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Recent Submissions

  • Indigenously Developed HD Video Transmission System for UAVs Employing a 3 × 3 MIMO Antenna System

    Akhter, Zubair; Bilal, Rana Muhammad; Telegenov, Kuat; Feron, Eric; Shamim, Atif (IEEE Open Journal of Antennas and Propagation, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-16) [Article]
    Real-time high-definition (HD) video transmission for long distances (.1 km) between an unmanned aerial vehicle (UAV) and a ground station is a challenging problem. The existing real-time solutions are limited to relatively low-quality video streaming, whereas an HD video, which is stored in the local memory, is accessible only when the UAV returns to the ground. In this study, a real-time HD video transmission system (VTS) with a multiple-input multiple-output (MIMO) antenna configuration and state-of-the-art coverage is proposed for security and inspection applications. The proposed VTS employs ultrathin, lightweight antennas that are suitable for seamless integration with a UAVfs body without any protrusion. A 3 × 3 MIMO configuration with large antenna bandwidths (3.9% at 2.4 GHz and 6.9% at 5.2 GHz ) enables the simultaneous transmission of multiple data streams with high data rates (>30 Mbps), and a high antenna gain ( 10 dBi) allows a relatively long communication range (>3 km). In field experiments, the UAV module (comprising thin conformal antennas, embedded electronics, an RF transceiver, and an HD camera) is attached to a commercial drone DJI Matrice 600 Pro. The HD videofs reception performance is investigated for operation in two frequency bands (2.4 and 5.2 GHz) for both horizontal and vertical antenna orientations. The maximum and average data rates for various distances are reported. Based on the conducted field experiments, it is found that the proposed VTS is capable of transmitting real-time HD video up to a 3.56-km distance with a receiver sensitivity of.76 dBm. The maximum achieved data rates at a 500-m distance are 10 and 43 Mbps for operation in the 2.4-and 5.2-GHz frequency bands, respectively.
  • High-Temperature Annealing Effects on Atomically Thin Tungsten Diselenide Field-Effect Transistor

    Khan, Muhammad Atif; Mehmood, Muhammad Qasim; Massoud, Yehia Mahmoud (Applied Sciences, MDPI AG, 2022-08-13) [Article]
    Two-dimensional (2D) material-based devices are expected to operate under high temperatures induced by Joule heating and environmental conditions when integrated into compact integrated circuits for practical applications. However, the behavior of these materials at high operating temperatures is obscure as most studies emphasize only room temperature or low-temperature operation. Here, the high-temperature electrical response of the tungsten diselenide (WSe2) field-effect transistor was studied. It is revealed that 350 K is the optimal annealing temperature for the WSe2 transistor, and annealing at this temperature improves on-current, field-effect mobility and on/off ratio around three times. Annealing beyond this temperature (360 K to 670 K) adversely affects the device performance attributed to the partial oxidation of WSe2 at higher temperatures. An increase in hysteresis also confirms the formation of new traps as the device is annealed beyond 350 K. These findings explicate the thermal stability of WSe2 and can help design 2D materials-based durable devices for high-temperature practical applications.
  • Deep-Learning Based Channel Estimation for RIS-Aided mmWave Systems with Beam Squint

    Abdallah, Asmaa; Celik, Abdulkadir; Mansour, Mohammad M.; Eltawil, Ahmed (IEEE, 2022-08-11) [Conference Paper]
    Reconfigurable intelligent surface (RIS) assisted wireless systems require accurate channel state information (CSI) to control wireless channels and improve overall network performance. However, CSI acquisition is non-trivial due to the passive nature of RIS, and the dimensions of the cascaded channel between transceivers increase with the large number of RIS elements, which requires high training overhead. Prior art has considered frequency-selective channel estimation without considering the beam squint effect in wideband systems, severely degrading channel estimation performance. This paper proposes a novel data-driven approach for estimating wideband cascaded channels of RIS-assisted multi-user millimeter-wave massive multiple-input multiple-output (MIMO) systems with limited training overhead, explicitly considering the effect of beam squint. To circumvent the beam squint effect, the proposed method exploits the common sparsity property among the different subcarriers as well as the double-structured sparsity property of the users’ angular cascaded channel matrices. The proposed data-driven cascaded channel estimation approach exploits denoising neural networks to detect channel supports accurately. Compared to beam squint effect agnostic traditional orthogonal matching pursuit (OMP) approaches, the proposed data-driven approach achieves 5-6dB less normalized mean square error (NMSE) and reduces the lower bound gap to only 1dB for the oracle least-square benchmark.
  • Laser-Powered UAVs for Wireless Communication Coverage: A Large-Scale Deployment Strategy

