Number Of Taps Research Articles

Non-uniform [formula omitted]-norm constraint based underwater acoustic channel adaptive estimation

It is known that the underwater acoustic channels (UAC) exhibit non-uniform cluster-sparse characteristics, meaning that the channel impulse response (CIR) typically consists of a large number of near-zero taps and with only a few none-zero ones assemble in clusters in a structured manner, moreover, the cluster structure is non-uniformly distributed on the time domain. In this paper, an improved proportionate affine projection algorithm (IPAPA) with the non-uniform l21-norm constraint is proposed for non-uniform cluster-sparse UAC estimation. Firstly, the auxiliary channel information is obtained via the correlation of training sequence, whereby the priori cluster-sparse structure positioning of UAC is realized. Then the non-uniform l21-norm is added on the IPAPA for the final accurate channel estimation: it encourages correlation among coefficients inside each group via the l2 norm and facilitates sparsity across all groups using the l1 norm. The results of numerical simulations and sea trial show that the proposed UAC estimation algorithm can achieve a better performance in terms of mean square error (MSE) compared to existing sparse channel estimation methods.

Deep‐learning‐based beamforming for rejecting interferences

Antenna arrays have been widely used for space and space–time processing to estimate the desired signals in the presence of narrowband and wideband interferences. Estimating the optimal weight vector is a challenging problem in space and space–time processing due to its high computational complexity. The problem escalates when the number of antennas and taps of filters for time-domain processing increases. In this study, a convolutional neural network is employed to estimate nearly-optimal weight vectors even when the number of available snapshots of the received signal is as low as 400 and a signal-to-noise ratio as low as −5 dB. Unlike the conventional processors, the authors proposed method requires no prior knowledge about the direction of arrival of the desired signal. In addition, due to its parallel architecture, the computational complexity of the neural processors is reasonable using a single graphical processing unit on a PC to run the algorithms. Through simulations of the uniform linear array in the presence of narrowband and wideband interferences, they demonstrate that the output signal-to-interference plus noise ratio (SINR) is very close (by <0.5 dB) to the max SINR obtained by the optimal weight vector of antenna arrays.

Performances of OSIC Detector of an UpLink OFDM Massive-MIMO System in Rayleigh and Ricain Fading Channels

This paper presents a least squares channel estimation for Massive-Multiple-Input Multiple- Output (Massive-MIMO) systems in next generation of wireless communications denominated 5G, combined with Orthogonal Frequency Division Multiplexing (OFDM) and 64-QAM modulation. In this paper, after determining the estimated channel, we first consider one OFDM symbol and presented the flat fading and the frequency-selective fading in the case when channel taps equal to one and strictly superior to one respectively. In addition to that, we consider the uplink transmission where the transmitter antenna equal to $$N_t=50$$ and a Base Station (BS) equipped with several antenna superior to that of transmitter, in the same way the data detected using a linear detectors Zero-Forcing and Minimum Mean Square Error. Moreover we improve their performance by an ordered successive interference cancellation (OSIC) method. Using two channels fading namely the Rayleigh and the Ricain respectively and evaluate their performance with a system of Massive-MIMO antenna. Increasing the number of channel taps increase the inter-symbol interference allows to degrade the performance of the system both the Rayleigh and Rician channel, even we used a pilot sequence equipowered, equispaced and phase shift orthogonal. Hence increasing the number of antennas arrays at the receiver (i.e BS) decreases more the Bit Error Rate, consequently increasing the performance of the system. the OSIC methods provide a best performance when the number of antenna grow in a smaller range of Signal-to-Noise Ratio.

