Bandwidth Estimates Research Articles

Bandwidth selection methods for non parametric regression with spatially correlated data

. In non parametric regression estimation, a critical and unavoidable step is to choose the smoothing parameters (bandwidth) to control the smoothness of the curve estimate. In the presence of spatially correlated errors, the traditional data-driven bandwidth selection methods, such as cross-validation and generalized cross-validation, do not work well for providing efficient bandwidth values. Moreover, the existing methods are based on estimation of correlation structure. As errors are unobservable, estimation of correlation is a big challenge. This article studies bandwidth selection methods for local linear regression (LLR) in the presence of correlated errors. For this purpose, we derive the weighted mean average square errors (WMASE) and use it along with bias-correlated generalized cross-validation (GCV) as bandwidth selection criterion. We then get the estimates of bandwidth by two ways: by minimizing the weighted mean average square errors (WMASE) and by using the bias-correlated generalized cross-validation (GCV) criterion. Due to its good properties, the composite likelihood (CL) is used to estimate the correlation. The results show that composite likelihood provides better estimates than maximum likelihood (ML) in the sense of producing more reasonable estimates of correlation parameters and bandwidth values. Also, our methods appear reasonably robust to the misspecification of the parametric correlation model. Moreover, the proposed methods work much better than ignoring the correlation and applying traditional methods. Finally, we apply our methods on water chemistry data collected about lakes in the Northeastern United States.

Designing transport scheme of 3D naked-eye system

3D naked-eye is constructed from multi-stream as a typical representation of stereoscopic video. Its enormous data volume and stringent low-delay transport requirements pose significant challenges for high-quality real-time transport. Through analysis and experimental verification that current streaming media transport frameworks using the server–client or peer-to-peer scheme face difficulties when transmitting 3D naked-eye in a one-to-one format. Besides, the existing bandwidth estimation algorithms cannot achieve the expected performance when dealing with delay-sensitive traffic. This results in low bandwidth utilization and slow bandwidth estimation, rendering it unfeasible to deliver multi-stream on time. We propose an effective transport framework with different modules for real-time multi-stream and introduce an Agent-to-Agent transport scheme that provides many-to-one connection as the main implementation way of 3D naked-eye transport framework. Additionally, we propose a direct bandwidth estimation algorithm to quickly match network bandwidth for low-delay transport. The Agent terminal centrally processes consolidates transports, and provides macro-level management of multiple video streams. The algorithm directly detects the available bandwidth using packet interval and packet rate models. Finally, using rate decision algorithm arbitrates the results to directly measure the maximum available bandwidth of the link. The Agent-to-Agent achieves 99% bandwidth utilization, addressing the limitations of existing streaming schemes in handling concurrent data streams. Our algorithm provides precise bandwidth estimates with minimal time overhead, meeting the requirements of a delay-sensitive 3D naked-eye system across diverse environments.

Trace formulas for magnetic Schrödinger operators on periodic graphs and their applications

We consider Schrödinger operators with periodic magnetic and electric potentials on periodic discrete graphs. The spectrum of such operators consists of a finite number of bands. Some of them and even all may be degenerate. We determine trace formulas for the magnetic Schrödinger operators. The traces of the fiber operators are expressed as finite Fourier series of the quasimomentum. The coefficients of the Fourier series are given in terms of the magnetic fluxes, electric potentials and cycles in the quotient graph from some specific cycle sets. Using the trace formulas we obtain new lower estimates of the total bandwidth for the magnetic Schrödinger operator in terms of geometric parameters of the graph, magnetic fluxes and electric potentials. We show that these estimates are sharp.

Guidance, Navigation and Control System for Multi-Robot Network in Monitoring and Inspection Operations

This work focuses on the challenges associated with autonomous robot guidance, navigation, and control in multi-robot systems. This study provides an affordable solution by utilizing a group of small unmanned ground vehicles and quadrotors that collaborate on monitoring and inspection missions. The proposed system utilizes a potential fields path planning algorithm to allow a robot to track a moving target while avoiding obstacles in a dynamic environment. To achieve the required performance and provide robust tracking against wind disturbances, a backstepping controller is used to solve the essential stability problem and ensure that each robot follows the specified path asymptotically. Furthermore, the performance is also compared with a proportional-integral-derivative (PID) controller to ensure the superiority of the control system. The system combines a low-cost inertial measurement unit (IMU), a GNSS receiver, and a barometer for UAVs to generate a navigation solution (position, velocity, and attitude estimations), which is then used in the guidance and control algorithms. A similar solution is used for UGVs by integrating the IMU, a GNSS receiver, and encoders. Non-linear complementary filters integrate the measurements in the navigation system to produce high bandwidth estimates of the state of each robotic platform. Experimental results of several scenarios are discussed to prove the effectiveness of the approach.

