algorithm to detect a slowly-moving target using an orthogonal frequency division multiplexing (OFDM) radar. We observe that the target and interference spectra are inherently sparse in the spatio-temporal domain. Hence, we exploit that sparsity to develop an efficient STAP technique that utilizes considerably lesser number of secondary data and produces an equivalent performance as the other existing STAP techniques. In addition, the use of an OFDM signal increases the frequency diversity of our system, as different scattering centers of a target resonate at different frequencies, and thus improves the target detectability. First, we formulate a realistic sparse-measurement model for an OFDM radar considering both the clutter and jammer as the interfering sources. Then, we apply a residual sparse-recovery technique based on the LASSO estimator to estimate the target and interference covariance matrices, and subsequently compute the optimal STAP-filter weights. Our numerical results demonstrate a comparative performance analysis of the proposed sparse-STAP algorithm with four other existing STAP methods. Furthermore, we discover that the OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.

Description: A narrowband mid-infrared (mid-IR) guided-mode resonance filter (GMRF) is designed and fabricated using a Hafnium Dioxide film/quartz wafer material system. The fabricated GMRF is then integrated into an erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a line-width less than 2 nm demonstrates the viability of GMRFs for wavelength selection in the mid-IR.

Description: We propose a mutually injection-locked tunable (MILT) laser for L-band generation based on arrayed waveguide grating and gain-saturated reflective semiconductor optical amplifiers. The laser generates a 3-dB bandwidth less than 0.05 nm and a high and uniform sidemode suppression ratio $({rm SMSR}>52~{rm dB},~Delta{rm SMSR}>3~{rm dB})$ over 40 L-band wavelengths. Using an MILT laser greatly reduced the phase noise, which is measured to be ${-}{rm 107.83}~{rm dBc}/{rm Hz}$ at a frequency of 10-kHz offset from the center. Furthermore, the 1.25-Gb/s directly modulated transmission performance of the MILT laser shows that there is a power penalty of ${sim}{rm 0.2}~{rm dB}$ over a 20-km single mode fiber.

Description: Remember James Bond and the Sony Ericsson cell phone he used to drive a BMW 750 iL in the 2008 Bond movie, Tomorrow Never Dies? Your smartphone and your car (and very likely you) aren't quite ready for that kind of driving experience, but the technology and automakers are getting closer to that level of capability

Description: IEEE Signal Processing Magazine (SPM) is a tutorial-style magazine that brings to the signal processing community bimonthly survey articles of the most recent advances in signal processing theory and applications. For this issue, the Editor-in-Chief invited Andrea Cavallaro and Andres Kwasinski, the area editors for columns and forum, to write a brief on their editorial work.

Description: Cooperation is known as an effective strategy in nature to achieve individual or common goals and is a key element in evolution for optimization, as Darwin pointed out in his famous work. Cooperation among weaker individuals (such as hyenas) has the potential to outperform stronger individuals (cheetahs) agnostic to the principle of cooperation. The concept of cooperation has been applied to mobile communication networks with the first appearance of so-called ad hoc networks or meshed networks. But this kind of cooperation is a special form of cooperation, later referred to as forced cooperation, controlled by an overlay unit and not built up by selfish individuals. The research field of social mobile clouds is looking into the possibility to increase the potential of cooperation among selfishly driven users by introducing novel technologies such as network coding as well as socially driven incentives introduced by several well known social networks.

Description: High Efficiency Video Coding (HEVC) is a new video compression standard developed jointly by ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Moving Pictures Expert Group (MPEG) through their Joint Collaborative Team on Video Coding (JCT-VC). The first version of HEVC will be finalized by the JCT-VC in January 2013. The HEVC project was launched to achieve major savings—e.g., reduction by about half for 1,280 # 720 high-definition (HD) and higher-resolution progressives can video—for equivalent visual quality relative to the bit rate needed by the widely used H.264/ MPEG-4 Advanced Video Coding (AVC) standard. For high resolution video where such additional compression is most urgently required, implementations of the current draft standard are already meeting or exceeding the targeted goal. We review the architecture and building blocks of HEVC, which were carefully selected with regard to compression capability versus complexity and to enable parallelism for the signal processing operations. Given the benefits that HEVC provides, it is likely to become the new primary reference for video compression.

Description: Provides a listing of current staff, committee members and society officers.

Description: Cognitive control is part of a wider framework called cognitive dynamic systems, which builds on a paradigm of cognition composed of five elements: perception??action cycle, memory, attention, intelligence, and language. Any closed-loop feedback control system is based on the perception??action cycle. Adaptive control systems, it can be argued, incorporate the attention and intelligence aspects of the paradigm, but not memory. The language component becomes relevant to a network of cognitive agents. Cognitive control depends on an understanding of the information gap - the distance between relevant information extracted from measurements and the sufficient information that is required. Cognitive control should not be thought of as a replacement system design paradigm; it is additive in nature. It augments state-control paradigms such as adaptive control and neurocontrol. Using cognitive control, we can improve the utilization of computational resources and manage risk more effectively.

Description: In modern wireless communication systems, it is very important to realize simultaneously high-efficiency and linear operation of power amplifiers. This paper-overview describes the historical aspect of the Doherty approach to the power-amplifier design introduced in 1936 and modern trends in Doherty amplifier (DA) design techniques using multistage and asymmetric multiway architectures. To increase efficiency over the power backoff range, the switchmode class-E, conventional class-F, or inverse class-F operation mode by controlling the second and third harmonics can be used in the load network. The DA with a series-connected load, and inverted, push–pull, balanced, and parallel Doherty architectures are also described and discussed. Finally, examples of the lumped DA implemented in monolithic microwave integrated circuits, digitally driven Doherty technique, and broadband capability of the two-stage DA are given.

Description: This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the co-authors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

Description: Advertisement: This publication offers open access options for authors. IEEE open access Publishing.

Description: This paper reports the design and implementation of a two-axis capacitive-type accelerometer using well-known two poly-Si processes. The accelerometer design consists of a pendulum proof-mass (bulk Si), a gimbal-spring (poly-Si film), and vertical-comb sensing electrodes. This design has three merits: 1) pendulum proof-mass to produce torque by in-plane acceleration; 2) high-aspect-ratio-micromachined (HARM) gimbal-springs enable the detection of two-axis accelerations; and 3) vertical-combs of different vertical positions enable the differential sensing electrodes design to detect the angular motion. In short, this paper exploits the vertical-comb electrodes for differential capacitive sensing to detect the two-axis in-plane accelerations. Measurement results show that the sensitivities (nonlinearity) of etch direction are 17.87 mV/G (2.65%) of X-axis, and 16.54 mV/G (2.71%) of Y-axis in the excitation range of 0.6~2 G. Due to the HARM gimbal-spring design, the cross axis sensitivity introduced by the Z-axis excitation is less than 0.3% for both X-axis and Y-axis sensing. However, the cross-axis error between the X-axis and the Y-axis sensing elements still need to be improved.

