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Instantaneous Frequency Estimation Using Discrete Evolutionary
, 2001
"... In this paper, we propose a method based on the discrete evolutionary transform (DET) to estimate the instantaneous frequency of a signal embedded in noise or noiselike signals. The DET provides a representation for nonstationary signals and a timefrequency kernel that permit us to obtain th ..."
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In this paper, we propose a method based on the discrete evolutionary transform (DET) to estimate the instantaneous frequency of a signal embedded in noise or noiselike signals. The DET provides a representation for nonstationary signals and a timefrequency kernel that permit us to obtain the timedependent spectrum of the signal. We will show the instantaneous phase and the corresponding instantaneous frequency (IF) can also be computed from the evolutionary kernel. Estimation of instantaneous frequency is of general interest in timefrequency analysis, and of special interest in the excision of jammers in direct sequence spread spectrum. Implementation of the IF estimation is done by masking and a recursive nonlinear correction procedure. The proposed estimation is valid for monocomponent as well as multicomponent signals in the noiseless and noisy situations. Its application to jammer excision in direct sequence spread spectrum communication is considered as an important application. The estimation procedure is illustrated with several examples.
Array processing for nonstationary interference suppression in DS/SS communications using subspace projection techniques
"... Combined spatial and timefrequency signatures of signal arrivals at a multisensor array are used for nonstationary interference suppression in directsequence spreadspectrum (DS/SS) communications. With random PN spreading code and deterministic nonstationary interferers, the use of antenna array ..."
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Combined spatial and timefrequency signatures of signal arrivals at a multisensor array are used for nonstationary interference suppression in directsequence spreadspectrum (DS/SS) communications. With random PN spreading code and deterministic nonstationary interferers, the use of antenna arrays offers increased DS/SS signal dimensionality relative to the interferers. Interference mitigation through spatiotemporal subspace projection technique leads to reduced DS/SS signal distortion and improved performance over the case of a single antenna receiver. The angular separation between the interference and desired signals is shown to play a fundamental role in trading off the contribution of the spatial and timefrequency signatures to the interference mitigation process. The expressions of the receiver SINR implementing subspace projections are derived and numerical results are provided.
Research Article A Reconfigurable GNSS Acquisition Scheme for TimeFrequency Applications
"... The extreme weakness of global navigation satellite system (GNSS) signals makes them vulnerable to almost every kind of interferences that, without adequate countermeasures, can heavily compromise the receiver performance. An effective solution is represented by timefrequency (TF) analysis that has ..."
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The extreme weakness of global navigation satellite system (GNSS) signals makes them vulnerable to almost every kind of interferences that, without adequate countermeasures, can heavily compromise the receiver performance. An effective solution is represented by timefrequency (TF) analysis that has proved to be able to detect and suppress a wide class of disturbing signals. However, high computational requirements have limited the diffusion of such techniques for GNSS applications. In this paper, we propose an effective solution for the efficient implementation of TF techniques on GNSS receivers. The solution is based on the key observation that the first block of a GNSS receiver, the acquisition stage, implicitly performs a sort of TF analysis. Thus, a slight modification in the traditional acquisition scheme enables the fast and efficient implementation of TF techniques for interference detection. The proposed method is suitable for different types of acquisition scheme and its effectiveness is proved by simulations and examples on real data. Copyright © 2008 D. Borio and L. Lo Presti. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.
Research Article Interference Excision in Spread Spectrum Communications Using Adaptive Positive TimeFrequency Analysis
"... This paper introduces a novel algorithm to excise single and multicomponent chirplike interferences in direct sequence spread spectrum (DSSS) communications. The excision algorithm consists of two stages: adaptive signal decomposition stage and directional element detection stage based on the Houg ..."