METHOD OF IMPROVED TDICCD DESIGN BASED ON SENSOR CLOCKING

Abstract. The final output signal quality of TDICCD is related to the key parameters such as working mode, output mode, signal-to-noise ratio, dynamic range and so on. We can improve these parameters of TDICCD by reasonably designing the sensor clocking. Therefore, this text discussed four methods of improved TDICCD sensor clocking to solve some problem in TDICCD application based on using the principle of TDICCD. The technique of TDICCD Taps merging can reduce the number of TDICCD Taps, which helps to reduce the size of the TDICCD rear-end circuit significantly; The technique of TDICCD continuous transfer clocking can improve the charge transfer efficiency, which helps to promote the final signal-to-noise ratio; The technique of pixel binning clocking can enlarge the dynamic range of image; The technique of TDICCD area-array working mode can extend the field of TDICCD working; The principle, derivation process, clocking sequence diagram and application range of these clocking design schemes are given in this paper. At the same time, it also explains its actual effect and the matters to be noted.

Measurement‐based determination of parameters for non‐stationary TDL models with reduced number of taps

This study proposes a new strategy of extracting parameters for tapped delay line (TDL) channel models from vehicle to infrastructure channel measurements. The proposed approach is based on an already existing method to derive parameters for a non-stationary model using first-order Markov chains. It will be shown that with the proposed method, the number of taps necessary to regenerate the delay spread of a channel can be significantly reduced. An approach will be discussed to evaluate the performance of the model. The feasibility of the method will be confirmed using channel sounding measurements.

PERFORMANCE STUDY OF FOUR EQUALIZATION TECHNIQUES OVER A WIRELESS COMMUNICATION CHANNEL

Abstract. Equalization techniques are commonly used in low to moderate data transmission over time varying wireless mobile channels. Their use is mainly to alleviate the detrimental effect of intersymbol interference brought about by the multipath phenomena of such channels. The wireless multipath channel is time varying which makes the use of adaptive equalization a necessity to cope with channel variations and consequently to overcome resulting intersymbol interference effects, restore the transmitted symbols, and extract the information being sent. The first part of this paper presents a comparison study of the performances of four representative methods of adaptive equalization. Linear and nonlinear structures each with both LMS and RLS adaptation algorithms are used in the investigation. In the second part of the paper, a computer simulation is carried out to investigate the relationship between the number of propagation paths of the wireless mobile channel and the number of taps in the incorporated adaptive equalizer. Four equalizer structures are used in this investigation which is based on Simulink software package to simulate a communication system incorporating these equalizers. The bit error rate (BER) performance is used as a measure for establishing this dependency. 000

Joint Superchannel Digital Signal Processing for Effective Inter-Channel Interference Cancellation

Modern optical communication systems transmit multiple frequency channels, each operating very close to its theoretical limit. The total bandwidth can reach 10 THz limited by the optical amplifiers. Maximizing spectral efficiency, the throughput per bandwidth is thus crucial. Replacing independent lasers with an optical frequency comb can enable very dense packing by overcoming relative drifts. However, to date, interference from non-ideal spectral shaping prevents exploiting the full potential of frequency combs. Here, we demonstrate comb-enabled multi-channel digital signal processing, which overcomes these limitations. Each channel is detected using an independent coherent receiver and processed at two samples-per-symbol. By accounting for the unique comb stability and exploiting aliasing in the design of the dynamic equalizer, we show that the optimal spectral shape changes, resulting in a higher signal-to-noise ratio that pushes the optimal symbol rate towards and even above the channel spacing, resulting in the first example of frequency-domain super-Nyquist transmission with multi-channel detection for optical systems. The scheme is verified both in back-to-back configuration and in single span transmission of a 21 channel superchannel originating from a 25 GHz-spaced frequency comb. By jointly processing three wavelength channels at a time, we achieve spectral efficiency beyond what is possible with independent channels. At the same time, one significantly relaxes the hardware requirements on digital-to-analog resolution and bandwidth, as well as filter tap numbers. Our results show that comb-enabled multi-channel processing can overcome the limitations of classical dense wavelength division multiplexing systems, enabling tighter spacing to make better use of the available spectrum in optical communications.