Description: In this survey, we present a comprehensive list of major known security threats within a cognitive radio network (CRN) framework. We classify attack techniques based on the type of attacker, namely exogenous (external) attackers, intruding malicious nodes and greedy cognitive radios (CRs). We further discuss threats related to infrastructure-based CRNs as well as infrastructure-less networks. Besides the short-term effects of attacks over CRN performance, we also discuss the often ignored longer term behavioral changes that are enforced by such attacks via the learning capability of CRN. After elaborating on various attack strategies, we discuss potential solutions to combat those attacks. An overview of robust CR communications is also presented. We finally elaborate on future research directions pertinent to CRN security. We hope this survey paper can provide the insight and the roadmap for future research efforts in the emerging field of CRN security.

Description: This paper is inspired by how cognitive control manifests itself in the human brain and does so in a remarkable way. It addresses the many facets involved in the control of directed information flow in a dynamic system, culminating in the notion of information gap, defined as the difference between relevant information (useful part of what is extracted from the incoming measurements) and sufficient information representing the information needed for achieving minimal risk. The notion of information gap leads naturally to how cognitive control can itself be defined. Then, another important idea is described, namely the two-state model, in which one is the system's state and the other is the entropic state that provides an essential metric for quantifying the information gap. The entropic state is computed in the perceptual part (i.e., perceptor) of the dynamic system and sent to the controller directly as feedback information. This feedback information provides the cognitive controller the information needed about the environment and the system to bring reinforcement leaning into play; reinforcement learning (RL), incorporating planning as an integral part, is at the very heart of cognitive control. The stage is now set for a computational experiment, involving cognitive radar wherein the cognitive controller is enabled to control the receiver via the environment. The experiment demonstrates how RL provides the mechanism for improved utilization of computational resources, and yet is able to deliver good performance through the use of planning. The paper finishes with concluding remarks.

Description: Carbon nanotubes (CNTs) improve the sensitivity of electrochemical biosensors. An optimized CNT/trasducer integration is required to realize accurate devices. The nanotube orientation on the sensor electrode is a key parameter. The role of the sidewalls and the tips in the electroactivity of the nanosensor is presently investigated in the literature. In addition, nanotube hydrophobicity is a drawback for biosensing purposes. Indeed, samples are always in water conditions and the integration biomacromolecules-CNTs are often required. In this paper, a comparison of CNTs with and without exposed walls before and after an acid treatment is proposed. It is done by using contact angle measurements and electrochemical measurements of the electroactive compound potassium ferricyanide. Finally, the electrochemistry of two biomolecules is investigated with those nanostructures more suitable for biodetection.

Description: This paper presents a comprehensive study of the design aspects of eddy-current displacement sensor (ECS) systems. In accordance with the sensor analysis presented in this paper, design strategies to compensate for important sensor imperfections are recommended. To this end, the challenges that are associated with ECS interfaces are identified, with focus on advanced industrial applications. This paper also provides a technical overview of the design advances of ECS interfaces proposed in the last decade and evaluates their pros and cons. Recently reported interface solutions for demanding industrial applications with respect to high resolution, stability, bandwidth, and low power consumption, at a sufficiently high excitation frequency, are addressed in more detail.

Description: Ambulatory monitoring of the electrocardiogram (ECG) is a highly relevant topic in personal healthcare. A key technical challenge is overcoming artifacts from motion in order to produce ECG signals capable of being used in clinical diagnosis by a cardiologist. An electrode-tissue impedance is a signal of significant interest in reducing the motion artifact in ECG recordings on the go. A wireless system containing an ultralow-power analog front-end ECG signal acquisition, as well as the electrode-tissue impedance, is used in a validation study on multiple subjects. The goal of this paper is to study the correlation between motion artifacts and skin electrode impedance for a variety of motion types and electrodes. We have found that the correlation of the electrode-tissue impedance with the motion artifact is highly dependent on the electrode design the impedance signal (real, imaginary, absolute impedance), and artifact types (e.g., push or pull electrodes). With the chosen electrodes, we found that the highest correlation was obtained for local electrode artifacts (push, pull, electrode) followed by local skin (stretch, twist, skin) and global artifacts (walk, jog, jump). The results show that the electrode-tissue impedance can correlate with the motion artifacts for local disturbance of the electrodes and that the impedance signals can be used in motion artifact removal techniques such as adaptive filtering.

Description: A single-chip smart flow sensor based on a thermal principle is presented. The device is fabricated through a commercial complementary metal-oxide-semiconductor (CMOS) process combined with a postprocessing procedure. A configurable electronic interface performing signal reading and nonideality compensation is integrated with the sensing structures on the same chip. The interface implements recently proposed approaches to offset and pressure effect compensation. Detailed experimental results are presented demonstrating correct operation of the proposed microsystem.

Description: In this paper, the results of the long-term temperature monitoring of the compact muon solenoid experiment (CMS) at CERN are shown. The measurements were carried out by means of a system based on fiber Bragg grating (FBG) sensors in wavelength-division multiplexing (WDM). Due to the harsh working conditions at the CMS, the FBG sensor represents the ideal candidate to realize a reliable and accurate sensing system. The sensing principles of the FBG sensor and its temperature characteristics are introduced. A temperature monitoring system based on FBG for high-energy physics applications is designed and installed. The sensing system was used successfully last year in monitoring the temperature of CMS bulkhead. The reported results show good reliability and high accuracy of the FBG sensing system during the long-time working stage.

Description: An inductance-capacitance-resistor (LCR) loop is composed, by connecting an inductive coil with a capacitance element end by end. Without any electric connection with other circuits, higher quality factor can be easily obtained. The loop is inserted into the electromagnetic coupling path of coil-based sensing system, such as the case of eddy-current sensor. When the system is working at the natural resonant frequency of the loop, the coupling efficiency and, therefore, the sensing performance could be improved significantly. Protocol systems, simulating the operation cases of wireless passive sensor and eddy current proximity sensor, are constructed and tested experimentally. The results indicate that, in case of coil-coupled wireless passive sensing system, the received signal's amplitude is enlarged remarkably with a coaxially inserted LCR loop. Moreover, when the loop is coaxially placed on top of the sensing coil of eddy current sensor, not only higher sensitivity and resolution, but also larger monotonic detection range could be achieved.

Description: In this paper, a measurement system for human joint movements monitoring based on a simple and low-cost intensity modulated fiber-optic curvature sensor is presented. The implemented curvature sensor is made up of a plastic optical fiber, which is optimized for small curvature measurements, and has a high sensitivity in a wide measuring range. The sensor sensitivity and resolution, in the measurement range, are 20 ${rm mV}/^{circ}$ and 1 $^{circ}$ , respectively. The fabrication process of proposed curvature sensor is also given. The implemented sensor is wearable, noninvasive, nonintrusive, and completely harmless. In this paper, the characteristics of the sensor measured in laboratory conditions as well as measurements of the human knee joint movements are given. Wireless electronics based on ZigBee are also presented. Therefore, the sensor has the possibility of wireless measurement. The main advantages of this sensor are simplicity, lightness, and flexibility. This sensor is also electrically safe and immune to electromagnetic interference. The application, which provides a possibility of remote human joints monitoring over the internet is implemented in the LabVIEW software package.

