GRID-Based Power Measurement in Digital Wireless Communication Systems

The combined use of multitaper estimation and wavelet thresholding has proved to be a very powerful digital- signal-processing algorithm in achieving the true power spectrum of signals that are peculiar to digital wireless communication systems and in ultimately carrying out accurate and repeatable power measurements. Nevertheless, the induced computational burden is too heavy. This paper mainly shows that GRID, which is currently one of the key technologies in deploying global-scale computing infrastructures, can make the aforementioned algorithm enforceable in a real-time context. A GRID computing-based approach for power measurement in digital wireless communication systems is proposed, which allows high levels of accuracy and repeatability in a significantly reduced measurement time. After a concise outline of the measurement algorithm, all of the adopted hardware and software strategies are described in detail. Major results concerning performance assessment and actual measurements are also given and discussed.     

Power Measurement in DVB-T Systems: On the Suitability of Parametric Spectral Estimation in DSP-Based Meters

Performance assessment and large-scale monitoring of terrestrial digital video broadcasting (DVB-T) transmission apparatuses are currently a pressing need due to the rapid growth of related broadcasting networks in many countries. Power measurements, in particular, play a very important role since RF and IF signal power, RF channel power, RF and IF power spectrum, noise (or unwanted) power, and power efficiency are relevant parameters to be measured as accurately as possible. Although modern spectrum analyzers and high-performance vector signal analyzers exhibit satisfying accuracy and repeatability, their cost, weight, and size make them unsuitable for the purpose. This paper is focused on the design and realization of a digital signal processing-based meter for power measurement in DVB-T systems that is capable of granting good accuracy, satisfying repeatability, reduced measurement time, and cost effectiveness. This paper deals with the digital signal processing algorithm to be implemented in the meter, paying attention to parametric power spectral density (PSD) estimators for their reduced memory requirement and potentially limited computational burden. In particular, a parametric estimation algorithm that is capable of assuring a fast measurement rate is implemented and made operative. The simulation and emulation stages are properly designed to regulate the most relevant parameters of the adopted PSD estimators according to the specific features of the signals involved; a number of experiments on actual DVB-T signals are conducted, the results of which are compared to those provided by competitive measurement solutions.      

A new method for power measurements in digital wireless communication systems

Repeatability problems, usually accompanied by low accuracy, are often experienced in power measurements, especially in those concerning spread spectrum signals, peculiar to digital wireless communication systems, and involving a specified frequency range. For this concern, a new method for power measurements is presented. The method applies original and straightforward digital signal-processing algorithms to the input signal power spectrum, preliminarily provided by optimized versions of well-known estimators, such as those based on weighted overlapped segment averaging and multitaper approaches. The outcomes of many experiments, conducted on spread spectrum signals of third-generation telecommunication systems, confirm the efficacy of the proposed method in assuring reliable and accurate results in various types of power measurement.     

A wavelet packet transform-based approach for interference measurement in spread spectrum wireless communication systems

This paper mainly concerns interference measurement in spread spectrum, wireless communication systems. A new digital signal-processing method is proposed, which proves to be nonintrusive and independent of the specific system considered. Thanks to the properties of the wavelet packet transform, the method is capable of extracting the interference that occurred from the spread spectrum signal, thus ensuring accurate interference magnitude and frequency estimates also in critical conditions: interference level much smaller than that characterizing the spread spectrum signal, and interference spectral content very close to the carrier frequency of the considered system.     

True-Power Measurement in Digital Communication Systems Affected by In-Channel Interference

A new cyclostationarity-based method for power measurement in digital communication systems in the presence of in-channel interference is proposed. The new method takes advantage of the signal-selective properties typical of algorithms based on cyclic spectral analysis. The true-power measure is achieved from the noisy data by estimating the cyclic spectrum of the desired signal at a cycle frequency not shared with noise and interference. The performance of the method is evaluated through several experiments on spread-spectrum and pulse-amplitude-modulated signals and with reference to different types of interfering signals. The method exhibits very good performance even when the desired and interfering signals completely overlap in both temporal and spectral domains.      

