Mohamed El-Tarhuni

• PhD Student at American University of Sharjah

CALL FOR PAPERS: We are pleased to announce that the 9th International Conference on Modeling, Simulation and Applied Optimization will be held in Marrakesh, Morocco on April 26th-28th 2023 (www.icmsao.org/). ICMSAO provides a venue for engineers, mathematicians, and scientists from all over the world to share their latest research results in the f...

Millimeter wave (mm-wave) communication is one of the key enabling technologies for meeting the requirements of the fifth generation (5G) wireless communication systems. It is, therefore, essential to have accurate information about the mm-wave radio channel characteristics for successful deployment of these systems. There are many recent mm-wave c...

In this paper, we propose an adaptive scheme to deliver scalable VoD streams over a cognitive radio network (CRN) that consists of a base station (BS) and multiple secondary users (SUs). The proposed scheme aims at improving the perceptual quality of the received videos at the SUs end while maintaining a continuous playback. To do so, the scheme op...

In this paper, a new technique for delay estimation of multipath components in wideband communication systems is proposed. The proposed scheme uses the Expectation Maximization algorithm at the output of an energy detector in order to separate the multipath components from the noise components. The proposed scheme provides comparable performance to...

We investigate the performance of modified non orthogonal multiple access (NOMA) which uses the modified low complexity Vertical Bell Laboratories Layered Space Time (C-V-BLAST) in an uplink massive multiple-input-multiple-output (MIMO) deployment with distributed single-antenna users and a large base-station array. Unlike previous work which assum...

In this study, an integrated scheme is proposed to stream real-time scalable videos from a base station to multiple secondary users over cognitive radio networks. The objective of the proposed scheme is to maintain continuous video playback with acceptable perceptual quality at the secondary users end. The proposed scheme is a channel allocation al...

In this paper, an adaptive integrated framework is devised to provide continuous video service from a base station to multiple secondary users over a cognitive radio network. A channel allocation algorithm is introduced to adaptively assign the available channels to the secondary users while taking into considerations their buffer occupancies as we...

In this paper, a Hierarchical Polynomial (HP) classifier is proposed to automatically classify M-PSK and M-QAM signals in Additive White Gaussian Noise (AWGN) and slow flat fading environments. The system uses higher order cumulants (HOCs) of the received signal to distinguish between the different modulation types. The proposed system divides the...

In this study, a framework is proposed to stream different scalable videos from a base station to multiple secondary users over cognitive radio networks. The objective of this work is to ensure that the secondary users will enjoy continuous video playback with acceptable perceptual quality. To achieve such goal, a channel allocation algorithm is in...

In this paper, we propose an improved spectrum access algorithm for cognitive radio applications using a Hidden Markov Model (HMM) for learning the primary user channel usage pattern. The proposed scheme maximizes the channel utilization without causing significant interference to the primary user. Simulation results show that the proposed algorith...

In this paper, a new automatic modulation classification system using a polynomial classifier is proposed. The feature set used in the proposed system is comprised of second, fourth and sixth higher order cumulants of the received signal. The polynomial classifier expands the feature vector into a higher dimensional space in which the different mod...

In this paper, we propose a Double-Dwell (DD) Carrier Frequency Offset (CFO) estimation algorithm for Orthogonal Frequency Division Multiplexing (OFDM) signals. The proposed scheme is based on a two-stage correlation operation to provide an initial co arse estimate of the carrier offset followed by a much finer search to improve the accuracy. The s...

In this paper, we examine joint optimization of the transmitter/receiver pulse shaping filter of an overlay cognitive wireless system that allows both the overlay (new) and the legacy (existing) users to share the spectrum at the same time without the need of sensing the spectrum. The composite sum of the mean-squared error (MSE) of the overlay sys...

We propose an Underwater Wireless Sensor Network (UWSN) for near-shore applications using electromagnetic waves (EM). We also introduce a realistic path loss model for estimating the attenuation encountered by EM waves in underwater environments. The proposed model takes into account the variation of the seawater complex-valued relative permittivit...

In this paper, the authors propose a framework that allows an overlay new system to operate simultaneously with a legacy existing system. By jointly optimizing the transmitter and the receiver filters of the overlay system, the sum of the mean-squared error MSE of the new system plus the excess MSE in the existing system due to the introduction of...