    Lahmeri, Mohamed-Amine; Kishk, Mustafa A.; Alouini, Mohamed-Slim (IEEE Transactions on Wireless Communications, IEEE, 2022-08-09) [Article]
    The use of unmanned aerial vehicles (UAVs) is strongly advocated for sixth-generation (6G) networks, as the 6G standard will not be limited to improving broadband services, but will also target the extension of the geographical cellular coverage. In this context, the deployment of UAVs is considered a key solution for seamless connectivity and reliable coverage. That being said, it is important to underline that although UAVs are characterized by their high mobility and their ability to establish line-of-sight (LOS) links, their use is still impeded by several factors such as weather conditions, their limited computing power, and, most importantly, their limited energy. In this work, we are aiming for the novel technology that enables indefinite wireless power transfer for UAVs using laser beams. We propose a novel UAV deployment strategy, based on which we analyze the overall performance of the system in terms of wireless coverage. To this end, we use tractable tools from stochastic geometry to model the complex communication system. We analyze the user’s connectivity profile under different laser charging capabilities and in different type of environments. We show a decrease in the coverage probability by more than 12% in moderate-to-strong turbulence conditions compared to low turbulence conditions. We also show how the connection rate to the aerial network significantly decreases in favor of the terrestrial network for short laser charging ranges. We conclude that laser-powered drones are considered interesting alternatives when placed in LOS with users, in low-to-moderate optical turbulence, and at reasonable ranges from the charging stations.
  • Waveguiding via Transformation Optics

    Elizarov, Maxim; Fratalocchi, Andrea (IEEE, 2022-08-09) [Conference Paper]
    We demonstrate that it is possible to surpass current limitations of nanophotonics and plasmonics by designing an artificial material which can emulate user-defined spatial refractive index distribution. The effective optical property of the material is engineered through the deformation of reflective substrate via transformation optics approach. We provide one of possible applications - subwavelength optical waveguide coupler device based on this technique.
  • Energy Efficiency Analysis of Charging Pads-powered UAV-enabled Wireless Networks

    Qin, Yujie; Kishk, Mustafa Abdelsalam; Alouini, Mohamed-Slim (arXiv, 2022-08-07) [Preprint]
    This paper analyzes the energy efficiency of a novel system model where unmanned aerial vehicles (UAVs) are used to provide coverage for user hotspots (user clusters) and are deployed on charging pads to enhance the flight time. We introduce a new notion of "cluster pairs" to capture the dynamic nature of the users' spatial distribution in order to exploit one of the top advantages of UAVs, which is the mobility and relocation flexibility. Using tools from stochastic geometry, we first derive a new distance distribution that is vital for energy efficiency analysis. Next, we compute the coverage probability under two deployment strategies: (i) one UAV per cluster pair, and (ii) one UAV per cluster. Finally, we compute the energy efficiency for both strategies. Our numerical results reveal which of the two strategies is better for different system parameters. Our work investigates some new aspects of the UAV-enabled communication system such as the dynamic density of users and the advantages or disadvantages of one- or two-UAV deployment strategies per cluster pair. By considering the relationships between the densities of user cluster pairs and the charging pads, it is shown that an optimal cluster pair density exists to maximize energy efficiency.
  • Origin of Interfacial Charges of Al2o3/Si and Al2o3/Gan Heterogeneous Heterostructures

