# Antonio NapolitanoParthenope University of Naples | Università Parthenope · Department of Engineering

Antonio Napolitano

PhD

## About

105

Publications

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2,016

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Introduction

Additional affiliations

January 2014 - March 2016

July 2013 - November 2013

June 2010 - July 2010

## Publications

Publications (105)

A new model for the electrocardiogram (ECG) signal is proposed. Specifically, the ECG signal is modeled as an amplitude-modulated and time-warped version of a cyclostationary process which is the sum of a periodic signal and a zero-mean cyclostationary term. For the proposed model, the second-order characterization is derived in both time and frequ...

Time series arising from measurements in many fields of physics, engineering, chemistry, biology, and econometrics, are commonly modeled as sample paths from an ensemble which, together with a probability measure, is called a stochastic process. Stationarity and ergodicity assumptions about this model are generally made for analytical convenience a...

Time-Frequency Signal Analysis and Processing (TFSAP) is a collection of theory and algorithms used for analysis and processing of nonstationary signals, as found in a wide range of applications including telecommunications, radar, and biomedical engineering. This book brings together the main knowledge of TFSAP, from theory to applications, in a u...

In the above article
[1]
, expression (A128), in the proof of Theorem 17 on page 672, has a missed term. Here, the missed term is considered and its convergence to zero is proved. The (conjugate) cyclic correlogram
$R_{x }^{(T)}(\alpha,\tau)$
is nonzero only for
$\tau \in [-T,T]$
. Thus, from (42b) and (43), we have the following corrected ve...

A new technique for locating a moving source radiating a wide-band almost-cyclostationary signal is proposed. For this purpose, the signals received on two possibly moving sensors are modeled as jointly spectrally correlated, a new nonstationarity model that allows one to describe the Doppler effect accounting for a time-scale or time-stretch facto...

The problem of time average estimation is addressed in the fraction-of-time probability framework. In this approach, the observed signal is modeled as a single function of time rather than as a sample path of a stochastic process. Under mild regularity assumptions on temporal cumulants of the signal, a central limit theorem (CLT) is proved for the...

The problem of bandpass sampling a continuous-time almost-cyclostationary signal is addressed. Sufficient conditions are derived such that the cyclic spectra of the complex envelope of the continuous-time signal can be reconstructed by samples obtained by bandpass sampling the continuous-time bandpass real signal.

Time-warped (TW) almost-cyclostationary (ACS) processes are obtained from ACS processes by linear time-variant transformations that modify the time scale. TW-ACS processes are shown to be a subclass of the oscillatory ACS processes, a recently introduced class of signals extending that of the ACS ones. The TW-ACS model is useful to describe signals...

For almost-cyclostationary processes, sufficient conditions are derived such that estimates of second-order cyclic probabilistic functions with estimated cycle frequencies are mean-square consistent and asymptotically complex normal. (Conjugate) cyclic autocorrelation functions and (conjugate) cyclic spectra are considered.
Under the derived condit...

This book gathers contributions presented at the 9th Workshop on Cyclostationary Systems and Their Applications, held in Gródek nad Dunajcem, Poland in February 2016. It includes both theory-oriented and practice-oriented chapters. The former focus on heavy-tailed time series and processes, PAR models, rational spectra for PARMA processes, covarian...

Two philosophically different approaches to the analysis of signals with imperfect cyclostationarity or polycy-clostationarity of the autocorrelation function due to warping are presented. The first approach consists of directly estimating the time-warping function (or its inverse) in a manner that transforms data having an empirical autocorrelatio...

The problem of cyclic spectrum estimation for almost-cyclostationary processes with unknown cycle frequencies is addressed. This problem arises in spectrum sensing and source location algorithms in the presence of relative motion between transmitter and receiver. Sufficient conditions on the process and the cycle frequency estimator are derived suc...

Recent developments and applications of cyclostationary signal analysis are reviewed in the
companion paper ``Cyclostationarity: New trends and applications''. In this paper, limits to the applicability of the cyclostationary model in the presence of relative motion between transmitter and receiver are enlightened. Two new classes of signals that e...

A concise survey of the literature on cyclostationarity of the last 10 years is presented and an extensive bibliography included. The problems of statistical function estimation, signal detection, and cycle frequency estimation are reviewed. Applications in communications are addressed. In particular, spectrum sensing and signal classification for...

