B.S. Sharif

Newcastle University, Newcastle-on-Tyne, England, United Kingdom

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Publications (281)126 Total impact

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    Dataset: 04251082
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    Dataset: 04699768
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    ABSTRACT: In this paper, the application of wireless information and power transfer to cooperative networks is investigated, where the relays in the network are randomly located and based on the decode-forward strategy. For the scenario with one source-destination pair, three different strategies for using the available relays are studied, and their impact on the outage probability and diversity gain is characterized by applying stochastic geometry. By using the assumptions that the path loss exponent is two and that the relay-destination distances are much larger than the source-relay distances, closed form analytical results can be developed to demonstrate that the use of energy harvesting relays can achieve the same diversity gain as the case with conventional self-powered relays. For the scenario with multiple sources, the relays can be viewed as a type of scarce resource, where the sources compete with each other to get help from the relays. Such a competition is modeled as a coalition formation game, and two distributed game theoretic algorithms are developed based on different payoff functions. Simulation results are provided to confirm the accuracy of the developed analytical results and facilitate a better performance comparison.
    03/2014;
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    ABSTRACT: This paper studies different secrecy rate optimization problems for a multiple-input–multiple-output (MIMO) secrecy channel. In particular, we consider a scenario where a communication through a MIMO channel is overheard by a multiple-antenna eavesdropper. In this secrecy network, we first investigate two secrecy rate optimization problems: 1) power minimization and 2) secrecy rate maximization. These optimization problems are not convex due to the nonconvex secrecy rate constraint. However, by approximating this secrecy rate constraint based on Taylor series expansion, we propose iterative algorithms to solve these secrecy rate optimization problems. In addition, we provide the convergence analysis for the proposed algorithms. These iterative optimization approaches are developed under the assumption that the transmitter has perfect channel state information. However, there are practical difficulties in having perfect channel state information at the transmitter. Hence, robust secrecy rate optimization techniques based on the worst-case secrecy rate are considered by incorporating channel uncertainties. By exploiting the S-Procedure, we show that these robust optimization problems can be formulated into semidefinite programming at low signal-to-noise ratios (SNRs). Simulation results have been provided to validate the convergence of the proposed algorithms. In addition, numerical results show that the proposed robust optimization techniques outperform the nonrobust schemes in terms of the worst-case secrecy rates and the achieved secrecy rates.
    IEEE Transactions on Vehicular Technology 01/2014; 63(4):1678-1690. · 2.06 Impact Factor
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    ABSTRACT: A new cost efficient automated planning and optimization method is proposed for OFDMA future-generation cellular networks targeting throughput maximization. The mathematical formulation is a non-linear multi-objective optimization problem subject to minimum interference, cost and similar resource constraints at each cell within a defined heterogeneous traffic environment. The fundamental objective is to maximize the individual cell throughput without deteriorating it over other cells, which results in a throughput equilibrium maximization over multiple cells. This implicitly implies traffic and co-channel interference congestion avoidance across the network whilst maintaining both cost efficiency and quality of service (QoS) policies. Optimal solution existence is subject to the network size, traffic and computational complexity constraints which converges to a throughput equilibrium or alternatively to the well known Nash Equilibrium (NE).
    IEEE Transactions on Wireless Communications 01/2014; 13(3):1153-1163. · 2.42 Impact Factor
  • 01/2013: pages 231-256;
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    ABSTRACT: In this work, a new low complexity linear precoded orthogonal frequency division multiplexing (LP-OFDM) system, called Haar-OFDM (H-OFDM), is proposed. The proposed system employs a fast precoder, denoted as inverse D-precoder (IDP), which is derived by merging the operations of the fast Haar precoder (FHP) and inverse fast Fourier transform (IFFT) as one transform. Interestingly, the number of arithmetic operations required by the H-OFDM system are noticeably smaller than the conventional OFDM. Furthermore, extensive simulation results demonstrate that the H-OFDM system is robust against the frequency-selectivity of the channel.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In this paper, an investigation is presented into infrared nanoantennas for solar energy harvesting at 10-μm wavelength, where considerable solar energy is available. These antennas have been modeled using both the integral equation model and the circuit model. The method of moments has been utilized to solve Hallen's and Pocklington's integral equations to find the current distribution over the antenna surface by considering the conductivity and the dielectric properties of gold at this wavelength, as well as its effect on the antenna performance. For verification of the obtained results, this antenna has been simulated using a finite element method-based electromagnetic simulator and both results were found to be consistent. In addition, the metal/insulator/metal (MIM) diode has been studied and its equivalent circuit is presented. Furthermore, a solar rectenna has been constructed by overlapping the antenna arms over a small area to incorporate the MIM diode. The circuit of the solar rectenna, with mathematical expressions for the elements of the equivalent circuit, is demonstrated. Finally, a parametric study into the effect of the MIM diode on the captured voltage is conducted.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(3):9000208-9000208. · 4.08 Impact Factor
