Critical Bandwidth Research Articles

Priority‐based online flow scheduling for network throughput maximization in software defined networking

SummaryData transmission in current networks is usually associated with strict priority enforcement for the purpose of quality of service (QoS). Under the case that priority flow requests are injected into the network sequentially without the information of future flow request arrivals, it is a challenging to achieve network throughput maximization for on‐line flow requests under the joint constraints of the flow's priority, bandwidth demand, and resource capacity. Software Defined Networking (SDN) can effectively solve the flow scheduling equilibrium problem between the priority of dynamic flow requests and the maximization of network throughput. Therefore, in this paper, we study on‐line flow request admission in SDN, the goal of which is to maximize the network throughput under the constraints of critical network bandwidth resources, flow priority, and bandwidth demands. First, we present the concept of flow routing cost and profit and a model to characterize the cost of using link resources and routing paths. Then, we propose an efficient on‐line priority flow scheduling algorithm (OPFSA) to solve priority flow request scheduling problem and analyze the competitive ratio of OPFSA. Our on‐line algorithm can reach throughput within of the highest possible throughput that can be achieved by an off‐line algorithm, where n is the number of node in the network. Finally, experimental results demonstrate that compared with SHORTEST‐SC, our proposed algorithm can enhance the cumulative bandwidth about 9% and 40% when general network size is 30 and 170 nodes, respectively, and improve the throughput about 25% in Fat‐tree network when pod size is 4.

Evaluation of silicon photomultipliers for multiphoton and laser scanning microscopy.

.The silicon photomultiplier (SIPM) is an emerging detector technology that enables both high sensitivity and high dynamic range detection of visible and near-infrared light at a fraction of the cost of conventional vacuum tube photomultiplier tubes (PMTs). A low-cost detection circuit is presented and the performance of a commercial SIPM is evaluated for high-speed laser scanning microscopy applications. For moderate-to-high-speed fluorescent imaging applications, the measurements and imaging results indicate that the SIPM exceeds the sensitivity of GaAsP PMTs, while providing higher dynamic range and better saturation behavior. For low speed or applications requiring large detector areas, the GaAsP PMT retains a sensitivity advantage due to large area and lower dark counts. The calculations presented show that, above a critical detection bandwidth, the SIPM sensitivity exceeds that of a GaAsP PMT.

A Cross-Layer Design for a Multihop, Self-Healing, and Self-Forming Tactical Network

In mission and time critical applications, bandwidth and delay optimizations are the key goals of communication systems. This paper presents a cross-layer framework design that reduces the call setup time, provides collision-free communication, and reuses the empty slots of Time Division Multiple Access (TDMA) protocol which otherwise causes low throughput and large delay. As number of communicating nodes in tactical networks is small as compared to commercial mobile ad hoc networks (MANETs), classical TDMA will yield huge number of empty slots and any Carrier Sense Multiple Access/Collision Detection (CSMA/CD) technique may cause more delay in some critical scenarios. Proposed methodology gives a Cross-Layer Architecture for Network (NET) Layer and Medium Access Control (MAC) Layer. Our design provides bandwidth efficient, collision-free communication to Software-Defined Radios (SDRs) in self-forming and self-healing tactical networks with low call setup time and multihop routing. For this purpose TDMA as MAC layer protocol and Ad Hoc On Demand Distance Vector (AODV) as Network Layer Routing Protocol are used. Our slot allocation (SA) algorithm, Cross-Layer TDMA (CL-TDMA), consists of control phase where AODV control packets are exchanged and data transfer phase where transmission of data and voice occurs. All active radios in vicinity gather information about communicating nodes based on the exchange of control packets by SDRs. Our algorithm then uses this information to help all active SDRs find slot(s) that will be used for collision-free transmission. A number of experiments are performed to establish improved performance of the proposed technique compared to other established techniques and protocols.

