60,072 research outputs found

    Classical and Bayesian Linear Data Estimators for Unique Word OFDM

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    Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM signaling concept, where the guard interval is built of a deterministic sequence - the so-called unique word - instead of the conventional random cyclic prefix. In contrast to previous attempts with deterministic sequences in the guard interval the addressed UW-OFDM signaling approach introduces correlations between the subcarrier symbols, which can be exploited by the receiver in order to improve the bit error ratio performance. In this paper we develop several linear data estimators specifically designed for UW-OFDM, some based on classical and some based on Bayesian estimation theory. Furthermore, we derive complexity optimized versions of these estimators, and we study their individual complex multiplication count in detail. Finally, we evaluate the estimators' performance for the additive white Gaussian noise channel as well as for selected indoor multipath channel scenarios.Comment: Preprint, 13 page

    Financial decentralization in Ukraine: prerequisites, problems, prospects

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    The purpose of the article is to analyze the prerequisites, advantages, problems and prospects for the development of the processes of financial decentralization in Ukraine. Initially, the article reveals the features of the federal and unitary arrangements of states. As research has shown, the principles of fiscal federalism have been increasingly used by unitary states. The legislative and normative legal acts regulating the implementation of the decentralization policy in Ukraine are justified and given. Characteristics of the formation of new structures, such as: united territorial societies and their sources of financing are characterized. Changes in incomes in local budgets as a result of decentralization are analyzed, and their significant growth is observed. The mechanism of horizontal leveling of the tax ability of territories has been developed, which helps to remove imbalances and unevenness, most of the budgets of Ukraine are recipients of budgetary funds, since they receive a basic subsidy. The influence of the development of information technologies on entrepreneurial activity in small towns and villages is determined. Information technology is a tool of points of growth of territories. Decentralization will not gradually increase due to urbanization processes, but will be accompanied by new development mechanisms, where the labor force and the means of production will unite and help create a qualitatively new environment

    MIMO pre-equalization and DFE for high-speed off-chip communication

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    In this contribution, we present a multiple-input multiple-output (MIMO) transceiver scheme for high-speed chip-to-chip communication over low-cost electrical interconnects. Linear MIMO pre-equalization at the transmitter is combined with decision feedback equalization (DFE) at the receiver to counteract the adverse effect of inter symbol interference (ISI) and crosstalk (XT). Considering an energy constraint at the transmit side, we derive elegant closed-form expressions for the equalization filters under a minimum mean square error (MMSE) criterion. Numerical analysis shows that the combination of linear MIMO pre-equalization and MIMO DFE allows to significantly improve the reliability of future high-speed off-chip communication

    A Closed-Form Approximated Expression for the Residual ISI Obtained by Blind Adaptive Equalizers with Gain Equal or Less than One

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    In this paper we propose for the real and two independent quadrature carrier case, a closed-form approximated expression for the achievable residual Inter-Symbol Interference (ISI) that depends on the step-size parameter, equalizer’s tap length, equalized output gain, input signal statistics, channel power and SNR. This expression is valid for blind adaptive equalizers, where the error that is fed into the adaptive mechanism which updates the equalizer‘s taps can be expressed as a polynomial function of order three of the equalized output and where the gain between the input and equalized output signal is less than or equal to one, as is in the case of Godard (gain = 1) and WNEW (gain < 1) algorithm. Since the channel power is measurable or can be calculated if the channel coefficients are given, there is no need to carry out simulation with various step-size parameters in order to reach the required residual ISI. In addition, we show two new equalization methods (gain dependent), which have shown to have improved equalization performance compared to Godard and WNEW

    Federal Aid to Schools: Its Limited Future

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    A brief history of the development of the limited-purpose Federal education programs is used as background to make a case for the diminishing likelihood of a major Federal initiative Beyond the presently enacted categorical grant programs. It is noted that present limited Federal programs, centering on education for the disadvantaged have been significant, are being improved and will likely remain the model for future Federal interventions

    Harnessing machine learning for fiber-induced nonlinearity mitigation in long-haul coherent optical OFDM

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    © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Coherent optical orthogonal frequency division multiplexing (CO-OFDM) has attracted a lot of interest in optical fiber communications due to its simplified digital signal processing (DSP) units, high spectral-efficiency, flexibility, and tolerance to linear impairments. However, CO-OFDM’s high peak-to-average power ratio imposes high vulnerability to fiber-induced non-linearities. DSP-based machine learning has been considered as a promising approach for fiber non-linearity compensation without sacrificing computational complexity. In this paper, we review the existing machine learning approaches for CO-OFDM in a common framework and review the progress in this area with a focus on practical aspects and comparison with benchmark DSP solutions.Peer reviewe
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