Simulated Performance of a DS Spread-Spectrum System in Impulsive Atmospheric Noise

Analytical evaluation of the effect of impulsive atmospheric noise on the performance of a direct-sequence spread-spectrum system has already been reported. In this paper, the error-rate performance of such a system using nonlinearities like soft clippers and hard limiters is evaluated using simulated noise samples. The results obtained compare well with the theoretically established results.     

An Assessment of Impulsive Noise via a Double-Ringing Model

The generation and propagation of impulsive noise detected using multiple level detectors on ships's data bus lines is examined in terms of a simple model. This model consists of random switching of an inductive load, followed by near-field coupling, and a double-ringing process. A method of analysis is introduced based on the concept of ?probability of peak.? This considers a generated impulse in terms of its amplitude only, which is assumed to be a random variable. The analysis is applied to a set of data obtained from on-ship measurement, and a match to the model obtained via curve fitting. Independent assessment supports the model, which yields the decrement of both ringing processes, and the likely maximum impulse amplitude.     

A Model for Assessing the Impact of an Impulsive Noise Process on Land-Mobile Communication

This paper develops a statistical model with which the impact of a given noise random process upon a land-mobile communication system (LMCS) can be assessed. This model is useful for computing an upper bound for the fraction of communication-system messages which are affected by any given EMI at any given interference level. Applications of the model include, for example, bounding the interference effects on land-mobile communication of the EMI produced by arbitrary electrical apparatus.     

冲击噪声环境下的快速实值算法

在冲击噪声环境中,包括MUSIC、ESPRIT和MNM在内的传统DOA算法估计性能急剧下降甚至失效,因此出现了一些基于分数低阶矩的稳健性算法,例如ROC-MUSIC和FLOM-MUSIC等。虽然在冲击噪声环境下,这些稳健性算法具有很好的工作性能,但是这些算法需要进行计算量较大的复数特征分解,从而不适宜实现DOA的快速有效估计。为了解决这一问题,提出了一种快速实值算法(FRA),由于该算法可在实数域工作并且不需要进行特征分解,所以它的计算量远小于现有算法,在同等条件下更有利于快速地估计DOA。计算机仿真证明该算法具有优良的DOA估计性能,适宜在冲击噪声环境下应用。     

On Impulsive Noise from Shinkansen

Measurements of impulsive noise radiating from individual bullet trains on the New Tokaido Line (called Shinkansen in Japanese) have been performed with the APD-CRD measuring apparatus using dipole antennas of vertical and horizontal types. Both an APD and a CRD have been simultaneously measured in a narrowband and at two frequencies of 50 and 100 MHz for noise samples taken in time succession for individual bullet trains. Based on the analysis of these measured APD's and CRD's, the following remarkable results have been obtained: APD's and CRD's, together with the parameters derived from individual APD's, average, rms, antilog of noise amplitudes, and the statistical parameter V0.1, can be grouped into three different environments of train speed and acceleration or deceleration. on. A model for the impulsive noise is presented, saying that any elementary section of overhead electric wire radiates impulses with amplitudes varying randomly during the time interval when it makes contact with pantographs on the top of vehicles. Good fits are shown between time variations of values of the statistical parameter V0.1 obtained as individual trains pass in front of the measuring site, and those of a certain related electric field calculated based on this model.     

大气噪声模型参数的非线性回归估计

Class B噪声模型是描述大气噪声的一种很好的统计物理模型。该文采用非线性回归算法估计Class B模型的参数。该算法从Class B噪声模型的特征函数出发,推导非线性回归模型,并优化算法迭代过程。同时设计了初始值估计方案,加速了算法的收敛。并采用特殊设计的序列计算对数特征函数,解决了特征函数估计的零点波动的问题。仿真和实测结果表明,该算法收敛快,精度高,有很高的实用价值。     

冲激噪声中的谐波恢复

谐波恢复是信号处理中的基本问题,在各种情况下的谐波恢复问题被广泛地研究了。SαS过程由于能很好地描述许多具有冲激特性的信号,因而受到了日益重视。文研究了复各向同性的白SαS噪声中的谐波恢复问题,利用SαS过程的性质,给出了一种基于子空间方法的频率估计算法。该算法与数据矩阵法和分数低阶矩法作了比较,仿真结果显示了所给算法的优越性。     

Azimuthal Variation of Measured HF Noise

HF noise (2-8 MHz) as a function of azimuth, frequency, and time of day was measured in England during the winter of 1966-1967. For a given frequency interval eight unequal azimuthal sectors (with five sectors between 45°-180°) were sampled each four hours in a standardized fashion. Power levels for the tenth, fiftieth, and ninetieth percentiles were derived and plotted. The results provide the integrated total external noise (both local and propagated). In addition to the well-known distinctive diurnal and frequency changes, a marked variation with azimuth is present. A separate examination of noise intensities measured simultaneously from several azimuths reveals strong differences with azimuth. The investigation indicates that noise levels as a function of azimuth are needed and are the ones to be applied to practical HF systems.     

Digital Signal Disturbed by Impulsive Noise

This paper presents and comments on test results and measurement procedures carried out mainly in the laboratory to investigate the degree of immunity of DTV reception in the presence of impulse noise. The objective of these tests was to compare the resilience to this type of noise provided by the DTV standards: ATSC, DVB-T and ISDB-T. The field test in the city of SÃo Paulo, Brazil, showed a high and unforeseen rate of places presenting considerable degradation caused by impulsive noise. Previous studies do not reflect the reality of the impulse noise found in the Brazilian environment. Under these circumstances, a need arises for simulating interference conditions caused by ignition motors, hairdryers, blenders, etc, in the laboratory. Our laboratory tests utilized an impulse noise generator that was constructed especially to emulate ignition noise, but which was shown to be equally satisfactory in emulating other kinds of impulse noise. This paper also describes the operating principles and specifications of the impulse noise generator.     

