Strong Impulsive Noise Research Articles

Maximum Rate Scheduling With Adaptive Modulation in Mixed Impulsive Noise and Additive White Gaussian Noise Environments

This article proposes an opportunistic scheduling scheme based on adaptive modulation for users in a mixed noise environment, where some users are under additive white Gaussian noise (AWGN) and other users are exposed to impulsive noise. Unlike the scenario, where all the users are in an AWGN environment, the maximum signal-to-noise ratio (SNR) scheduler does not provide the maximum capacity if users are in a mixed noise environment. In the proposed scheduling scheme, called maximum rate scheduler, the user with the highest rate (or highest modulation order), instead of highest SNR, is selected. To evaluate the performance of the proposed scheduling scheme, the analyses of average spectral efficiency, outage probability and system capacity are provided along with a simple calculation of SNR thresholds for adaptive modulation in an impulsive noise environment satisfying target symbol error rate (SER). Simulation results illustrate that system capacity with the proposed scheduling given target SER = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and the average spectral efficiency are improved by 156% and 124%, respectively, at SNR = 5 dB when a strong impulsive noise is present.

Fault Diagnosis of Rotating Machinery Based on Multi-Sensor Signals and Median Filter Second-Order Blind Identification (MF-SOBI)

Feature extraction plays a crucial role in the diagnosis of rotating machinery faults. However, the vibration signals measured are inherently complex and non-stationary and the features of faulty signals are often submerged by noise. The principle and method of blind source separation are introduced, and we point out that the blind source separation algorithm is invalid in an environment of strong impulse noise. In order to solve the problem of fast separation of multi-sensor signals in an environment of strong impulse noise, first, the window width of the median filter (MF) is calculated according to the sampling frequency, so that the impulse noise and part of the white noise can be effectively filtered out. Next, the filtered signals are separated by the improved second-order blind identification (SOBI) algorithm. At the same time, the method is tested on the strong pulse background noise and rub impact dataset. The results show that this method has higher efficiency and accuracy than the direct separation method. It is possible to apply the method to real-time signal analysis due to its speed and efficiency.

Robust joint estimation for time delay and Doppler frequency shift based on generalised sigmoid cyclic cross‐ambiguity function

In this study, a novel concept, i.e. the tuneable sigmoid cyclic correlation, is proposed, and a relative estimator, named the generalised sigmoid cyclic cross-ambiguity function, is also derived to deal with impulsive noise and co-channel interference. Based on these concepts, a robust joint estimation method for time delay and Doppler frequency shift is proposed as well. Both theoretical analysis and simulations demonstrate the superior performances of the proposed approach over other existing methods, especially under strong impulsive noise.

Combating impulsive noise for multicarrier underwater acoustic communications

This paper presents a novel multicarrier communication scheme that is specially designed for underwater acoustic channels with dominant impulsive noise. A novel multicarrier signaling structure is introduced at the transmitter. Thanks to the signaling structure, the received signal is shown satisfying some special properties even after various channel distortions. By exploiting these properties, we propose two receiver processing algorithms, one for signaling parameter estimation and the other for symbol recovery. The two algorithms take fully into account the presence of strong impulsive noise, and both are shown capable of offering inherent robustness against it. The proposed design is first evaluated via extensive simulations and then tested in a recent sea-going experiment. Both simulated and experimental results validate the proposed design and confirm its merits. [This work was supported by US Office of Naval Research.]

Performance Comparison on Three Time Delay Estimation Algorithms Using Experiments

Time delay estimation (TDE) is applied in many areas. Its estimation performance plays an important role in many actual systems, such as malfunction sound location. In this paper, estimation performances of three TDE algorithms, correlation, covariance, and fractional lower order covariance, are compared. Traditional, additive noises in the actual collected signals are described by Gaussian distribution. However, they have often impulsiveness in practice, and are modeled as α-stable distribution. First, correlation, covariance, and fractional lower order covariance method are analyzed in theory. Then, computer simulation experiments are carried out. Computer sound card records pure audio signals, different pulse intensity noises added to simulate actual environments. Next, results of three algorithms for time delay estimation were obtained in different signal to noise ratio (SNR) conditions. Under the same conditions, estimated RMS (root-mean-square) errors of three algorithms are analyzed and compared. Experimental results show that under low SNR and strong impulsive noise environments, fractional lower order covariance method indicates best estimation performance.

