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A fifth-order Volterra kernal estimation algorithm for a bandpass nonlinear system was derived.

Space-time block codes (STBCs) from coordinate interleaved orthogonal designs (CIODs) offer several advantages including full-diversity and single-symbol decodability. In an effort to assess their performance in quasi-static frequency- nonselective i.i.d, Nakagami-m fading channels, we analyze the error rate, outage capacity, and information outage probability. First, based on an accurate closed-form formula for the average symbol pairwise error rate (SPER). we derive tight union upper and lower bounds on the symbol-error rate (SER). Second, we apply Gaussian and Gamma approximations to provide closed- form expressions for the outage capacity. Third, using high signal-to-noise ratio (SNR) and moment-matching approximation techniques, we also derive accurate closed-form approximations for the information outage probability (IP). Finally, we show that STBCs from CIODs provide fall-diversity by deriving SER-based and IOP-based asymptotic and instantaneous diversity orders, Monte-Carlo simulations show that the analytical results agree with simulation experiments. [ABSTRACT FROM AUTHOR]

International standard bodies have specified an instrument capable of detecting and assessing the severity of lighting flicker, which is called a flickermeter. However, a deficiency with regard to flicker caused by high-frequency interharmonics has been reported in the recent literature. In this paper, another deficiency of the International Electrotechnical Commission (IEC) flickermeter with regard to low-frequency interharmonics, whose frequencies are below the difference between the fundamental frequency and the cutoff frequency of a bandpass filter of the IEC standard flickermeter, will be discussed and illustrated based on analysis and numerical experiments. A new approach based on down-up sampling in the discrete-time sample domain is also proposed to address the flicker-detection problem associated with interharmonics. We demonstrate the efficacy of the proposed method by a comparison with the current flickermeter standard in the presence of interharmonics. [ABSTRACT FROM AUTHOR]

We analyze the effect of time-selective fading on the information outage probability and diversity order of Alamouti transmit diversity with joint maximum likelihood, symbolwise linear maximum likelihood, zero forcing, and decision feedback detectors. In contrast to the existing bit error rate (BER) and bit error outage (BEO) analyses, we evaluate the information outage probabilities and corresponding asymptotic diversity orders for each detector. From the theoretical and simulation results, we demonstrate that, when the channel is time selective, the asymptotic diversity orders for the four detectors approach two, zero, one, and one, respectively. [ABSTRACT FROM AUTHOR]

This paper develops a signal processing, time-frequency analysis-based analytic solution to locate transient capacitor switching disturbances. The flow of transient disturbance energy caused by the capacitor switching is determined by the time and frequency localized phase difference. Cross time-frequency analysis provides time- and frequency-localized phase difference between the transient voltage and current disturbance waveforms which determine the direction of transient disturbance energy flow. The time and frequency localization properties of the proposed scheme allows one to expand the application to complicated power distribution systems without knowledge of system parameters, capacitor size, and configuration. The proposed scheme has been verified by the Electromagnetic Transients Program simulation for all possible spatial locations of the capacitor switching. [ABSTRACT FROM AUTHOR]

Per-flow congestion control helps endpoints fairly and efficiently share network resources. Better utilization of network resources can be achieved, however, if congestion management algorithms can determine when two different flows share a congested link. Such knowledge can be used to implement cooperative congestion control or improve the overlay topology of a P2P system. Previous techniques to detect shared congestion either assume a common source or destination node, drop-tail queueing, or a single point of congestion. We propose in this paper a novel technique, applicable to any pair of paths on the Internet, without such limitations. Our technique employs a signal processing method, wavelet deizoising, to separate queueing delay caused by network congestion from various other delay variations. Our wavelet-based technique is evaluated through both simulations and Internet experiments. We show that, when detecting shared congestion of paths with a common endpoint, our technique provides faster convergence and higher accuracy while using fewer packets than previous techniques, and that it also accurately determines when there is no shared congestion. Furthermore, we show that our technique is robust and accurate for paths without a common endpoint or synchronized clocks; more specifically, it can tolerate a synchronization offset of up to one second between two packet flows. [ABSTRACT FROM AUTHOR]

By combining multiple-input multiple-output (MIMO) communication with the orthogonal frequency division multiplexing (OFDM) modulation scheme, MIMO-OFDM systems can achieve high data rates over broadband wireless channels. In this paper, to provide a bandwidth-efficient solution for MIMO-OFDM channel estimation, we establish conditions for channel identifiability and present a blind channel estimation technique based on a subspace approach. The proposed method unifies and generalizes the existing subspace-based methods for blind channel estimation in single-input single-output OFDM systems to blind channel estimation for two different MIMO-OFDM systems distinguished according to the number of transmit and receive antennas. In particular, the proposed method obtains accurate channel estimation and fast convergence with insensitivity to overestimates of the true channel order. If virtual carriers (VCs) are available, the proposed method can work with no or insufficient cyclic prefix (CP), thereby potentially increasing channel utilization. Furthermore, it is shown under specific system conditions that the proposed method can be applied to MIMO-OFDM systems without CPs, regardless of the presence of VCs, and obtains an accurate channel estimate with a small number of OFDM symbols. Thus, this method improves the transmission bandwidth efficiency. Simulation results illustrate the mean-square error performance of the proposed method via numerical experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a new switched MIMO system where the MIMO includes both diversity-based MIMO and spatial multiplexing MIMO (SM-MIMO). The proposed scheme is a closed-loop system where the feedback bits are sent back to the transmitter to indicate the channel quality. The switching operation is employed among groups of a certain number of transmit antennas. For diversity-based MIMO systems, the switching operation aims to improve the link performance, while the goal of the switching for the SM-MIMO systems is to increase the data rate. The authors analyze and optimize the proposed systems and show that there is considerable benefit in terms of performance and practical use. [ABSTRACT FROM AUTHOR]

For reasonable power quality assessment of transient disturbances in electric power systems, new transient power quality indices are developed based on a signal processing technique, time-frequency analysis. Based on the time-frequency distribution of a transient disturbance, a set of time-frequency based power quality indices are developed. In this paper, the instantaneous disturbance energy ratio, normalized instantaneous disturbance energy ratio, instantaneous frequency, and instantaneous K-factor are suggested for transient power quality assessment. Time-frequency based power quality indices allow one to quantify the effects of transient disturbances with high-resolution and accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains. The approach rests upon time-frequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. This latter capability is of particular interest when testing communication cables and systems. Sensitivity in detecting the reflected signal is provided by a time-frequency cross-correlation function. The approach is verified by experimentally locating various types of faults, located at various distances, in RG 142 and RG 400 coaxial cables. [ABSTRACT FROM AUTHOR]