Mohamed El-Tarhuni

MMSE power allocation for image and video transmission over wireless channels

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 analytical framework for the power allocation technique is developed. Two techniques of power allocation; fixed and adaptive, are investigated in the paper. Simulation results show that the proposed scheme provides a gain of about 3 dB in Eb/N0 in AWGN channels and about 4 dB in flat fading channels over conventional equal-power allocation system. This gain is achieved without any increase in bandwidth, as opposed to that achieved with channel coding. The gains achieved with this algorithm come at the expense of slight increase in the peak-to-average power ratio of the transmitted signal

A robust PN code tracking algorithm for frequency selective Rayleigh-fading channels

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 the tracking performance. We show that the mean-squared tracking error performance of the proposed scheme is not affected by the presence of closely spaced paths (e.g., one to three chips), unlike that of conventional delay locked loops. We also show that the tap-weight distribution of the filter provides accurate estimates of the multipath delays. For example, at E/sub b//N/sub 0/=5 dB, 98% of the time the path estimates lie within one sample (1/5 of a chip) from the actual delays. Furthermore, simulation results suggest that multipath delays over a wide range of terminal speeds can be tracked successfully. The proposed scheme is well suited for wideband code-division multiple-access systems where a large number of closely-spaced multipath components need to be tracked and used in RAKE combining.

Comparison of linear and polynomial classifiers for co-operative cognitive radio networks

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 lead to interference with licensed users. In this paper, we propose a new framework for CR spectrum sensing based on linear and polynomial classifiers. A cooperative CR network is considered in this paper with CR nodes collaborating in making the decision about spectrum availability. Simulation results indicate that both polynomial and linear classifiers provide high detection rate of primary users with a constant false alarm rate at very small signal to noise ratio conditions. For instance, the proposed techniques can achieve above 90% detection probability at Eb/N0 = −7dB with observation window of 50 bits and 10% false alarm rate. It is also shown that the performance improves as we increase the sensing time for both schemes.

An Underwater Wireless Sensor Network with Realistic Radio Frequency Path Loss Model

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 permittivity with frequency in contrast to previous work that treats the permittivity as a real-valued constant parameter. Furthermore, the proposed model accounts for the impedance mismatch at the seawater-air boundary, which results in a more realistic estimate of the signal attenuation. Simulation results show the expected signal levels underwater for different scenarios. A prototype implementation to measure the path loss is also presented.

A novel finger assignment algorithm for RAKE receivers in CDMA systems

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 RAKE receiver finger assignment algorithm (FAA) based on estimates of the signal-to-interference ratio (SIR) per path, as opposed to signal strength in the conventional schemes. We also introduce a simple algorithm to produce these SIR estimates. A performance comparison between the proposed scheme and the already existing schemes is presented. We show that the proposed scheme provides a significant performance improvement relative to that of the conventional schemes. For instance, the proposed scheme provides gains of up to 3.0 dB at bit error rate 10/sup -4/, relative to the conventional scheme.

An Adaptive Hierarchical QAM Scheme for Enhanced Bandwidth and Power Utilization

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 transmission efficiency. The source bit stream is divided into multiple sub-streams which are simultaneously transmitted, each on a different priority level. When using A-HQAM, the high priority sub-stream maintains an acceptable bit error rate performance over all channel conditions. As the channel condition improves, the required protection for the high priority sub-stream is reduced allowing for increasing the protection level of lower priority sub-streams. Hence, the number of sub-streams with acceptable BER performances is incrementally increased as the channel condition improves. Analysis and simulation results show that the proposed A-HQAM not only enhances the transmission efficiency but also provides reduced peak to average power ratio (PAPR). The proposed scheme offers reduced complexity by using one constellation size, unlike conventional adaptive schemes which require the use of several constellation sizes. Moreover, a practical A-HQAM implementation is presented which enables the receiver to successfully demodulate the received signal without knowing the varying transmission parameters.

Adaptive Radio Resource Management for Multi-Operator WCDMA Based Cellular Wireless Networks with Heterogeneous Traffic

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 earlier user acceptance for WCDMA and its related services. In this paper a novel radio resource management strategy known as adaptive partitioning with borrowing (APB) is proposed to cope with the implied new architectural changes. This strategy is devoted to achieve an efficient usage of the available pool of radio resources while satisfying the required quality of service (QoS) in heterogeneous traffic 3G wireless networks. Grade of service (GoS) and resources utilization are considered in this study to evaluate the network performance. Simulation results indicate that the proposed APB resource allocation provides higher resource utilization under all load conditions leading in turn to increased revenue. Moreover it provides the best balance between the system utilization and the required QoS

Automatic modulation classification based on high order cumulants and hierarchical polynomial classifiers

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 overall modulation classification problem into several hierarchical binary sub-classifications. In each binary sub-classification, the HOCs are expanded into a higher dimensional space in which the two classes are linearly separable. It is shown that there is a significant improvement when using the proposed Hierarchical polynomial structure compared to the conventional polynomial classifier. Moreover, simulation results are shown for different block lengths (number of received symbols) and at different SNR values. The proposed system showed an overall improvement in the probability of correct classification that reaches 100% using only 512 received symbols at 20 dB compared to 98% and 98.33% when using more complicated systems like Genetic Programming with KNN classifier (GP-KNN) and Support Vector Machines (SVM) classifiers, respectively.

Improving electrical engineering education at the American University of Sharjah through continuous assessment

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 programs educational objectives and outcomes. These tools include alumni, employer, and graduate advisor surveys. Results of such surveys are used to continuously improve the program curriculum, design activities, and the overall educational experience of the students. We believe that the techniques utilised in this process are crucial to the level of success that the ELE program at AUS has achieved over a relatively short-time frame. This has been reflected in the excellent academic reputation of AUS in the Middle East. Furthermore, the ELE program at AUS has received ABET accreditation in 2006 for a period of six years, which makes it the first ELE program to be fully accredited by ABET outside the USA.

Multipath Detection Using Boolean Satisfiability Techniques

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, for example, pseudo-random (PN) code, to effectively search through the entire space by eliminating subspaces that do not contain a possible solution. The paper presents a framework for modeling the multipath detection problem as a SAT application. It also provides simulation results that demonstrate the effectiveness of the proposed scheme in detecting the multipath components in frequency-selective Rayleigh fading channels.