Direction of Arrival (DOA) Estimation for Coherent and Uncorrelated Signals in Environments of Strong Impulsive Noise

Direction of Arrival (DOA) Estimation for Coherent and Uncorrelated Signals in Environments of Strong Impulsive Noise

폭발파 모델을 이용한 실내 음장 해석에 관한 연구

A portable recoilless guided missile generates a strong back blast and impulsive noise at the nozzle when it launches. In the case of indoor operations, the hazard of the blast noise from a recoilless weapon increases due to limited indoor spaces. Also, the noise levels determine the operational feasibility of a weapon; therefore, it is important to predict the blast noise levels distribution in the indoor space in advance. In addition, computational fluid dynamics (CFD) method generally used for fluid related simulations, requires high computing cost and time to simulate the whole domains. The domain includes both blast wave region and large and various indoor space region. Therefore, an efficient method for predicting the far-field noise level within a short time should be developed. This paper describes an analysis model for predicting the indoor noise distributions by considering the shape effect of the building within a short time. A new developed blast wave model was implemented using the noise source. Additionally, noise reflections at the closed surfaces such as walls and noise transmissions at the opened surfaces such as windows and doors were considered in calculating the noise levels. The predicted noise levels were compared with the experimental data obtained from the indoor launch test to validate the reliability of program.

An Analog–Digital Hardware for L-Estimate Space-Varying Image Filtering

An analog---digital hardware solution for implementation of the L-estimate space-varying filtering has been proposed. The considered filter form is based on the robust space/spatial-frequency representation and provides efficient denoising of two-dimensional signals/images corrupted by heavy-tailed noise. Moreover, for images with fast-varying details and textures, the L-estimate filtering outperforms the commonly used filters. However, it requires significant processing time, since the space/spatial-frequency representation is calculated for each pixel, on a window by window basis. Therefore, in order to make it feasible for practical applications, a fast implementation of L-estimate space-varying filtering is proposed using a combined analog---digital approach. It provides efficient real-time processing of images corrupted by strong mixed Gaussian and impulse noise.

A Model of Electromagnetic Interferences Induced by Corona Discharges for Wireless Channels in Substation Environments

The design of robust receivers in environments with strong impulsive noise may be challenging due to their high-amplitude events and their rare but nonnegligible occurrence. In substation environments, these impulsive noises are predominant. They are induced by corona discharges such as electrical arcs or partial discharges in the air. The emitted radiations can occupy a wide range of frequencies typically reaching a few gigahertz with very high amplitude. In this paper, we develop a generalized model of impulsive electromagnetic interference induced by corona discharges for wireless channels. Radiations emitted by these sources are generally transient impulses, their occurrences follow cyclostationary process, due to their generation by an alternative current. In this model, we both take into account the physical mechanism of these discharges and the induced electromagnetic radiations. Experimental results validate the approach in terms of first- and second-order statistics such as amplitudes, interarrival time, occurrences, and power spectrum densities of impulsive transient noise.

Fast averaging peer group filter for the impulsive noise removal in color images

In the paper, a new approach to the impulsive noise removal in color images is presented. The new filtering design is based on the peer group concept, which determines the membership of a central pixel of the filtering window to its local neighborhood, in terms of the number of close pixels. Two pixels are declared as close if their distance in a given color space does not exceed a predefined threshold value. A pixel is treated as not corrupted by the impulsive noise process, if its peer group consists of at least two close pixels, otherwise this pixel is replaced by a weighted average of uncorrupted samples from the local neighborhood. The peer group size assigned to each pixel is used for the averaging operation, so that pixels which have many peers are taken with higher weight. The new filtering design proved to restore efficiently color images corrupted by even strong impulsive noise, while preserving tiny image details. The beneficial property of the proposed filter is its very low computational complexity, which allows its application in real-time image processing tasks.

휴대용 유도탄의 후방 안전영역 평가방법에 관한 연구

Recoilless weapons, which lead strong back blast and impulse noise more than 160 dB, have been used in compliance with the regulation of the safety zone for the safe operations. However, the safety zone regulations for the newly developed weapons should be prepared since the existing guidelines do not provide any information concerning the reason for the safety zone. In this study, the outdoor launch tests were performed to collect the data such as noise, pressure and temperature of the back blast. An assessment method using data obtained from launch tests has been proposed to determine the safety zone. The safety zone has been determined with consideration for the following criteria: Impulse noise, temperature and pressure of the back blast and blast angle. As a results, new safety zones for them have been established for the recoilless weapon developed by ADD (Agency for Defense Development). We expect that this research can be used as a guideline for establishing a new safety zone regulation of similar weapon to be developed.

Robust Turbo Decoding in a Markov Gaussian Channel

Strong impulse noise is widely known to adversely affect conventional receivers designed only to consider background noise. Although sophisticated receivers offer substantial performance improvements, fully exploiting the impulse statistics, which are generally not time invariant and are difficult to model accurately, can be unrealistic. Alternatively, without making assumptions regarding the underlying impulse channel model, the authors' previously developed robust decoding schemes can achieve performance equivalent to that of their optimal counterparts in impulse noise channels. In this letter, a robust turbo decoding metric is proposed to address the inherent memory in an impulse channel: a 2-D trellis is used to adapt for channel state transitions when statistics on the memory impulse channel model are lacking. The simulation results verified the robustness of the proposed decoder in harsh environments.