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This paper introduces a novel algorithm to excise single and multicomponent chirplike interferences in direct sequence spread spectrum (DSSS) communications. The excision algorithm consists of two stages: adaptive signal decomposition stage and directional element detection stage based on the HoughRadon transform (HRT). Initially, the received spread spectrum signal is decomposed into its timefrequency (TF) functions using an adaptive signal decomposition algorithm, and the resulting TF functions are mapped onto the TF plane. We then use a line detection algorithm based on the HRT that operates on the image of the TF plane and detects energy varying directional elements that satisfy a parametric constraint. Interference is modeled by reconstructing the corresponding TF functions detected by the HRT, and subtracted from the received signal. The proposed technique has two main advantages: (i) it localizes the interferences on the TF plane with no crossterms, thus facilitating simple filtering techniques based on thresholding of the TF functions, and is an efficient way to excise the interference; (ii) it can be used for the detection of any directional interferences that can be parameterized. Simulation results with synthetic models have shown successful performance with linear and quadratic chirp interferences for single and multicomponent interference cases. The proposed method excises the interference even under very low SNR conditions of −10 dB, and the technique could be easily extended to any interferences that could be represented by a parametric equation in the TF plane. Copyright © 2007 S. Krishnan and S. Erküçük. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.
EVOLUTIONARY WIENERMASK RECEIVER FOR MULTIUSER DIRECT SEQUENCE SPREAD SPECTRUM
"... In this paper, we propose a channel estimation procedure that together with a timefrequency Wiener mask permits the design of coherent receivers for direct sequence spread spectrum (DSSS) communication systems. Such a receiver excises intentional or nonintentional jamming signals while detecting t ..."
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In this paper, we propose a channel estimation procedure that together with a timefrequency Wiener mask permits the design of coherent receivers for direct sequence spread spectrum (DSSS) communication systems. Such a receiver excises intentional or nonintentional jamming signals while detecting the sent bit. Transmission channels spread the message signals in time and frequency and are typically modeled as random, timevarying systems. The estimation of the parameters of the channel model for one of the users, in uplink transmission, is possible by means of the spreading function obtained from the discrete timefrequency evolutionary (DET) kernel of the received signal and the pseudonoise code corresponding to the user. Excision of arbitrary jamming signals, present in the received signal, is done by means of a Wiener mask implemented with the DET. The performance of the proposed receiver is illustrated by means of simulations, with different levels of channel noise, Doppler frequency shifts, jamming signals and different number of users.
Jammer Excision in Spread Spectrum Communications via Discrete Evolutionary Transform
"... In this paper, we propose timefrequency jammer excision techniques for direct sequence spread spectrum communications. One method is based on the estimation of the instantaneous frequency (IF) of each of the chirp jammer components using a combination of the discrete evolutionary and the Hough ..."
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In this paper, we propose timefrequency jammer excision techniques for direct sequence spread spectrum communications. One method is based on the estimation of the instantaneous frequency (IF) of each of the chirp jammer components using a combination of the discrete evolutionary and the Hough transforms. The second method is based in Wiener masking, and reduces the interference in a meansquare fashion. In the first method, the jammer is synthesized and subtracted from the baseband received signal, while in the second method a meansquare estimate of the message is obtained. The IFbased method applies equally well to multicomponent chirp jammers with constant or timevarying amplitudes, and instantaneous frequencies not necessarily parametrically modeled. A statistical analysis of this method is developed based on the signal to interference and noise ratio. We will show that the Wiener masking method is a general method requiring the spectrum of the spreading function. The two methods are illustrated by simulations. 1
Parametric Methods Comparisons for Parameter Estimation of Polynomial Phase Signals*
"... Parameter estimation of polynomial phase signals (PPSs) is of great interest in various practical applications. In this paper, parametric methods for parameter estimation of polynomial phase signals are discussed and compared. The suboptimal maximum likelihood estimation methods, such as the highor ..."
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Parameter estimation of polynomial phase signals (PPSs) is of great interest in various practical applications. In this paper, parametric methods for parameter estimation of polynomial phase signals are discussed and compared. The suboptimal maximum likelihood estimation methods, such as the highorder ambiguity function (HAF) and the product HAF (PHAF) are presented. The polynomial time frequency transform (PTFT) is introduced as the maximum likelihood estimation method. Comparisons are given in estimation variance, output SNR, error propagation effect, and computation time to show the advantages and disadvantages of the two kinds of estimation methods.