    Wang, Chuanju; AlQatari, Feras S.; Khandelwal, Vishal; Lin, Rongyu; Li, Xiaohang (Elsevier BV, 2022-08-04) [Preprint]
    Al2O3 is a broadly employed dielectric and significant interfacial charges occur at Al2O3/semiconductor interfaces. However, the charge origin is often unclear that severely impacts device engineering and design. Al2O3/Si and Al2O3/GaN are two of the most common heterogeneous heterostructures (H2s) for many crucial devices including GaN transistors and Si solar cells. While negative charges are extensively observed in Al2O3/Si, positive charges exist in Al2O3/GaN, both of which are not well understood. In this study, we performed in-depth interfacial studies of the Al2O3/Si and Al2O3/GaN H2s to clarify the origin of the interfacial charges. Stoichiometry deviations were found at the interfaces of the two H2s where Al surpasses O for Al2O3/GaN, whereas O dominates at the Al2O3/Si interface. Therefore, we propose that the different interfacial charges are caused by nonstoichiometry atomic ratios of Al2O3 at the interface. The study indicates the important role of the semiconductor surface on the device performance, provide a deep understanding on the origin of interfacial charges at the insulator-semiconductor interfaces.
  • Beamforming Design for Integrated Sensing and Communication Systems with Finite Alphabet Input

    Cong, Dingyan; Guo, Shuaishuai; Zhang, Haixia; Ye, Jia; Alouini, Mohamed-Slim (IEEE Wireless Communications Letters, IEEE, 2022-08-04) [Article]
    Joint beamforming for integrated sensing and communication (ISAC) is an efficient way to combine two functionalities in a system at the waveform level. This letter proposes a beamforming design for ISAC systems with finite alphabet signaling. We formulate a problem to maximize the minimum Euclidean distance (MMED) among noise-free received signal vectors under a sensing constraint and a given power constraint. To tackle the formulated optimization problem, we transform it into a semi-definite programming (SDP) and solve it by the semi-definite relaxation (SDR) method. Comprehensive comparisons with existing schemes show that our proposed beamforming offers lower symbol error rate (SER), higher mutual information, and also better sensing performance than existing ISAC beamforming designs.
  • Conditional Contact Angle Distribution in LEO Satellite-Relayed Transmission

    Wang, Ruibo; Talgat, Anna; Kishk, Mustafa Abdelsalam; Alouini, Mohamed-Slim (IEEE Communications Letters, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-03) [Article]
    This letter characterizes the contact angle distribution based on the condition that the relay low earth orbit (LEO) satellite is in the communication range of both the ground transmitter and the ground receiver. As one of the core distributions in stochastic geometry-based routing analysis, the analytical expression of the Cumulative Distribution Function (CDF) of the conditional contact angle is derived. Furthermore, the conditional contact angle is applied to analyze the inaccessibility of common satellites between the ground transmitter and receiver. Finally, with the help of the conditional contact angle, coverage probability and achievable data rate in LEO satellite-relayed transmission are studied.
  • Negative Frames Matter in Egocentric Visual Query 2D Localization

    Xu, Mengmeng; Fu, Cheng-Yang; Li, Yanghao; Ghanem, Bernard; Perez-Rua, Juan-Manuel; Xiang, Tao (arXiv, 2022-08-03) [Preprint]
    The recently released Ego4D dataset and benchmark significantly scales and diversifies the first-person visual perception data. In Ego4D, the Visual Queries 2D Localization task aims to retrieve objects appeared in the past from the recording in the first-person view. This task requires a system to spatially and temporally localize the most recent appearance of a given object query, where query is registered by a single tight visual crop of the object in a different scene. Our study is based on the three-stage baseline introduced in the Episodic Memory benchmark. The baseline solves the problem by detection and tracking: detect the similar objects in all the frames, then run a tracker from the most confident detection result. In the VQ2D challenge, we identified two limitations of the current baseline. (1) The training configuration has redundant computation. Although the training set has millions of instances, most of them are repetitive and the number of unique object is only around 14.6k. The repeated gradient computation of the same object lead to an inefficient training; (2) The false positive rate is high on background frames. This is due to the distribution gap between training and evaluation. During training, the model is only able to see the clean, stable, and labeled frames, but the egocentric videos also have noisy, blurry, or unlabeled background frames. To this end, we developed a more efficient and effective solution. Concretely, we bring the training loop from ~15 days to less than 24 hours, and we achieve 0.17% spatial-temporal AP, which is 31% higher than the baseline. Our solution got the first ranking on the public leaderboard.
  • Coverage Enhancement of Underwater Internet of Things Using Multi-Level Acoustic Communication Networks