Impulsive Noise Characterization of In-Vehicle Power Line

Impulsive noise can have a great influence on the performance of in-vehicle power line communication systems. Intensive noise measurements in the time domain were thus carried out on five different vehicles. Preliminary trials were first made on a stationary vehicle and the motor idling, but the characteristics of the measured low-amplitude pulses greatly vary from one car to another. We thus emphasize the characteristics of high-amplitude pulses, greater than 70 mV, observed when the vehicles were moving in traffic, during a 20-min trip. Noise is statistically characterized in terms of duration, frequency content, peak amplitude, and time interval between successive pulses. Stochastic models based on mathematical distribution functions and fitting the experimental distribution of the various pulse characteristics are proposed. It has been found that interarrival time, i.e., the time interval between two successive pulses, is rather short and would be thus the most critical parameter when optimizing the power line communication physical layer.      

A Statistical Technique for the Treatment of Rarely Occurring Impulsive Noise

This treatment of rarely occurring impulsive noise is based upon the development of probability distributions for the peaks of impulses incident on a receptor data bus. Monitoring equipment designed to fit in restricted shipboard conditions was used to take long-term measurements of the common-mode voltage levels on data bus lines on board two ships. Impulses registered at the monitoring point were seen to be clustered in the form of bursts. Damped ringing of unterminated cable shields was put forward as one of the main mechanisms causing impulse clustering. The measured results were compared with the theory and excellent matches were achieved.     

Atmospheric Noise Study Program

Replacement of noise grade maps by a computer program will give more accurate results than are now obtained. The means for accomplishing the change are discussed.     

短波宽带信道中噪声与干扰建模

短波通信系统依靠电离层传播,具有通信距离远,灵活性高,抗干扰性强,成本低廉等特点,是一种重要的国防军事通信手段。传统短波通信受电离层特性影响而有效带宽较窄,导致数据传输速率极低。因此,提高信道容量实现高速数据传输的短波宽带通信系统越来越受到重视。短波宽带信道建模是短波宽带通信系统正常发挥性能的关键,对短波宽带通信系统的设计与实际应用具有重要的实际意义。结合现有短波宽带信道的衰落特性模型,介绍了短波宽带信道噪声和干扰模型,并进行了比较和可靠性分析,发现现有模型形式比较单调统一,但和实际测量数据一致,能有效描述短波宽带通信中信道噪声与干扰特性,模型已经比较完善。最后,提出了进一步研究的重点方向。     

脉冲噪声下一种自适应ASR稳健滤波方法

在基于alpha稳定分布模型的脉冲噪声处理领域中,经典滤波方法多采用Cauchy分布和Meridian分布等alpha稳定分布特例,其脉冲抑制能力有限。对此,该文基于M估计理论和$ {\rm{AS}}\alpha {\rm{S}} $分布模型,构造稳健滤波代价函数簇,提出ASR稳健滤波方法,利用影响函数分析其稳健性,构建稳健滤波的统一理论基础,将Myriad滤波,Meridian滤波统一起来。给出线性度参数表达式,并采用阈值选择法实现自适应选择。此外,提出AS-FT滤波方法,以线性调频(LFM)信号在脉冲噪声下的参数估计为例,表明ASR滤波方法的稳健性。仿真实验表明,ASR稳健滤波方法,与中值滤波、Myriad滤波、分数低阶等传统的稳健滤波方法相比,具有良好的鲁棒性。     

Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed.     

Revision of Atmospheric Noise Data

It is suggested that noise grade maps may be given for two frequencies rather than one to improve the accuracy of predictions. Further, predictions should be given for spot hours rather than on a time block, basis as the time block concept has serious shortcomings.     

脉冲噪声下一种自适应ASR稳健滤波方法

在基于alpha稳定分布模型的脉冲噪声处理领域中,经典滤波方法多采用Cauchy分布和Meridian分布等alpha稳定分布特例,其脉冲抑制能力有限.对此,该文基于M估计理论和ASαS分布模型,构造稳健滤波代价函数簇,提出ASR稳健滤波方法,利用影响函数分析其稳健性,构建稳健滤波的统一理论基础,将Myriad滤波,Meridian滤波统一起来.给出线性度参数表达式,并采用阈值选择法实现自适应选择.此外,提出AS-FT滤波方法,以线性调频(LFM)信号在脉冲噪声下的参数估计为例,表明ASR滤波方法的稳健性.仿真实验表明,ASR稳健滤波方法,与中值滤波、Myriad滤波、分数低阶等传统的稳健滤波方法相比,具有良好的鲁棒性.     

A Simple Analytical Model for the Envelope Distribution of a Sinusoidal Carrier in Atmospheric Radio Noise

A recent article by Omura and Shaft [1] proposed modeling atmospheric radio noise as a narrow-band process having a lognormal envelope distribution. Based on such a model, an approximate expression is derived for the envelope probability distribution of a sinusoidal carrier in atmospheric radio noise. The results are compared with measured distribution of the instantaneous amplitude out of a wide-band envelope detector Watt and Plush [2], and show good agreement over the range of input carrier-to-noise ratios for which measurements were made.     

Impulsive Noise in Noncoherent M-ary Digital Systems

This concise paper analyses the performance of noncoherentM-ary digital systems in presence of a generalized stationary Poisson impulsive noise process, with a receiver operating as a maximum likelihood detector in white Gaussian interference. Methods to bound the error probability for ASK, PSK, and FSK systems in the cases where the noise is impulsive and quasi-Gaussian are described and the results discussed.