METHOD FOR EVALUATION QUALITY PARAMETERS OF TELECOMMUNICATIONS SERVICES

Currently, cellular networks have become widespread, the operators of which simultaneously use the infrastructure of the second-generation GSM networks, DCS to build third-generation W-CDMA networks that provide broadband multiple access with code division. At the same time, the problem of providing high-speed Internet connections is exacerbated due to the growing volume of data of diverse types transmitted over the Internet. When testing the entire network coverage area, the total number of voice calls increases, so a method of long-term measurement of the bit rate of information transmission via wireless communication channels is proposed, which does not increase the service information in the network. Mathematical modeling of Internet traffic consumption using the proposed measurement method is performed and entropy estimates of information channel bandwidth are given.

Two-sided estimates of total bandwidth for Schrödinger operators on periodic graphs

<p style='text-indent:20px;'>We consider Schrödinger operators with periodic potentials on periodic discrete graphs. Their spectrum consists of a finite number of bands. We obtain two-sided estimates of the total bandwidth for the Schrödinger operators in terms of geometric parameters of the graph and the potentials. In particular, we show that these estimates are sharp. It means that these estimates become identities for specific graphs and potentials. The proof is based on the Floquet theory and trace formulas for fiber operators. The traces are expressed as finite Fourier series of the quasimomentum with coefficients depending on the potentials and cycles of the quotient graph from some specific cycle sets. In order to obtain our results we estimate these Fourier coefficients in terms of geometric parameters of the graph and the potentials.</p>

Optimal bandwidth estimators of kernel density functionals for contaminated data

In this study, we provide simulation-based exploration and characterization of the two most crucial kernel density functionals that play a central role in kernel density estimation, considering the probability density functions that are members of the location-scale family. Kernel density functional estimates are known to rely on the choice of preliminary bandwidth. Normal-scale estimators are commonly used to obtain preliminary bandwidth estimates, with the assumption that the data come from normal distribution. Here, we present an alternative approach, called the Cauchy-scale estimators, to obtain preliminary bandwidth estimates. In this approach, data are assumed to come from a Cauchy distribution. Furthermore, analysis results related to the sampling distribution of bandwidth estimators based on the normal- and Cauchy-scale approaches are presented. As a case study, we provide a comprehensive characterization of different contamination levels with a simulation study constructed for the random samples from normal distributions with various parameters and various contamination levels. The proposed preliminary bandwidth selection shows lower variance in both mixture and contaminated data in our simulations. Besides, functional bandwidth presents results similar to the simulation results in the applications we made on the real data set.

Собственные параметры идеального четырехполюсника для согласования малошумящих усилителей

The problem of broadband matching of active elements in terms of noise figure is inevitably encountered in the design of broadband low-noise microwave amplifiers. Despite the fact that this problem differs from the classical problem of broadband matching of signal source and load, it can be reduced to a form suitable for applying methods for solving the classical problem. For this purpose, in this work, the own parameters of a reactive two-port network are derived that match active elements in terms of noise figure in the entire frequency band, where the data for calculating this coefficient are determined. The own parameters of such a two-port network, on the one hand, make it possible to construct methods for the synthesis of input matching circuits of low-noise amplifiers and other devices where low noise matching is required. On the other hand, the own parameters allow one to construct estimates of the maximum achievable bandwidth for a matching circuit of a given complexity.

Auroral Kilometric Radiation and Electron Pairing

We suggest that pairing of bouncing medium-energy electrons in the auroral upward current region close to the mirror points may play a role in driving the electron cyclotron maser instability to generate an escaping narrow band fine structure in the auroral kilometric radiation. We treat this mechanism in the gyrotron approximation, for simplicity using the extreme case of a weakly relativistic Dirac distribution instead the more realistic anisotropic Juettner distribution. Promising estimates of bandwidth, frequency drift and spatial location are given.