    Xu, Jiajie; Kishk, Mustafa Abdelsalam; Alouini, Mohamed-Slim (IEEE Internet of Things Journal, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-03) [Article]
    Underwater acoustic communication networks (UACNs) are considered a key-enabler to the underwater internet of things (UIoT). UACN is regarded as essential for various marine applications such as monitoring, exploration, and trading. However, a large part of existing literature disregards the 3-dimensional (3D) nature of the underwater communication system. In this paper, we propose a K-tier UACN that acts as a gateway that connects the UIoT with the Space-Air-Ground-Sea Integrated System (SAGSIS). The proposed network architecture consists of several tiers along the vertical direction with adjustable depths. On the horizontal dimension, the best coverage probability (CP) is computed and maximized by optimizing the densities of surface stations (SSs) in each tier. On the vertical dimension, the depth of each tier is also optimized to minimize inter-tier interference and maximize overall system performance. Using tools from stochastic geometry, the total CP of the proposed K-tier network is analyzed. For given spatial distribution of UIoT device’s depth, the best CP can be achieved by optimizing the depths of the transceivers connected to the SSs through a tether. We verify the accuracy of the analysis using Monte-Carlo simulations. In addition, we draw multiple useful system-level insights that help optimize the design of underwater 3D networks based on the given distribution of UIoT device’s depths.
  • Source Reconstruction of Electronic Circuits in Shielding Enclosures Based on Numerical Green’s Function and Application in Electromagnetic Interference Estimation

    Wang, Zi An; Xiao, Zhi Fei; Mao, Jun Fa; Jiang, Li Jun; Bagci, Hakan; Li, Ping (IEEE Transactions on Microwave Theory and Techniques, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-02) [Article]
    In this work, to characterize the radiated emission from electronic circuits in shielding enclosure, an improved electric dipole-based source reconstruction method (SRM) is developed. Moreover, by resorting to this reconstructed equivalent source, the estimation of electromagnetic interference (EMI) between different circuit modules in the enclosure can be conveniently and accurately evaluated. Different from the free-space SRM, the equivalent dipoles of the proposed SRM are directly placed over the shielding box enclosed circuit board, and the numerical Green’s function (NGF) is developed to bridge the connection between the equivalent dipoles and the planar scanned magnetic near-field. With the NGF strategy, the effects of surrounding environments (including the presence of substrate, ground plane, and shielding enclosure) are inclusively considered, which makes the proposed SRM valid for any complex EM environments in theory. Since the proposed SRM also has the capability of reproducing the radiated emission inside the shielding enclosure, it is critically helpful to evaluate the EMI between different circuit modules inside the shielding enclosure. To reach this aim, the Rayleigh-Carson Reciprocity theorem is referred, in which the original EM coupling problem is decomposed into the “forward problem” and “reverse problem.” A Huygens box enclosing the victim circuit module is built and the EM fields on the box are obtained using the reconstructed dipoles in both problems. Then the EMI can be calculated accordingly. Therefore, the novelty and merits of the proposed approach are threefold: 1) the physically-based equivalent dipole model considers the interactions between the radiation sources and the surrounding objects, leading to the accurate prediction of radiated emissions both outside and inside the enclosure; 2) due to the utilization of the NGF, there is no approximation involved in the solution of the dipole’s radiation, thus improving the calculation precision; and 3) the near-field coupling between multiple electronic circuit modules inside the shielding enclosure can be identified precisely, which is useful for diagnostics of radiation sources. The effectiveness of this algorithm is verified by representative numerical examples.
  • Current Trend in Optical Internet of Underwater Things