Application of specialized software systems for determination of normal and emergency operation modes parameters of power distribution networks

The paper analyzes the normal and emergency operation of rural distribution electric networks applying specialized software system - RASTRWIN PC, which is used at many power network enterprises in Russia. This specially designed program uses the RASTRWIN PC calculation core - Astra.dll, which calculates normal and emergency network conditions. It is used to solve the problem of calculating the modes of distribution networks 6-10 kV. To achieve greater accuracy of results, we use the scaling network parameters (currents, voltages, loads). For greater accuracy in calculating emergency conditions, the currents of the previous pre-emergency operation mode are used, as well as the dependence of the load current on the voltage in the network in emergency operation mode. The paper also substantiates the equivalent of the distribution network scheme based on a comparison of the calculation results of the modes for the full network section scheme and a simplified scheme. It is done to reduce labor costs when drawing up a design diagram of a distribution power network with a large number of taps on feeders. Using the developed program for a section of a distribution power network with the voltage 10 kV, normal and emergency operation modes of the network were calculated.

Quantitative assessment of fine motor skills in children using magnetic sensors

AimWe aimed to establish objective and quantitative data on fine motor development in typically developing children using magnetic sensors. MethodsThe study included 110 Japanese elementary school children volunteers (57 boys, 53 girls). The participants were instructed to tap their thumbs and index fingers together repetitively for 10 s. After attaching coils to the participants’ right and left thumbs and index fingers, participants executed “in-phase” and “anti-phase” tapping. We used two-way analysis of variance to analyze the influences of age and sex on fine motor development. ResultsThe “number of taps” significantly increased with age, while the “standard deviation (SD) of tapping interval” significantly decreased. More than half of the “acceleration” parameters significantly increased with age. Boys performed significantly faster than girls in some parameters of “velocity” and “acceleration,” while girls had significantly lower “SD of local maximum velocity in opening motion” and “SD of local minimum velocity in closing motion.” DiscussionWe established both objective and quantitative reference data on fine motor development in typically developing Japanese children aged between 7 and 12 years using magnetic sensors. We revealed that this system can monitor real-time details of the parameters involved in the finger-tapping movement in children without complications. This device could be useful for obtaining objective and quantitative data on fine motor skills in the clinical assessment of developmental coordination disorder, assessments of educational intervention, or rehabilitation and discovery of new therapeutic agents.

Optimization of Cervical and Ocular Vestibular Evoked Myogenic Potential Testing Using an Impulse Hammer in Adults, Adolescents, and Children.

To characterize cervical and ocular vestibular evoked myogenic potential (c- and oVEMP) responses using an impulse hammer (IH) in adults and pediatrics at standardized force levels and evaluate: the relationship of force level on VEMP amplitude, sternocleidomastoid (SCM) contraction on cVEMP amplitude, required number of tap stimuli, and subject comfort. Using these data, optimal testing parameters were selected. Prospective study. Tertiary referral center. Seventy-eight healthy adults, adolescents, and children with no hearing or vestibular deficits. All subjects received c- and oVEMP testing using IH and 500 Hz tone burst air conduction stimuli. Adults received hard, medium, and soft force levels. Adolescents and children received medium and soft force levels. A comfort questionnaire was administered pre- and post-testing. IH VEMP response parameters (response rates, latency, cVEMP pre-stimulus SCM Electromyography [EMG], and peak-to-peak amplitude) were assessed per force level. Subjective reporting for patient comfort was also assessed. VEMP response rates ranged from 92 to 100%. Force had a linear relationship with VEMP amplitude. SCM contraction had a linear relationship with raw cVEMP amplitude; however, dissipated with amplitude normalization. Force level did not impact the number of taps needed. A minimum peak force of 15 to 20 N, accounting for SCM contraction, and using a lower EMG monitoring limit for cVEMP is recommended to elicit reliable responses. Overall, IH VEMP is appropriate and comfortable to use in adults and pediatrics and can be useful when an air conduction stimulus is contraindicated or not preferred.

