• 2-D LDPC Codes and Joint Detection and Decoding for Two-Dimensional Magnetic Recording

      Matcha, Chaitanya Kumar; Roy, Shounak; Bahrami, Mohsen; Vasic, Bane; Srinivasa, Shayan Garani; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018-02)
      Two-dimensional magnetic recording (TDMR) is a promising technology for boosting areal densities (ADs) using sophisticated signal processing algorithms within a systems framework. The read/write channel architectures have to effectively tackle 2-D inter-symbol interference (ISI), 2-D synchronization errors, media and electronic noise sources, as well as thermal asperities resulting in burst erasures. The 1-D low-density parity check (LDPC) codes are well studied to correct large 1-D burst errors/erasures. However, such 1-D LDPC codes are not suitable for correcting 2-D burst errors/erasures due to the 2-D span of errors. In this paper, we propose construction of a native 2-D LDPC code to effectively correct 2-D burst erasures. We also propose a joint detection and decoding engine based on the generalized belief propagation algorithm to simultaneously handle 2-D ISI, as well as correct bit/burst errors for TDMR channels. This paper is novel in two aspects: 1) we propose the construction of native 2-D LDPC codes to correct large 2-D burst erasures and 2) we develop a 2-D joint signal detection-decoder engine that incorporates 2-D ISI constraints, and modulation code constrains along with LDPC decoding. The native 2-D LDPC code can correct >20% more burst erasures compared with the 1-D LDPC code over a 128 x 256 2-D page of detected bits. Also, the proposed algorithm is observed to achieve a signal-to-noise ratio gain of >0.5 dB in bit error rate performance (translating to 10% increase in ADs around the 1.8 Tb/in(2) regime with grain sizes of 9 nm) as compared with a decoupled detector-decoder system configuration over a small 2-D LDPC code of size 16 x 16. The efficacy of our proposed algorithm and system architecture is evaluated by assessing AD gains via simulations for a TDMR configuration comprising of a 2-D generalized partial response over the Voronoi media model assuming perfect 2-D synchronization.
    • 3-D Printed Parts for a Multilayer Phased Array Antenna System

      Yu, Xiaoju; Liang, Min; Shemelya, Corey; Roberson, David A.; Wicker, Ryan; MacDonald, Eric; Xin, Hao; Univ Arizona; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018-10-01)
      In this work, a three-dimensional printable multilayer phased array system was designed to demonstrate the applicability of additive manufacturing for radio frequency (RF) systems. A hybrid process incorporating a thermal wire-mesh embedding method for conductors and thermoplastic material extrusion for dielectrics is employed. The designed phased array, operating at 3.5 GHz, consists of three functional layers: a 1-to-4 Wilkinson divider at the bottom, embedded voltage-controlled phase shifters at the center, and patch antennas on the top. Standalone parts of the proposed multilayer phased array were printed to verify the integrated dielectric-conductor printing process as well as the incorporation of active semiconductor devices at room temperature.
    • 5 kW Near-Diffraction-Limited and 8 kW High-Brightness Monolithic Continuous Wave Fiber Lasers Directly Pumped by Laser Diodes

      Fang, Qiang; Li, Jinhui; Shi, Wei; Qin, Yuguo; Xu, Yang; Meng, Xiangjie; Norwood, Robert A.; Peyghambarian, Nasser; Univ Arizona, Coll Opt Sci (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-10)
      Tandem pumping technique are traditionally adopted to develop > 3-kW continuous-wave (cw) Yb3+-doped fiber lasers, which are usually pumped by other fiber lasers at shorter wavelengths (1018 nm e.g.). Fiber lasers directly pumped by laser diodes have higher wall-plug efficiency and are more compact. Here we report two high brightness monolithic cw fiber laser sources at 1080 nm. Both lasers consist of a cw fiber laser oscillator and one laser-diode pumped double cladding fiber amplifier in the master oscillator-power amplifier configuration. One laser, using 30-mu m-core Yb3+-doped fiber as the gain medium, can produce > 5-kW average laser power with near diffraction-limited beam quality (M-2<1.8). The slope efficiency of the fiber amplifier with respect to the launched pump power reached 86.5%. The other laser utilized 50-mu m-core Yb3+-doped fiber as the gain medium and produced > 8-kW average laser power with high beam quality (M-2: similar to 4). The slope efficiency of the fiber amplifier with respect to the launched pump power reach 83%. To the best of our knowledge, this is the first detailed report for > 5-kW near-diffraction-limited and > 8-kW high-brightness monolithic fiber lasers directly pumped by laser diodes.
    • Angular Photodiode Array-Based Device to Detect Bacterial Pathogens in a Wound Model

