Dragos Nicolae Vizireanu

Single sine wave parameters estimation method based on four equally spaced samples

This article presents a general method to determine all the parameters of a single wave carrier signal i.e. the frequency, phase, amplitude and DC component, based on four different samples. The analytical formulas are derived for arbitrary samples and finally particularised for equally spaced samples. To check the fairness of our formulas, simulations have been performed in two different scenarios: when the sine-wave that is sampled is affected by white Gaussian noise and when the samples are quantised on a given number of bits. The results show that the relative error of the estimated parameters is decreasing linearly as the signal-to-noise ratio (SNR) increases, with a slope of 0.1/20 dB. When the samples are quantised on a given number of bits, the relative error is decreasing almost linearly with approximately for each extra bit in the sample representation. An increase of the number of bits is more then 15 is no longer useful since the performances are no longer increasing from that point.

Analytical formula for three points sinusoidal signals amplitude estimation errors

In this note, we show that the amplitude estimation of sinusoidal signals proposed in Wu and Hong [Wu, S.T., and Hong, J.L. (2010), ‘Five-point Amplitude Estimation of Sinusoidal Signals: With Application to LVDT Signal Conditioning’, IEEE Transactions on Instrumentation and Measurement, 59, 623–630] is a particular case of Vizireanu and Halunga [Vizireanu, D.N, and Halunga, S.V. (2011), ‘Single Sine Wave Parameters Estimation Method Based on Four Equally Spaced Samples’, International Journal of Electronics, 98(7), pp. 941–948]. An analytical formula for amplitude estimation errors as effects of sampling period deviation is obtained.

Robust wavelet-based video watermarking scheme for copyright protection using the human visual system

The development of the information technology and computer networks facilitates easy duplication, manipulation, and distribution of digital data. Digital watermarking is one of the proposed solutions for effectively safeguarding the rightful ownership of digital images and video. We propose a public digital watermarking technique for video copyright protection in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet subbands. The method is a combination of spread spectrum and quantization-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key by means of quantization. The selected wavelet detail coefficients from different subbands are quantized using an optimal quantization model, based on the characteristics of the human visual system (HVS). Our HVS-based scheme is compared to a non-HVS approach. The resilience of the watermarking algorithm is tested against a series of different spatial, temporal, and compression attacks. To improve the robustness of the algorithm, we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a good perceptual quality and high resistance to a large spectrum of attacks.

Multiuser Systems Implementations in Fading Environments

The theory of multiuser detection technique has been developed during the 90s [Verdu, 1998], but its application gained a high potential especially for large mobile networks when the base station has to demodulate the signals coming from all mobile users [Verdu, 1998; Sakrison, 1966]. The performances of multiuser detection systems are affected mostly by the multiple access interference, but also by the type of channel involved and the impairments it might introduce. Therefore, important roles for improving the detection processes are played by the type of noise and interferences affecting the signals transmitted by different users. Selection of spreading codes to differentiate the users plays an important role in the system performances and in the capacity of the system [Halunga & Vizireanu, 2009]. There are important conclusions when the signals of the users are not perfectly orthogonal and/or when they have unequal amplitude [Kadous& Sayeed, 2002], [Halunga & Vizireanu, 2010]. In a wireless mobile communication system, the transmitted signal is affected by multipath phenomenon, which causes fluctuations in the received signal’s amplitude, phase and angle of arrival, giving rise to the multipath fading. Small-scale fading is called Rayleigh fading if there are multiple reflective paths that are large in number and there is no line-of-sight component. The small-scale fading envelope is described by a Rician probability density function [Verdu, 1998], [Marcu, 2007]. Recent research [Halunga & Vizireanu, 2010] led us to several conclusions related to the performances of multiuser detectors in different conditions. These conditions include variation of amplitudes, selective choice of (non) orthogonal spreading sequences and analysis of coding/decoding techniques used for recovering the original signals the users transmit. It is very important to mention that the noise on the channel has been considered in all previous simulations as AWGN (Additive White Gaussian Noise). This chapter implies analysis of multiuser detection systems in the presence of Rayleigh and Rician fading with Doppler shift superimposed over the AWGN noise. The goal of our research is to illustrate the performances of different multiuser detectors such as conventional detector and MMSE (Minimum Mean-Square Error) synchronous linear detectors in the presence of selective fading. The evaluation criterion for multiuser systems performances is BER (Bit Error Rate) depending on SNR (Signal to Noise Ratio). Several conclusions will be withdrawn based on multiple simulations.

Performance evaluation for multiuser detectors

This paper presents three multiuser detectors structures: the conventional detector, the optimum detector and the MMSE detector. The error probability performances are evaluated and compared one another, as functions of signal to noise ratio, of number of users and the correlation coefficients between them. Finally, several conclusions are highlighted, with respect to the level of performance achieved and implementation complexity.

Measurements of the electrical characteristics in DC and AC regime for an epinephrine BOI device

The electrical properties of the chemical mediators at synapses level could be investigated in vitro, with some test biodevices. One of neurotransmitters, like epinephrine, placed on an insulator support and contacted with metal electrodes, provides a Biomaterials On Insulators - BOI-type, structure. The test device is inspired from the pseudo-MOS technique, frequently used in the Silicon On Insulator characterisation. The DC regime study allows some polarography experiments. A behavior like the Field Effect Transistor was also investigated in DC regime, biasing a third terminal - the gate. A gate voltage control on the current is expected. It is still linear, emphasising none inversion layer onset. The AC regime measurements of the BOI device provided some conductometry results, providing the epinphrine resistivity.

Improved Minkowsky Metric for Image Region Partition

In this paper we present an improved method for image partition. Image partition plays an important role in video segmentation techniques; it uses different region growth algorithms for separating an image into regions and objects. This enhances the characterization on an image using video descriptors and can be used in image retrieval or image comparison applications. The proposed segmentation method uses the Minkowsky metric for region detection. In addition, it uses different threshold values in order to achieve perceptually significant areas. The simulation results indicate good performances of the proposed method for colour image segmentation.

A New Class of S-Type Current Controlled Nonlinear Negative Resistances

The paper presents a new method for generating S-type nonlinear current controlled negative resistances. The presented method can be used to obtain a large number of nonlinear resistances. We apply the method for a negative resistance device, using bipolar transistors, described by theoretical characteristics and performances and we compare the results with the theoretical specifications

A Time-Recursive Adaptive Algorithm for Colored Noise Reduction in Speech Enhancement

We propose an improved spectral subtraction method for the reduction of colored acoustic noise added to the speech. Our implementation uses a time-recursive algorithm for estimation of the noise power spectral density and a multi-band spectral over subtraction method to reduce the colored noise. Simulations show a better quality in terms of Itakura Saito distance and perceptual evaluation of quality for the enhanced speech. Using the proposed speech enhancement method, a very good speech quality with less musical noise and with minimal speech distortion is obtained.

Error Probability Evaluation for Multiuser Detection Algorithms

This paper presents three multiuser detectors structures: the conventional detector, the optimum detector and the MMSE detector. The error probability performances are evaluated and compared one another, as functions of signal to noise ratio, of number of users and the correlation coefficients between them. Finally, several conclusions are highlighted, with respect to the level of performance achieved and implementation complexity.