Design for reliability of multifunctional PV inverters used in industrial power factor regulation

Industrial consumers are widely known for their high demand for active and reactive power. Thus, these consumers have a great interest in the local generation using PV plants to reduce the energy bill. However, the traditional PV systems reduce the active power absorbed from the grid and, consequently, the installation power factor. Under such conditions, fees are being charged due to the low facility power factor. This work carries out an overall study on the effects of the installation of a PV plant on the industrial power factor. Moreover, solutions based on traditional capacitor banks or multifunctional PV inverters are benchmarked. The case study of an industrial power plant located in Brazil is discussed. The results indicate that the traditional capacitor bank solution cannot correct the power factor all time due to its limited number of taps. Nevertheless, the multifunctional PV inverter can provide a precise reactive power compensation, which improves the power factor and eliminates the additional fees. However, a PV system reliability reduction of 24.1% is observed compared to the traditional operation, while inverter oversizing preserves the system reliability even by correcting power factor.

Scheduled Step-Size Subband Adaptive Filter Algorithm With Implemental Consideration

This article proposes a scheduled step-size normalized subband adaptive filter (NSAF) algorithm in stationary system environment. The mean-square deviation of the NSAF according to the step size is analyzed geometrically to construct a pre-designed trajectory. The mean-square deviation learning curve of the NSAF algorithm is forced to follow the pre-designed trajectory. This method removes the need for the NSAF algorithm to introduce tuning parameters and does not add any additional online computation. The table of the scheduled step sizes can be reconstructed online in proportion to not only the number of taps but also the number of subbands once they are scheduled offline. The novel memory-efficient scheduling scheme minimizes the memory space required and simplifies operation without performance degradation. Because of these features, the proposed algorithm performs as well as the variable-step-size NSAFs studied previously, and is very suitable for chip level implementation in terms of computational complexity and memory space. Simulation results show that the proposed algorithm is robust against external environment change and has good performance compared to the existing variable step-size algorithms without any additional online computation and tuning parameter.

Bazične motoričke sposobnosti kao prediktori savladavanja poligona za provjeru motoričkih znanja

The aim of this study was to determine the impact of motor abilities on mastering an obstacle course and define quantitative differences in basic motor abilities between the students awarded poor grades and the students awarded higher grades based on the result achieved on the obstacle course designed to test motor skills. The results of regression analysis demonstrated that motor abilities are important for mastering an obstacle course for testing motor skills and, on the basis of them, we may predict the result that defines the students' specific skills. Moreover, the results of the Student's t-test for independent samples demonstrated a statistically significant difference in the level of motor abilities between the students awarded poor grades and those awarded higher grades. The difference is defined by statistically significantly better values of the results achieved on motor tests: the maximum number of sit-ups (MPTP), stick mobility (MOKP), hand tapping (MTAP) and Cooper's 12 minute run test (MKUP), achieved by the students with higher grades, based on which we can assume that these variables are predictive of successful mastery of the obstacle course for testing motor skills. The results obtained might contribute to a better organization of training work in teaching, especially regarding an approach to improving motor abilities that dominantly have an impact on mastering an obstacle course designed to test motor skills.

Robust Multichannel Linear Prediction for Online Speech Dereverberation Using Weighted Householder Least Squares Lattice Adaptive Filter

Speech dereverberation has been an important component of effective far-field voice interfaces in many applications. Algorithms based on multichannel linear prediction (MCLP) have been shown to be especially effective for blind speech dereverberation and numerous variants have been introduced in the literature. Most of these approaches can be derived from a common framework, where the MCLP problem for speech dereverberation is formulated as a weighted least squares problem that can be solved analytically. Since conventional batch MCLP-based dereverberation algorithms are not suitable for low-latency applications, a number of online variants based on the recursive least squares (RLS) algorithm have been proposed. However, RLS-based approaches often suffer from numerical instability and their use in online systems can further be limited due to high computational complexity with a large number of channels or filter taps. In this paper, we aim to address the issues of numerical robustness and computational complexity. More specifically, we derive alternative online weighted least squares algorithms through Householder RLS and Householder least squares lattice (HLSL), which are numerically stable and retain the fast convergence capability of the RLS algorithm. Furthermore, we derive an angle-normalized variant of the HLSL algorithm and show that it is robust to speech cancellation for a wide range of forgetting factors and filter taps. Finally, we support our findings through experimental results and demonstrate numerical and algorithmic robustness, long-term stability, linear complexity in filter taps, low memory footprint, and effectiveness in speech recognition applications.