      Sweeney, Robin E.; Yoon, Jeong-Yeol; Univ Arizona, Dept Biomed Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-11)
      We have developed a device that is able to rapidly and specifically diagnose bacterial pathogens in a wound model based on Mie scatter spectra from a tissue surface. The Mie scatter spectra collected is defined as the intensity of Mie scatter over the angle of detection from a tissue surface. A 650-nm LED perpendicular to the surface illuminates a tissue sample (90 degrees) and photodiodes positioned in 10 degrees increments from 10 degrees to 80 degrees of backscatter act as the detectors to collect these Mie scatter spectra. Through principal component analysis of the Mie scatter spectra collected, we have shown significant differences between Mie scatter spectra of tissues with bacterial pathogens versus those without, as well as significant differences between each species of bacteria tested. The device developed has been tested with a porcine dermis wound model, with samples inoculated with one of three bacterial species (Staphylococcus aureus, Escherichia coli, or Salmonella Typhimurium). Such a device could be critical in the monitoring of a wound for infection and rapid, specific diagnosis of a bacterial wound infection, which would significantly reduce the time and cost associated with specific diagnosis of a bacterial wound infection currently.
    • Artificial Neural Networks-Based Intrusion Detection System for Internet of Things Fog Nodes

      Pacheco, Jesus; Benitez, Victor H.; Félix-Herrán, Luis C.; Satam, Pratik; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-04-15)
      The Internet of Things (IoT) represents a mean to share resources (memory, storage computational power, data, etc.) between computers and mobile devices, as well as buildings, wearable devices, electrical grids, and automobiles, just to name few. The IoT is leading to the development of advanced information services that will require large storage and computational power, as well as real-time processing capabilities. The integration of IoT with emerging technologies such as Fog Computing can complement these requirements with pervasive and cost-effective services capable of processing large-scale geo-distributed information. In any IoT application, communication availability is essential to deliver accurate and useful information, for instance, to take actions during dangerous situations, or to manage critical infrastructures. IoT components like gateways, also called Fog Nodes, face outstanding security challenges as the attack surface grows with the number of connected devices requesting communication services. These Fog nodes can be targeted by an attacker, preventing the nodes from delivering important information to the final users or to perform accurate automated actions. This paper introduces an Anomaly Behavior Analysis Methodology based on Artificial Neural Networks, to implement an adaptive Intrusion Detection System (IDS) capable of detecting when a Fog node has been compromised, and then take the required actions to ensure communication availability. The experimental results reveal that the proposed approach has the capability for characterizing the normal behavior of Fog Nodes despite its complexity due to the adaptive scheme, and also has the capability of detecting anomalies due to any kind of sources such as misuses, cyber-attacks or system glitches, with high detection rate and low false alarms.
    • Challenges in Building an End-to-End System for Acquisition, Management, and Integration of Diverse Data From Sensor Networks in Watersheds: Lessons From a Mountainous Community Observatory in East River, Colorado

      Varadharajan, Charuleka; Faybishenko, Boris; Henderson, Amanda; Henderson, Matthew; Hendrix, Valerie C.; Hubbard, Susan S.; Kakalia, Zarine; Newman, Alexander; Potter, Benjamin; Steltzer, Heidi; et al. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-12-05)
      The U.S. Department of Energy's Watershed Function Scientific Focus Area (SFA), centered in the East River, Colorado, generates diverse datasets including hydrological, geological, geochemical, geophysical, ecological, microbiological and remote sensing data. The project has deployed extensive field infrastructure involving hundreds of sensors that measure highly diverse phenomena (e.g. stream and groundwater hydrology, water quality, soil moisture, weather) across the watershed. Data from the sensor network are telemetered and automatically ingested into a queryable database. The data are subsequently quality checked, integrated with the United States Geological Survey's stream monitoring network using a custom data integration broker, and published to a portal with interactive visualizations. The resulting data products are used in a variety of scientific modeling and analytical efforts. This paper describes the SFA's end-to-end infrastructure and services that support the generation of integrated datasets from a watershed sensor network. The development and maintenance of this infrastructure, presents a suite of challenges from practical field logistics to complex data processing, which are addressed through various solutions. In particular, the SFA adopts a holistic view for data collection, assessment and integration, which dramatically improves the products generated, and enables a co-design approach wherein data collection is informed by model results and vice-versa.
    • Compact Crossed-Dipole Antennas Loaded With Near-Field Resonant Parasitic Elements