The Great Internet TCP Congestion Control Census

In 2016, Google proposed and deployed a new TCP variant called BBR. BBR represents a major departure from traditional congestion control as it uses estimates of bandwidth and round-trip delays to regulate its sending rate. BBR has since been introduced in the upstream Linux kernel and deployed by Google across its data centers. Since the last major study to identify TCP congestion control variants on the Internet was done before BBR, it is timely to conduct a new census to give us a sense of the current distribution of congestion control variants on the Internet. To this end, we designed and implemented Gordon, a tool that allows us to measure the congestion window (cwnd) corresponding to each successive RTT in the TCP connection response of a congestion control algorithm. To compare a measured flow to the known variants, we created a localized bottleneck and introduced a variety of network changes like loss events, changes in bandwidth and delay, while normalizing all measurements by RTT. We built an offline classifier to identify the TCP variant based on the cwnd trace over time.

ШИРОКОСМУГОВІ АНТЕНИ НА ОСНОВІ КІЛЬЦЕВОЇ ГЕОМЕТРІЇ

В роботі розглянуто варіанти моделей квазіфрактальних кільцевих структур. Для їх синтезу запропонований векторний опис фрактальної трансформації окремих сегментів початкової геометричної форми. Поєднання декомпозиції геометричної форми та багатовимірного фрактального підходу дозволяє спростити синтез фрактальних 3D-структур та/або використовувати кілька видів фракталів, у тому числі, з різною кількістю ітерацій. Такий підхід дозволяє досягти широкосмуговості та багатодіапазонності антенних систем. При цьому досліджено вплив рівня сегментації та варіантів схеми живлення на просторово-частотні характеристики антени. Через складність опису взаємодії антен неевклідової геометрії з радіохвилями для їх синтезу та аналізу обрано методи чисельного моделювання. Для аналізу просторово-частотних характеристик проектованих антенних рішень використані такі показники, як зворотні втрати, діаграма спрямованості та коефіцієнт стоячої хвилі. Отримані оцінки відносної смуги пропускання δf = 0,9 свідчать про перспективність запропонованого підходу для реалізації антенних систем з високим рівнем широкосмуговості

Stored Energies and Q-Factor of Two-Dimensionally Periodic Antenna Arrays

The Q-factor for lossless three-dimensional structures with two-dimensional periodicity is here derived in terms of the electric current density. The derivation in itself is shape-independent and based on the periodic free-space Green's function. The expression for Q-factor takes into account the exact shape of a periodic element, and permits beam steering. The stored energies and the radiated power, both required to evaluate Q-factor, are coordinate independent and expressed in a similar manner to the periodic Electric Field Integral equation, and can thus be rapidly calculated. Numerical investigations, performed for several antenna arrays, indicate fine agreement, accurate enough to be predictive, between the proposed Q-factor and the tuned fractional bandwidth, when the arrays are not too wideband (i.e., when $Q\geq 5$). For completeness, the input-impedance Q-factor, proposed by Yaghjian and Best in 2005, is included and agrees well numerically with the derived Q-factor expression. The main advantage of the proposed representation is its explicit connection to the current density, which allows the Q-factor to give bandwidth estimates based on the shape and current of the array element.

Reduced bias nonparametric lifetime density and hazard estimation.

Kernel-based nonparametric hazard rate estimation is considered with a special class of infinite-order kernels that achieves favorable bias and mean square error properties. A fully automatic and adaptive implementation of a density and hazard rate estimator is proposed for randomly right censored data. Careful selection of the bandwidth in the proposed estimators yields estimates that are more efficient in terms of overall mean squared error performance, and in some cases achieves a nearly parametric convergence rate. Additionally, rapidly converging bandwidth estimates are presented for use in second-order kernels to supplement such kernel-based methods in hazard rate estimation. Simulations illustrate the improved accuracy of the proposed estimator against other nonparametric estimators of the density and hazard function. A real data application is also presented on survival data from 13,166 breast carcinoma patients.