    Guo, Yujian; Kong, Meiwei; Alkhazragi, Omar; Sait, Mohammed; Kang, Chun Hong; Ashry, Islam; Yang, Qunhui; Ng, Tien Khee; Ooi, Boon S. (IEEE Photonics Journal, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-02) [Article]
    Our Earth is a “blue planet” that 70% of the surface is covered by the oceans, but most area of oceans remain largely unexplored. Besides supporting the Earth's ecosystem and moderating climate change, oceans are rich in economically relevant natural resources ready for harvesting, such as fishery, oil and gas, and mineral resources. Ocean observation and monitoring are therefore essential for environmental preservation and sea exploration. With the availability of advanced communication techniques, researchers began to look into distributed data acquisition and ocean interconnectivity, which engendered the concepts of intelligent ocean and the Internet-of-Underwater-Things (IoUT) framework. The framework is gaining traction since one could incorporate fiber sensing, acoustic, radio frequency, and optical wireless communication technologies to establish stable, broad-coverage, and massive ocean networks. The development of underwater internet beyond acoustic communication is still in its relative infancy, and therefore more aggregated research efforts from the related communities will be required to eventually achieve breakthroughs in comprehensive IoUT technologies. This review sheds light on the practical considerations and solutions to the challenges and robustness of the optical IoUT network in terms of channel characterization, turbulence studies, mobility, receiver optimization, and the application layer.
  • Broad-Band Polarization-Insensitive Metasurface Holography with a Single-Phase Map

    Javed, Isma; Kim, Joohoon; Naveed, Muhammad Ashar; Oh, Dong Kyo; Jeon, Dongmin; Kim, Inki; Zubair, Muhammad; Massoud, Yehia Mahmoud; Mehmood, Muhammad Qasim; Rho, Junsuk (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-08-01) [Article]
    The remarkable potential of metasurface holography promises revolutionary advancements for imaging, chip-integrated augmented/virtual reality (AR/VR) technology, and flat optical displays. The choice of constituent element geometry constrains many potential applications purveyed through polarization-independent optical response. The limited capabilities and degree of freedoms in commonly used meta-atoms restrict the design flexibility to break the conventional trade-off between polarization-insensitivity and bandwidth. Here, we propose a geometric phase-enabled novel design strategy to break this conventional trade-off. The proposed strategy ensures the realization of broad-band polarization-insensitivity through a simplified design procedure. An identical output wavefront manipulation is achieved by adjusting the phase delay freedom of geometric phase engineering under different incident polarization conditions. For proof of concept, a metahologram device is fabricated by an optimized complementary metal–oxide–semiconductor (CMOS)-compatible material of hydrogenated amorphous silicon (a-Si:H). This metahologram device reproduces the required hologram with high image fidelity and efficiency under different polarization scenarios of white light incidence. Due to the simple design strategy, low computational cost, and easy fabrication, the proposed technique can be an excellent candidate for realizing polarization-insensitive metahologram devices.
  • Optical and interfacial characteristics of a heterojunction between (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 and α-Al2O3 crystals