상호 정보 포텐셜과 델타함수를 이용한 블라인드 알고리듬의 복잡도 개선

ABSTRACT The equalization algorithm based on the cross-information potential concept and Dirac-delta functions (CIPD) has outstanding ISI elimination performance even under impulsive noise environments . The main drawback of the CIPD algorithm is a heavy computational burden caused by the use of a block processing method for its w eight update process. In this paper, for the purpose of reducin g the computational complexity, a new method of the gradient calc ulation is proposed that can replace the double summation with a single summation for the weight update of the CIPD algorithm. In the simulation results, the proposed method produces the sa me gradient learning curves as the CIPD algorithm. Even under stro ng impulsive noise, the proposed method yields the same results while having significantly reduced computational complexity regardless of the number of block data, to which that of the e conventional algorithm is proportional. ☞ keyword : cross-information potential, Dirac-delta, computation al complexity, impulsive noise, CIPD.

멀티콥터를 이용한 수직방향 DTV 신호 레벨 측정

DTV 필드 테스트는 실내와 실외에서 전계강도와 수신 가능성 등을 측정하는 것으로 실외의 경우 측정 차량을 도로에서 수평적으로 이동하면서 9m 높이의 안테나를 사용 DTV 신호를 측정하였다. 현대의 고층 빌딩과 같은 수직 집단 구조의 주거 형태에서는 수직적인 DTV 신호 측정을 통하여 수직 방향 전파 환경 분석이 필요하다. 특히 전면에 장애물이 많아 다중 경로 간섭과 임펄스 잡음의 영향으로 전계강도가 수신 임계값인 <TEX>$43dB{\mu}V/m$</TEX> 이상인 경우에도 수신이 불가한 경우가 있어 건물 밀집지역이나 특수한 측정 환경에 적합한 필드 측정 및 분석이 절대적으로 필요하다. 이를 위하여 자유롭게 비행하면서 DTV 수신신호 레벨을 측정할 수 있는 비행체 옥토형 멀티콥터를 개발하고 시험을 거쳐 실용성 있게 성능을 개선하였다. 휴대형 소형 DTV 수신신호 레벨 측정기와 안테나 및 데이터 전송용 M/W 송신기 또는 녹화용 장비가 탑재되어 DTV 수신신호 레벨 측정이 가능한 이 멀티콥터를 이용하여 전파환경이 다른 3지역의 측정을 통해 신뢰성 검증과 실용성을 입증하였다. 수직 방향 수신신호 레벨 측정은 수직 방향 전파 환경 변화가 큰 장소, 고층 아파트 같은 집단적 수직 주거 형태, 도보나 차량으로 접근이 불가능한 지역 등 측정점의 특수한 환경에 적합한 데이터를 얻을 수 있어 기존의 수평적 필드 테스트에서는 접근하기 어려운 장소의 전파 변화 분석에 유용하게 사용할 수 있다. DTV field tests have been performed to measure field strength and to check reception ratio on indoor and outdoor sites. They use an antenna of 9m to measure DTV signal in case of outdoor measurement on the road. Modern skyscrapers require the analysis of vertical-directional wave propagation by measuring vertical-directional DTV signal. Even if the field strength is above the reception threshold of <TEX>$43dB{\mu}V/m$</TEX>, the reception is impossible in case of strong multi-path or high impulse noise. So, vertical-directional field measurement is essential in environment of tall buildings. In this paper, we developed an octo type multi-copter to measure vertical-directional DTV signal level. A compact and portable DTV signal level meter, an antenna, a microwave transmitter for data transmission, and a recording equipment are equipped in the multi-copter. Three different sites are selected to test the measurement system. Developed measurement system using the multi-copter is very useful in measuring vertical-directional DTV signal, especially in apartments, non-accessible area by vehicles, and forbidden areas.

Quantum-inspired cultural bacterial foraging algorithm for direction finding of impulse noise

In order to resolve direction finding problem in the presence of impulse noise, a quantum-inspired cultural bacterial foraging algorithm (QCBFA) is proposed. The proposed QCBFA applies the quantum knowledge strategy and new quantum foraging equations to bacterial foraging optimisation algorithm (BFOA), and thus has the advantages of low computational complexity and fast convergence. As a key step of QCBFA algorithm, chemotactic movement is modelled as guided cultural behaviour and thus may improve the capability of BFOA to find the optimal solution. Then we applied the proposed QCBFA to direction finding problem in the presence of impulse noise, which is a hot spot in signal processing of array. Then, based on QCBFA and infinite norm maximum likelihood (INML) algorithm, a new direction finding method is proposed, which is called as QCBFA-INML algorithm. Monte Carlo simulations have showed that the QCBFA-INML method has excellent direction finding performance for non-coherent and coherent signals in the strong impulse noise.

