Encoding Of Signals Research Articles

Optimizing Information Theory Based Bitwise Bottlenecks for Efficient Mixed-Precision Activation Quantization

Recent researches on information theory shed new light on the continuous attempts to open the black box of neural signal encoding. Inspired by the problem of lossy signal compression for wireless communication, this paper presents a Bitwise Bottleneck approach for quantizing and encoding neural network activations. Based on the rate-distortion theory, the Bitwise Bottleneck attempts to determine the most significant bits in activation representation by assigning and approximating the sparse coefficients associated with different bits. Given the constraint of a limited average code rate, the bottleneck minimizes the distortion for optimal activation quantization in a flexible layer-by-layer manner. Experiments over ImageNet and other datasets show that, by minimizing the quantization distortion of each layer, the neural network with bottlenecks achieves the state-of-the-art accuracy with low-precision activation. Meanwhile, by reducing the code rate, the proposed method can improve the memory and computational efficiency by over six times compared with the deep neural network with standard single-precision representation. The source code is available on GitHub: https://github.com/CQUlearningsystemgroup/BitwiseBottleneck.

Algorithm based on 2‐bit adaptive delta modulation and fractional linear prediction for Gaussian source coding

A novel 2-bit adaptive delta modulation (ADM) algorithm is presented based on uniform scalar quantization and fractional linear prediction (FLP) for encoding the signals modelled by a Gaussian probability density function. The study focusses on two major areas: realization of a 2-bit adaptive quantizer based on Q-function approximation that significantly facilitates quantizer design; and implementation of a recently introduced FLP approach with the memory of two samples, which replaces the first-order linear prediction used in standard ADM algorithms and enables improved performance without increasing transmission costs. It furthermore represents the first implementation of FLP in signal encoding, therefore confirming its applicability in a real signal-processing scenario. Based on the performance analysis conducted on a real speech signal, the proposed ADM algorithm with FLP is demonstrated to outperform other 2-bit ADM baselines by a large margin for the gain in signal-to-noise ratio achieved over a wide dynamic range of input signals. The results of this research indicate that ADM with adaptive quantization based on Q-function approximation and adaptive FLP represents a promising solution for encoding/compression of correlated time-varying signals following the Gaussian distribution.

Interactions of Whisking and Touch Signals in the Rat Brainstem.

Perception is an active process, requiring the integration of both proprioceptive and exteroceptive information. In the rat's vibrissal system, a classical model for active sensing, the relative contribution of the two information streams was previously studied at the peripheral, thalamic, and cortical levels. Contributions of brainstem neurons were only indirectly inferred for some trigeminal nuclei according to their thalamic projections. The current work addressed this knowledge gap by performing the first comparative study of the encoding of proprioceptive whisking and exteroceptive touch signals in the oralis (SpVo), interpolaris (SpVi), and paratrigeminal (Pa5) brainstem nuclei. We used artificial whisking in anesthetized male rats, which allows a systematic analysis of the relative contribution of the proprioceptive and exteroceptive information streams along the ascending pathways in the absence of motor or cognitive top-down modulations. We found that (1) neurons in the rostral and caudal parts of the SpVi convey whisking and touch information, respectively, as predicted by their thalamic projections; (2) neurons in the SpVo encode both whisking and (primarily) touch information; and (3) neurons of the Pa5 encode a complex combination of whisking and touch information. In particular, the Pa5 contains a relatively large fraction of neurons that are inhibited by active touch, a response observed so far only in the thalamus. Overall, our systematic characterization of afferent responses to active touch in the trigeminal brainstem approves the hypothesized functions of SpVi neurons and presents evidence that SpVo and Pa5 neurons are involved in the processing of active vibrissal touch.SIGNIFICANCE STATEMENT The present work constitutes the first comparative study of the encoding of proprioceptive (whisking) and exteroceptive (touch) information in the rat's brainstem trigeminal nuclei, the first stage of vibrissal processing in the CNS. It shows that (1) as expected, the rostral and caudal interpolaris neurons convey primarily whisking and touch information, respectively; (2) the oralis nucleus, whose function was previously unknown, encodes both whisking and (primarily) touch touch information; (3) a subtractive computation, reported at the thalamic level, already occurs at the brainstem level; and (4) a novel afferent pathway probably ascends via the paratrigeminal nucleus, encoding both proprioceptive and exteroceptive information.

