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ABSTRACT: WiMAX (world interoperability for microwave access) continues its development to achieve high capacity services with large cell coverage. Although, users at the cell border achieves only poor signal to interference plus noise ratio (SINR) conditions due to the high amount of interference from neighboring cells. In Egypt the 3.5 GHz band is expected to be used for the IEEE 802.16e mobile WiMAX networks because the band is licensed and interference is under control. Furthermore, higher transmission powers are allowed and a better range and coverage than at 5.8 GHz can be obtained. Therefore we will discuss in this paper the challenges facing coverage vs throughput for the SUI channel model performed at 3500 MHz at the city of Alexandria, Egypt through statistical analysis and real-time simulation software to discover the effects of channel characteristics, channel model and forward error correction techniques when designing and planning a mobile WiMAX network.
Radio Science Conference, 2009. NRSC 2009. National; 04/2009
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ABSTRACT: OFDM Wireless systems are currently in the focus of research and development. High hardware cost of such systems is an initiative to redesign the critical functional blocks in order to satisfy timing and power constrains as well as to minimize overall circuit complexity and cost. One such critical functional block is the CoOrdinate Rotation DIgital Computer (CORDIC) that can be used in various applications in OFDM systems. In this paper we apply optimization algorithms to the CORDIC processor in terms of power, area and speed for efficient FPGA implementation. Three CORDIC modules have been selected and modified to satisfy optimization requirements. The circuits have been described in Very high speed integrated circuit Hardware Description Language (VHDL), synthesized, and implemented on Xilinx Spartan-3A FPGAs kit board using ISEtrade design tool suite. The prototyped results have been tested using suitable testbench waveforms. Mapping and timing reports have been summarized. Using Matlab code relation between the delay for the published and prototyped modules has been plotted.
Computer Engineering & Systems, 2008. ICCES 2008. International Conference on; 12/2008
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ABSTRACT: In this paper, we present a modified ultra-wideband (UWB) antenna for ultra-wideband applications such as Wireless Communication and WiMax systems. It consists of a two circular-disc patch fed by a 50 Omega coaxial feed line. The obtained bandwidth (SWR les 2) is about 10 GHz (from 0.650 to 10 GHz with a bandwidth ratio (1:15.4)). The radiation characteristics are as expected for dipole antennas.
Wireless Communications and Mobile Computing Conference, 2008. IWCMC '08. International; 09/2008
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ABSTRACT: WiMAX (Worldwide Interoperability for Microwave Access) has the potential to impact all forms of telecommunications. In a fixed wireless communication, WiMAX can replace the telephone company's copper wire networks, the cable TV's coaxial cable infrastructure while offering Internet Service Provider services. In its mobile variant, WiMAX has the potential to replace cellular networks. However, it still facing real challenge for low complexity and efficient system implementation. It supports NLOS environment with high data rate transmission and high mobility up to 125km/hr. In this paper, two main issues are discussed. The first one presents models for simulating OFDM WiMAX system in Simulink including channel estimation and equalization subsystems in MATLAB functions. Next, the effect of channel estimation error on the performance of MIMO VBLAST receivers in uncorrelated Rayleigh flat fading channels is investigated,
Communications Workshop, 2008. LCW 2008. IEEE Lebanon; 07/2008
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ABSTRACT: 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.
Information and Communications Technology, 2007. ICICT 2007. ITI 5th International Conference on; 01/2008
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ABSTRACT: 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.
Computer Engineering & Systems, 2007. ICCES '07. International Conference on; 12/2007
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ABSTRACT: 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.
Radio Science Conference, 2007. NRSC 2007. National; 04/2007
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ABSTRACT: A new blind channel estimation algorithm is proposed based on the finite alphabet property of the transmitted symbols and the correlation between the channel attenuations at the adjacent subcarriers. The new method preserves the classical OFDM transmitter structure with cyclic prefix (CP) used in all standardized multicarrier systems (such as DAB, IEEE802.11a, Hiperlan/2, etc.) as well as the newly proposed OFDM with zero padding (ZP). The new method proves to provide an unbiased channel estimates and its performance is independent of the channel zero locations. The new method also works using only short data records for channels with short delay spread (e.g., indoor channels).