XMAS: An Efficient Mobile Adaptive Streaming Scheme Based on Traffic Shaping

Adaptive video streaming can provide adequate Quality of Experience by dynamically adjusting video rates in responding to fluctuating service conditions. However, adaptive video streaming shows dismal performances in wireless networks where several players share a wireless bottleneck link. This paper proposes a novel video rate selection scheme called XMAS for efficient video streaming in wireless networks. XMAS consists of two components: an available bandwidth estimation part and a video rate selection part. To redress the problem of inaccurate bandwidth estimation due to peculiar on-off transmission patterns of mobile video streaming, we devised a novel client-based traffic shaping scheme that effectively throttles server's packet transmission. Equipped with accurate bandwidth estimates, XMAS determines target transmission rates considering playback buffer levels. We implemented XMAS on Linux and performed rigorous experiments to analyze its behavior and performance. Our performance results showed that XMAS achieves up to 20% increase in average video rates while reducing rebuffer rates significantly.

Decorrelation Bandwidth of Intercore Crosstalk in Weakly Coupled Multicore Fibers With Multiple Interfering Cores

The decorrelation bandwidth of the intercore crosstalk (ICXT) power generated in a weakly coupled multicore fiber (MCF) with multiple interfering cores is studied. For the first time, this is accomplished using a closed-form expression of the equivalent autocovariance function of the ICXT power that enables evaluating the correlation between the ICXT power generated at two different frequencies using a theoretical model to describe the stochastic evolution of the ICXT over time. It provides fast and reliable estimates of the decorrelation bandwidth of the ICXT induced by multiple interfering cores with arbitrary relative time delays (skews) between cores, which represents a crucial tool to assist the design of new MCF systems. Validation of the autocovariance and decorrelation bandwidth expressions by numerical simulation and with experimental results published by other authors is accomplished. In contrast to the single interfering case, the equivalent autocovariance of the ICXT induced by multiple interferers may present several inflexion points along the frequency lag due to the different core contributions that may be characterized by different skews. For MCFs with similar skews between cores, the equivalent autocovariance has, approximately, a sinc-squared shape with the decorrelation bandwidth, defined as the first zero of equivalent autocovariance, occurring at the frequency lag, in Hz, given by the inverse of the skew. When the decorrelation bandwidth of the ICXT induced by multiple interfering cores is much lower or much higher than the signal bandwidth, the ICXT mechanism can be considered as uncorrelated noise or as a static coupling component, respectively. When the decorrelation bandwidth is similar to the signal bandwidth, the ICXT mechanism should be treated as correlated noise.

Mammalian behavior and physiology converge to confirm sharper cochlear tuning in humans

Frequency analysis of sound by the cochlea is the most fundamental property of the auditory system. Despite its importance, the resolution of this frequency analysis in humans remains controversial. The controversy persists because the methods used to estimate tuning in humans are indirect and have not all been independently validated in other species. Some data suggest that human cochlear tuning is considerably sharper than that of laboratory animals, while others suggest little or no difference between species. We show here in a single species (ferret) that behavioral estimates of tuning bandwidths obtained using perceptual masking methods, and objective estimates obtained using otoacoustic emissions, both also employed in humans, agree closely with direct physiological measurements from single auditory-nerve fibers. Combined with human behavioral data, this outcome indicates that the frequency analysis performed by the human cochlea is of significantly higher resolution than found in common laboratory animals. This finding raises important questions about the evolutionary origins of human cochlear tuning, its role in the emergence of speech communication, and the mechanisms underlying our ability to separate and process natural sounds in complex acoustic environments.

Impact of stimulus bandwidth on the estimate of the upper-frequency limit of hearing in toothed whales

No consensus on the stimuli used in toothed whale hearing tests using evoked potential methods currently exists. However, stimulus bandwidth should directly affect determination of the upper-frequency limit (UFL) of hearing because of the steep reduction in hearing sensitivity at frequencies immediately below the UFL—the broader the stimulus bandwidth, the greater the amount of spectral “splatter” into lower frequencies where hearing is more sensitive. To test this hypothesis, variability in auditory evoked potential thresholds to tone-pips (with variable bandwidth) and amplitude-modulated tones was determined in dolphins near their UFL of hearing and ½ to 1 octave below where hearing is more sensitive. Subjects included both normal and hearing-impaired dolphins. At frequencies where hearing was sensitive and the audiogram was relatively flat, negligible changes in the hearing threshold with changing stimulus bandwidth were observed. Conversely, thresholds near the UFL of hearing declined with increasing stimulus bandwidth, regardless of whether dolphins had normal hearing or hearing impairment, and resulted in broadened hearing bandwidth estimates. Thus, it is recommended that stimulus bandwidth be reported in hearing tests where the UFL is tested since stimulus bandwidth affects thresholds through spectral splatter into lower frequency bands where hearing is more sensitive.