Exact expressions for the quadratic distributions' variance of signals corrupted with white stationary, white non-stationary, and colored stationary noise are derived. It has been shown that the signal-dependent part of variance is closely related to the nonnoisy distribution values.

For an almost-cyclostationary signal, mean-square consistent and asymptotically complex normal estimators of the cyclic statistics exist, provided that the signal has finite or practically finite memory and the cycle frequency is perfectly known. In the paper, conditions are derived to obtain a mean-square consistent and asymptotically complex norm...

This book reports on the latest advances in the analysis of non-stationary signals, with special emphasis on cyclostationary systems. It includes cutting-edge contributions presented at the 7th Workshop on “Cyclostationary Systems and Their Applications,” which was held in Gródek nad Dunajcem, Poland, in February 2014. The book covers both the theo...

A detailed analytical model is derived for the GPS-L1 signal which is shown to be second-order cyclostationary. Closed forms for the periodically time-variant autocorrelation function and for the cyclic autocorrelation functions and cyclic spectra are derived for the complex envelope of this signal. Conjugate statistics are also derived. It is show...

A passive localization algorithm is proposed for moving
sources emitting man-made signals. The method models
the received signals on two sensors as (singularly) almost cyclostationary.
It is not based on the usual so called narrow-band
assumption that limits bandwidth, data-record length,
and relative radial speed between source and sensors. Thus,...

In this chapter, the effects of the relative motion between a GPS satellite and a stationary receiver on the Earth are addressed. An analysis of the satellite motion is carried out to justify the assumption of constant relative radial speed within observation intervals adopted in the applications. It is shown that the transmitted cyclostationary si...

The relative motion between transmitter and receiver introduces nonstationarity to stationary signals and modifies the nonstationarity of nonstationary signals. Several Doppler channel models of interest transform almost-cyclostationary (ACS) processes, which are an appropriate nonstationary model for modulated signals adopted in communications, ra...

The central limit theorem is proved within the framework of the functional approach for signal
analysis. In this framework, a signal is modeled as a single function of time rather than a stochastic
process. Distribution function, expectation, and all the familiar probabilistic parameters are built starting
from this single function of time by resor...

The problem of synchronization of Doppler-stretched GPS signals is addressed. A new synchronization technique for the course acquisition code is proposed, which does not assume that the so called narrow-band condition is satisfied. Thus, the Doppler effect is modeled as a frequency shift on the carrier and a stretching of the complex envelope. As a...

The relative motion between transmitter and receiver modifies the nonstationarity properties of the transmitted signal. In particular, the almost-cyclostationarity property exhibited by almost all modulated signals adopted in communications, radar, sonar, and telemetry can be transformed into more general kinds of nonstationarity. A proper statisti...

This chapter addresses the functional approach for signal analysis. This approach is an alternative to the classical one based on stochastic processes since signals are modeled as single functions of time rather than realizations of stochastic processes. An approach for signal analysis which is alternative to classical one based on stochastic proce...

Spectral analysis with nonuniform frequency resolution of nonstationary stochastic processes is addressed. The frequency-warping operation aimed at increasing the frequency resolution is shown to modify the nonstationarity kind of the analyzed process. Specifically, in several cases of interest, the frequency-warped process is shown to belong to th...

The digital X-ray detectors often generate stripe artifact in the sinogram which in turn creates ring artifact in the reconstructed micro-Computed Tomography (µ-CT), C-Arm CT, and most recent dental CT images. Such ring artifacts not only obscure ...

The problem of sampling continuous-time spectrally correlated (SC) processes is addressed. SC processes have Loève bifrequency spectrum with spectral masses concentrated on a countable set of support curves in the bifrequency plane. This class of nonstationary processes extends that of the almost-cyclostationary processes and occurs in wideband mob...

In this paper, stochastic processes with higher order statistical functions decomposable into an almost-periodic function plus a residual term not containing finite-strength additive sinewave components are considered. These processes arise in mobile communications when almost-cyclostationary (ACS) processes pass through time-varying channels. They...

The problem of waveform selection for range-Doppler estimation in wide-band multistatic radars is addressed. The transmitted signal is assumed to be cyclostationary, and cyclostationarity properties are exploited for range-Doppler estimation in severe noise and interference environments. Simulation studies are carried out to investigate waveform pa...