Power Measurements in DVB-T Systems: New Proposal for Enhancing Reliability and Repeatability

The rapid growth of digital video broadcasting by terrestrial transmission (DVB-T) has created the need for new measurement methods, as well as new test equipment that is capable of providing reliable and repeatable results. Some problems are, in fact, being experienced with power measurements, particularly with those involving the integration of the input signal power spectrum over a certain frequency interval. Trying to give a proper answer to the cited need, a digital signal processing method, which has already been proposed in the literature and specialized for power measurements in spread spectrum systems, is optimized here to be operative in the presence of DVB-T signals as well. Suitable stages, in simulation and emulation environments, are designed and applied to optimally regulate key parameters of the method, thus making it assure negligible bias and high repeatability in most operative conditions. The results of a number of experiments on actual DVB-T signals also give evidence of the method's efficacy with respect to competitive measurement solutions.      

Reducing the peak-to-average power ratio using unitary matrix transformation

A theoretical analysis is presented to show that in orthogonal frequency division multiplexing systems, the peak-to-average power ratio (PAPR) can be reduced by performing a unitary matrix transformation on the input vector of N symbols. The authors also prove that this transformation does not degrade the bit error rate (BER) or power spectral density (PSD) performance. Based on this, the inverse discrete Fourier transform matrix is proposed as the unitary matrix to reduce the PAPR. The simulation results show that the proposed scheme can obtain significant PAPR reduction while maintaining good performance in the BER and the PSD. To further evaluate the performance of the proposed scheme, the authors compare it with some well known PAPR reduction techniques by simulations. It is demonstrated that the proposed scheme can offer better system performance and achieve a better compromise with regard to the PAPR reduction, BER, spectral efficiency and computational complexity.     

基于PSD的强背景下光点位置探测技术研究

目前基于PSD的光电探测应用大多是以激光入射,有效信号远强于背景,为了满足更大的测量需求,本文提出了一种基于PSD的强背景下探测闪光点空间位置的方法.设计了预处理电路将PSD产生的微弱电流信号转换为电压信号并经过高速AD转换为数字信号,分析了背景信号对PSD测量结果的影响,提出了在软件中减去背景和暗电流以提取有效信号并对其进行精确计算的方法.用LED做闪光点在不同室外背景下进行了相关实验,结果表明:该方法可以实现200 kHz的高速测量,有效去除了不同背景和暗电流的影响,强背景下测量线性误差在±1.2％以内.     

On the Suitability of GRID Service Technology for Distributed Measurements Based on Complex Digital Signal Processing Algorithms

Digital signal processing algorithms are nowadays playing an increasingly more important role in most measurement processes. Furthermore, in the presence of poorly digitized data, reliable and repeatable measurement results can often be assured by complementing the adopted procedure with a suitable processing stage. The realization of a ldquocollectionrdquo of measurement algorithms to be shared among researchers and technicians who work on similar topics should, thus, be advisable. Complex algorithms, however, suffer from critical drawbacks, in terms of computational burden and hardware resources, when applied to very long acquired records. The authors suggest the adoption of GRID Service as an innovative solution to provide researchers with a ldquocollectionrdquo of measurement algorithms and concurrently overcome the cited drawbacks. GRID Service is a new hardware/software approach that is capable of merging the higher computational performance of parallel GRID computing with key mechanisms and standards of Web service. It would be very possible to migrate complex measurement algorithms into services that are available and accessible on the Internet. As an application example, the authors present a GRID service mandated to power measurement in digital wireless communication systems.     