Low computing resource consumption fully digital foreground calibration technique for time-interleaved analog-to-digital converter

A time-interleaved analog-to-digital converter (TI-ADC) uses several sub-analog-to-digital converters (sub-ADCs) to achieve a high sampling rate. Its applications include communication systems, oscilloscopes, healthcare instruments, etc. However, the presence of sub-ADC channel mismatches such as offset, gain and sample-time mismatches can significantly degrade the performance of TI-ADCs. This paper proposes a fully digital foreground calibration technique for the TI-ADC, including mismatch correction and estimation blocks. Unlike existing techniques, the proposed technique requires low computational resources. As the resource for complex computing in a field-programmable gate array (FPGA) is mainly the digital signal processor (DSP), the mismatch correction block unifies each computing unit in the FPGA into a multiply adder to achieve low DSP consumption. To further reduce the use of DSP resources, the selection of an optimal number of taps of the finite impulse response filter used for mismatch correction is discussed. The optimal-tap filter that uses the lowest amount of DSPs while satisfying the required signal-to-noise and distortion ratio flat area bandwidth is presented. A real-time hardware correction block was implemented for an 8 Gs/s TI-ADC system with two sub-ADC channels, and the results with this hardware verify the low computing resource consumption feature of the proposed calibration technique.

Residual stress detection of welded parts based on excitation vibration response

With the rapid development of the equipment industry, people pay more attention to the stress research of materials. However, there is no more suitable and effective method to detect the variation of residual stress. To find an efficient and useful method to analyze the residual stress of the welded parts, this article selects the Q235 component as the research object and produces a detection robot with the core of processing vibration signal and extracting signal data. In combination with the vibration signal extracted by the robot, we study the influence law of the residual stress of the material through numerical simulation and experimental verification. The detection of residual stress is related to the change in the number of taps of the robot and the increase or decrease in the number of taps of the robot. We used the vibration signal extracted by the robot and analyzed the orthogonal parameters of the high-frequency induction welding process parameters to obtain a set of the most unique process parameters: The tapping angle was 7° and the tapping frequency was 300 Hz. We also set up the robot to extract and analyze the vibration signal using four different hammerheads. The results show that the sub-resonance analysis results as the standard, the deviation of the steel head and the aluminum head hammer is about ±10, the result is more accurate, and the frequency of the nylon and plastic hammer is lower, because it is softer. When the hammer is struck, the contact time of the hammerhead with the workpiece is lengthened, so that a lower frequency can be excited.

Temperature sensing scheme based on fiber ring microwave photonic filter with erbium doped fiber amplification

AbstractThe temperature sensing scheme based on fiber ring microwave photonic filter (MPF) with erbium doped fiber amplification (EDFA) is proposed and experimentally demonstrated. The fiber ring is used as the time delay element, as well as a sensing element, and by introducing an EDFA to compensate the loss in the fiber ring, the number of the effective sampling taps and thus the suppression ratio are increased. When the EDFA power is set at 0.74 mW, the 3 dB bandwidth of the passband and suppression ratio of the MPF are estimated to be 82.5 kHz, and 15 dB, respectively. The superior sharp passband characteristics make the fiber ring MPF with an EDFA very advantageous for sensing. In our experiment, temperature sensing by using the fiber ring MPF with an EDFA has been carried out for demonstration. The temperature variations induce refractive index changes of the fiber, which will change the time delay of each tap of the fiber ring MPF, and as a result, the FSR of the MPF will be changed. By tracing the peak point shift of the MPF's passband, the temperature variations can be monitored. Our experimental results show that there is a good linear relationship between temperature change and frequency shift, and by measuring passbands with different frequencies, different sensitivity can be obtained. In our experiment, the sensitivity is estimated to be −5.89, −11.74, and − 17.7 kHz/°C, respectively, when the passbands at 0.8, 1.6, and 2.4 GHz are adopted for temperature monitoring.