The paper deals with Doppler-stretched wide-band signals occurring in mobile communications and in radar/sonar problems in the presence of moving targets in the case of constant relative radial speeds. Loève bifrequency spectrum and cross-spectrum are used to characterize in the spectral domain the received signal and to jointly characterize the tr...

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...

In this paper, the problem of estimating second-order statistics of continuous-time generalized almost-cyclostationary (GACS) processes is addressed. GACS processes in the wide sense have autocorrelation function almost-periodic in time whose generalized Fourier series expansion has both frequencies and coefficients that depend on the lag shifts. A...

In this paper, the problem of sampling continuous-time spec- trally correlated (SC) processes is addressed. SC processes have Lo` eve bifrequency spectrum with spectral masses con- centrated on a countable set of support curves. This class of nonstationary processes extends that of the almost- cyclostationary processes and occurs in wide-band mobil...

In this paper, the problem of estimating higher-order statistics of generalized almost-cyclostationary (GACS) processes is addressed. The class of the GACS processes extends that of the almost-cyclostationary (ACS) processes and models the output of Doppler channels excited by ACS processes. The proposed estimator is shown to be mean-square consist...

In this paper, the problem of estimating the cyclic autocor-relation function of a continuous-time generalized almost-cyclostationary (GACS) process is addressed. GACS pro-cesses in the wide sense have autocorrelation function almost-periodic in time whose generalized Fourier series ex-pansion has both frequencies and coefficients that depend on th...

In this paper, a new technique to design signals for secure communications is proposed, which provides data securing at the physical layer in noncooperative environments. Specifically, the proposed technique does not allow to an unauthorized third party the discovery of the modulation format and, hence, the demodulation of the signal. The technique...

In this paper, the problem of estimating second-order cross-moments of generalized almost-cyclostationary (GACS) processes is addressed. GACS processes have statistical functions that are almost-periodic functions of time whose (generalized) Fourier series expansions have both frequencies and coefficients that depend on the lag shifts of the proces...

In this paper, the problem of estimating the spectral correlation density of spectrally correlated stochastic processes is addressed. These processes have Loeve bifrequency spectrum with spectral masses concentrated on a countable set of support curves in the bifrequency plane. The almost-cyclostationary processes are obtained as a special case whe...

In this paper, two recently introduced classes of nonstationary processes are reviewed: The class of the generalized almost-cyclostationary (GACS) processes and the class of the spectrally correlated (SC) processes. GACS processes exhibit multivariate statistical functions that are almost-periodic functions of time whose Fourier series expansions h...

In this paper, a discrete-time estimator is proposed for second-order moments of continuous-time generalized almost-cyclostationary (GACS) processes. GACS processes have statistical functions that are almost-periodic functions of time whose Fourier series expan-sions have both frequencies and coefficients that depend on the lag shifts of the proces...

In this paper, the mathematical foundation of the functional (or nonstochastic) approach for signal analysis is established. The considered approach is alternative to the classical one that models signals as realizations of stochastic processes. The work follows the fraction-of-time probability approach introduced by Gardner. By applying the concep...

In this letter, the cyclostationarity properties of a general class of long-code direct-sequence spread-spectrum (DS-SS) signals are analyzed, and it is shown that these properties can be exploited in long-code DS code-division multiple-access systems. Specifically, it is shown that a continuous-time DS-SS signal exhibits cyclostationarity at cycle...

A new algorithm to estimate amplitude, delay, phase, and frequency offset of a received signal is presented. The frequency-offset estimation is performed by maximizing, with respect to the conjugate cycle frequency, the projection of the measured conjugate-cyclic-autocorrelation function of the received signal over the true conjugate second-order c...

In this paper, a concise survey of the literature on cyclostationarity is presented and includes an extensive bibliography. The literature in all languages, in which a substantial amount of research has been published, is included. Seminal contributions are identified as such. Citations are classified into 22 categories and listed in chronological...

In this paper, a new technique to design signals for secure transmissions is proposed. The proposed technique does not allow to an unauthorized third party to discover the modulation format and, hence, to demodulate the signal. The proposed signal-design technique consists in adopting a non relatively measurable sequence as spreading sequence for a...

In this paper, the problem of blind estimation of signal parameters of wide-band signals in mobile communications systems is addressed. It is shown that the wide-band assumption implies that a nonunit time-scale factor needs to be accounted for in the received-signal model even for moderate data-record lengths. Cyclostationarity and conjugate cyclo...