Improved two-dimensional dynamic S-EMG Signal compression with robust automatic segmentation

This work presents an automatic and robust algorithm for surface electromyography signals segmentation in dynamic experimental protocol. The signals are segmented based on the peak burst occurrence. The two-dimensional array is constructed and used as input of a 2D signal encoder. The two-dimensional matrix lines may be long enough to have several bursts. The algorithm includes, besides segmentation modules, several others to eliminate the occurrence of false positives. An encoder that combines the AV1 and JPEG2000 toolset is used to compress data. Basically, depending on the target compression rate the encoder uses AV1 or JPEG2000. Examples of segmentation for electromyography signals digitalized from lower and upper limbs are shown. Data compression results for real electromyography signals data bank are presented. A performance comparison with other works reported in the literature is also included.

A multi-channel peripheral nerve stimulator with integrate-and-fire encoding

Activation of peripheral nervous system (PNS) fibres to produce variable tactile and proprioceptive sensations in advanced bidirectional prosthetic limbs relies on neural stimulators with high spatial selectivity, dynamic range and resolution. A multi-channel application-specific integrated circuit (ASIC) is developed for PNS fibre activation using a wide dynamic range (10 nA–5 mA), high-resolution (30 nA step, 100 ns pulse accuracy) current stimulator, dissipating 0.73–2.75 mW at 3 V. The ASIC also enables encoding of external pressure signals via an integrate-and-fire methodology. Electrophysiological data of compound nerve action potentials were recorded for a range of stimulus amplitudes and pulse widths. This data was used to benchmark the performance of the ASIC with a known neural stimulator.

High frequency demodulation technique for instantaneous angular speed estimation

This paper adapts the super-heterodyne method from telecommunication field to speed estimation from an optical encoder signal. After a presentation of our gear box test bench and the associated electronic devices, the paper explains the classical methods for Instantaneous Angular Speed (IAS) estimation from an optical encoder. Firstly, elapsed time method that measures the interval between consecutive (rising) edges of an optical encoder is investigated: aliasing problem and quantification effect are explained. Secondly, frequency demodulation technique based on temporally sampled optical encoder signal is investigated. An analysis of this signal shows its imperfections (crosstalk, presence of a second order harmonic, …). The necessity of a high-sampling frequency, the aliasing problem and the noise impact are also illustrated. Next, this method is compared with elapsed time. In the second section, a new method is proposed: high frequency demodulation. This method uses an analog frequency shifting before sampling the signal. Therefore, the required sampling frequency is reduced and linked with the speed fluctuation frequency. Spectrum of optical encoder signal is analysed and used to explain how to set up the frequency shift and limitations. Finally, a comparison is made with elapsed time.

An encoder signal-based approach for low-speed planetary gearbox fault diagnosis

Low-speed rotating machines are extensively used in heavy industry. Among those, the planetary gearbox is a pivotal component with a high power–weight ratio and large loadbearing capacity, which inevitably fail due to the tough working conditions. The fault signature in such conditions is rather weak due to the complex planetary structure and the low rotating speed. Hence, the diagnosis of planetary gearbox problems in low-speed working conditions is considered as a bottleneck issue. In view of this, a rotary encoder signal, instead of conventional vibration, is initially applied to capture the fault-related information from the low-speed planetary gearbox. Then, a periodic group sparse-robust principal component analysis (PGS-RPCA) model with adaptive parameter programming, called adaptive PGS-RPCA (APGS-RPCA) is presented to extract the weak fault transient immersed in harmonic interferences and heavy noise. Finally, the effectiveness of the presented APGS-RPCA approach is verified via an experimental encoder signal at a very low input frequency. The diagnostic results show that the presented approach is superior to the conventional approach, and it may provide a promising solution for health monitoring of low-speed rotating machinery.

КОРЕКЦІЯ ПОХИБОК У ПРИЛАДАХ ДЛЯ ВИМІРЮВАННЯ ПАРАМЕТРІВ ЕЛЕКТРИЧНОЇ ЕНЕРГІЇ

A study of methods for correcting amplitude and phase errors in devices for measuring the parameters of electric power with digital signal processing with a sampling frequency multiple of the network frequency was made. The generalized flow diagram of measuring device that consists of a few entrance channels was presented. Mathematical expositions that explain the process of correction of additive and multiplicative errors are given. Through a temporal diagram a few variants of encoding of entrance signals are shown. The possibility of correcting phase errors by shifting the moment of the ADC start-up and by turning the axes and transforming the coordinates of the voltage and current vectors is shown. The possibility of correction when measuring the reactive and reactive powers is investigated. Referencese 11, table 1, figures 5.