Queueing Theoretic Approach to Playout Buffer Model for HTTP Adaptive Streaming

HTTP-based adaptive streaming (HAS) has recently been widely deployed on the Internet. In the HAS system, a video content is encoded at multiple bitrates and the encoded video content is segmented into small parts of fixed durations. The HAS client requests a video segment and stores it in the playout buffer. The rate adaptation algorithm employed in HAS clients dynamically determines the video bitrate depending on the time-varying bandwidth. Many studies have shown that an efficient rate adaptation algorithm is critical to ensuring quality-of-experience in HAS systems. However, existing algorithms have problems estimating the network bandwidth because bandwidth estimation is performed on the client-side application stack. Without the help of transport layer protocols, it is difficult to achieve accurate bandwidth estimation due to the inherent segment-based transmission of the HAS. In this paper, we propose an alternative approach that utilizes the playout buffer occupancy rather than using bandwidth estimates obtained from the application layer. We start with a queueing analysis of the playout buffer. Then, we present a buffer-aware rate adaptation algorithm that is solely based on the mean buffer occupancy. Our simulation results show that compared to conventional algorithms, the proposed algorithm achieves very smooth video quality while delivering a similar average video bitrate.

Frequency selectivity in macaque monkeys measured using a notched-noise method

The auditory system is thought to process complex sounds through overlapping bandpass filters. Frequency selectivity as estimated by auditory filters has been well quantified in humans and other mammalian species using behavioral and physiological methodologies, but little work has been done to examine frequency selectivity in nonhuman primates. In particular, knowledge of macaque frequency selectivity would help address the recent controversy over the sharpness of cochlear tuning in humans relative to other animal species. The purpose of our study was to investigate the frequency selectivity of macaque monkeys using a notched-noise paradigm. Four macaques were trained to detect tones in noises that were spectrally notched symmetrically and asymmetrically around the tone frequency. Masked tone thresholds decreased with increasing notch width. Auditory filter shapes were estimated using a rounded exponential function. Macaque auditory filters were symmetric at low noise levels and broader and more asymmetric at higher noise levels with broader low-frequency and steeper high-frequency tails. Macaque filter bandwidths (BW3dB) increased with increasing center frequency, similar to humans and other species. Estimates of equivalent rectangular bandwidth (ERB) and filter quality factor (QERB) suggest macaque filters are broader than human filters. These data shed further light on frequency selectivity across species and serve as a baseline for studies of neuronal frequency selectivity and frequency selectivity in subjects with hearing loss.

BELIA: bandwidth estimate‐based link increase algorithm for MPTCP

As a set of extensions to the regular Transmission Control Protocol (TCP), Multipath TCP (MPTCP) enables the multi-homed devices to access one data stream through multiple paths. MPTCP congestion window control is the crucial part of maintaining the fair network resource allocation, especially in the coexist scene of MPTCP applications and regular TCP applications. However, the current MPTCP congestion window control is facing two major problems: (i) the lack of the lost-packet detections, and (ii) the lack of the analysis mechanisms on the through-load relationships. These two problems combined may affect the accuracy of the congestion window allocations and the performance of MPTCP. In this study, the authors propose a bandwidth estimate-based link increase algorithm (BELIA). With the analysis of the link congestion occurrence mechanisms, they utilise a batch filter to estimate the real bandwidth of the links and define the link condition set C r to demonstrate the possibility of the congestion occurrence. For every loss, BELIA decides whether to cut window size off referring to the bandwidth estimates and C r . Hence, they proved that BELIA satisfies three design goals of MPTCP. Moreover, the authors' simulations show that BELIA performs better than some typical MPTCP congestion control algorithms under the same circumstances.