Nicolae Vizireanu

Performance evaluation for conventional and MMSE multiuser detection algorithms in imperfect reception conditions

This paper presents three multiuser detectors structures: the conventional detector, the MMSE and the adaptive detector. The error probability performances are evaluated and compared one another, as functions of signal to noise ratio, for a system with four users, and different intercorrelation coefficients and users amplitudes. Based on those simulations, a number of conclusions are drawn with respect to the effects of the intercorrelation between users or unequal amplitudes on the detectors performances.

Imperfect cross-correlation and amplitude balance effects on conventional multiuser decoder with turbo encoding

The present work aims to illustrate the improvement that turbo encoding/decoding algorithms can bring to a multiuser detection system, evaluated in terms of bit error rate (BER). Extended simulations have been performed for conventional multiuser detection algorithms and are still under study for other algorithms, like the optimal, the MMSE and the classical MMSE ones. Simulations have been performed in both optimal conditions and imperfect ones, like non-equal power of users and non-zero correlations between them and for different number of users. Several interesting conclusions have been highlighted with respect to parameters influence on overall system performances.

Morphological skeleton decomposition interframe interpolation method

The interframe interpolation method presented consists of partial changing, using the growing size of structuring elements, of the morphological skeleton decomposition subsets of a binary input or grayscale frame with the morphological skeleton decomposition subsets of a binary output or grayscale frame. One of the interpolated frames obtained by this method is similar to the reference frame. Computer simulations illustrate the results.

Fast communication: Nonlinear spectral subtraction method for colored noise reduction using multi-band Bark scale

We propose an improved spectral subtraction method for the reduction of colored acoustic noise added to the speech in a helicopter cockpit or in a car caused by the engine sound. Our implementation uses an over-estimation subtraction method for spectral subtraction. The noise signal does not affect uniformly the speech signal over the whole spectrum. A nonlinear multi-band Bark scale frequency spacing approach is proposed 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.

Quantisation-based video watermarking in the wavelet domain with spatial and temporal redundancy

In this article we introduce a new public digital watermarking technique for video copyright protection working 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 sub-bands. The method is a combination of spread spectrum and quantisation-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key. The resilience of the watermarking algorithm was tested against a series of eight different attacks using different videos. To improve the resilience of the algorithm we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a very good perceptual quality with mean peak signal-to-noise ratio values of the watermarked videos of more than 40 dB and high resistance to a large spectrum of attacks.

An improved spectral subtraction method for speech enhancement using a perceptual weighting filter

We propose an improved spectral subtraction method for reducing acoustic noise added to speech in noisy environments like helicopter cockpit or car engine. This implementation uses oversubtraction method for spectral subtraction. Residual noise can be masked by exploiting the masking properties of the human auditory system. A psychoacoustically motivated weighting filter was included to eliminate residual musical noise. Simulations showed a better quality with no distortion for the enhanced speech and the musical noise was effectively masked.

Using Off-Line Handwriting to Predict Blood Pressure Level: A Neural-Network-Based Approach

We propose a novel, non-invasive, neural-network based, three-layered architecture for determining blood pressure levels of individuals solely based on their handwriting. We employ four handwriting features (baseline, lowercase letter “f”, connecting strokes, writing pressure) and the result is computed as low, normal or high blood pressure. We create our own database to correlate handwriting with blood pressure levels and we show that it is important to use a predefined text for the handwritten sample used for training the system in order to have high prediction accuracy, while for further tests any random text can be used, keeping the accuracy at similar levels. We obtained over 84% accuracy in intra-subject tests and over 78% accuracy in inter-subject tests. We also show there is a link between several handwriting features and blood pressure level prediction with high accuracy which can be further exploited to improve the accuracy of the proposed approach.

Multiple point Android digital image authentication

Digital images have been accepted as evidence in courts of law for a long time. One mandatory aspect for the admission of photographic evidence is the need for authentication. A spontaneous scene is very likely to be photographed with a smartphone rather than a classical camera. Android powered devices count for around 80% of smartphones worldwide. There is a high probability that an image used as evidence has been captured with this type of device. Android uses JPEG format for storing captured images. JPEG headers embedded information exhibits a wide variation across different models and manufacturers. By taking advantage of this variation, the authentication method described in this article employs a multiple point verification of both intrinsic and extrinsic properties of the analyzed image. The extrinsic properties are being obtained from a 185 entries database of Android powered devices. Authentication is performed straight-forward, allowing the authenticity decision to be made at different points in the process, without the need of a full analysis to be employed beforehand.

Performances of decorrelating MUD using STBC for image transmissions in rayleigh fading channel

The scope of this paper is to simulate and analyse the effect of Rayleigh flat fading on the performances of the decorrelating multiuser detector (MUD) when grey-type images are transmitted through a CD/CDMA system. To reduce the fading effects Multiple - Input Single/Multiple - Output (MISO, MIMO) radio channels will be taken into consideration and the received images will be compared with the original ones using three metrics, namely: the bit error rate, the peak signal-to-noise ratio and the structural similarity index.

Comparison of "Spread-Quantization" Video Watermarking Techniques for Copyright Protection in the Spatial and Transform Domain

In spite of the existence of watermarking technique for all kinds of digital data, most of the literature addresses the watermarking of still images for copyright protection and only some work is extended to video watermarking. Video watermarking is distinct from image watermarking, because there is more data available to both the attacker as well as to the watermarker. This additional data volume allows the payload to be more redundantly and reliably embedded.