The Quantum Nature of Color Perception: Uncertainty Relations for Chromatic Opposition.

In this paper, we provide an overview on the foundation and first results of a very recent quantum theory of color perception, together with novel results about uncertainty relations for chromatic opposition. The major inspiration for this model is the 1974 remarkable work by H.L. Resnikoff, who had the idea to give up the analysis of the space of perceived colors through metameric classes of spectra in favor of the study of its algebraic properties. This strategy permitted to reveal the importance of hyperbolic geometry in colorimetry. Starting from these premises, we show how Resnikoff’s construction can be extended to a geometrically rich quantum framework, where the concepts of achromatic color, hue and saturation can be rigorously defined. Moreover, the analysis of pure and mixed quantum chromatic states leads to a deep understanding of chromatic opposition and its role in the encoding of visual signals. We complete our paper by proving the existence of uncertainty relations for the degree of chromatic opposition, thus providing a theoretical confirmation of the quantum nature of color perception.

Research on automatic detection system of encoder accuracy based on PID algorithm

After the encoder completes the installation and adjustment work, its accuracy needs to be checked again to confirm whether it meets the acceptance conditions. This process is usually manually operated by inspectors, and the inspection efficiency is low and there are certain manual errors. In order to improve this situation, an encoder automatic precision inspection system based on PID algorithm is designed. In this article, the working principle and structure of the detection platform are introduced in the first part, and then designs the corresponding detection software and operation interface according to its working characteristics. Finally, the platform was tested in combination with the actual detection products, and the encoder signal acquisition results were given, which further verified the accuracy and reliability of the detection device. The results showed that the accuracy detection platform can accurately and conveniently realize the error detection of the encoder’s function, and to a certain extent overcome the detection error caused by the drift of the photoelectric autocollimator during the detection process.

Self-Switching Kerr Oscillations of Counterpropagating Light in Microresonators.

We report the experimental and numerical observation of oscillatory antiphase switching between counterpropagating light beams in Kerr ring microresonators, where dominance between the intensities of the two beams is periodically or chaotically exchanged. Self-switching occurs in balanced regimes of operation and is well captured by a simple coupled dynamical system featuring only the self- and cross-phase Kerr nonlinearities. Switching phenomena are due to temporal instabilities of symmetry-broken states combined with attractor merging, which restores the broken symmetry on average. Self-switching of counterpropagating light is robust for realizing controllable, all-optical generation of waveforms, signal encoding, and chaotic cryptography.

Adult-like neural representation of species-specific songs in the auditory forebrain of zebra finch nestlings.

Encoding of conspecific signals during development can reinforce species barriers as well as set the stage for learning and production of species-typical vocalizations. In altricial songbirds, the development of the auditory system is not complete at hatching, so it is unknown the degree to which recently hatched young can process auditory signals like birdsong. We measured in vivo extracellular responses to song stimuli in a zebra finch (Taeniopygia guttata) secondary auditory forebrain region, the caudomedial nidopallium (NCM). We recorded from three age groups between 13days post-hatch and adult to identify possible shifts in stimulus encoding that occur before the opening of the sensitive period of song motor learning. We did not find differences in putative cell type composition, firing rate, response strength, and selectivity across ages. Across ages narrow-spiking units had higher firing rates, response strength, accuracy, and trial-by-trial reliability along with lower selectivity than broad-spiking units. In addition, we showed that stimulus-specific adaptation, a characteristic of adult NCM, was also present in nestlings and fledglings. These results indicate that most features of secondary auditory processing are already adult-like shortly after hatching. Furthermore, we showed that selectivity for species-specific stimuli is similar across all ages, with the greatest fidelity in temporal coding in response to conspecific song and domesticated Bengalese finch song, and reduced fidelity in response to owl finch song, a more ecologically relevant heterospecific, and white noise. Our study provides the first evidence that the electrophysiological properties of higher-order auditory neurons are already mature in nestling songbirds.