Description: We present experimental demonstrations of a self-repairing polymer waveguide strain sensor packaged in a polyimide capillary. The waveguide is fabricated between two multi-mode optical fibers through an ultraviolet curable resin and operates as a strain sensor by interrogation of the infrared power transmission through the waveguide. The packaging improves the performance of the sensor as compared to a previous unpackaged version, by removing previous “no-response” zones. The resulting sensor output is monotonic throughout the measurement range. The hysteresis in the sensor behavior among multiple loading cycles is also significantly reduced. A jump in the sensor output voltage is observed after the sensor self-repair process, which presents challenges for calibration of the sensor.

Description: Control of lighting systems that adapt to daylight is known to be energy efficient. An underlying challenge in such control is the estimation of daylight level. We consider the problem of disaggregated estimation of the daylight and artificial light levels in a lighting system. To facilitate this disaggregation, the light output from each light source is modulated and the system operates under a carrier sense multiple access with collision avoidance protocol. At the light sensor, the received electrical signal is a superposition of the light contributions from daylight and artificial light sources. We present algorithms to process the sensor signal to estimate the daylight and artificial light levels. An optimum joint least-squares estimator is analyzed and, subsequently, two practical successive estimation algorithms are proposed. The performance of these algorithms is evaluated analytically and validated via experimental results.

Description: The design of complex analog interfaces would largely benefit from model-based development and compositional methods to improve the quality of its final result. However, analog circuit behaviors are so tightly intertwined with their environment that: 1) abstractions needed for model-based design are often not accurate, thus making it difficult to achieve reliable system performance estimations, and 2) generic, design-independent interfaces that are needed to develop compositional techniques are very difficult to define. In this paper, we propose a platform-based design methodology that uses analog contracts to develop reliable abstractions and design-independent interfaces. A contract explicitly handles pairs of properties, representing the assumptions on the environment and the promises of a component under these assumptions. Horizontal contracts encode composition rules that constrain how library elements should be “legally” used. Vertical contracts define under which conditions an aggregation of components satisfies the requirements posed at a higher level of abstraction. If both sets of contracts are satisfied, we can produce implementations by composition and refinement that are correct by construction. We demonstrate the effectiveness of this approach on the design of an ultra-wide band receiver used in an Intelligent Tire system, an on-vehicle wireless sensor network for active safety applications.

Description: A smart system for flow measurement is presented, consisting of a micromachined thermal flow sensor combined with a smart front-end electronic interface. The flow sensor is based on a novel thermal transduction method, which combines the hot-film and calorimetric sensing principles. The sensor consists of four germanium thermistors embedded in a thin membrane and connected to form a Wheatstone bridge supplied with a constant DC current. In this configuration, both the bridge unbalance voltage and the voltage at the bridge supply terminals are functions of the flow offering high initial sensitivity, i.e., near zero flow and wide measurement range, respectively. The front-end interface is based on a CMOS relaxation oscillator circuit where the frequency and the duty cycle of a rectangular-wave output signal are related to the bridge unbalance voltage and the voltage at the bridge supply terminals, respectively. Furthermore, the amplitude of the output signal is a linear function of the operating temperature. In this way, a single output signal advantageously carries two pieces of information related to the flow velocity and provides an additional measurement of the sensor operating temperature, which enables the correction of the temperature dependence of the sensor readouts. The system has been experimentally characterized for the measurement of nitrogen gas flow velocity at different sensor temperatures. The initial sensitivities at room temperature result 13.7 kHz/(m/s) and 23.5%/(m/s), in agreement with FEM simulations, for frequency and duty cycle readouts, respectively, with an equivalent velocity resolution of about 0.5 and 1.3 cm/s.

Description: An automated data fusion and visualization process is developed for nondestructive evaluation and direct visualization of internal defects of concrete structures based on impact-echo testing using source–receiver arrays. In the process, the ratio between the amplitudes of major echo peaks in the frequency spectrum (after noise reduction) and the bottom echo signal is proposed as a feature parameter for data fusion. The fused results then go through image segmentation, which combines thresholding and region growing to extract defect regions for visualization. The effectiveness of the automated data fusion and visualization process is validated using both numerical simulation and experimental testing.

Description: Integrated complementary metal-oxide-semiconductor (CMOS)-microelectro mechanical systems (MEMS) beam-array resonators that take advantage of the pull-in effect to surmount limitations of standard CMOS foundry processes have been demonstrated to attain electrode-to-resonator gap spacing at a deep-submicrometer range. Such deep-submicrometer gaps lead to much larger electromechanical coupling coefficient and smaller motional impedance as compared with conventional CMOS-MEMS technologies. In addition, a unique frequency tuning capability by modulating the mechanical boundary conditions (“BC”) of the resonators has also been proposed. Furthermore, the mechanically coupled array approach used in this paper not only provides five times smaller motional impedance compared with that of a single resonator but offers superior power handling capability due to higher stiffness of the arrayed resonator. In such an array design, high velocity coupling for beam-array resonators effects a single resonance behavior without spurious modes. With the increase of an applied dc-bias which simultaneously serves for functions of pull-in and resonator operation, the upward frequency shift of resonance caused by boundary condition change offers opposite tuning mechanism against the well-known effect of electrical stiffness. As a result, frequency variation induced by the BC-modulation and electrical stiffness would yield a frequency-insensitive region under a certain dc-bias voltage. Furthermore, the use of metal/oxide composite materials for resonator structures in this paper substantially alleviates residual stress often seen in the CMOS layers as compared to mere-metal resonators.

Description: We report the fabrication and characterization of a surface plasmon resonance (SPR)-based fiber-optic sensor for the detection of low-density lipoprotein (LDL). The probe is prepared by first coating a 50-nm-thick gold film on the unclad portion of the optical fiber core and then immobilizing 4-aminothiophenol (4-ATP), followed by antiapolipoprotein B, over the 4-ATP/Au surface. Spectral interrogation technique is used for the characterization of the probe. SPR spectra are recorded for sample solutions of LDL with concentrations in the range of 0–190 mg/dl. Sensitivity of the sensor is found to be 0.18387 nm per mg/dl. Furthermore, the response time of the sensor is very small (around 2 min). The sensor can be utilized in online monitoring as well. This paper may result in the commercialization of a miniaturized low-cost reusable fast and accurate optical fiber sensor for the detection of LDL level in human blood.