A Gray-Box Method for Stability and Controller Parameter Estimation in HVDC-Connected Wind Farms Based on Nonparametric Impedance

Estimation of critical control parameters is a desirable tool feature for stability analysis and impedance shaping of high voltage dc (HVdc) connected wind farms. Accurate estimation of such parameters would be enabled by access to detailed models, which is not always the case in real wind farms. Industrial secrecy is one of the main factors hindering the access to such models. This paper proposes a gray-box method that, with basic assumptions about the control structure of the wind energy conversion system (WECS), can estimate the parameters of its controllers. The method is based on the measurements of frequency domain equivalent impedance combined with nonparametric impedance identification used in the solution of an inverse problem. The method makes possible to specify which part of the equivalent WECS impedance has a major impact on the stability of the system and according to this, reshape the impedance to enforce stability. Once the critical controller bandwidth is identified with this method, an instability mitigation technique is proposed based on reshaping the impedance by retuning the critical controllers of the interconnected converters. In order to avoid interaction between the HVdc rectifier and the WECS inverter, the controllers of both converters need to be retuned in such a way that the q -axis impedance magnitude of the HVdc system is kept lower than the q -axis impedance magnitude of the wind farm at the frequency of the phase-locked loop bandwidth. The results show that the method ensures the stability of the system by retuning only the critical controller parameters.

A Ka Band FMCW Transceiver Front-End With 2-GHz Bandwidth in 65-nm CMOS

A fully integrated Ka band frequency modulation continuous wave single-chip radar transceiver front-end is proposed in 65-nm CMOS technology. By utilizing VCO with multi-biasing varactor banks, the critical bandwidth and linearity have been improved. To address the challenges of losses and complexities in local oscillator (LO) distribution chain, a three-way transformer-based power divider is proposed and implemented to split the input differential signals to three outputs, in three orthogonal directions. The poly phase filter is also used to obtain the in-phase and quadrature LO signals. To minimize the reflections between the poly phase filter and the following stages, a 1:2 transformer is inserted to provide sufficient matching. For the receiver part, differential cascode amplifier with neutralization capacitors is implemented in the low noise amplifier to obtain gain and stability. By utilizing double balanced passive mixers, noise performances of I/Q paths are improved at low intermediate frequency. The transceiver demonstrates 4.4-dBm output power, 2-GHz bandwidth with 7.5-cm range resolution, and 5.9–7.5 dB double side band noise figure at 4 MHz. The whole transceiver front-end consumes 132 mW from 1.2 V and 2.16 mm2 die size.

How ambient noise may shape peripheral auditory sensitivity: a theoretical model on the trade-off between signal detection and recognition

Ambient noise affects hearing in natural environments and may therefore affect the evolution of animal acoustic signals and auditory sensitivity. An earlier fitness model examining variable ambient noise conditions predicted higher sensitivity as the best strategy for species living in quiet habitats as opposed to lower sensitivity for the ones in noisy habitats. The trade-off between detection and recognition of acoustic signals appeared to be a key factor determining hearing sensitivity for acoustic communication in the presence of noise. The original model focused on the best auditory range of two U-shaped audiograms differing in sensitivity only (i.e., low and high). Here the model is extended by employing additional sensitivity levels and investigating the full range of hearing in order to examine (a) conditions favoring auditory sensitivity in a model characterized by the presence of multiple sensitivity and sound levels, and (b) the importance of other audiogram features, such as bandwidth and shape, which are assessed by analyzing the fitness consequences associated with bandwidth variation in the auditory system displaying best sensitivity. The model also allows theoretical insights into the importance of the detection-recognition trade-off for the evolution of the auditory critical bandwidths and ratios. The model predicted that a successful receiver should evolve an auditory system of either low or high sensitivity, but not intermediate. When low sensitivity pays, the audiogram shape should follow the profile of maximum noise levels encountered in the receiver’s environment. When high sensitivity pays, the audiogram should maximize bandwidth. A high sensitivity system with larger critical bandwidths may be successful only if the ensuing cost due to lower detection performance is outweighed by the benefit of improved sound recognition.

