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In this paper, we propose a method on the training based on channel estimation issues for relay networks that employ amplify-and-forward (AF) transmission scheme. We have to point out that jointly estimating the channel from source to relay and relay to destination suffers from many drawbacks in fast fading case because the estimation of previous pilots is not suitable for current channel. In this...
Timing estimation of the receive pulse is a crucial component for communication systems as well as localization with ultra wideband impulse radio. Standard timing estimation algorithms might not be applicable due to stringent requirements on complexity and power consumption of the receiver. Therefore, we consider maximum likelihood timing estimation at the output of a generalized energy detection...
Code reuse through copying and pasting leads to so-called software clones. These clones can be roughly categorized into identical fragments (type-1 clones), fragments with parameter substitution (type-2 clones), and similar fragments that differ through modified,deleted, or added statements (type-3 clones). Although there has been extensive research on detecting clones, detection of type-3 clones...
Performance of some suboptimal detectors can be improved by adding independent noise to their observations. In this paper, the effects of adding independent noise to observations of a detector are investigated for binary composite hypothesis-testing problems in a generalized Neyman-Pearson framework. Sufficient conditions are derived to determine when performance of a detector can or cannot be improved...
In this paper, the detection performance of OSGO and OSSO CFAR detectors embedded in heavy-tailed Pearson distributed clutter is analyzed. We derive the closed mathematic form expressions of probability of false alarm rate and detection probability of the two CFAR schemes. While the processing speed of OSGO and OSSO CFAR is two times of that of OS CFAR, simulation results indicate that OSGO CFAR detector's...
In order to improve the radar's detection performance under Pearson distributed background clutter, the problem of designing CA-CFAR detector based on fuzzy logic is studied in this paper. A kind of distributed fuzzy CA-CFAR detection scheme including two detectors is proposed here. Two detectors compute the values of the membership function to the false alarm space from the samples of the reference...
This paper address issues that arise in copyright protection systems of digital images, which employ blind watermark verification structures in the curvelet domain. First, we observe that statistical distribution with heavy algebraic tails, such as the alpha-stable family, are in many cases more accurate modeling tools for the curvelet coefficients than families with exponential tails such as generalized...
In this paper, we investigate the detection of a band-limited signal with unknown central frequency, exact bandwidth and the spectrum in white Gaussian noise with unknown variance. We propose a practically implementable Generalized Likelihood Ratio (GLR) detector with these unknown parameters and verify its performance through some simulation examples. Furthermore, in order to evaluate the performance...
In this paper, a new M-estimator based multiuser detection in asynchronous flat-fading non-Gaussian CDMA channels is considered. A new closed-form expression is derived for the characteristic function of the multiple-access interference signals. Simulation results are provided to prove the effectiveness of the derived bit-error probabilities obtained with this expression in asynchronous flat-fading...
The main objective of this paper is to describe and simulate the application of an interference cancelling technique named Amplitude Domain Processing (ADP) in navigation. ADP is the simplified algorithm of locally optimum detection theory. According to statistical theory, ADP is a non-linear and digital technology and it can eliminate interferences according to the statistical characteristics of...
Assessing that a probability of false alarm is below a given significance level is a crucial issue in watermarking. We propose an iterative and self-adapting algorithm which estimates very low probabilities of error. Some experimental investigations validates its performance for a rare detection scenario where there exists a close form formula of the probability of false alarm. Our algorithm appears...
In this paper, we adapt two blind detector structures for additive spread-spectrum image watermarking to the host signal characteristics of the dual-tree complex wavelet transform (DT-CWT) domain coefficients. The research is motivated by the superior perceptual characteristics of the DT-CWT and its active use in watermarking. To improve the numerous existing watermarking schemes in which the host...
The paper proposes a new Markov chain based CFAR detector for polarimetric data using low level data fusion and high level decision fusion. The Markov chain based CFAR detector extends traditional PDF based CFAR detection to first-order Markov chain model by considering both correlation between neighboring pixels and PDF information in CFAR detection. With the additional correlation information, the...
In this paper, we address the problem of automatic target detection in Weibull clutter and multiple target situations, without any prior knowledge of neither the non stationary clutter statistics in which the radar operates nor the number of outliers that may be present in the reference window. In doing this, we develop the forward and backward order statistic automatic constant false censoring and...
This paper focuses on optimal detection of quadrature phase-shift keying (QPSK) and binary phase-shift keying (BPSK) direct sequence spread spectrum (DS-SS) signals in additive white Gaussian noise (AWGN) with unknown spreading sequence and other parameters. Using complex Gaussian mixture signal model and invariance principle, we derive constant-false-alarm-rate (CFAR) invariant detectors such as...
In this paper, we propose an adaptive PN code acquisition scheme, named FAHAP (fuzzy adaptive hybrid acquisition processor). The proposed system combines an antenna diversity technique and a hybrid search scheme. Two fuzzy adaptive detectors (CA-CFAR and OS-CFAR) are used. Each detector computes the value of the membership function spanned by the false alarm space from the reference cell samples and...
Spectrum sensing is a key feature in cognitive radio networks. We propose a locally optimum (LO) detector, which is known to be optimum at low SNR. This is desirable in cognitive radio since the primary user's signal may exhibit a very low power at the cognitive user's transmitter. We focus here on linear modulation in the presence of an unknown phase shift and additive white Gaussian noise. In the...
Passive wireless sensors have emerged as a new technology to measure a vast majority of phenomena in our daily life. Passive sensors require no power source, and therefore their application domains are numerous, including health care, infrastructure protection, and national security, among many others. The deployment of wireless passive sensors and their readers has changed how detection needs to...
Signal detection problems are traditionally viewed as statistical hypothesis testing. In absence of the a priori probabilities, such as in radar, the Neyman-Pearson criterion is used where a certain false alarm probability is set, and the probability of detection is maximised. In signal sensing problems of cognitive radio, the main constraint is to avoid the interference with the primary user. Once...
Since 1981, the conventional ATC (automatic train control) system has been used on the Yamanote and Keihin-Tohoku Lines, which are the most crowded commuter routes in Tokyo. The conventional ATC is a ground oriented system with cumbersome wayside equipment. Therefore, they have several problems and an obstacle to improvements in transportation service. The D-ATC system with on-board intelligence was...
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