Performance evaluation of FSK and CPFSK optical communicationsystems: a stable and accurate method

The modified moments method for evaluating the performance of coherent optical FSK and CPFSK systems is presented. Since the classical procedure becomes ill-conditioned as the order of the moments increases, we consider the construction of Gaussian quadrature rules (GQR) from the modified moments. The analysis accounts for the influences of IF bandwidth, transmitter and local oscillator laser phase noise, postdetection filters, and additive Gaussian noise. It is found that the proposed approach is a highly reliable and efficient method for calculating the error probability. A comparison with results obtained from the Gaussian quadrature rule, Gaussian approximation method, and analytical approximation formulas shows that this technique is very accurate. Analytical expressions are derived for FSK and CPFSK receivers which include polarization and phase diversity techniques. The use of numerical programming to avoid many unnecessary computations is discussed. This evaluation method can be used to account for the effects of crosstalk in multichannel systems and the influence of error-control codes     

A deterministic particle method for the kinetic model of semiconductors: The homogeneous field model

We present a new particle method for the simulation of the semiconductor Boltzmann equation—the weighted particle method. This method differs from the Monte-Carlo method by the approximation of the collision operator—we allocate each particle a weight which varies in time according to the collision integral. This integral is evaluated by means of a quadrature formula, which does not require the use of random numbers. The aim of this paper is to show that this method gives accurate results on physically relevant problems. Linear as well as non-linear collision integrals can be handled the same way by this method. Precise representations of the distribution functions are available, which allow a good insight into the physical processes. In this paper, we only consider the homogeneous field model with an emphasis on the collision operator. Numerical results are presented with a comparison with the Monte-Carlo method.     

Rake-MMSE-equalizer performance for UWB

The performance of a joint rake and minimum mean square error (MMSE) equalizer receiver for high data rate ultra-wideband communications is studied in this paper. The proposed receiver combats inter-symbol interference by taking advantage of the rake and equalizer structure. The receiver performance is investigated using a semianalytical approach and Monte-Carlo simulation. The effects of the number of rake fingers and equalizer taps on the error performance are examined.     

A Modified Simulation-Based Multi-Signal Modeling for Electronic System

Multi-signal model is an effective modeling method applicable to large scale complex system. In this paper, an improved simulation-based modeling method for parametric fault is put forward. Two times of Monte-Carlo simulation are done in normal tolerance. Based on the estimated sample variance obtained from the first Monte-Carlo simulation, the analysis runs of the second Monte-Carlo is determined empirically to reduce the simulation cost. Then the statistical distribution of data from the second Monte-Carlo simulation is judged qualitatively by normality test. After that, an adaptive method is adopted to estimate the threshold range for signal feature in normal state, which can improve modeling precision. At last, the effectiveness of the proposed method is verified and the performances are compared to manifest the advantage of the proposed method. The work in this paper is valuable for future further research of complex system test and diagnosis based on multi-signal.     

一种基于DTTL环的FSK定时同步方法

首先给出了现有FSK定时同步算法的优缺点,接着研究了一种基于DTTL环的FSK定时同步方法。此定时方法结构简单,且易于数字实现。最后,并利用MATLAB软件做了仿真,证明了此方法的可行性及有效性。     

一种快速的组合电路RTL功耗估算器

提出了一种快速分析组合RTL模块功耗的方法,经过建立模块功耗库,可快速计算出任意输入向量驱动的电路功耗.该方法使用泰勒一阶近似的公式模型,并在建库过程中采用Monte-Carlo模拟方法.ISCAS85 benchmark电路模拟的结果显示,该方法的误差可以在5%以内.     

Accurate performance evaluation of weakly coherent optical systems

An accurate performance evaluation approach which uses a closed-form exact analytical expression of the phase noise moments is presented. This enables one to derive a high-order Gaussian quadrature rule for the integrations needed to take into account the phase noise in the computation of error probability. A systematic comparison with results obtained through a Monte Carlo simulation shows that the approach is more accurate than previous methods. The analysis is performed on ASK and FSK heterodyne receivers with integrate-and-dump filtering, envelope detection, and optimized postdetection low-pass filtering. The feasibility of ASK and FSK heterodyne systems at bit rates comparable to the spectral line bandwidth of the laser sources is confirmed. The theory applied seems to be adequate to attack other problems, such as the evaluation of the effects of crosstalk between the FSK filters or among frequency division multiplexed channels     