Concentration dependent luminescence and cross-relaxation energy transfers in Tb3+ doped fluoroborate glasses

Recently, mixed-former glasses have attracted a large attention due to the appropriate combinations of the chemical, physical and optical properties of each glass former. In this scenario, the optical properties of fluoroborate glasses doped with rare earth ions is of importance due to their good transparency window from ultra-violet to near-infrared region, good rare-earth solubility, long excited state lifetime of such ions, and high mechanical strength. In this work, we had studied the optical properties of the Tb3+ doped fluoroborate glasses, focusing on the concentration dependent behavior of luminescence dynamics of 5D3 and 5D4 exited states of this ion. The blue-to-green intensity ratio, lifetime of the emitting levels under various excitation wavelengths, cross-relaxation rate, ion-ion critical distance and emission gain bandwidth are calculated.

Macros to conduct tests of multimodality in SAS

ABSTRACTThe Dip Test of Unimodality and Silverman's Critical Bandwidth Test are two popular tests to determine if an unknown density contains more than one mode. While the tests can be easily run in R, they are not included in SAS software. We provide implementations of the Dip Test and Silverman Test as macros in the SAS software, capitalizing on the capability of SAS to execute R code internally. Descriptions of the macro parameters, installation steps, and sample macro calls are provided, along with an appendix for troubleshooting. We illustrate the use of the macros on data simulated from one or more Gaussian distributions as well as on the famous iris dataset.

Mode testing, critical bandwidth and excess mass

The identification of peaks or maxima in probability densities, by mode testing or bump hunting, has become an important problem in applied fields. This task has been approached in the statistical literature from different perspectives, with the proposal of testing procedures which are based on kernel density estimators or on the quantification of excess mass. However, none of the existing proposals provides a satisfactory performance in practice. In this work, a new procedure which combines the previous approaches (smoothing and excess mass) is presented and compared with the existing methods, showing a superior behaviour. A real data example on philatelic data is also included for illustration purposes.

Parallel and hierarchical architectures of 4-channel MFP digitizer

Two alternative architectures of 4-channel mixing-filtering-processing (MFP) digitizers are presented. Both architectures use four analogue-to-digital converters (ADCs), but differ in terms of layout, and are named parallel and hierarchical. Unlike conventional time-interleaved digitizers, which require ADCs characterized by relaxed sampling rate but critical bandwidth specifications, the proposed architectures are less demanding in terms of both ADCs’ sampling rate and bandwidth, thus allowing less noise into the digitizer. Two digital signal processing techniques, needed to combine the digitized streams produced by the ADCs and obtain a digital representation of the input signal, are described for both parallel and hierarchical architectures. These techniques are developed on the basis of suitable error models, also discussed in the paper, and allow removing gain and aliasing errors due to analogue impairments by means of streamline calibration. The results of behavioural simulations carried out to assess the performance of the two alternative 4-channel MFP architectures are finally shown.

Arrays of rectangular subcritical speech bands: Intelligibility improved by noise-vocoding and expanding to critical bandwidths.

A previous study [Warren, Bashford, and Lenz (2017). J. Acoust. Soc. Am. 141, EL222-EL227] reported that arrays of subcritical width rectangular speech bands can produce near ceiling sentence intelligibility. The present study used noise-vocoded subcritical band speech arrays with analysis bandwidths of 4%, 2%, 1%, or 0.5% of center frequency. Intelligibility decreased when analysis and noise carrier bandwidths were matched. However, expanding carrier noise bandwidths to a critical bandwidth of 1/3-octave (26%) produced array intelligibilities either equaling or substantially exceeding that of the original speech band arrays. Implications concerning bandwidth requirements of envelope processing and the redundancy of envelope cues are discussed.