This paper presents a novel pattern recognition approach to spectrum sensing in collaborative cognitive radio systems. In the proposed scheme, discriminative features from the received signal are extracted at each node and used by a classifier at a central node to make a global decision about the availability of spectrum holes for use by the cognit...

In this paper, the authors propose a framework that allows an overlay new system to operate simultaneously with a legacy existing system. By jointly optimizing the transmitter and the receiver filters of the overlay system, the sum of the mean-squared error MSE of the new system plus the excess MSE in the existing system due to the introduction of...

Hierarchical quadrature amplitude modulation (HQAM) enables unequal priority transmission through the use of non-uniformly spaced constellations. In this paper, we propose an adaptive HQAM (A-HQAM) scheme where the ratios between the constellation distances are regularly adjusted based on the channel condition with the objective of maximizing the t...

In wireless communication paradigms such as cognitive radio, the overlay user operates only when the channel is idle. We propose a framework that allows simultaneous co-channel operation of both the legacy and the overlay user. The sum of the mean-squared error (MSE) of the new system plus the excess MSE in the existing system due to the introducti...

We introduce an improved image transmission scheme over wireless channels with flat Rayleigh fading. The proposed scheme jointly optimizes bit power and modulation level to maximize the peak signal-to-noise ratio (PSNR) of the reconstructed image and hence improves the perceptual quality of the received image. In this optimization process, the sign...

Frequency synchronization in orthogonal frequency division multi-plexing systems is very crucial to avoid degradation due to inter-carrier interference. In this paper, we introduce a new scheme for frequency synchronization that uses a pilot-based double-dwell search strategy to estimate the frequency offset. The proposed algorithm exploits the pred...

In this paper, a pilot-assisted two-stage carrier frequency offset (CFO) estimation algorithm is proposed for OFDM signals. The proposed scheme performs a coarse search over a window of possible carrier offsets to obtain an initial estimate of the CFO. Then, a fine search is carried over a much smaller search window to obtain better accuracy of the...

In this paper, spectrum sensing in OFDM-based cognitive radio systems is modeled as a pattern recognition problem. The proposed scheme uses a linear classifier to decide on when the spectrum is busy (class 1) or not busy (class 2). Two types of feature vectors are compared in this work, namely energy estimates and cross-correlation estimates using...

A new technique for multipath detection in wideband mobile radio systems is presented. The proposed scheme is based on an intelligent search algorithm using Boolean Satisfiability (SAT) techniques to search through the uncertainty region of the multipath delays. The SAT-based scheme utilizes the known structure of the transmitted wideband signal, f...

In this paper, we implement an adaptive modulation and channel coding scheme for image transmission over Rayleigh fading channels. We propose a new approach where the modula- tion level and coding rate are selected based on the importance of the compressed bit stream and channel conditions. The proposed scheme attempts to meet a predefined target b...

In this paper, we compare the performance of two peak-to-average power ratio (PAPR) reduction schemes. Specifically, selected mapping (SLM) and partial transmit sequence (PTS) schemes are investigated. The analysis was performed for an OFDM system aligned with the IEEE 802.16e standard with 256 and 1024 subcarriers. The results indicate that SLM ha...

In this paper, we propose an adaptive modulation scheme for image transmission over fading channels. The proposed scheme partitions the received signal-to-noise (SNR) space as well as the transmitted information based on its importance. Then, it jointly considers the channel condition and the importance of the transmitted bitstream when deciding on...

This paper proposes a cooperative spectrum sensing scheme for cognitive radio networks using a polynomial classifier. The proposed scheme utilizes either coherent or cyclostationary features in the received signal at each node and the extracted features are used by a central node to make to a global decision about the availability of spectrum holes...

PN code tracking is one of the most important factors that affect the performance of spread spectrumreceivers. It is desirable to maintain PN code tracking for a long period of time and with high accuracy.This paper presents a non-coherent digital delay-locked loop (DLL) for code tracking in direct-sequencespread spectrum (DS-SS) systems. The propo...

Cognitive radio (CR) is a promising technology for improving the utilization of the scarce radio spectrum by allowing secondary users to regularly sense the spectrum and opportunistically access the under-utilized frequency bands. However, spectrum sensing in CR environment is a challenging task due to varying radio channel conditions and might lea...

This paper presents a new technique for multipath detection in wideband mobile radio systems. An intelligent search algorithm using Boolean Satisfiability (SAT) techniques is used to search for the multipath delays. The proposed algorithm finds the multipath components with high probability and hence allows the system to utilize the inherent divers...

