Onsy Abdel Alim

Iris recognition using discrete wavelet transform and artificial neural networks

The iris of the human eye has a highly detailed pattern which is unique for each individual and stable over years. It is now considered as an important and reliable biometric tool for personal identification. A new technique for extracting iris texture using the 2D-DWT at different decomposition levels is suggested. Recognition rates of about 95% have been achieved using ANN classifiers.

Determination of the Region of Interest in the Compression of Biomedical Images

Compression of medical images should be lossless to preserve details and to avoid wrong diagnosis. However, to achieve high compression ratios while maintaining image quality, only regions of interest (ROI). i.e., abnormal regions need to be losslessly compressed. The rest of the image if lossy compressed can lead to a reasonable overall compression ratios. In this paper, two techniques for determining and extracting the ROI of an MRI brain image are proposed. The first technique is based on the mean squared error (MSE) between a normal and an abnormal brain images. The region that shows high MSE is the ROI. In the other technique, selection of the ROI is based on the gray levels of the image. Any region that possesses a gray level that noticeably differs from the surroundings is the ROI.

Simulation of channel estimation and equalization for WiMAX PHY layer in simulink

WiMAX top level SIMULINK model with all system details has been implemented for simulation purpose. This paper has focused on channel estimation with different interpolation approaches for fixed/mobile OFDM system with parameters from WiMAX standards. The Doppler shift had a greater impact on the relative performancebetween the different channel estimators and interpolation approaches. One of the most interesting properties that were discovered is the big impact the interpolation method has over the estimating method in case of mobile case. The result from the simulation is that the low complexity LS method performs about the same for SNR as LMS which is more complex estimator, before Doppler shift but it has different behavior after that.

Channel estimation and equalization for fixed/mobile OFDM WiMAX system in simulink

WiMAX (Worldwide Interoperability for Microwave Access) is a technology for wireless broadband and the core technique for the fourth-generation (4G) wireless mobile communications. However it still facing real challenge for low complexity and efficient system implementation. It supports non-line-of-sight environment with high data rate transmission and high mobility up to 125 Km/hr. WiMAX adopted OFDM/OFDMA in physical layer for fixed/mobile applications respectively. Integrated WiMAX model including Channel estimation and equalization are an active area for many recent researches. This paper presents a model for simulating OFDM WiMAX system in Simulink including channel estimation and equalization subsystems in MATLAB functions. Performance has been tested applying Additive White Gaussian Noise (AWGN) channel for fixed system and Doppler shifts due to changes in high and low relative velocity has been calculated and applied to the Simulink channel model for mobile system. Different iterative approaches for channel estimation and equalization have been modeled and evaluated. BER versus SNR curves at high and low Doppler shifts have been used for comparing these models.

Linear FM chirp filters in pulse compression radars

Using a complex Fresnel integral algorithm, the authors extend results of other authors from a time-bandwidth product of 50 up to 720. They analyze a rectangular linear FM filter having a 300-MHz center frequency, 120-MHz bandwidth, and 6-μs dispersion time T. Two different methods of rectangular FM cosine square tapering are compared. In the first method, the tapers are of length T/12 at the two edges inside the dispersion time T, while in the second, tapers of length αT are added to the duration T (α=0.05 and 0.1). The results show that the skirt steepness, the sidelobe rejection, and the Gibbs ripples of the wave spectrum, as well as the reduction of insertion loss and the suppression of Fresnel ripples, are best at α=0.1.

A new method for dynamic road mapping of coronary angiography cardiac catheterization cine loops

In this paper a new method for road mapping for cardiac catheterization cine loops were introduced. The method depends on detecting the edges of the coronary vessels after the dye injection during the catheterization operation and drawing a road map for the vessels so that the angiographer can navigate through these drawn paths with his catheter under fluoroscopy X-ray exposure. Canny technique was used to detect the edges of these gray scale high-resolution images. It was used to detect the vessel edges due to its high level of detection for this kind of images. The method estimate and track the heart motion during the operation and draw the road map in a real dynamic way. The road map is super imposed over the same fluoroscopy monitor so that the angiographer can navigate with the catheter through the detected coronary artery without any need for another monitor for road map. This method will offer dose limitation for the patient, easy manipulation in PTCA operations for inserting stents and balloons in coronary vessels.

Performance of MIMO antenna techniques on IEEE 802.16E

WiMAX systems are based on the IEEE 802.16-2004 and IEEE 802.16e-2005 standards which define a physical (PHY) layer and the medium access control (MAC) layer for broadband wireless access systems operating at frequencies below 11 GHz. Multiple-antenna techniques can be used to increase diversity and improve the bit error rate (BER) performance of wireless systems, increase the cell range, increase the transmitted data rate through spatial multiplexing, and/or reduce interference from other users. In this paper we are going to discuss the use of multiple-antenna techniques in mobile WiMAX systems. We first present a general description of multi-input multi-output (MIMO) systems, which can be used for different purposes including diversity, spatial multiplexing and interference reduction. Next, we focus on the multi-antenna profiles adopted for WiMAX systems, discuss their relative merits, and address the implementation issues. Finally, we simulate the performance of the different MIMO techniques proposed by the WiMAX forum and compare the results.

Speech and Video Transmission Over Wireless ATM Networks

The increasing importance of portable computing/telecommunications applications has motivated the studies on broadband wireless network technologies such as wireless ATM (asynchronous transfer mode) or WATM. Orthogonal frequency division multiplexing (OFDM) is especially suitable for high-speed communication due to its resistance to inter symbol interference ISI. This paper describes an ATM network with wireless access for multimedia communications. The network has been specifically designed to serve as a testbed on which evaluate the effect of OFDM wireless channel. The paper overviews and simulates the ATM technology concepts and the requirements of wireless ATM from mobility and modulation technique

Achieving Fairness, Simplicity, and Near Optimal Performance in Rate Adaptation Algorithms for Wireless Multiuser OFDM Systems

In this paper, we introduce the rate adaptation problem in adaptive wireless multiuser OFDM systems and illustrate its optimal solution. Due to the high complexity of this solution, we illustrate a previously proposed two-step algorithm that was suggested to simplify the adaptation process. This algorithm is based on equal distribution of power on OFDM subcarriers. We then propose a new modification on the first step of this algorithm, which makes the second step unnecessary. Finally, an enhanced version of the newly proposed single step algorithm is suggested to reach a near optimal performance

Adaptive modulation assisted with long range channel prediction for wideband fading channels

The main problem facing adaptive modulation schemes is the signaling delay inherent to such systems. A technique has been proposed by Duel Hallen et al. [1997, 2000] based on long range channel prediction for the narrowband case to alleviate the dramatic effects that this delay might have when static design is used. In this paper, this channel prediction algorithm is extended to the more general case of wideband adaptive modulation systems. The simulation results show significant improvement when using the wideband channel predictor proposed.