An intelligent healthcare system for detection and classification to discriminate vocal fold disorders

The growing population of senior citizens around the world will appear as a big challenge in the future and they will engage a significant portion of the healthcare facilities. Therefore, it is necessary to develop intelligent healthcare systems so that they can be deployed in smart homes and cities for remote diagnosis. To overcome the problem, an intelligent healthcare system is proposed in this study. The proposed intelligent system is based on the human auditory mechanism and capable of detection and classification of various types of the vocal fold disorders. In the proposed system, critical bandwidth phenomena by using the bandpass filters spaced over Bark scale is implemented to simulate the human auditory mechanism. Therefore, the system acts like an expert clinician who can evaluate the voice of a patient by auditory perception. The experimental results show that the proposed system can detect the pathology with an accuracy of 99.72%. Moreover, the classification accuracy for vocal fold polyp, keratosis, vocal fold paralysis, vocal fold nodules, and adductor spasmodic dysphonia is 97.54%, 99.08%, 96.75%, 98.65%, 95.83%, and 95.83%, respectively. In addition, an experiment for paralysis versus all other disorders is also conducted, and an accuracy of 99.13% is achieved. The results show that the proposed system is accurate and reliable in vocal fold disorder assessment and can be deployed successfully for remote diagnosis. Moreover, the performance of the proposed system is better as compared to existing disorder assessment systems.

An epileptic seizure detection system based on cepstral analysis and generalized regression neural network

This study introduces a new and effective epileptic seizure detection system based on cepstral analysis utilizing generalized regression neural network for classifying electroencephalogram (EEG) recordings. The EEG recordings are obtained from an open database which has been widely studied with many different combinations of feature extraction and classification techniques. Cepstral analysis technique is mainly used for speech recognition, seismological problems, mechanical part tests, etc. Utility of cepstral analysis based features in EEG signal classification is explored in the paper. In the proposed study, mel frequency cepstral coefficients (MFCCs) are computed in the feature extraction stage and used in neural network based classification stage. MFCCs are calculated based on a frequency analysis depending on filter bank of approximately critical bandwidths. The experimental results have shown that the proposed method is superior to most of the previous studies using the same dataset in classification accuracy, sensitivity and specificity. This achieved success is the result of applying cepstral analysis technique to extract features. The system is promising to be used in real time seizure detection systems as the neural network adopted in the proposed method is inherently of non-iterative nature.

An Improved Adaptive Scheduling Strategy Utilizing Simulated Annealing Genetic Algorithm for Data Center Networks

Data center networks provide critical bandwidth for the continuous growth of cloud computing, multimedia storage, data analysis and other businesses. The problem of low link bandwidth utilization in data center network is gradually addressed in more hot fields. However, the current scheduling strategies applied in data center network do not adapt to the real-time dynamic change of the traffic in the network. Thus, they fail to distribute resources due to the lack of intelligent management. In this paper, we present an improved adaptive traffic scheduling strategy utilizing the simulated annealing genetic algorithm (SAGA). Inspired by the idea of software defined network, when a flow arrives, our strategy changes the bandwidth demand dynamically to filter out the flow. Then, SAGA distributes the path for the flow by considering the scheduling of the different pods as well as the same pod. It is implemented through software defined network technology. Simulation results show that the bisection bandwidth of our strategy is higher than state-of-the-art mechanisms.

Achromatic critically coupled racetrack resonators

In this paper, we investigate the spectral response of whispering-gallery-mode (WGM) resonators coupled to their access waveguide with a view to design their constitutive waveguides to promote critical-coupling over a wide spectral range and thereby facilitate their use for high-sensitivity sensing or nonlinear frequency conversion applications. The carried-out theoretical analysis is based on the universal response functions of singlemode and unidirectional devices. A coupled-mode treatment of the coupling region enables to derive two sets of favorable designs. The identified resonator/access waveguide systems exploit waveguides with mismatched propagation constants forming a coupling section exhibiting either an achromatic beat-length or an achromatic power-transfer coefficient. This generic model is followed by a numerical case study of vertically-coupled Si3N4 racetrack resonators. The conventional (quasi-)phase-matched configuration, treated as a reference case, is shown to display a critical-coupling bandwidth of 23 nm at a wavelength of 1550nm, whereas the proposed new designs demonstrate critical bandwidths larger than 330nm, i.e. exhibit bandwidths enhanced by more than one order of magnitude.