The problem of blind parameter estimation in multiple-access communication systems with circular transmissions is addressed. A non-data aided algorithm based on the higher-order cyclostationarity features of the received signal is proposed to estimate amplitude, phase, time delay, and frequency shift of each user.Furthermore, a reduced-complexity v...

This chapter introduces the class of second-order generalized almost- cyclostationary signals in the classical stochastic approach. Time series belonging to this class are characterized by multivariate statistical functions that are almost- periodic functions of time whose Fourier series expansions can exhibit coefficients and frequencies depending...

The aim of this work is to present a new method of Value-at-Risk calculation using the fraction-of-time probability approach used in signal processing (see e.g Leśkow and Napolitano (2001)). This method allows making statistical type inferences based only on a single observation of phenomenon in time. Such setup is very convenient for time series d...

The problem of estimating second-order statistical functions of generalized almost-cyclostationary (GACS) processes is addressed. The class of such nonstationary processes includes, as a special case, the almost-cyclostationary (ACS) processes. ACS processes filtered by Doppler channels and communications signals with time- varying parameters are f...

The problem of blindly estimating the parameters of a Doppler channel for noncircular transmissions in multiple-access communication systems is addressed. A nondata-aided algorithm based on the cyclostationarity features of the received signal is proposed to estimate amplitude, phase, time delay, and frequency shift of each user. Under mild assumpt...

In this paper, the class of the spectrally correlated stochastic processes is introduced. Processes belonging to this class exhibit a Loe`ve (1963) bifrequency spectrum with spectral masses concentrated on a countable set of support curves in the bifrequency plane. Thus, such processes have spectral components that are correlated. The introdu...

The asymptotic performance analysis of a recently proposed Doppler-channel blind identification algorithm for noncircular transmissions in multiple-access systems is presented. It is shown that, under mild assumptions, the proposed algorithm provides mean-square consistent estimates of the unknown parameters. Moreover, it is shown that this algorit...

The problem of blind parameter estimation of circular transmissions in multiple-access systems is addressed. A non-data aided algorithm based on the higher-order cyclostationarity features of the received signal is proposed to estimate amplitude, phase, time delay, and frequency shift of each user. Furthermore, a reduced complexity algorithm is pro...

In this paper, the problem of sampling a continuous-time generalized almost-cyclostationary (GACS) signal is addressed. The class of such nonstationary signals includes, as a special case, the almost-cyclostationary (ACS) signals. ACS signals filtered by some linear time-variant channels are further examples. It is shown that the discrete-time sign...

For pt. I see ibid., vol.50, no.12, p.2947-61 (2000). In Part I, the problem of the linear time-variant (LTV) filtering is addressed in the fraction-of-time (FOT) probability framework. The adopted approach, which is an alternative to the classical stochastic one, provides a statistical characterization of the systems in terms of functions that can...

The problem of linear time-variant filtering is addressed in the fraction-of-time (FOT) probability framework. The adopted approach, which is an alternative to the classical stochastic one, provides a statistical characterization of the system in terms of time averages of functions of time rather than ensemble averages of stochastic processes. Thus...

In this paper, the problem of sampling a continuous-time generalized almost-cyclostationary (GACS) signal is addressed. The class of such nonstationary signals includes, as a special case, the almost-cyclostationary (ACS) signals. ACS signals filtered by some linear time-variant channels are further examples. It is shown that the discrete-time sign...

The aim of this work is to introduce the concept of the quantile and propose its prediction algorithms using the fraction-of-time probability approach. In such an approach, unlike the classical one based on stochastic processes, statistical functions and probability concepts are defined starting from a single observed time series instead of an ense...

In this paper, the problem of the single sample-path based spectral correlation measurement for a new class of nonstationary stochastic processes is addressed. Processes belonging to this class, referred to as spectrally correlated processes, exhibit a Loeve bifrequency spectrum with spectral masses concentrated on a countable set of support curves...

A blind algorithm for the estimation of amplitude, phase, and
relative time delay of each user in multiple-access communication
systems is proposed. This algorithm is based on the cyclostationarity
features of the received signals and provides estimates of the unknown
parameters that are intrinsically immune to the effects of noise and
interference...

Continuous-phase modulated (CPM) signals play a prominent role in
modern communication systems due to their desirable constant-modulus
property and the ability to control their power and bandwidth
efficiencies. Popular CPM signals include the classical minimum-shift
keyed (MSK) signal, the LREC family of signals also known as
continuous-phase frequ...