In this paper, a joint adaptive power allocation and channel coding optimization scheme is proposed. This scheme exploitsthe difference in importance among bits used to represent an image or video signal. An offline iterative algorithm is developedto find the optimum combination of coding and power to be used for the transmission of individual bits...

This paper evaluates different multipath selection techniques for RAKE receiver application in ultra wideband (UWB) systems based on time-hopped pulse position modulation (TH-PPM). Three multipath selection criteria were investigated; namely path energy, path peak to average power ratio (PAPR), and the path cross-correlation. Different multi-path r...

In mobile radio communication systems using spread spectrum technology, an accurate estimate of the signal propagation delay is needed in order to recover the transmitted data. This process is usually done using a pseudo noise (PN) code acquisition algorithm to search for the correct propagation delay within a window of possible delays. In this pap...

The electrical engineering (ELE) program at the American University of Sharjah (AUS) is designed to fulfill the ABET criteria. Several assessment tools are used to qualitatively and quantitatively measure the level of achievement of the program's educational objectives and outcomes. These tools include alumni, employer, and graduate advisor surveys...

In this paper we propose a fair-scheduling algorithm for the transmission of video frames over wireless links. The scheme is based on the occupancy of the video decoder buffer. When the occupancy of the decoder buffer of a given video client becomes increasingly small and approaches a starvation threshold, it gets treated with a higher priority and...

In wideband code division multiple access (WCDMA) systems rake reception is used to combine signal energies of the different multipath components to form a composite signal with better characteristics. A component that is critical to the proper operation of rake receivers is the path searcher. The searcher estimates the delays of the multipath comp...

Space-time spreading (STS) is an appealing open-loop transmit diversity scheme, which has recently been included into the cdma2000 standard. It has been shown that the performance of the STS scheme is highly sensitive to fading coefficient estimation errors, particularly when the channel is highly time dispersive. In practical systems, channel esti...

In this paper, an experimental Free Space Optics (FSO) communication system is implemented and used to characterize the free space channel under different UAE weather conditions. The setup is composed of discrete components that provide for flexible implementation and testing. The effects of fog and sand on the communication link are investigated....

Dispersion-compensating fibers (DCF) location optimization is studied for WDM systems that use return-to-zero (RZ), chirped RZ (CRZ) and carrier-suppressed RZ (CSRZ) modulation schemes. Only uniform DCF spacing is considered. The analysis shows that when partial dispersion compensation is used, as is the case in practice to reduce four-wave mixing...

In conventional CDMA receivers, the detection of multipath components and RAKE finger management is normally based on the received signal energy per path. These schemes essentially overlook the interference component contaminating the total received power. Consequently, they exhibit poor multipath detection capability especially at low signal-to-in...

In this paper, a new scheme for delay estimation of multipath components in a direct-sequence spread spectrum system is presented. The proposed scheme is based on a conventional energy detector followed by an independent component analysis (ICA) algorithm. The ICA algorithm effectively decomposes the received signal into the independent paths and n...

In this paper, a low-complexity power allocation scheme for M-QAM is proposed with no need for feedback of channel state information. The Optimization is based on bit power allocation according to the importance of bits to the overall image quality. An iterative off-line algorithm is presented to find the optimum power and modulation level allocate...

Multipath detection is very important for the proper operation of wideband communication systems. Conventional detectors using constant threshold result in suboptimal performance since they either fail to detect a multipath component or provide a wrong path to the receiver. In this paper, two adaptive constant false alarm rate (CFAR) multipath dete...

Efficient image transmission over wireless networks is challenged with the limited bandwidth and time-varying nature of the underlying channels. In this paper, we propose a joint variable modulation and power allocation scheme for transmission of compressed images. In our scheme, the modulation level and allocated power are jointly optimized to min...

In this paper, optimization of minimum mean square error for image transmission using a variable M-QAM system is proposed for improving both power and bandwidth efficiencies. Optimization is based on bit power allocation according to the importance of bits to the overall image quality. An iterative off-line algorithm is presented to find the optimu...

Joint optimization of bit energy and channel coding is proposed to improve the quality of image transmission. The amount of bit energy and whether coding is used or not is decided based on minimizing the mean square error of the image; equivalently, maximizing the peak signal-to-noise ratio (PSNR). An off-line iterative algorithm to find the optimu...