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    ABSTRACT: In this letter, a Sum-Product algorithm (SPA) utilizing soft distances is shown to be more resilient to impulsive noise than conventional likelihood-based SPAs, when the noise distribution is unknown. An efficient version of the soft distance SPA is also developed but with half the storage requirements and running time.
    IEEE Transactions on Communications 01/2013; 61(6):2113-2116. · 1.75 Impact Factor
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    ABSTRACT: There is considerable interest in the use of wireless sensor networks (WSNs) for distributed sound capture and acoustic source localisation (ASL) where array elements are spaced over a large area. High sampling rates, such as digital audio at 44.1 kHz, pose a major challenge for efficient wireless personal area network (WPAN) standards such as IEEE 802.15.4 (Zigbee) with an absolute maximum data throughput of 250 kbps. This paper investigates the effect of sampling frequency on the accuracy of time delay estimation using different algorithms in the time domain, such as basic cross correlation (BCC) and generalised cross correlation (GCC), frequency and content based features such as envelope, including generalised phase spectrum (GPS) and envelope-GPS (EGPS). Experimental and simulation studies have been undertaken which show that frequency domain and content based features algorithms can achieve more accurate time delay estimation at low sampling frequencies than time domain algorithms if the appropriate signal contents are extracted. Therefore they are more appropriate for wireless ASL applications.
    Applied Acoustics 01/2013; · 1.10 Impact Factor
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    ABSTRACT: In this paper, an investigation is presented into nanogap-based bowtie nanoarrays for THz energy detection, with the aim of optimizing their geometrical parameters utilizing finite-element method (FEM) based simulations. The bowtie elements of the array are connected by feeding lines, which are used to transfer the captured electric field away from the antenna's center to a common feeding gap. The performance of the bowtie nanoarray has been compared with a single bowtie element constructed using the same device area. The obtained results demonstrated that the array outperforms the single element bowtie. Subsequently, a parametric study is carried out on important geometrical parameters of the array to optimize its performance. The results demonstrate that the optimum spacing between array elements is 2.9 m, whereas the best line width of the feeding lines is 50 nm. Additionally, it has been found that a 25 nm gap offers the highest electric field at resonance. Furthermore, a bowtie nanoarray is designed based on the optimized parameters of the parametric study. Finally, the effects of the incident angle and curvature of the edges of the array elements and feeding lines have also been studied and their impact on the overall performance is presented in this paper.
    Terahertz Science and Technology, IEEE Transactions on. 01/2013; 3(5):524-531.
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    ABSTRACT: In this paper, a study is conducted into optimization of quantum and coupling efficiency of solar rectennas. The optical antenna impedance is calculated using Method of Moment, whereas the Metal/Insulator/Metal (MIM) diode characteristics are calculated using Simmons' formula of tunneling current. The diode resistance and the responsivity have been determined based on the I–V characteristics of the MIM diode. Additionally, the quantum and coupling efficiency have been calculated from the diode and antenna resistances as well as the diode responsivity. Furthermore, both efficiencies have been optimized by finding the optimum values of the insulator layer thickness and the metal work function difference.
    Antennas and Propagation Conference (LAPC), 2013 Loughborough; 01/2013
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    ABSTRACT: Physical layer network coding (PNC) is a novel technique that allows two users to exchange messages in a wireless network. PNC takes place at a relay node and exploits the interference caused by incoming signals from the two users to increase throughput. In this paper, the performance of a two-way relay network employing PNC is evaluated with three types of error-correcting codes used at the source and destination nodes, namely low-density parity-check codes, turbo codes and bit-interleaved coded modulation with iterative decoding (BICM-ID). All three coding schemes perform similarly in a single user system on the AWGN channel with no relay, but results obtained when employing PNC show that although there is an overall degradation in their performance of all three codes, the LDPC code performance is more seriously affected due to the Sum-Product decoding algorithm being less robust to unreliable symbols broadcast from the relay.
    Wireless and Mobile Networking Conference (WMNC), 2013 6th Joint IFIP; 01/2013
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    ABSTRACT: Throughput maximization is generally the major objective when allocating resources in orthogonal frequency division multiple access (OFDMA)networks. Traditionally, dynamic allocation methods were developed to exploit multi-user diversity in these networks. These techniques achieved significant gain in throughput by adopting relaxed convex models to define system upper bound capacity. Frequency diversity, on the other hand, is only considered to a certain extent in order to meet user service constraints. The vast majority of existing research relies on these techniques. Separately, research considering combining frequency diversity and multi-user diversity in full has been scarce. The results of our research in this paper show that using this dual diversity combining can substantially maximize system capacity and resource efficiency, and minimize outage probability whilst users' quality of service (QoS) demands are maintained.
    Vehicular Technology Conference (VTC Spring), 2013 IEEE 77th; 01/2013