Single-step digital backpropagation for subcarrier-multiplexing transmissions.

We propose and demonstrate a single-step digital back propagation (DBP) algorithm for metro and regional transmissions with high order modulation formats. Based on subcarrier-multiplexing (SCM)-DBP, two modifications are made to improve performance and reduce complexity for the targeted link scenarios. First, an infinite impulse response (IIR) filter is adopted in self-subcarrier nonlinear compensation. Second, the second stage chromatic dispersion (CD) compensation is incorporated into an existing adaptive filter. Through experiment, we demonstrate the performance of the proposed scheme, denoted as M-SCM-DBP, for single channel 34.94-GBd SCM PDM-32QAM transmission. With 86.3% complexity reduction compared with the low-pass filter assisted DBP, the proposed M-SCM-DBP achieves 0.6-dB Q2 improvement for SCM-PDM-32QAM transmission over 960-km standard single mode fiber (SSMF). The reach extension of 36% to 1220-km is achieved with only 30.5 complex multiplications per sample, in comparison with the linear compensation scheme. Since the adaptive filter is used to simultaneously compensate 50% CD and other linear impairments, we also investigate the required number of filter taps and its polarization tracking ability.

Statistical Sparse Channel Modeling for Measured and Simulated Wireless Temporal Channels

Time-domain wireless channels are generally modeled by Tapped Delay Line (TDL) model and its variants. These models are not effective for channel representation and estimation when the number of multipath taps is large. Compressive sensing (CS) provides a powerful tool for sparse channel modeling and estimation. Most of the research has been focusing on sparse channel estimation, while sparse channel modeling (SCM) is rarely considered for centimetre-wave channels. In this paper, we investigate statistical sparse channel modeling, using both measured and simulated channels over a frequency range of 6 to 8.5 GHz. We first introduce the triple equilibrium principle to explore the trade-off between sparsity, modeling accuracy, and algorithm complexity in SCM, and provide a methodology for characterizing the sparsity of time-domain channels using single-measurement-vector compressive sensing algorithms. Using mainly the selected wavelet dictionary and various CS reconstruction (aka recovery) algorithms, we then present comprehensive statistical sparse channel models, including channel sparsity, magnitude decaying profile, sparse coefficient distribution and atomic index distribution. Connections between the parameters of conventional TDL and sparse channel models are mathematically established. We also propose three methods for generating simulated channels from the developed sparse channel models, which validates their effectiveness.

Efficient multitap equalization for FBMC‐OQAM systems

AbstractThis work provides a simple yet efficient multitap equalization structure for filter bank multicarrier systems, which is a candidate waveform for the next generation (5G) of mobile communication systems. More specifically, we analyze the system performance under medium‐ to high‐frequency selective channels. In this scenario, the single‐tap equalizer is not enough to compensate the channel effects, and then, a multitap equalizer need to be deployed. In the literature, the available equalization structures that are more efficient in aggressive scenarios are generally quite complex, whereas the less complex alternatives do not perform satisfactorily in such conditions. In this context, we propose a new multitap equalization approach in the frequency domain, aiming at reducing the computational complexity while improving the system robustness against high‐frequency selectivity conditions. For a wide range of number of taps and antennas, the proposed minimum mean square error–based frequency domain equalizer presents a much reduced computational complexity, ie, less than 1% of the conventional minimum mean square error–based time domain complexity. The operation, advantages, performance, and the main differences between multitap equalization schemes against the simple one‐tap equalizer for filter bank multicarrier systems are comprehensively discussed.