In this paper, joint optimization of bit energy and coding is considered for improving the quality of compressed image transmission over wireless channels. The proposed scheme works iteratively to find the best combination of energy distribution among the transmitted bits as well as if coding should be used or not. The minimum mean-square error cri...

In current and next 3G and beyond mobile wireless systems, sharing the radio access network has become an important issue for 3G mobile operators. Sharing network infrastructure amongst operators offers an alternative solution to reduce the investment in the coverage phase of WCDMA, allows increased coverage, reduces time to market, and allows earl...

In this paper, we present a semi-analytical approach for analyzing the serial concatenation (SCC) of a high rate convolutional code and a precoded intersymbol interference (ISI) channel. The significance of the proposed approach is that it can be used to identify, for a given outer high rate code and fixed ISI channel, the precoder that results in...

An improved technique for image transmission over wireless channel with flat Rayleigh fading is considered in this paper. The proposed scheme minimizes the mean-square error in image transmission rather than the bit error rate. The minimization is done by optimizing the power allocated to each bit according to its importance to the image quality al...

In this paper, joint optimization of power allocation and channel coding is proposed for image transmission over wireless channels. The proposed scheme works, iteratively to find the optimum combination of coding and power transmitted for individual bits to minimize the mean square error for better image quality. It is shown that bits of significan...

In this paper, performance evaluation for the access channel in third generation CDMA 2000 mobile radio systems is presented. Probability of detection, probability of false alarm, and mean acquisition time are presented in a typical frequency selective Rayleigh fading mobile radio channel. The results provide a general guidelines foe selection of t...

In this paper, a new technique for power allocation to transmitted bits according to their significance on the message quality is presented. The proposed scheme is based on optimizing the power allocation to minimize the mean-square error rather than the bit error probability of image and video signals transmitted over fading wireless channels. An...

This paper addresses the problem of multipath detection in CDMA systems. In conventional CDMA receivers, the detection of multipath components and RAKE finger management is normally based on the received signal energy per path. These energy-based schemes essentially overlook the interference component contaminating the total received power. Consequ...

We investigate the impact of imperfect multipath detection on the performance of CDMA systems employing space-time spreading. Conventionally, multipath components are detected and assigned to the RAKE fingers based on their average energy content. It is shown that the errors produced by the conventional scheme in detecting the potential multipath c...

The Cramer-Rao lower bound (CRLB) and minimum mean-square error (MMSE) lower bound on the variance of phase estimation in CDMA receivers in AWGN and slow and fast Rayleigh fading conditions are presented. The bounds are useful as benchmark information for implementation of channel estimator algorithms needed for coherent combining in CDMA receivers...

In this letter, we propose a new tracking scheme that is robust against multipath fading for pseudonoise (PN) code tracking in direct-sequence-spread spectrum systems. The proposed scheme employs an adaptive filter whose taps are adapted using a block least-mean square algorithm and it results in minimizing the effect of multipath interference on t...

In CDMA systems, assignment of the RAKE fingers to the correct multipath components is crucial for the receiver to combat fading and to take advantage of the multipath diversity. This is particularly important since the number of fingers available is normally limited in order to maintain low receiver complexity. In this paper, we introduce a new RA...

A PN code tracking loop for DS-CDMA is presented with main focus on the third generation cdma2000 system. The proposed tracking scheme is based on a modified early-late delay-locked loop (DLL) structure that utilizes three non-coherent correlators and post-detection accumulations. A lock detector is used to maintain the signals aligned for a long p...

The paper is focused on estimating the signal-to-interference ratio (SIR) per multipath component in CDMA systems operating over frequency selective Rayleigh fading channels. A per-path SIR estimator is proposed and its performance is compared to the Cramer-Rao bound (CRB) derived for this problem. To account for the hardware limitations of portabl...

In this paper, a new scheme for assigning RAKE fingers in CDMA systems is proposed. The proposed finger assignment strategy uses the per-path signal-to-interference ratio (SIR) rather than the average signal strength commonly used in conventional systems. Significant improvement in performance is achieved in terms of the bit-error probability and p...

In this paper, we discuss an approach for analyzing the serial concatenation of a high rate convolutional code and a preceded intersymbol interference (ISl) channel. The proposed approach is simple and can be used to identify the preceder that results in the lowest error rate floor analytically without resorting to simulations. Also, the proposed a...