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    ABSTRACT: In this paper, a study is conducted into nanogap-based, bowtie nano-array for solar energy collection, with the aim of optimizing its geometrical parameters utilizing Finite Element Method (FEM) based simulations. The optimization parameters include the metal thickness and the gap size, where it is found that the optimal metal thickness is 95 nm. The proposed optimized bowtie nano-array has been integrated with a metal-insulator-metal (MIM) diode to construct a rectenna for solar radiation rectification at 37.5 μm wavelength. The characteristics of the MIM diode have been analyzed and discussed. Finally, the effect of the incident angle on the rectenna performance has been investigated.
    Antennas and Propagation (EUCAP), 2012 6th European Conference on; 01/2012
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    ABSTRACT: This paper presents an efficient blind symbol timing estimation scheme for orthogonal frequency-division multiplexing (OFDM) systems with constant modulus constellation. The proposed technique is designed to estimate symbol timing offsets by minimizing the power difference between subcarriers with similar indices over two consecutive OFDM symbols based on the assumption that the channel slowly changes over time. The proposed power difference estimator (PDE) is totally blind because it requires no prior information about the channel or the transmitted data. Monte Carlo simulation is used to assess the PDE performance in terms of the probability of correct timing estimate $P_{\rm lock-in}$. Moreover, we propose a new performance metric denoted as the deviation from safe region (DSR). Simulation results have demonstrated that the PDE performs well in severe frequency-selective fading channels and outperforms the other considered estimators. The complexity of the PDE can be significantly reduced by incorporating a low-cost estimator to provide initial coarse timing information. The proposed PDE is realized using feedforward and early-late gate (ELG) configurations. The new PDE-ELG does not suffer from the self-noise problem inherent in other ELG estimators reported in the literature.
    IEEE Transactions on Vehicular Technology 01/2012; 61(2):509-520. · 2.06 Impact Factor
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    ABSTRACT: Multi-carrier systems are significantly affected by inter-carrier interference (ICI) produced by both travelling wave tube amplifiers (TWTAs) utilized in satellite systems and carrier frequency offsets (CFOs). To reduce the ICI, an improved version of the partial transmit sequences (PTS) scheme is proposed based the distortion-to-signal power ratio (DSR) measurements. Monte Carlo simulation results demonstrated that the proposed system outperforms the conventional PTS in terms of bit error rate (BER), effective signal-to-noise ratio (ESNR) and complementary cumulative distribution function (CCDF).
    Communications and Information Technology (ICCIT), 2012 International Conference on; 01/2012
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    ABSTRACT: High sampling frequencies in acoustic wireless sensor network (AWSN) are required to achieve precise sound localisation. But they are also mean analysis time and memory intensive (i.e., huge data to be processed and more memory space to be occupied which form a burden on the nodes limited resources). Decreasing sampling rates below Nyquist criterion in acoustic source localisation (ASL) applications requires development of the existing time delay estimation techniques in order to overcome the challenge of low time resolution. This work proposes using envelope and wavelet transform to enhance the resolution of the received signals through the combination of different time-frequency contents. Enhanced signals are processed using cross-correlation in conjunction with a parabolic fit interpolation to calculate the time delay accurately. Experimental results show that using this technique, estimation accuracy was improved by almost a factor of 5 in the case of using 4.8 kHz sampling rate. Such a conclusion is useful for developing precise ASL without the need of any excessive sensor resources, particularly for structural health monitoring applications.
    Journal of Sensors 01/2012; 2012.
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    ABSTRACT: This paper presents an efficient technique for reducing the bit error rate (BER) of orthogonal frequency-division multiplexing (OFDM) signals transmitted over nonlinear solid-state power amplifiers (SSPAs). The proposed technique is based on predicting the distortion power that an SSPA would generate due to the nonlinear characteristics of such devices. Similar to the selective-mapping or partial-transmit-sequence (PTS) schemes, the predicted distortion is used to select a set of phases that minimize the actual SSPA distortion. Simulation results confirmed that the signal-to-noise ratio that is required to obtain a BER of $ \sim\!\!\hbox{10}^{-4}$ using the proposed technique is less by about 8 dB when it is compared to the standard PTS utilizing 16 partitions. Moreover, complexity analysis demonstrated that the proposed system offers a significant complexity reduction of about 60% compared to state-of-the-art methods.
    IEEE Transactions on Vehicular Technology 01/2012; 61(5):2330-2336. · 2.06 Impact Factor
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    ABSTRACT: We propose a cross-layer resource allocation strategy, called joint bit and power allocation (JBPA), for adaptive modulation and coding (AMC)-based orthogonal frequency division multiple access (OFDMA) systems in which both coding rates and modulation order can be changed. The objective of this strategy is to maximise the system throughput as a function of the bit error rate and spectral efficiency. The JBPA strategy takes into account the total transmission power constraints and the related channel state information in order to select the suitable modulation and coding scheme for each sub-channel. The performance in terms of average throughput of the proposed strategy is examined and compared with those of the resource allocation approaches for AMC-OFDMA systems in the context of WiMAX technology. The simulation results show that the proposed JBPA strategy significantly outperforms the other approaches.
    IET Science Measurement ? Technology 01/2012; 6(3):149-158. · 1.00 Impact Factor