Encoder Calibration Method for High Precision Servo Systems With a Sinusoidal Encoder

The sinusoidal encoder is used as an absolute position (velocity) transducer to implement the position (velocity) of actuators in many industrial applications. However, the performance of the position (velocity) can be degraded due to nonideal factors such as differential amplitudes of the encoder signals, offset, and phase shift. To analyze this problem, we formulate the relationship between the coefficients of ideal signals and the nonideal signals characteristic, which is an ellipse formed by plotting the encoder signals versus each other. In this article, we propose a nonideal signal calibration for the imperfect components of existing sinusoidal signals to improve position (velocity) regulation performance. The fictitious cosine function is used to detect the phase shift between the sine and cosine signals, and it can be designed by using the frequency of sinusoidal signals. The proposed method is validated by simulation and experimental implementation, showing noticeable improvement in estimating nonideal signal components, Lissajous error curve, phase distribution, and the position (velocity) error signal. Experimental results show that the proposed method is able to obtain the components of the nonideal signals and the accurate position (velocity) with a small error in real time, while other calibration methods are difficult to apply to fast motion.

Clutter-Masked Waveform Design for LPI/LPD Radarcom Signal Encoding.

In this work we propose a method of in situ clutter deconvolution and modeling using experimentally obtained UWB radar data. The obtained clutter models are then used for random sequence encoding of radar-communication (radarcom) signals to achieve clutter-masked transmissions and improve communication security. We present the results of clutter modeling from the laboratory data obtained with the software-defined radar system. We then show that such clutter-masked radarcom signals generated using the local clutter model are highly likely to be interpreted as just clutter returns by an unauthorized interceptor. We also present the results of communication and radar performance of these radarcom signals and contrast them with those obtained using a linear frequency modulated waveform. It is shown that the proposed radarcom design method has high potential to achieve secure communications in adversarial conditions, while simultaneously addressing radar sensing needs.

Algorithms for the Encoding and Reception of OFDM Signals Based on Manipulation with Minimum Frequency Shift

The developed algorithms for the encoding and reception of OFDM signals using minimum frequency shift keying (OFDM-MSK signals) are considered and investigated. OFDM-MSK signals have low out-of-band power compared to OFDM signals using phase shift keying. It is shown that the developed algorithms for the encoding and reception use a lattice structure of signals with a continuous phase with a minimum frequency shift in combination with a productive algorithm for fast spectral transformation in the Fourier basis.

Research on error compensation method of encoder signal based on cloud computing

Research on error compensation method of encoder signal based on cloud computing

"Abstract model of the Ternary Machine Signal Encoding"

"Abstract model of the Ternary Machine Signal Encoding"

Research on Error Compensation Method of Encoder Signal Based on Cloud Computing

In order to improve the performance of encoder signal error compensation, this paper proposes a method of encoder signal error compensation based on cloud computing. This method uses near-field sou...

Implementation of Singular Spectrum Analysis in Industrial Robot to Detect Weak Position Fluctuations

A fault or mechanical flaw causes several feeble swings in the position signal. Identification of such swings by encoders can help to identify machine performance and health status and provide a convenient alternative to a vibration-based monitoring system. In operations, the trend is usually several orders higher than the interested magnitude swings, thus increasing the difficulty of identifying feeble swings without signal deformity. Moreover, the swings can be intricate, and the amplitude can be changed under a nonstationary operating condition. Singular spectrum analysis (SSA) for detecting feeble position swings from the rotary encoder signal is suggested in this paper to address this issue. It allows the complex signal of the encoder to be reduced to a variety of explainable noise-containing components, a collection of periodic oscillations, and a trend. The numerical simulation reveals the achievement of the technique. It demonstrates that the SSA is superior to the empirical mode decomposition in terms of accuracy and ability. In addition, rotary encoder signals from the robot arm are evaluated to identify the causes of oscillation at junctions during industrial robot movements. The proposed route for the robotic arm is proven to be feasible and reliable.

Loss-tolerant quantum key distribution with mixed signal states

The security of measurement device-independent quantum key distribution (MDI QKD) relies on a thorough characterization of one's optical source output, especially any noise in the state preparation process. Here, we provide an extension of the loss-tolerant protocol [Phys. Rev. A 90, 052314 (2014)], a leading proof technique for analyzing the security of QKD, to MDI QKD protocols that employ mixed signal states. We first reframe the core of the proof technique, noting its generalization to treat $d$-dimensional signal encodings. Concentrating on the qubit signal state case, we find that the mixed states can be interpreted as providing Alice and Bob with a virtual shield system they can employ to reduce Eve's knowledge of the secret key. We then introduce a simple semidefinite programming method for optimizing the virtual operations they can perform on the shield system to yield a higher key rate, along with an example calculation of fundamentally achievable key rates in the case of random polarization modulation error.