Description: This paper introduces a new foundation for ultra-cooperative communications based on very low signal-to-noise ratio (SNR) channels between mobile sensor nodes grouped in spatially distributed clusters. In this new framework, we define a cluster entity as a sensor network of wireless nodes with, but not limited to, scale-free topology. We define a physical wireless scale-free model for the clusters that extends the abstract scale-free model developed by Barabasi-Albert for network graphs to the wireless channel. Our air interface model is based on orthogonal frequency division multiplexing with Rayleigh flat fading channels and additive white Gaussian noise. For intracluster communications, we have developed the new concept of consensus in a wireless network framework to improve performance. This new approach is ideal for distributed long-range low power sensor networks with ultra-low power signals well below the noise floor. For a cluster size of 100 nodes, we achieve BER of at an SNR of ${-}{rm 25}~{rm dB}$ in Rayleigh fading. This method enables reliability in both fading channels for intracluster communications and can support ultra-long range or ultra-low power communications links. We establish the fundamental principles involving the relationship between cluster sizes and communication performance, and illustrate $7times$ gains in range performance using HATA path loss models.

Description: A low power temperature sensor followed by a switched capacitor amplifier, a buffer stage, and a 12-bit successive approximation analogue-to-digital converter (ADC) for autonomous multi-sensor systems is presented. The proposed design is accurate within 0.01 $^{circ}{rm C}$ from ${-}{rm 55}^{circ}{rm C}$ to 125 $^{circ}{rm C}$ . A proportional to absolute temperature source was used as a temperature sensor. The read-out enables a differential reading of a reference and actual temperature. The subsequent ADC digitizes the output signal. The ADC has a figure-of-merit of 66 fJ/conversion-step at a bit-clock of 50 kHz. The system is implemented in an NXP CMOS 0.14- $mu{rm m}$ technology. The die area is 0.27 ${rm mm}^{2}$ , and the whole system consumes less than 16 $mu{rm W}$ . Design and measurements are presented.

Description: In this paper, research on a vibration sensor (accelerometer) that converts mechanical load to an electrical signal is carried out. An accelerometer mathematical model is developed to select the best damping rate value to reduce the measurement error as much as possible. The main purpose of this paper is to enhance the vibration sensor performances (choice of the best value of damping rate and minimization of measurement error by increasing sensor precision and reliability). The developed model is validated by computer simulation and experimental tests. The obtained results have demonstrated that an appropriate damping rate can reduce measurement error of relative movement to 1%.

Description: A simple sensor system designed to monitor the temperature or strain of a certain number of critical points along a structure is presented and demonstrated. It is based on the remote interrogation of fiber Bragg gratings (FBGs) placed in series by means of a Brillouin fiber laser. Three FBGs were interrogated 50 km from the processing unit using 8 mW of Brillouin pump. Heterodyne detection brings forth a signal-to-noise ratio of approximately 40 dB in our measurements.

Description: The publication offers a note of thanks and lists its reviewers.

Description: One of the fundamental issues in sensor networks is the coverage problem, which reflects how well a field is monitored or tracked by sensors. Various versions of this problem have been studied, such as object, area, barrier, and hole coverage problems. In this paper, we define a new $k$ -angle object coverage problem in a wireless sensor network. Each sensor can only cover a limited angle and range, but can freely rotate to any direction to cover a particular angle. Given a set of sensors and a set of objects at known locations, the goal is to use the least number of sensors to $k$ -angle-cover the largest number of objects such that each object is monitored by at least $k$ sensors satisfying some angle constraint. We propose centralized and distributed polynomial-time algorithms to solve this problem. Simulation results show that our algorithms can be effective in maximizing coverage of objects. A prototype system is developed to demonstrate the usefulness of angle coverage.

Description: Morphological image processing is a type of processing based on the theory of mathematical morphology, by which the spatial forms or the structures of objects in an image are modified. This objects-oriented image processing is advantageous for a sensor to make a decision, although is not good enough for visual aesthetics (or entertainment) purposes. Therefore, morphological image processing is suitable for sensing applications. It is noted that there are two special features associated with the video sensor networks: 1) limited resource and 2) the nonvisual aesthetics (or not for entertainment) purpose. Therefore, an approach of particular image processing on the sensor network is proposed in this paper. In this approach, the image is compressed using the quad tree data structure and is also processed in this structure using morphological operations to achieve the sensing purpose. Both the speed and the compression efficiencies of this proposed approach are verified from the sensor's perspective in our experiments.

Description: The remotely powered underwater acoustic sensor networks (RPUASN) paradigm is introduced, whereby sensor nodes harvest and store the power supplied by an external acoustic source, indefinitely extending their lifetime. Necessary source characteristics are determined. Feasibility is illustrated with realistic examples, and open research issues are pointed out. Performance of RPUASN is directly related to the sensing coverage and communication connectivity over the field the sensor nodes are deployed. The required number of RPUASN nodes and the volume which is guaranteed to be covered by the nodes are analyzed in terms of electrical power, range, directivity, and transmission frequency of the external acoustic source, and node power requirements.

Description: Conferences are one of the most important parts of business for the IEEE societies for a variety of reasons. This month¿s President¿s Page is shared with Abbas Jamalipour, ComSoc¿s Vice President¿Conferences for 2012-2013.

Description: The First Women's Workshop on Communications and Signal Processing was held at the Banff International Research Station (BIRS) July 13-15. It brought together 27 women researchers for a weekend of technical presentations, posters and networking. The workshop was organized by Sheila Hemami (Cornell University), Urbashi Mitra (University of Southern California), Milica Stojanovic (Northeastern University), and Katie Wilson (Santa Clara University). The primary focus of this workshop was academic research, but we believe this workshop model could be adapted for women in industry as well. We would like to thank BIRS, the Office of Naval Research, the IEEE Signal Processing Society, and the IEEE Communications Society for their grants, which helped make the workshop possible. More information can be found at http://www.birs.ca/events/2012/2-day-workshops/12w2147.

Description: Provides a listing of upcoming conference events of interest to practitioners and researchers.

Description: 3GPP studies indicate that for mobile networks to be competitive for mass machine-type applications, it is important to optimize their support for the expected huge growth of connected devices due to uptake of machine-type communications. In this article we briefly describe the architectural enhancements in 3GPP systems to better facilitate machine type communication. We highlight key architectural changes, functionality of new network elements to support new features such as device triggering, packet switched subscriptions including short message service via PS domain and SMS in MME. We also describe overload control mechanisms to prevent overload situations caused by synchronous connection requests from large numbers of MTC devices to the 3GPP system. Finally, we discuss how this work is expected to evolve in future 3GPP releases.

Description: As a companion effort to the development of the Wireless Communication Engineering Technologies (WCET) certification, ComSoc also invested in the creation of a book covering much of the material that forms the basis for the WCET certification examination. To be clear, A Guide to the Wireless Engineering Body of Knowledge (WEBOK) was never intended to be a study guide for the exam or to cover every topic that might be the subject of a question on the exam. Indeed, no editor or contributing author to the WEBOK has any role in writing or selecting questions for the exam, nor is anyone involved in the creation of the exam a contributor to the WEBOK.