Signal Processing Advances in Wireless Communications, 2004 IEEE 5th Workshop on; 08/2004
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ABSTRACT: 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.
Radio Science Conference, 2004. NRSC 2004. Proceedings of the Twenty-First National; 04/2004
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ABSTRACT: A new blind channel estimation algorithm is proposed based on the finite alphabet property of the transmitted symbols and the correlation between the channel attenuations at the adjacent subcarriers. The new method preserves the classical OFDM transmitter structure with cyclic prefix (CP) used in all standardized multicarrier systems (such as DAB, IEEE802.Ha, Hiperlan/2, etc.) as well as the newly proposed OFDM with zero padding (ZP). The new method proves via simulations to provide an unbiased channel estimates and its performance is independent of the channel zero locations.
Radio Science Conference, 2004. NRSC 2004. Proceedings of the Twenty-First National; 04/2004
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ABSTRACT: 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 image sequences. Canny method was used to detect the vessel edges due to its high level of detection for this kind of images. The method will estimate and track the heart motion during the operation and draw the road map in a real time dynamic way. The road map will be 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.
Engineering in Medicine and Biology Society, 2003. Proceedings of the 25th Annual International Conference of the IEEE; 10/2003
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ABSTRACT: A set of hard real time (HRT) connection scan can be admitted only if the worst-case end-to-end delays of cells belonging to individual connections are less than their deadlines. Using a new optimal leaky bucket regulator algorithm to provide simple and user programmable mean of traffic regulation to meet the delay requirements of the hard real time connections, by selecting the burst parameters (β) of the leaky bucket to meet connections deadline is designed and analyzed. The implemented algorithm is optimal in the sense that it always selects a set of burst parameters whose mean value is minimal and by which the delay requirements of the hard real time connections can be met. As well as, improving the system performance, in terms of connection admission probability. The implemented algorithm is new in the sense that it uses the leaky bucket regulator as a method for guaranteeing the end-to-end deadline of hard real time networks not as it was traditionally used as a policing mechanism when the source traffic does not conform to network characteristics.
Radio Science Conference, 2003. NRSC 2003. Proceedings of the Twentieth National; 04/2003
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ABSTRACT: 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.
Radio Science Conference, 2003. NRSC 2003. Proceedings of the Twentieth National; 04/2003
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ABSTRACT: The bare ear and the stethoscope were until recently of great help in classifying most heart diseases especially those related to valve problems. The newly developed electronic stethoscope and phonocardiography represent useful tools for recording heart sound signals. In this paper a diagnostic technique for heart diseases using heart sounds is suggested. Wavelet decomposition and mel cepstrum are used for feature extraction. Classification of the different heart diseases is then done using hidden Markov models (HMM). Three different techniques have been used and compared. The obtained recognition rates (RR) were 97.3%, 98.2%, and 99.1%.
Electrotechnical Conference, 2002. MELECON 2002. 11th Mediterranean; 02/2002
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ABSTRACT: Future mobile systems will support services with different data rates. In this paper, we propose centralized feed-forward feedback architectures for adaptive minimum mean square error (MMSE) detectors for asynchronous multirate direct sequence code division multiple access (DS-CDMA) systems. A multipath Rayleigh fading channel is assumed. The MMSE detector is implemented using the recursive least squares (RLS) algorithm. We compare between the different. proposed architectures and the results are verified using simulations.