数显仪特征部分的误差分析

评价了数显仪特征部分误差分析方法,包括:采样/保持电路、模数转换单元的误差,并通过典型例子和列表数据分析了多种误差源及其综合计算方法.此外,还通过对现代动态范围内平均位误差风险因子量化(BERF)的评述,进一步探讨了传统意义上的数值化模拟系统与现代的建立在BERF-ε原理基础上的数显仪量化误差极限分析之间的关系.正因为后者建立在揭示噪声量子涨落性的直方图和量子相关性的功率谱密度测量上,所以能更客观地表征噪声的量子特性.     

Frequency Multiplication Effects on Oscillator Instability

The effects which frequency multiplication produces on the power spectral density of an oscillator is examined as a function of the multiplication ratio and the power spectral density of the phase noise process. In addition, the power spectral density (PSD) of the multiplied-up oscillation is interconnected with the frequency standard L(f). It is explicitly demonstrated how errors are introduced when one attempts to define the rms fractional frequency deviation ?f(?)/f0 and the Allan variance ?2y(?) using the measurement of L(f). Finally, the genesis of spectral spreading of the PSD due to frequency multiplication is demonstrated in such a way that this interesting and important phenomena can be grasped by the practicing engineer.     

基于无线信道IPTV业务性能的测试方法

研究了宽带无线移动通信系统的业务测试技术,提出了无线信道条件下的IPTV业务性能的测试方法,并根据该方法,搭建了一套测试系统.通过实地的测试,获得了室内/室外宽带无线信道环境下的时延、抖动、丢包率等实际的测试结果,基于测试数据,分析了系统的相关性能,同时验证了测试方法的可操作性.     

Fatigue life prediction under wide band random loading

In this paper, a method for the high‐cycle fatigue life prediction of components subjected to gaussian, stationary, wide band random loading is presented. It allows the user to evaluate the fatigue life of components subjected to uniaxial stress states directly from the stress power spectral density (PSD), avoiding onerous simulations in time domain. The proposed method can be applied to random stress processes having PSD of any shape, and the fatigue life predictions obtained are more accurate than that provided by most of the frequency domain techniques proposed in literature.     

Peak-to-average power ratio reduction using second order cone programming based tone reservation for terrestrial digital video broadcasting systems

High peak-to-average power ratio (PAPR) is a critical issue in any multicarrier systems using orthogonal frequency division multiplexing, as terrestrial digital video broadcasting (DVB). It can result in low power efficiency and large performance degradation of systems, due to the nonlinearity of high-power amplifier (HPA). A PAPR reduction method based on tone reservation technique with second-order cone programming (SOCP) approach in terrestrial DVB systems is proposed. The authors first demonstrate the superiority of the SOCP optimisation algorithm compared with an iterative gradient-based algorithm, using the current DVB-T parameters: significant PAPR reduction gains can be achieved with only a very small set of subcarriers in the useful bandwidth, making the proposed method more promising in terms of spectral efficiency. Moreover, the proposed solution presents a very good trade-off between PAPR reduction gain and mean transmitted power increase. An overall study, taking into account the limitation of the power level of the dedicated subcarriers and the evaluation of the performances in presence of a nonlinear HPA, is presented. These performances are given in terms of adjacent channel power ratio and bit error rate. The resulting PAPR reduction gain demonstrates that the relevance of the proposed method for the future DVB-T standard is straightforward.     

New formulation of Cholesky decomposition and applications in stochastic simulation