Description: As global deployments of Long Term Evolution (LTE)-based fourth generation (4G) networks are gaining momentum, the effective realization of a mobile broadband experience is facing new challenges and increasing expectations from the perspectives of both network operators and end users. Not only is mobile data traffic growing exponentially, but new multimedia applications on smart mobile devices and also the more stringent demands on the quality of service.

Description: Advanced interference mitigation techniques relying on multipoint coordination have attracted significant attention from the wireless industry and academia in the past few years. In 3GPP LTE-Advanced, a work item on Coordinated Multiple Point transmission and reception (CoMP) was initiated in September 2011, and it is one of the core features of Release 11. The objective of this work item is to provide the necessary specification support to efficiently realize the benefits of cooperative transmission in the downlink and cooperative reception in the uplink. This article discusses the specification support for CoMP and the motivations behind the specific design choices. The deployment scenarios that were considered for the application of CoMP in Release 11 are also presented.

Description: Transmissions in different cells of a time-division duplex system are typically synchronous in order to eliminate the base station-to-base station and terminal-to-terminal interference. The synchronous operation limits dynamic resource configuration for downlink and uplink transmissions. Today, as a large percentage of mobile traffic is generated in hotspots and indoor environments, heterogeneous networks comprising high-power/wide-area and low-power/local-area network nodes are becoming a reality. Such heterogeneous networks provide opportunities to exploit dynamic uplink-downlink configuration in TDD systems, adapting to the individual traffic needs of a specific cell area. This article presents a tutorial overview of dynamic uplink-downlink configuration and interference management in time-division Long Term Evolution, including motivations, target deployment scenarios, opportunities and challenges, system requirements, design aspects, and performance evaluations.

Description: The Third Generation Partnership Project defined multimedia broadcast/multicast service in 2005 to optimize the distribution of video traffic. This standard covers the terminal, radio, core network, and user service aspects. This MBMS standard has evolved into enhanced MBMS (eMBMS) that builds on top of the 3GPP Long Term Evolution standard. eMBMS evolution brings improved performance thanks to higher and more flexible LTE bit rates, single frequency network operations, and carrier configuration flexibility. 3GPP Rel-11 also brings improvements in the areas of service layer with, for example, video codec for higher resolutions and frame rate, and forward error correction. eMBMS allows offloading of the LTE network and backhaul. It enables the possibility to deliver premium content to many users with secured quality of service in defined areas. Other important use cases are pushed content via user equipment caching and machine-to-machine services. This article describes the relevant use cases for eMBMS in terms of service. It then gives a tutorial on eMBMS, in particular highlighting the evolution over MBMS. The scope comprises the radio access, core network, and service layer.

Description: Recently, a workshop on ¿Antenna Design and Fabrication¿ was held at Mehran University of Engineering and Technology (MUET), Jamshoro, Pakistan, on 3-4 Sep 12 . However, this was no ordinary workshop because not only were the participants students but the organisers and instructors for the event were also students.

Description: Markets for network resources have become increasingly important. Such resources include bandwidth in wireline networks to wireless spectrum. It is clear that if the markets are not properly designed, they can function rather poorly, even leading to market failure. This then leads to suboptimal use of network resources. In this article, we present the game theoretic framework behind the market design principles for network resources. We present some of the extant work on network market mechanisms in the context of wireline networks in part I. Part II [1] relates to network market design in the context of wireless systems. We also discuss some of the key challenges for the future.

Description: The tremendous growth in demand for broadband data is forcing ISPs to use pricing as a congestion management tool. This changing landscape of Internet access pricing is evidenced by the elimination of flat rate data plans in favor of usage-based pricing by major wired and wireless operators in the US and Europe. But simple usage-based fees suffer from the problem of imposing costs on all users, irrespective of the network congestion level at a given time. To effectively reduce network congestion, appropriate incentives must be provided to users who are willing to time-shift their data demand from peak to off-peak periods. These pricing incentives can either be static (e.g., two-period daytime/nighttime prices) or computed dynamically (e.g., dayahead pricing, real-time pricing). Data plans that offer such incentives to consumers fall under the category of time-dependent pricing (TDP). Many ISPs across the world are currently exploring various forms of TDP to manage their traffic growth. This article first outlines the sources of today¿s challenges, and then discusses current trends from regulatory and technological perspectives. Finally, we review representative pricing proposals for incentivizing the time-shifting of data.

Description: Mobile data traffic is expected to grow exponentially in the next few years due to the explosive growth of mobile web and video traffic on smartphones. Wireless operators have invested heavily to make infrastructural improvements by installing new cell towers and offloading cellular data traffic to Wi-Fi to resolve congestion. They are also exploring the use of behavioral and economic interventions to manage congestion. To understand the role of interventions, we distributed smartphones to students at Purdue University, loaded with applications to perform monitoring and location tracking with user consent. We conducted two experiments: first with 14 phones of one type, then with 30 phones of two types. Wi-Fi traffic and cellular network data usage were collected and analyzed to characterize and quantify the changes in usage behaviors; the second experiment also captured location data during compliance/non-compliance to incentive messages. The trial seeks not only to experiment with incentives and disincentives to observe their effectiveness, but also to understand current mobile broadband and Wi-Fi usage behaviors in a campus environment. Our results indicate a high level of compliance with economic incentives and disincentives. Detailed analysis further showed correlation with two psychological measures of each user (agreeableness and neuroticism). In addition, we found schemes with probabilistic payments of higher incentive amounts getting more positive results compared to schemes with definite payments with lower incentive amounts, despite similar total payout.

Description: Auction theory, as a subfield of economics, provides useful tools to model, analyze, and optimize radio resource management in cognitive radio environments. By using an auction, radio resources such as subchannel, time slot, and transmit power can be allocated among licensed and unlicensed users in the system, following market laws. Due to the flexibility of mechanism design, there are various auction mechanisms that have been applied to cognitive radio systems with different characteristics. In this article, we first provide an overview of the basics of general auctions. Then the motivations and specific design issues in applying auctions to wireless network architectures and protocols are discussed. Then we review the state of the art in the use of auction theory and mechanism design in cognitive radio networks. This will enable the readers to have a general view of auction fundamentals, as well as the recent development and applications of auction theory in the emerging cognitive wireless networks.