    Alfaraj, Nasir; Li, Kuang-Hui; Braic, Laurentiu; Hedhili, Mohamed N.; Guo, Zaibing; Ng, Tien Khee; Ooi, Boon S. (Optical Materials Express, Optica Publishing Group, 2022-08-01) [Article]
    In this article, we determine the band alignment at the thermodynamically stable heterointerface between a (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 crystal and bulk c-plane sapphire, namely, (0001)-oriented α-Al2O3. The β-(In0.072Ga0.928)2O3 layer was deposited on the bulk sapphire crystal using pulsed laser deposition. The β-(In0.072Ga0.928)2O3 and α-Al2O3 valence and conduction band offsets (VBO and CBO, respectively) were found to be 0 ± 0.1 and 4.87 ± 0.1 eV, respectively. Accordingly, we identified a type-I α-Al2O3/β-(In0.072Ga0.928)2O3 heterojunction. X-ray diffraction measurements confirmed (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 high-quality films with in-plane rotations of every 120∘, whereas Rutherford backscattering spectrometry was employed to verify the bulk composition. We employed high-resolution X-ray photoelectron spectroscopy to measure the core level binding energies of Al 2p and Ga 2p3/2 with respect to the valence band maxima of the β-(In0.072Ga0.928)2O3 and α-Al2O3 layers, respectively. Then, we measured the energy separation between the Al 2p and Ga 2p3/2 core levels at the interface of the heterojunction. β-(InGa)2O3 is a wide-bandgap semiconductor, while α-Al2O3 is a well-known dielectric. Together, they can be employed to fabricate reliable and efficient power electronic devices. We also combined high-resolution transmission electron microscopy, X-ray diffraction, and fast Fourier transform algorithms to characterize the dislocations at the interface.
  • Distributed Resource Management in Downlink Cache-Enabled Multi-Cloud Radio Access Networks

    Reifert, Robert-Jeron; Ahmad, Alaa Alameer; Dahrouj, Hayssam; Chaaban, Anas; Sezgin, Aydin; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim (IEEE Transactions on Vehicular Technology, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-01) [Article]
    A compound of several clouds, jointly managing large-scale inter-cloud and intra-cloud interference, promises to be a practical solution to account for the ambitious premises of beyond fifth generation networks. This paper considers a multi-cloud radio access network (MC-RAN), where each cloud is connected to a distinct set of cache-enabled base stations (BSs) via limited capacity fronthaul links. The BSs are equipped with local cache storage and baseband processing capabilities, as a means to alleviate the fronthaul congestion problem. The paper then investigates the problem of jointly assigning users to clouds and determining their beamforming vectors so as to maximize the network-wide energy efficiency subject to fronthaul capacity and transmit power constraints. This paper solves such a mixed discrete-continuous, non-convex optimization problem using fractional programming and successive inner-convex approximation techniques to deal with the non-convexity of the continuous part of the problem, and l0-norm approximation to account for the binary association part. A highlight of the proposed algorithm is its capability of being implemented in a distributed fashion across the multiple clouds through a reasonable amount of information exchange. The numerical simulations illustrate the pronounced role the proposed algorithm plays in improving the energy efficiency of large-scale cache-enabled MC-RANs, especially at the high interference regime.
  • Real-Time Testing of Synchrophasor-Based Wide-Area Monitoring System Applications Acknowledging the Potential Use of a Prototyping Software Toolchain

    Kumar, Lalit; Ahmed, Shehab; Vanfretti, Luigi; Kishor, Nand (International Transactions on Electrical Energy Systems, Hindawi Limited, 2022-07-30) [Article]
    This article presents a study on real-time testing of synchrophasor-based “wide-area monitoring system’s applications (WAMS application).” Considering the growing demand of real-time testing of “wide-area monitoring, protection, and control (WAMPAC)” applications, a systematic real-time testing methodology is formulated and delineated in diagrams. The diagrams propose several stages through which an application needs to be assessed (sequentially) for its acceptance prior to implementation into a production system. However, only one stage is demonstrated in this article which comprises the use of a prototyping software toolchain and whose potential is assessed as sufficient for preliminary real-time testing (PRTT) of WAMS applications. The software toolchain is composed of two components: the MATLAB software for application prototyping and other open-source software that allows ingesting prerecorded phasor measurement unit (PMU) signals. With this software toolchain, a PRTT study is presented for two WAMS applications: “testing of the PMU/phasor data concentrator (PDC)” and “testing of wide-area forced oscillation (FO) monitoring application.”
  • Max-Min Data Rate Optimization for RIS-aided Uplink Communications with Green Constraints