一种频率编码信号瞬时频率提取新方法

针对小波变换法在提取频率编码信号脉内特征中的不足,提出了将时频重排和时频脊线相结合的时频联合分析方法。首先通过Morlet小波计算信号的小波谱,再对小波谱进行时频重排,最后由重排后的时频图提取时频脊线,得到频率编码信号的脉内特征。该方法在低信噪比下,能准确提取频率编码信号脉内特征信息。最后利用计算机仿真验证了该方法的可行性。     

Periodic switching diversity effect on co-channel interference performance of a digital FM land mobile radio

The effect of periodic switching diversity on the bit error rate (BER) performance of a binary frequency-shift keying (FSK) system in the presence of co-channel interference is described. The distribution of the signal-to-interference energy ratio per bit presented to the FM detector is found and the diversity effect on the BER performance in a Rayleigh fading environment is analyzed. The diversity effect on the BER performance in a Manchester-coded FSK system with limiter-discriminator detection is verified by laboratory simulation tests using a Rayleigh fading simulator.     

高阶累积量和分形理论在信号调制识别中的应用研究

提出了将信号高阶累积量和分形盒维数相结合的特征提取方法。信号高阶累积量特征具有良好的抗噪性能,被广泛应用于调制识别。2ASK和BPSK的高阶累积量、以及2FSK,4FSK,8FSK的高阶累积量相等,使得只提取信号高阶累积量不足以区分信号。针对这一问题,引入信号的分形盒维数,提取信号的高阶累积量和分形盒维数构成联合特征参数,构建级联神经网络分类器,对信号进一步进行分类。对2ASK, 4ASK, BPSK, 4PSK, 2FSK, 4FSK, 16QAM七种信号进行了仿真,结果表明,该方法提取的特征参数计算复杂度低,具有较好的抗噪性能。在信噪比不低于5dB、测试样本数不少于200的条件下,正确识别率达到了85%以上。      

FSK Bit Synchronization by Combined AM

A bit-synchronization method in a frequency-shift-keying (FSK) data channel has been investigated experimentally and results are presented. The bit-timing information is conveyed by a square wave, with a frequency of half the data bit rate, modulated onto the signal amplitude. It has been shown that for a system using a peak-peak-to-peak frequency deviation of 0.7 times the bit rate and a receiver bandwidth restricted to 1 times the bit rate, the minimum error rates are obtained for an amplitude modulation index of 0.1. Further, in order for the system to have a performance comparable with an ordinary FSK system with the same values of frequency deviation and receiver predetection bandwidth and with perfect timing available at the receiver, an additional signal power of 0.9 dB is needed.     

A Modified Monte-Carlo Simulation Technique for the Evaluation of Error Rate in Digital Communication Systems

Digital communication systems are frequently operated over nonlinear channels with memory. The analysis of the performance of these systems is difficult and no complete analytical treatment of the problem has been obtained before. Several recent efforts have been directed toward the computation of error probabilities via Monte-Carlo simulation using a complete system model. These simulations require excessively large sample sizes and are not practical for estimating very low values of error probabilities. This paper presents a modified Monte-Carlo simulation technique for estimating error probabilities in digital communication systems operating over nonlinear channels. An importance-sampling technique is used to modify the probability density function of the noise process in a way to make simulation possible. Theoretical results as well as realistic examples are presented, showing that the number of samples needed for simulation is reduced considerably.     

Towards a real-time minimally-invasive vascular intervention simulation system

Recently, foundations rooted in physics have been laid down for the goal of simulating the propagation of a guide wire inside the vasculature. At the heart of the simulation lies the fundamental task of energy minimization. The energy comes from interaction with the vessel wall and the bending of the guide wire. For the simulation to be useful in actual training, obtaining the smallest possible optimization time is key. In this paper, we, therefore, study the influence of using different optimization techniques: a semianalytical approximation algorithm, the conjugate-gradients algorithm, and an evolutionary algorithm (EA), specifically the GLIDE algorithm. Simulation performance has been measured on phantom data. The results show that a substantial reduction in time can be obtained while the error is increased only slightly if conjugate gradients or GLIDE is used.     