Description: In this article, we discuss a spectrum trading mechanism implemented by the spectrum broker in TV whitespaces. TVWS are spectrum frequency bands unused by DTV, interleaved in both frequency and space. Underutilization of these bands results from the fact that the DTV transmission systems now operational in the spectrum from 470 to 790 MHz are multifrequency systems employing high tower and high power network geometries, and must be managed for interference between transmitters. We motivate the use of a spectrum broker, an entity that manages the TVWS secondary spectrum market. Such a TVWS broker¿s responsibilities include planning the possible broad uses of the available spectrum in the TVWS; packaging the spectrum for short-term disposal through trading mechanisms; serving the broker¿s customers, with spectrum-leasing contracts; and acting as the port of call to handle interference caused by its customers to the primary DTV systems or between its customers themselves. We discuss the spectrum broker¿s merchant and auction modes for spectrum trading. In the merchant mode, the base price is decided by the allocation procedure, which considers various factors influencing the value of TVWS in a given place. In the auction mode, the customers¿ demands and bids decide the final price of the spectrum. We discuss the auction design and show results of the spectrum trading mechanisms, which have been successfully applied in a real-world test scenario in the area of Munich, Germany.

Description: This issue of the Consumer Communications and Networking series, featuring four articles, touches on four different aspects of emerging technologies from radio communications in a digital home to workflow management in connected smart homes and inter-destination synchronization for multimedia applications to mobile application stores. Let us look into the details of each article.

Description: In the Internet of Services, users are surrounded by lots of connected devices and remote services with the potential for real-time interaction. While users could manually command their operation, it will be extremely convenient to have an environment where interaction workflows could easily be defined so that services could operate autonomously following those patterns. This article presents a system to allow individuals with no specific programming skills to define and execute those interaction workflows using graphical abstractions. The system has been validated inside a smart home scenario, as a good representative of the future Internet of Services environment due to the presence of multiple heterogeneous devices and services from different domains.

Description: Currently, the media consumption paradigm is changing from a single end user to a group shared experience. Now, social communication opportunities may be exploited (e.g., conferencing while watching television), facing lots of technological (e.g., synchronization, universal session handling, scalability) and perceptual (e.g., presence awareness, QoE) challenges. This article focuses on one of these major challenges ahead in new emerging social interactive multimedia applications, which is the synchronization of different media streams across multiple locations, known as inter-destination multimedia synchronization (IDMS). We describe the three kinds of temporal multimedia synchronization, and summarize some related work and examples of applications in which IDMS is needed. The article includes a discussion about an RTP/ RTCP-based IDMS solution the authors have been working on, as well as the standardization status regarding this kind of synchronization.

Description: The mobile user experience has been significantly altered with the arrival of mobile broadband widespread deployments, massive improvements in available smartphones, and a shift in user habits toward a more participative, communicative role. In this context, mobile application stores have revolutionized software and content delivery. These stores focus on the applications, building around them an ecosystem of developers and consumers. The store greatly lessens the barrier between these agents, providing significant benefits to both developers and consumers. In this article we analyze this phenomenon, describing its originating factors and fundamental characteristics. We also perform a more detailed study on the two most successful application stores, identifying different approaches to implementing the model.

Description: Telecommunications service providers continue to focus on providing additional network capacity to meet growing needs for bandwidth in their access, metro, and long-haul networks. Global optical transport industry suppliers have accelerated their efforts over the past three years on improving spectral efficiency while reducing cost per bit. While the industry has witnessed the growing use of advanced modulation formats such as DP-QPSK and coherent detection, a broad-based search for approaches to increase transmission speeds for each optical channel, a larger number of wavelength- division multiplexing (WDM) channels, and space multiplexing over a larger number of fiber cores is in progress.

Description: Network traffic demands are forecast to increase for the foreseeable future, with the challenge being to meet the demand while maintaining or lowering network costs. Simply increasing capacity will not be sufficient; overall bandwidth utilization also needs to improve. A combination of improved transport capacity through increased spectral efficiency and bit rate along with better network utilization by integrating subchannel electrical grooming into the transmission system will be required. Smarter ways to utilize optical capacity are key since transmission costs have been decreasing slower than grooming and switching costs. Integrated transport and switching can improve the efficiency of the client network using techniques such as port virtualization and transit traffic reduction. The baseline for transport networks will be 100 Gb/s PM-QPSK using 50 GHz channel spacing. Moving from a fixed DWDM channel arrangement to support flexible grid and super channels will allow tighter channel (carrier) spacing and should increase capacity by 30 to 50 percent. For shorter distances higher-order modulation such as 16-QAM can double network capacity. To better optimize network efficiency, an architecture that flexibly combines lower rate (sub-100 Gb/s) clients to form channels (carriers) and then superchannels will be required.

Description: Minimization of drive tests is a feature introduced in 3GPP Release 10 that enables operators to utilize users¿ equipment to collect radio measurements and associated location information, in order to assess network performance while reducing the OPEX associated with traditional drive tests. However, in the increasingly complex wireless packet data networks of today, performance is affected by many different factors and cannot easily be estimated by simple radio measurements. Therefore, in 3GPP Release 11 specifications, MDT is enhanced in order to provide a more complete view of network performance. This article describes the MDT enhancements added in Release 11, explains how measurements collected by MDT can be used to draw conclusions that are relevant for network management, and discusses similarities and differences between MDT and traditional drive tests.

Description: Market-based approaches have promising potential for allocating network resources. Part I of this article introduced the game theoretic underpinnings of market design and argued for the need to jointly consider market design with the underlying engineering issues in communication networks. Example research questions in this area were reviewed for wireline networks. In this part, we turn to network market design for wireless systems and in particular for the flexible sharing of wireless spectrum. We use this as a vehicle for discussing challenges that arise in the design of markets in the presence of externalities.

Description: Today¿s communication networks are highly complex, carry heterogeneous traffic in diverse environments, and are often owned by multiple profit-making entities. To successfully maintain, optimize, and upgrade such large distributed networks, it is important to design new economic incentive mechanisms as well as develop new technologies. The market deregulation of the telecommunication industry in many countries makes such economic consideration even more urgent, as there are often conflicting goals between the regulators and the commercial operators. In this feature topic we present six articles that naturally group into three trendy topics in this important emerging research discipline.

Description: With the ever growing usage of various wireless technologies and services, more and more handheld devices are equipped with multiple radio transceivers (e.g., LTE, WiFi, Bluetooth, and GNSS). As a result, in-device coexistence interference has become a serious problem due to the extreme proximity of multiple radio transceivers within the same device. It has been shown by the studies of 3GPP that for some specific frequency bands, concurrent operations of LTE and ISM/GNSS radios working in adjacent or sub-harmonic frequencies will result in significant in-device coexistence interference that cannot be completely eliminated by filter technology. This motivates 3GPP to introduce signaling mechanisms and procedures, which enable the devices to effectively solve the indevice coexistence problems with help from the LTE network. This article first discusses the scenarios in which coexistence interference may happen, and then provides an overview of main solutions and related procedures specified in 3GPP Release-11 standards for LTE. In addition, some aspects of device-internal coordination and implementation to facilitate the coexistence scenarios are also discussed.