In this paper, median-based estimation methods for the cyclic
polyspectrum are proposed. The algorithms do not require a priori
knowledge of the β submanifolds, that is, they do not require the
knowledge of all of the lower order cycle frequencies of the time-series
available for the estimation of the cyclic polyspectrum. Therefore, such
methods ar...

A new nonparametric algorithm for the identification of linear
time-invariant systems is proposed. The method is based on the cyclic
correlations of the input and output signals with a nonlinear
transformation of the input signal. Consequently, although it exploits
the higher order cyclostationarity properties of the input and output
signals, its c...

The aim of this work is to introduce the concept of the condence bound via the fraction-of-time probability approach. This approach allows to use information coming from only one realization of the phenomena under study while the observation time is increasing. The construction of the empirical and a large-sample condence interval is presented and...

In this paper, the linear almost-periodically time-variant (LAPTV)
filtering of generalized almost-cyclostationary (GACS) signals is
considered in the fraction-of-time probability framework. It is shown
that in general GACS signals, when processed by LAPTV filters, deliver
output signals with zero power

This paper considers the problem of estimating amplitude, phase,
time delay, and frequency shift of each user in a multiple-access
communication system. An algorithm based on the cyclostationarity
features of the received signal is proposed. It provides estimates of
the unknown parameters that are intrinsically immune to the effects of
noise and in...

In this paper, the higher-order characterization of linear
time-variant systems in the time domain is introduced in the
fraction-of-time probability framework. Specifically, the Nth-order
system temporal moment function is defined as the operator that
transforms the almost-periodic component of the input Nth-order lag
product into the almost-period...

This paper deals with the estimation of the parameters required in
practical implementation of several multiuser detectors. Specifically, a
blind algorithm for the estimation of amplitudes, phases, and relative
time delays of each user in a multiple-access system is proposed. This
algorithm is based on the cyclostationarity features of the received...

In this paper, the class of generalized almost-cyclostationary
(GACS) time series is introduced. Time series belonging to this class
are characterized by multivariate statistical functions that are
almost-periodic functions of time whose Fourier series expansions can
exhibit coefficients and frequencies depending on the lag shifts of the
time serie...

The paper investigates the effects of multirate systems on the
higher order wide-sense cyclostationarity (WSCS) properties of
discrete-time series. To this end, definitions and properties of the
cyclic higher order statistics, which were introduced for
continuous-time series in the fraction-of-time probability framework,
are first extended to discr...

The role played by the higher-order wide-sense cyclostationarity properties in Rice's representation of a signal is investigated. Specifically, formulas relating higher-order cyclic spectra of signals involved in Rice's representation of a signal exhibiting cyclostationarity are derived. It is shown that some known results relative to second-order...

In this paper, the higher-order wide-sense stationarity or cyclostationarity properties of a continuous-time-series and those of the discrete-time-series of its samples are related in the fraction-of-time probability framework. In particular, for a cyclostationary continuous-time-series, it is shown how the ratio of the sampling period to the cyclo...

A contribution to the theory of higher-order cyclostationarity very recently introduced to generalize the second-order cyclostationarity theory is given. Input/output relations in terms of cyclic higher-order statistics for multi-input multi-output linear almost-periodically time-variant systems that are excited by cyclostationary inputs are derive...

In many signal processing applications, it is advantageous to exploit the signal selectivity and noise tolerance that are typical of the algorithms based on the spectral line generation that often can be accomplished by using quadratic nonlinear transformations. The linear time-variant systems are classified as random and nonrandom in the fraction-...

A modification that applies to some recently proposed
cyclostationarity-based methods for TDOA estimation is introduced. It
relaxes an assumption on the noise and interference environment that
characterizes all cyclostationarity-based methods so far proposed. It is
shown that the modified techniques can assure satisfactory performances
in noise and...

## Projects

Project (1)

Time-warped almost-cyclostationary signals are shown to be a subclass of the oscillatory almost-cyclostationary signals, a recently introduced class of signals that generalizes that of the almost-cyclostationary signals [Cyclostationarity: Limits and Generalizations, Signal Processing, March 2016].
Applications are considered in mobile communications, low-probability-of-intercept signal design for communications and radar, and electrocardiogram signal analysis.