Monte Carlo simulation plays a significant role in the mechanical and structural analysis due to its versatility and accuracy. Classical spectral representation method is based on the direct decomposition of the power spectral density (PSD) or evolutionary power spectral density (EPSD) matrix through Cholesky decomposition. This direct decomposition of complex matrix usually results in large computational time and storage memory.In this study, a new formulation of the Cholesky decomposition for the EPSD/PSD matrix and corresponding simulation scheme are presented. The key idea to this approach is to separate the phase from the complex EPSD/PSD matrix. The derived real modulus matrix evidently expedites decomposition compared to the direct Cholesky decomposition of the complex EPSD/PSD matrix. In the proposed simulation scheme, the separated phase can be easily assembled. The modulus of EPSD/PSD matrix could be further decomposed into the modulus of coherence matrix (or lagged coherence matrix), which describes the basic coherence structure of stochastic process. The lagged coherence matrix is independence of time and thus remarkably improves the Cholesky decomposition efficiency.The application of the proposed schemes to Gaussian stochastic simulations is presented. Firstly, the previous closed-form wind speed simulation algorithm for equally-spaced locations is extended to a more general situation. Secondly, the proposed approach facilitates the application of interpolation technique in stochastic simulation. The application of interpolation techniques in the wind field simulation is studied as an example.     

Design of a robust and secure digital signature scheme for image authentication over wireless channels

The introduction of 3G wireless communication systems, together with the invasive distribution of digital images and the growing concern on their originality triggers an emergent need of authenticating images received by unreliable channels, such as public Internet and wireless networks. To meet this need, a content-based image authentication scheme that is suitable for an insecure network and robust to transmission errors is proposed. The proposed scheme exploits the scalability of a structural digital signature in order to achieve a good trade off between security and image transfer for networked image applications. In this scheme, multi-scale features are used to make digital signatures robust to image degradations and keydependent parametric wavelet filters are employed to improve the security against forgery attacks. This scheme is also able to distinguish tampering areas in the attacked image. Experimental results show the robustness and validity of the proposed scheme.     

基于广义置信区间的测量系统能力比较

研究了测量系统分析中对测量同一产品质量特性的两个测量系统能力的比较方法。基于广义推断法,提出了一种比较两个测量系统能力的方法。通过重复性与再现性（R&R）试验研究,利用广义推断法对两个测量系统能力的比较指数建立相应的广义置信区间,并进行计算机仿真。结果表明,基于广义置信区间的方法,可以有效地比较两个测量系统的能力。     

Spectral density of oscillator with bilinear stiffness and white noise excitation

The power spectral density of an oscillator with bilinear stiffness excited by Gaussian white noise is considered. A method originally proposed by Krenk and Roberts [J Appl Mech 66 (1999) 225] relying on slowly changing energy for lightly damped systems is applied. In this method an approximate solution for the power spectral density at a given energy level is obtained by considering local similarity with the free undamped response. The total spectrum is obtained by integrating over all energy levels weighting each with the stationary probability density of the energy. The accuracy of the approximate analytical solution is demonstrated by comparing with results obtained by stochastic simulation. It is shown how the method successfully captures the broadening of the resonance peak and the presence of higher harmonics in the power spectral density of strongly non-linear systems.     

Measurement and compensation of fictitious power undernonsinusoidal voltage and current conditions

The definitions of power are reviewed to establish a method for fictitious power measurement and to derive fictitious power compensation criteria in power systems with nonsinusoidal currents and voltages. A time-domain definition of power, using correlation techniques, is proposed. This leads to the proposal of a network parameter. A combination of digital and analog signal-processing techniques is proposed in the measurement and analysis of the components of power. The results of simulated and practical power measurements, the latter on an experimental electronic pulsewidth-modulated power converter, used for fictitious power compensation are given     

Adaptive spectral doppler estimation

In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence. The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to provide good spectral resolution and contrast even when the observation window is very short. The 2 adaptive techniques are tested and compared with the averaged periodogram (Welch's method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set of matched filters (one for each velocity component of interest) and filtering the blood process over slow-time and averaging over depth to find the PSD. The methods are tested using various experiments and simulations. First, controlled flow-rig experiments with steady laminar flow are carried out. Simulations in Field II for pulsating flow resembling the femoral artery are also analyzed. The simulations are followed by in vivo measurement on the common carotid artery. In all simulations and experiments it was concluded that the adaptive methods display superior performance for short observation windows compared with the averaged periodogram. Computational costs and implementation details are also discussed.