    Subhash, Athira; Kammoun, Abla; Elzanaty, Ahmed; Kalyani, Sheetal; Al-Badarneh, Yazan H.; Alouini, Mohamed-Slim (arXiv, 2022-07-30) [Preprint]
    Smart radio environments aided by reconfigurable intelligent reflecting surfaces (RIS) have attracted much research attention recently. We propose a joint optimization strategy for beamforming, RIS phases, and power allocation to maximize the minimum SINR of an uplink RIS-aided communication system. The users are subject to constraints on their transmit power. We derive a closed-form expression for the beam forming vectors and a geometric programming-based solution for power allocation. We also propose two solutions for optimizing the phase shifts at the RIS, one based on the matrix lifting method and one using an approximation for the minimum function. We also propose a heuristic algorithm for optimizing quantized phase shift values. The proposed algorithms are of practical interest for systems with constraints on the maximum allowable electromagnetic field exposure. For instance, considering 24-element RIS, 12-antenna BS, and 6 users, numerical results show that the proposed algorithm achieves close to 300% gain in terms of minimum SINR compared to a scheme with random RIS phases.
  • Weight Vector Tuning and Asymptotic Analysis of Binary Linear Classifiers

    Niyazi, Lama; Kammoun, Abla; Dahrouj, Hayssam; Alouini, Mohamed-Slim; Al-Naffouri, Tareq Y. (IEEE Open Journal of Signal Processing, IEEE, 2022-07-29) [Article]
    Unlike its intercept, a linear classifier's weight vector cannot be tuned by a simple grid search. Hence, this paper proposes weight vector tuning of a generic binary linear classifier through the parameterization of a decomposition of the discriminant by a scalar which controls the trade-off between conflicting informative and noisy terms. By varying this parameter, the original weight vector is modified in a meaningful way. Applying this method to a number of linear classifiers under a variety of data dimensionality and sample size settings reveals that the classification performance loss due to non-optimal native hyperparameters can be compensated for by weight vector tuning. This yields computational savings as the proposed tuning method reduces to tuning a scalar compared to tuning the native hyperparameter, which may involve repeated weight vector generation along with its burden of optimization, dimensionality reduction, etc., depending on the classifier. It is also found that weight vector tuning significantly improves the performance of Linear Discriminant Analysis (LDA) under high estimation noise. Proceeding from this second finding, an asymptotic study of the misclassification probability of the parameterized LDA classifier in the growth regime where the data dimensionality and sample size are comparable is conducted. Using random matrix theory, the misclassification probability is shown to converge to a quantity that is a function of the true statistics of the data. Additionally, an estimator of the misclassification probability is derived. Finally, computationally efficient tuning of the parameter using this estimator is demonstrated on real data.
  • Effect of Winding Design on The Performance of Predictive Current Control of Six-Phase Induction Machine-Based Propulsion Systems

    Shawier, Abdullah; Abdel-Majeed, Mahmoud; Abdel-Azim, Wessam E.; Abdel-Khalik, Ayman S.; Hamad, Mostafa S.; Ahmed, Shehab; Hamdan, Eman; Elmalhy, Noha A. (IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2022-07-29) [Article]
    Electric propulsion based on six-phase machines in marine propulsion and automotive traction applications are undergoing rapid development due to its high capacity, fault tolerance, reduced size, and reduced torque pulsations. Among different control techniques of six-phase machines, direct controllers, such as finite control set model predictive control (FCS-MPC), have extensively been studied in recent literature. One of the main problems of this controller type is the relatively poor current quality due to circulating xy current components. This problem has been tackled in literature through enhanced control techniques and/or winding design. Following both approaches, this paper extends a previous study to deeply investigate the effect of winding design on the performance of the model predictive control applied to a six-phase induction machine (SPIM). Three six-phase winding layouts have been compared, namely, dual-three phase (D3P), asymmetrical (A6P) and symmetrical (S6P) configurations. The main objective of this study is to investigate the effect of winding chording when standard three-phase stator frames are employed on the current quality of different winding configurations under classical predictive current control (PCC). A 1.5Hp prototype system has been used for this experimental comparative study.

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