Optimal noncoherent detection of FSK signals transmitted overlinearly time-selective Rayleigh fading channels

Linearly time-varying fading models are used to investigate noncoherent detection of frequency shift keying (FSK) signals transmitted over frequency-flat fading channels. The structure of the optimal noncoherent FSK detector is derived and a novel analytical technique is proposed to compute the error performance of noncoherent FSK detectors in fast fading. Error performance results obtained by computer simulation are in excellent agreement with the analytical predictions     

对FSK信号最佳干扰效果及效能研究

这里介绍了FSK调制信号的优缺点和实际应用情况,分析了FSK信号解调的特点,并建立了通信系统模型和各种干扰样式模型。基于相干解调情况下,分析了各种干扰样式情况下的理论误码率,通过仿真和实际测试得出了各种干扰样式对FSK信号的干扰效果。其次分析了通信信号和干扰信号的传播损耗,并计算了在不同通信距离和干扰距离时通信接收机的干信比,最终得出了最佳干扰样式下的效能。     

On improved confidence bounds for system reliability

In this paper, new bounding strategies are presented to improve confidence interval estimation for system reliability based on component level reliability, and associated uncertainty data. Research efforts have been focused on two interdependent areas: 1) development & improvement of analytical approaches for quantifying the uncertainty associated with the system reliability estimate when data regarding component reliability is available; and 2) based on these analytical approaches, generating statistical inference methods that can be used to make accurate estimations about the reliability of a system. The analytical approach presented relies on a recursive rationale that can be applied to obtain the variance associated with the system reliability estimate, provided the system can be decomposed into a series-parallel configuration. The bounding procedure is independent of parametric assumptions regarding component time to failure, and can be applied whenever component reliability data are available. To assess the validity of the proposed procedure, three test cases have been analyzed. For each case, Monte-Carlo simulation has been used to generate component failure data, based on nominal component reliability values. Based on these simulated data, lower bounds have been constructed, and then compared against nominal system reliability to generate an expected confidence level. The results obtained exhibit a significant improvement in the accuracy of the confidence intervals for the system reliability when compared with existing approximation methods. The procedure described is effective, relatively simple, and widely applicable.     

FSK避障雷达的APFFT测距及误差补偿

由于频移键控(Frequency-Shift Keying,FSK)体制避障雷达在动目标分辨与测量上的明显优势,基于FSK体制避障雷达系统的基本原理和结构,通过Matlab建立了测量系统与信号模型,使用全相位快速傅里叶变换（All-phase Fast Fourier Transformation,APFFT)算法进行了相关测量仿真和测量参数计算。通过对不同条件下的仿真结果分析,得出了测量结果误差产生的原因,并提出了相应的误差补偿方法,大大降低了测量误差,使得相对误差降低至0.1%以下。另外,还对多目标的分辨与测量进行了仿真。     

A Signalling Scheme for Frequency-Shift-Keying Channels With Noiseless Feedback

Stochastic approximation is applied to the design of a frequency-shift-keying (FSK) feedback scheme. FSK signals are transmitted over a channel with additive white Gaussian noise (AWGN) and the frequency estimate is fed back to the transmitter. A signaling scheme similar to the Schalkwijk-Kailath amplitude-shift-keying (ASK) scheme is derived and performance curves are presented. The scheme performs much better than ASK or FSK without feedback; however, under the average-power limitation, its performance is, in general, inferior to that of ASK feedback schemes.     

一种重要抽样仿真方法的研究及应用

介绍了蒙特-卡洛仿真原理,分析了改进型的蒙特-卡洛仿真即重要抽样(IS)的原理及其在通信中的应用,特别是在高速光纤通信的偏振模色散(PMD)仿真中的应用价值.实验证明,采用重要抽样的仿真方法可以得到大差分群时延(DGD)值的小概率事件,并且系统配置比用蒙特-卡洛的仿真方法简单得多.     

Prony and Polynomial Approximations for Evaluation of the Average Probability of Error Over Slow-Fading Channels

A novel and simple semianalytical method for evaluating the average probability of transmission error for digital communication systems that operate over slow-fading channels is presented. The proposed method applies a sum of exponentials fit known as the Prony approximation to the conditional probability of error. Hence, knowledge of the moment-generating function of the instantaneous signal-to-noise ratio (SNR) at the detector input can be used to obtain the average probability of error. Numerical results show that knowledge of the conditional probability of error at only a small number of points and the sum of only two exponentials are sufficient to achieve very high accuracy; the relative approximation error of the exact average probability of error is less than 6% in most of the cases considered. Furthermore, a piecewise polynomial approximation of the conditional probability of error is investigated as an alternative to the sum of exponentials fit. In this case, knowledge of the partial moments of the instantaneous SNR at the detector input can be used to obtain the average probability of error. Numerical results indicate that, to achieve good accuracy, the method based on the polynomial approximation requires that the product of the polynomial degree and the number of approximation subintervals be larger than 10.