Radio Science Nineteenth National Conference of the Proceedings NRSC 2002; 02/2002
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ABSTRACT: We study the performance of a DS-CDMA blind multiuser detector in
multipath Rayleigh fading channels for high data rates where the delay
spread can be larger than one symbol duration. We study blind recursive
least squares (RLS) detectors with an additional constraint on the
energy of the filter tap weights. This constraint prevents the
cancellation of the desired signal in case the estimated subspace of the
desired signal suffers from a mismatch. Simulations show that in cases
of high signal to interference and noise ratios (SINR) as well as in
cases of severe inter-symbol interference (ISI), our proposed detector
is superior to previously proposed detectors for multipath
channels
Info-tech and Info-net, 2001. Proceedings. ICII 2001 - Beijing. 2001 International Conferences on; 02/2001
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ABSTRACT: Most benign breast tumors possess well-defined, sharp boundaries that delineate them from surrounding tissues, as opposed to malignant tumors. Computer techniques proposed to date for tumor analysis have concentrated on shape factors of tumor regions and texture measures. While shape measures based on contours of tumor regions can indicate differences in shape complexities between circumscribed and spiculated tumors, they are not designed to characterize the density variations across the boundary of a tumor. In this paper we propose a region-based measure of image edge profile acutance which characterizes the transition in density of a region of interest (ROI) along normals to the ROI at every boundary pixel. We investigate the potential of acutance in quantifying the sharpness of the boundaries of tumors, and propose its application to discriminate between benign and malignant mammographic tumors. In addition, we study the complementary use of various shape factors based upon the shape of the ROI, such as compactness, Fourier descriptors, moments, and chord-length statistics to distinguish between circumscribed and spiculated tumors. Thirty-nine images from the Mammographic Image Analysis Society (MIAS) database and an additional set of 15 local cases were selected for this study. The cases included 16 circumscribed benign, seven circumscribed malignant, 12 spiculated benign, and 19 spiculated malignant lesions. All diagnoses were proven by pathologic examinations of resected tissue. The contours of the lesions were first marked by an expert radiologist using X-Paint and X-Windows on a SUN-SPARCstation 2 Workstation. For computation of acutance, the ROI boundaries were iteratively approximated using a split/merge and end-point adjustment technique to obtain the best-fitting polygonal approximation. The jackknife method using the Mahalanobis distance measure in the BMDP (Biomedical Programs) package was used for classification of the lesions using acutance and the shape factors as features in various combinations. Acutance alone resulted in a benign/malignant classification accuracy of 95% the MIAS cases. Compactness alone gave a circumscribed/spiculated classification rate of 92.3% with the MIAS cases. Acutance in combination with a moment-based shape measure and a Fourier descriptor-based measure gave four-group classification rate of 95% with the MIAS cases. The results indicate the importance of including lesion edge definition with shape information for classification of tumors, and that the proposed measure of acutance fills this need.
IEEE Transactions on Medical Imaging 12/1997; 16(6):799-810. · 3.64 Impact Factor
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ABSTRACT: Much work has been performed in the area of automatic recognition
of the sonar signals to reduce the operator load when confronted with
many beams of data concurrently. This paper describes a neural network
system which is capable of recognizing different types of sonar signals.
The given results show that neural network techniques have the potential
as possible implementation solutions for the recognition of a target
with complex geometrical shape
Information, Communications and Signal Processing, 1997. ICICS., Proceedings of 1997 International Conference on; 10/1997
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ABSTRACT: Distinguishing between benign and malignant breast tumors requires
careful analysis of their shape complexity and radiographic definition.
In this paper we examine the usefulness of shape factors such as
compactness, moments, Fourier descriptors, and statistics of chord
lengths in distinguishing between circumscribed/spiculated and
benign/malignant masses. A database of 54 tumors was used in pattern
classification experiments. Classification accuracies of 95% for
circumscribed/spiculated, 76% for benign/malignant, and 77% for
four-group classification were obtained, which indicate the usefulness
of the proposed methods in breast cancer diagnosis
Electrical and Computer Engineering, 1996. Canadian Conference on; 06/1996