비-가우시안 잡음하의 적응 시스템을 위한 바이어스된 영-오차확률

영-오차확률 성능 기준은 오차 샘플들이 직류 바이어스 잡음의 영향을 받을 때 적응 시스템에 사용되기에는 제약이 따른다. 이 논문에서는 바이어스 변수를 오차 분포에 도입하고 바이어스된 오차확률에서 오차를 0 으로 하여 새로운 성능 기준인 바이어스된 영-오차확률을 제안하였다. 또한, 확장 필터 구조를 기반으로 제안된 성능 기준을 최대화 함으로써 적응 알고리듬을 도출하였다. 통신 채널 등화에 대한 시뮬레이션 결과로부터 제안된 성능기준에 기반한 이 알고리듬이 강한 충격성 잡음과 직류-바이어스 잡음의 환경에서 동요 없이 오차 샘플들을 0 으로 집중시키는 성능을 보였다. The criterion of zero-error probability provides a limitation on error probability functions being used for adaptive systems when the error samples are shifted by the influence of DC-bias noise. In this paper, we employ a bias term in the error distribution and propose a new criterion of the biased zero-error probability with error being zero. Also, by maximizing the proposed criterion on expanded filter structures, a supervised adaptive algorithm has been derived. From the simulation results of supervised equalization, the algorithm based on the proposed criterion yielded zero-centered and highly concentrated error samples without disturbance in the environments of strong impulsive and DC-bias noise.

랜덤 심볼열의 바이어스된 분포를 이용한 정보 포텐셜과 블라인드 알고리즘

Blind algorithms based on Information potential of output samples and a set of symbols generated in random order at the receiver go through performance degradation when biased impulsive noise is added to the channel since the cost function composed of information potentials has no variable to deal with biased signal. Aiming at the robustness against biased impulsive noise, we propose, in this paper, a modified information potential, and derived related blind algorithms based on augmented filter structures and a set of random-order symbols. From the simulation results of blind equalization for multipath channels, the blind algorithm based on the proposed information potential produced superior convergence performance in the environments of strong biased impulsive noise.

Utilizing nonlinear ELF generation in modulated ionospheric heating experiments for communications applications

Modulated high‐frequency heating of the D region ionosphere near the auroral electrojet can generate extremely low frequency (ELF; 3 Hz–3 kHz) radio waves. The modulated heating process is nonlinear and generates harmonics at integer multiples of the ELF modulation frequency. Quaternary phase shift keying, a digital modulation technique is applied to ELF waves to demonstrate transmission of digital data. Data were successfully decoded at a nearby receiver and the bit error rate computed. Square wave modulation of the high‐frequency heater results in stronger signals and hence a smaller bit error rate. Simulations of the communication system using ELF waveforms and noise signals derived from ELF observations are also conducted. These simulations show that using higher harmonics of the ELF signal to improve the signal‐to‐noise ratio can reduce the bit error rate, although only when these harmonics are below ~4.5 kHz because of radio atmospherics (sferics) generating strong impulsive noise at higher frequencies.

충격성 잡음이 있는 수중 통신 채널의 적응 등화를 위한 확률밀도함수 정합 알고리듬

In this paper, a supervised adaptive equalization algorithm based on probability density function (PDF) matching method is introduced and its decision-feedback version is proposed for underwater communication channels with strong impulsive noise and severe multipath characteristics. The conventional least mean square (LMS) algorithm based on mean squared error (MSE) criterion has shown to be incapable of coping with impulsive noise and multipath effects commonly shown in underwater communications. The linear PDF matching algorithm, which shows immunity to impulsive noise, however, has revealed to yield unsatisfying performance under severe multipath environments with impulsive noise. On the other hand, the proposed nonlinear PDF matching algorithm with decision feedback proves in the simulation to possess superior robustness against impulsive noise and multipath characteristics of underwater communication channels.

고전압 COS 퓨즈용 소음기의 소음저감 및 전류차단 성능에 관한 실험적 연구

This experimental study describes the noise reduction and the feasibility of short current of a silencer for a high voltage COS(cut out switch) fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the strong impulse noise over 150 dB(A) is generated. For the purpose of the reduction of impulse noise, in this study, the diffuser type and the reactive type silencers have been designed and tested, respectively. And also the electrical test on the short current is performed. From the experimental results, the well designed reactive type silencer has been shown to have the noise reduction of about 20 dB(A). It has been found that the feasibility of short current for the COS fuse is closely related to the porosity of the silencer.