Publication Stats

903 Citations
126.00 Total Impact Points

Institutions

  • 1994–2013
    • Newcastle University
      • School of Electrical and Electronic Engineering
      Newcastle-on-Tyne, England, United Kingdom
  • 2009–2011
    • Khalifa University
      Abū Z̧aby, Abu Dhabi, United Arab Emirates
    • CUNY Graduate Center
      New York City, New York, United States
    • Louisiana State University
      • Department of Electrical Engineering
      Baton Rouge, LA, United States
  • 2009–2010
    • Khalifa University of Science Technology & Research
      Abū Z̧aby, Abu Dhabi, United Arab Emirates
  • 2007
    • Kuwait University
      Al Kuwayt, Al Asimah Governorate, Kuwait
  • 1993–2007
    • University of Newcastle
      • • School of Electrical Engineering and Computer Science
      • • Department of Electrical Engineering
      Newcastle, New South Wales, Australia
  • 2005
    • Sultan Qaboos University
      • Department of Electrical and Computer Engineering
      Muscat, Muhafazat Masqat, Oman
  • 2004–2005
    • United Arab Emirates University
      Al Ain, Abu Dhabi, United Arab Emirates
    • The University of Waikato
      Hamilton City, Waikato, New Zealand
  • 2003
    • Multimedia University
      Kuala Lumpor, Kuala Lumpur, Malaysia