Multipath propagation is a major source of degradation in the performance of conventional PN code tracking loops. The mean-square tracking error of a conventional delay-locked loop (DLL) exhibits an irreducible floor due to the presence of closely spaced multipath components. We present a new PN code tracking algorithm that does not suffer from the...

The impact of chip waveform shaping on the synchronization performance of DS-CDMA signals is investigated. Acquisition and tracking performance are compared for signals with both full-response and partial response pulses. To ensure fair comparison, all pulses are prefiltered to occupy the same bandwidth. It is shown that full-response pulses signif...

The acquisition-based capacity of a DS/CDMA system is defined as the maximum number of simultaneous users that can achieve PN code acquisition with certain reliability. This paper introduces a novel PN code acquisition scheme utilizing an LMS adaptive filter structure to estimate the delay offset of the desired user in the presence of multiple acce...

A novel hybrid scheme utilizing an adaptive FIR filter is proposed for acquisition of DS-SS signals. Timing information on the delay offset between the incoming DS-SS signal and the locally generated replica of the spreading code is extracted from the tap-weight vector of the acquisition adaptive filter. Expressions for the mean acquisition time, d...

This paper investigates tracking of direct-sequence spread-spectrum (DS/SS) signals based on an adaptive filtering technique. It is shown that a previously proposed hardware for code acquisition is also capable of code-tracking, and, hence, by performing both acquisition and tracking with the same circuitry, a significant simplification in the over...

The capacity of a DS/CDMA system is essentially limited by the performance of the acquisition sub-system; i.e. the maximum number of users that can achieve signal acquisition with a certain degree of reliability. This paper presents a new code acquisition scheme utilizing an FIR adaptive filter that significantly outperforms matched filter based sc...

The mean acquisition time performance for a direct-sequence spread-spectrum (DS/SS) code acquisition technique utilizing a finite impulse response (FIR) least-mean-square (LMS)-adaptive filter is investigated in fading conditions. The optimum tap-weight vector for the adaptive filter is derived and computer simulation results are presented to asses...

The mean acquisition time performance for a code acquisition scheme utilizing an FIR adaptive filter is investigated. Both frequency selective and frequency nonselective Rayleigh fading channels are considered. It is shown that fading causes a performance degradation of less than 3 dB for both the coherent and noncoherent cases when the carrier pha...

This paper investigates the tracking of DS/SS signals based on an adaptive filtering technique. It is shown that a previously proposed system for code acquisition is also capable of code tracking and, by performing both acquisition and tracking with the same circuitry, significant simplification in the overall DS/SS receiver is gained. Analytical r...

The authors investigate the mean-square error (MSE) tracking performance of a DS/SS code tracking system based on an adaptive filtering technique proposed earlier. The ability of this scheme to track a fast linearly changing delay and delay changing in a random walk model is presented. It is shown that the proposed scheme outperforms the maximum li...

Code acquisition in direct sequence spread-spectrum systems must occur before data demodulation can start. In this paper, a new hybrid approach to code acquisition is proposed by using an adaptive filter. The proposed system tests several phases concurrently and, hence, offers fast acquisition with small hardware requirements. Moreover, the same sy...

The performance of a direct sequence spread spectrum (DS-SS) code division multiple access (CDMA) communications systems is highly dependent upon the set of spreading sequences used in these systems. The multiple access interference could become very large if the spreading sequences are not carefully selected. A new numerical optimization procedure...

In this paper, we study a serial concatenation scheme comprising a high-rate convolutional code and a precoded inter-symbol interference (ISI) channel. We devise techniques that lead to the joint optimization of precoder and interleaver for a fixed convolutional code and precoded ISI channel, where optimality is in the sense of achieving the lowest...

In this paper, an experimental setup for transmitting images using a direct-sequence spread spectrum wireless communication system with various adaptive Constant False Alarm Rate (CFAR) detectors is presented. Images are sent at a chip rate of 12.5 MHz operating at 2.4 GHz carrier over a wireless indoor channel. Different CFAR detectors such as CA-...

In this paper, an intelligent anti-personnel landmine detection system is proposed. The system generates continues electromagnetic waves in the (2-8GHz) range through a wave guide and analyzes the reflected signal to decide on the presence of a landmine under the ground. A multi-layer model to represent the interaction of the signal with the soil a...