Description: The future digital home (DH) is envisioned as a place where a plethora of diverse personal and machine-to-machine communications will coexist to support different applications in areas such as information and entertainment, home automation, home health care and home security and management. Wireless technologies are usually the preferred solution to cope with DH communications for their ease of installation and use. However, expected capacity demand and the lack of coordination between an increasing number of diverse wireless devices in use within the DH is seriously challenging the performance and usability of wireless technologies. This article outlines a novel technical solution intended to enhance capacity and quality of DH wireless communications. The proposed solution establishes a radio-independent coexistence framework where key operational radio settings of DH devices are coordinately determined, and new spectrum sources other than traditional ISM bands can be exploited for DH communications. The addressed solution enables a business player to offer management services for DH wireless communications so that ordinary users can be relieved of complex management tasks likely to arise within the DH. The article discusses how potential management service providers could benefit from the proposed solution. Besides, the functional architecture of the proposed solution together with the set of procedures necessary for the management of the DH wireless communications are outlined. A realistic indoor scenario is presented as an illustrative use case to show how proper decision making logic in managing the DH could improve the efficiency by selecting the most suitable spectrum for in-house wireless communications. Finally, the main implementation issues are identified and discussed in order to outline a feasible roadmap

Description: As line interfaces in communications chassis transition to 100 Gb/s and higher per port, many in the industry question when electrical backplanes inside these chassis will give way to optical ones. Provided that the maximum card-to-card distance over a backplane remains at one meter, two observations point to an electrical-to-optical transition near the end of this decade: commercial links transition from electrical to optical at the bandwidth-distance product of 100 Gb/s .m [1], and backplane line rates double every two process nodes and will reach 100 Gb/s in four process nodes. But optical solutions will need to overcome incumbency, or economics will call for electrical backplane solutions. To set up a framework for comparing backplane solutions, this article first defines a canonical backplane model to enumerate possible backplane implementations. Using this model, this article identifies 10 practical future backplane implementations, of which four are electrical and six optical. This article further describes how electrical solutions could be viable beyond this decade. It then outlines three necessary conditions for optical solutions to unseat the incumbent. Finally, it argues that optical solutions have an inherent advantage to scale systems with inter-chassis links, an advantage that could tip the balance in favor of optics in future backplanes.

Description: The bandwidth efficiency and relative costs for 100 Gb/s WDM transport and switching architectures are compared in North American and pan-European long-haul networks. The first architecture uses muxponders and ROADMs for end-to-end wavelength transport with no digital sub-wavelength grooming. The other two utilize digital OTN switching, as either a standalone OTN switch or a converged integrated WDM/switch system, to efficiently groom services onto WDM wavelengths. Results show the integrated WDM/switch architecture utilizes the fewest WDM wavelengths and client service interfaces, and an integrated WDM/switch architecture using photonic integrated circuit technology provides the lowest operational costs.

Description: The purpose of this article is to examine some of the models commonly used to represent fading as well as the information-theoretic metrics most commonly used to evaluate performance over those models. We raise the question of whether these models and metrics remain meaningful in light of the advances that wireless systems have undergone over the last two decades. A number of weaknesses are pointed out, and ideas on possible fixes are put forth. Some of the identified weaknesses have to do with models that, over time, have become grossly inadequate. Other weaknesses have to do with changes in the operating conditions of wireless systems, and others with the coarse and asymptotic nature of some of the most popular performance metrics (¿diversity¿ and ¿multiplexing¿).

Description: Running desktop-as-a-service solutions in remote data centers is an emerging means of delivering virtual PCs in an inexpensive, secure, and easy-to-maintain way. The fact that such solutions rely on the presence of connectivity between users and their virtual PCs poses a challenging operational question: what is the quality of experience of the user when running a particular application inside the thin-client protocol? The challenge is to understand whether the path between the client and the server has enough resources to sustain the rendering of the specific application. To address this question, we propose a method that exploits statistical classification to infer on-the-fly the class of applications running inside a given thin-client connection. We then correlate such information with the key factor that limits thin-client performance (i.e., network latency) to obtain the current user¿s QoE. We evaluate how machine-learning techniques can robustly detect applications that exchange data over the Microsoft Remote Desktop Protocol, with promising results (over 80 percent of accuracy for multimedia content). To the best of our knowledge, this is the first attempt of using statistical techniques to monitor thin-client applications for QoE detection.

Description: Bitstream-based methods are intuitively suited for quality assessment of networked video services, and are currently under intense investigations in terms of research and standardization activities. This article examines the factors that may affect the quality of the networked video, and reviews the state-of-the-art techniques as well as standardization progress in bitstreambased video quality assessment. According to different levels of access to the bitstream, three types of models are described and compared: the parametric, packet layer, and bitstream-layer models.

Description: Listing of the advertisers represented in this issue.

Description: It has been widely asserted that TDM PON technology will not be able to effectively cope with future increases in subscriber bandwidth demand, and that WDM PON architectures must succeed it. In this article we compare the historical trend of TDM PON bandwidth supply and the growth of residential bandwidth demands to the end of this decade, and conclude that bandwidth supply is growing much faster than the demand, calling into question the need for WDM PON. Further, we distinguish between sustained bandwidth demand and burst bandwidth demand, and further conclude that TDM PON will deliver future ultra-high speed services more efficiently than WDM PON.

Description: The slab-thickness dependence of the photonic bandgap in air-bridge photonic-crystal slabs was theoretically investigated by the 3-D plane-wave expansion method. The photonic bandgap was found to achieve a maximum for a certain slab thickness depending on air-hole volume filling factor. A kink in the photonic bandgap width versus slab thicknesses was observed, and found to be due to a transition in the nature of the modes at the top of the bandgap. Through a systematic investigation, a linear relation between the optimized slab thickness for the maximum photonic bandgap versus air-volume filling factor was found to hold over a wide range of air-volume filling factors. The linear relation also holds for photonic-crystal slabs composed of other materials and would favor the design and application of various 2-D photonic-crystal-slab devices such as reflectors, cavities, and waveguides.

Description: The interaction of low-order modes with photonic crystals (PhCs) has been a promising technique to increase light extraction efficiency (LEE) of LEDs. In this paper, numerical simulations based on the finite-difference time-domain method were carried out to explore different mechanisms that can effectively improve this interaction. The results showed that deeply etched PhCs have inefficient light extraction since they would decrease the effective thickness of the unetched layer and cut off some guided modes. By applying the Al x Ga 1-x N confining layer, the distribution of guided modes was changed. The cap layer mode was isolated from the GaN buffer, and larger LEE was achieved. Furthermore, dramatic increments with oscillations were found in the LEE by using embedded PhCs. Resonances of the Bloch mode localized within these PhCs, which caused the oscillations, were further modified by a shallow Al x Ga 1-x N confining layer. With the optimized parameters, over eightfold increment in LEE was achieved. In addition, dislocations caused by higher Al content and thicker Al x Ga 1-x N layer were avoided. This proposed structure could be a very promising candidate for high extraction efficiency LEDs.