On the relationships between otoacoustic emissions, auditory evoked potentials, and psychoacoustical performance

Performance was measured on several common psychoacoustical tasks for about 70 subjects. The measures included simultaneous and temporal masking, masking by tones and by complex sounds, critical bandwidth, release from masking, and detection in the quiet. Also measured were spontaneous, click-evoked, and distortion-product otoacoustic emissions (OAEs) and auditory evoked potentials (AEPs, short and middle latency). Of interest were the correlations between psychoacoustical performance and the various physiological measures as well as any mean differences by sex and by menstrual cycle. Subjects were tested behaviorally in same-sex crews of 4–8 members, and behavioral testing required from 8 to 10 weeks for each crew. Correlation and effect size were the primary measures of interest. Resampling was used to determine implied significance for the various comparisons studied. Some correlations between physiological measures were moderately high, but the correlations between psychoacoustical tasks and the different physiological measures were generally low, although there were some unexpected differences by racial background. That is, the individual differences observed in psychoacoustical performance generally were not related to the individual differences in the various physiological measures. For these subjects, at least, psychoacoustical performance seemed unrelated to the mechanisms underlying OAEs and AEPs. [Work supported by NIDCD (DC000153).]

Effect of concert hall acoustics on tonal consonance of orchestra sound

The sound of pitched orchestral instruments consists of harmonic frequencies which, in performances, are transmitted over room acoustics. The amplitude relations of the harmonic peaks affect the timbre of one tone. When two or more notes are played together, the effect of consonance and dissonance becomes prominent. The degree of consonance for intervals of musical pitches have been explained by the frequency separation of their harmonic components in relation to the width of critical bands in human hearing. When the playing dynamics is varied, the changes in the instruments’ spectral envelopes are foreseen to alter also the consonance of simultaneous notes. Furthermore, the room acoustics influence the overall harmonic spectra conveyed to the listeners. This paper presents experiments on the tonal consonance of orchestra instruments at contrasting dynamic levels in various concert halls. By combining binaural hall measurements and anechoic instrument recordings with a consonance-estimating model, the following hypothesis is investigated: do the acoustics of concert halls change the orchestra sound’s consonance in different music dynamics?

Critical bandwidth speech: Arrays of subcritical band speech maintain near-ceiling intelligibility at high amplitudes.

Removal of transition bands from narrow speech passbands through very steep filtering has made it possible to isolate and determine (for the first time) intelligibility of critical bandwidth as well as subcritical bandwidth speech. These rectangular bands have unique intelligibilities when heard singly, paired, or in various multiband arrays spanning the speech spectrum. Thus, a particular sparse spectral array of unfamiliar everyday sentences in this study has demonstrated 98% intelligibility up to 100 dB. Some theoretical and practical applications are suggested.

State distributions in two-dimensional parameter spaces of a nonlinear optical loop mirror-based, mode-locked, all-normal-dispersion fiber laser.

We present the results of numerical simulations of dissipative soliton generation using nonlinear Schrödinger equations in an all-normal-dispersion (ANDi) mode-locked fiber laser based on a nonlinear optical loop mirror (NOLM). Firstly, systematic and computationally intensive analysis of the pulse state distributions in two-dimensional parameter spaces of an ANDi fiber laser was conducted. In addition, we determined that unstable non-vanishing regions including pulsation and noise-like pulses are directly related to the saturable absorptions of NOLMs and that two critical filter bandwidths separate those regions from stable ones. Finally, we found that the multi-pulsing power threshold can be maximized by using an optimal optical filter bandwidth.

Non-Parametric Testing of U-Shapes, with an Application to the Midlife Satisfaction Dip

Many theories in economics predict U-shaped relationships between variables. However, satisfactory tools to examine U-shapes are lacking. After explaining the limitations of the commonly employed quadratic specification, I propose a non-parametric test of U-shaped regression functions based on critical bandwidth. The test allows one to determine whether an inherent U-shape exists between two variables or the relationship is instead caused by correlation with other variables. I apply the test to the commonly observed U-shape of life satisfaction in age, and find that much of the U-shape can be explained by the increase in financial satisfaction that typically occurs later in life. This novel insight into a long-studied puzzle is not revealed by using a quadratic specification. A user-friendly and efficient R package is provided.