The parameter of the stable non-Gaussian noise sequence is modulated by the binary message sequence to achieve a secure communication system. The characteristic exponent 'alpha' of a stable non-Gaussian noise sequence carries the binary information. The receiver of the proposed random communication system demodulates the received signal by estimating the parameters of the transmitted noise sequence to recover the binary message sequence.

Abstract-The ridges obtained from chaotic signals can give the relevant information about the phase structures of the dynamical systems. Therefore, a new wavelet ridge determination method for the noisy signals and nonstationary signals, which is based on the singular value decomposition (SVD) has been proposed in this paper. The proposed method has been compared with Carmona method for monocomponent signals, and multicomponent signals. The proposed method is computationally more effective than the Carmona method to determine the actual ridges. Also, the ridges of the periodic limit cycles and chaotic attractors have been determined by using the SVD-based method to find the degree of chaoticity.Index Terms-Instantaneous frequency, singular value decomposition (SVD), wavelet ridge.

The digital communication system is based on the skewed alpha-stable ([Formula: see text]-stable) noise sequence which is chosen as the random carrier to modulate the binary message at the transmitter side. Antipodal characteristic of the skew parameter beta ([Formula: see text]) is exploited for decoding information at the receiver side to obtain a secure communication system. A fast estimator used in this paper is based on Modified Extreme Value Method (MEVM) to extract the binary message from the signal received through the Additive White Gaussian Noise (AWGN) channel. Our proposed receiver is achieving better bit error rate (BER) versus Mixed Signal to Noise Ratio (MSNR) than previously introduced receivers which are based on Sinc and Logarithmic estimators. MEVM estimator is indeed less complex compared to the Sinc and Logarithmic estimators and hence more fast. Additionally, the criterion to measure the security level of random communication system, which is based on [Formula: see text]-stable noise sequence, has also been introduced.

In this study, the pilot-assisted synchronisation method for a random communication system (RCS) has been proposed. The pilot symbol, which has alpha-stable distribution, has been used to establish synchronisation and to maintain covertness in the RCS. The introduced synchronisation block (SB) consists of fractional lower-order covariance-based correlators (FLOCCs), threshold detectors (TDs) and the synchronisation control block. To measure the performance of the proposed SB, the performance criterion, i.e. confidence ratio (CR), has been proposed. The reliability of the proposed SB can be enhanced by altering the CR and the achieved CR by using the FLOCCs and TDs in SB.

a b s t r a c tIn this paper, the continuous time wavelet entropy (CTWE) of auditory evoked potentials (AEP) has been characterized by evaluating the relative wavelet energies (RWE) in specified EEG frequency bands. Thus, the rapid variations of CTWE due to the auditory stimulation could be detected in post-stimulus time interval. This approach removes the probability of missing the information hidden in short time intervals. The discrete time and continuous time wavelet based wavelet entropy variations were compared on non-target and target AEP data. It was observed that CTWE can also be an alternative method to analyze entropy as a function of time.