Description: The proposed hybrid plasmonic waveguide comprises a semiconductor cylindrical nanowire embedded in a low-index dielectric above a metallic substrate with two grooves carved into the surface, between which a nanoscale metallic ridge is formed. Comparing the original hybrid plasmonic structure having a flat metal surface with the proposed structure significantly reduces the lateral mode size of the hybrid modes, and moderately increases the propagation distance. The mode area and propagation distance dependences on the geometry and material parameters are studied. A parametric plot of the figure of merit shows that the proposed structure outperforms the original hybrid structure. The mode performances can be improved further by rounding the metallic ridge corners with the maximum radius. Under an equal confinement of light, the propagation distance of the present structure is three times larger than that of the previously published hybrid structure.

Description: In this paper, we have investigated the mode patterns in real space and reciprocal space, and threshold gain at different band edges in GaN-based photonic crystal surface-emitting lasers (PCSELs) by using the multiple-scattering method. The characteristics at each band edge (Γ1 , K2, and M3) of PCSELs are simulated and discussed. In addition, GaN-based PCSELs operated at different band edges have been fabricated and measured. The experimental results of threshold show good agreement with the simulation results.

Description: We theoretically investigate the electromagnetic enhancement by a T-shaped nanogroove in a metallic substrate. Compared with a single bare groove without the top trench, a T-shaped groove can achieve a much higher enhancement factor of electric field by more than two times. To explain this improved field enhancement, we build up an intuitive model that explicitly incorporates the mode resonance in the central groove and the excitation and collection of surface waves by the top trench. The model can accurately reproduce the fully vectorial data and thus allows an in-depth analysis of the physics of the field enhancement. Analysis of the model shows that the resonance in the groove can be further enhanced by the excited surface waves that are collected by the top trench and further coupled into the groove. Surface plasmon polariton is shown to be not the unique surface wave that enhances the groove resonance and taking into account another so-called quasi-cylindrical wave will give the full contribution. Our results are helpful for intuitively designing field-enhancement devices that employ surface waves to further enhance the field concentration or resonance.

Description: Wavelength-tunable narrow-linewidth red-light emission generated from Si quantum dots (Si-QDs) that are embedded in Si-rich SiO x /SiN x :Si-QDs distributed Bragg reflector (DBR) are demonstrated using low-temperature and low-plasma chemical vapor deposition. With increasing layer thickness Δ d of the 20-pair SiO x /SiN x :Si-QD DBR structure, its narrow linewidth and high-extinction-ratio transmittance peak between central and nearby stopband serve as high- Q filter to sharpen the broadband Si-QD photoluminescence (PL) from 140 to 19 nm. By comparing the PL intensity of 667 nm for a DBR with the 20-time multiplied single-pair case, an enhancement factor of 1.86 is in good agreement with the theoretical estimation of 1.74. The transmitted PL peak wavelength λ p of PL spectrum is tunable from 667 to 706 nm, as predicted by a relationship between the shifted wavelength and the refractive index of Δλ p ≅ 2 ( n SiO x + n SiN x ) Δ d . The transmitted PL response can be simulated from the luminescence summation of each light-emitting layer within the DBR structure.

Description: We report the characterization of correlated photon pairs generated in dispersion-engineered silicon slow-light photonic crystal waveguides pumped by picosecond pulses. We found that taking advantage of the 15-nm flat-band slow-light window ( vg ~ c /30), the bandwidth for correlated photon-pair generation in 96- and 196-μm-long waveguides was at least 11.2 nm, while a 396-μm-long waveguide reduced the bandwidth to 8 nm (only half of the slow-light bandwidth due to the increased impact of phase matching in a longer waveguide). The key metrics for a photon-pair source: coincidence to accidental ratio (CAR) and pair brightness were measured to be a maximum 33 at a pair generation rate of 0.004 pair per pulse in a 196- μm-long waveguide. Within the measurement errors, the maximum CAR achieved in 96-, 196-, and 396-μm-long waveguides is constant. The noise analysis shows that detector dark counts, leaked pump light, linear and nonlinear losses, multiple pair generation, and detector jitter are the limiting factors to the CAR performance of the sources.

Description: We investigate electromagnetically amplified local fields or hot spots created by surface nanoantennas for subdiffraction-limited plasmon-enhanced microscopy under total internal reflection at angled light incidence. Different shapes of near-field hot spots were calculated by varying geometrical parameters of nanoantenna structures. An inverse relationship between full-width-at-half-maximum (FWHM) and ellipticity of a hot spot was found. Among the three patterns considered, square nanoantenna patterns provided the smallest FWHM ellipticity product with a spot size of approximately 53 × 110 nm 2 due to efficient plasmon localization. The size of a nanopattern affects FWHM significantly by producing a smaller hot spot if the size decreases. The effects of other parameters are also discussed.

Description: The purpose of this issue is to highlight the recent progress and trends in the development of novel nano- and quantum photonic technologies. The articles published in this issue cover a broad range of areas, including: 1) novel nanophotonic light sources??both classical (lasers) and nonclassical (single- and entangled photon sources); 2) nonlinear optics in nanophotonic structures; 3) quantum optics and quantum information processing based on nanophotonics platform; 4) efficient devices for optical interconnects and optical information processing based on novel nanophotonic structures. This issue contains 25 papers, including eight invited, authored by well-established research groups and promising scientists from all over the world. The invited articles include extended reviews on entangled photon generation using silicon nanowire waveguides; cavity quantum electrodynamics and lasing oscillation in single quantum dot photonic crystal nanocavity systems; quantum plasmonic circuits; theoretical analysis of few-photon single-atom cavity quantum electrodynamics; semiconductor quantum dot micropillar microcavities for quantum optics in solid state; nanofiber-based optical trapping of cold neutral atoms; switching and counting with atomic vapors in photonic-crystal fibers; and production of multiple diamondbased single-photon sources. The contributed articles cover a broad variety of key nanophotonics and quantum photonics research areas, including recently obtained results on bright single-photon emission from a quantum dot in a circular Bragg grating microcavity, supercontinuum generation in nanostructured silicon waveguides, electrically driven photonic crystal nanocavity devices, and silicon quantum dots.

Description: Entangled photon pair generation is an important technology for realizing quantum information systems. Among various entangled photon pair sources, a source based on spontaneous four-wave mixing (SFWM) in a silicon wire waveguide (SWW) is now drawing attention. Thanks to the very large third-order nonlinearity in an SWW, we can realize highly efficient SFWM in a short ( ~ 1 cm) waveguide, which will possibly lead to an integrated entanglement source on a silicon chip. In this paper, we review recent progress on SWW-based entanglement sources. This study reviews the basic theory of SFWM, and then describes correlated and entangled photon generation experiments using SWWs and applications to quantum information experiments.