      Ta, Son Xuat; Lee, Keekeun; Park, Ikmo; Ziolkowski, Richard W.; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-02)
      Two compact planar crossed-dipole antennas loaded with near-field resonant parasitic (NFRP) elements are reported. The NFRP and crossed-dipole elements are designed for the desired circularly polarized (CP) radiation. By placing the NFRP element over the driven element at angles of 0 degrees and 45 degrees, respectively, dual-band and broadband CP antennas are realized. All radiating elements of antennas are 35 mm x 35 mm x 0.508 mm (0.187 lambda(0) x 0.187 lambda(0) x 0.0027 lambda(0) at 1.6 GHz) in size. The dual-band CP antenna has a measured vertical bar S-11 vertical bar < -10-dB bandwidth of 226 MHz (1.473-1.699 GHz) and measured 3-dB axial ratio (AR) bandwidths of 12 MHz (1.530-1.542 GHz) and 35 MHz (1.580-1.615 GHz) with minimum AR CP frequencies of 1.535 GHz (AR = 0.26 dB) and 1.595 GHz (AR = 2.08 dB), respectively. The broadband CP antenna has a measured vertical bar S-11 vertical bar< -10-dB bandwidth of 218 MHz (1.491-1.709 GHz) and a 3-dB AR bandwidth of 145 MHz (1.490-1.635 GHz). These compact antennas yield bidirectional electromagnetic fields with high radiation efficiency across their operational bandwidths.
    • Compact, Frequency-Reconfigurable Filtenna With Sharply Defined Wideband and Continuously Tunable Narrowband States

      Tang, Ming-Chun; Wen, Zheng; Wang, Hao; Li, Mei; Ziolkowski, Richard W.; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-10)
      A compact, frequency-reconfigurable filtenna with sharp out-of-band rejection in both its wideband and continuously tunable narrowband states is presented. It is intended for use in cognitive radio applications. The wideband state is the sensing state and operationally covers 2.35-4.98 GHz. The narrowband states are intended to cover communications within the 3.05-4.39 GHz range, which completely covers the Worldwide Interoperability for Microwave Access (WiMAX) band and the satellite communications C-band. A p-i-n diode is employed to switch between these wide and narrowband operational states. Two varactor diodes are used to shift the operational frequencies continuously among the narrowband states. The filtenna consists of a funnel-shaped monopole augmented with a reconfigurable filter; it has a compact electrical size: 0.235 lambda(L) x 0.392 lambda(L), where the wavelength lambda(L) corresponds to the lower bound of its operational frequencies. The measured reflection coefficients, radiation patterns, and realized gains for both operational states are in good agreement with their simulated values.
    • A Comparison of Radar Polarimetry Data of the Moon From the LRO Mini-RF Instrument and Earth-Based Systems

      Carter, Lynn M.; Campbell, Bruce A.; Neish, Catherine D.; Nolan, Michael C.; Patterson, G. Wesley; Jensen, J. Robert; Bussey, D. B. J.; University of Arizona (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-04)
      The Mini-RF radar, launched on the Lunar Reconnaissance Orbiter, imaged the lunar surface using hybrid-polarimetric, transmitting one circular polarization and receiving linear H and V polarizations. Earth-based radar operating at the same frequency has acquired data of the same terrains using circular-polarized transmit waves and sampling circular polarizations. For lunar targets where the viewing geometry is nearly the same, the polarimetry derived from Mini-RF and the earth-based data should be very similar. However, we have discovered that there is a considerable difference in circular polarization ratio (CPR) values between the two data sets. We investigate possible causes for this discrepancy, including cross-talk between channels, sampling, and the ellipticity of the Mini-RF transmit wave. We find that none of these can reproduce the observed CPR differences, though a nonlinear block adaptive quantization function used to compress the data will significantly distort some other polarimetry products. A comparison between earth-based data sets acquired using two different sampling modes (sampling received linear polarizations and sampling circular polarizations) suggests that the CPR differences may be partially due to sampling the data in a different receive polarimetry bases.
    • Copying a Plasmonic Signal From an Optical Signal

      Koo, Sung-Ryoung; Kim, Guhwan; Lee, Dong Hun; Kim, Kyung-Jo; Lee, Myung-Hyun; Univ Arizona, Coll Opt Sci (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-08)
      We propose a plasmonic signal copier (PSC) composed of a gapped surface plasmon polariton waveguide (SPPW) and an optical waveguide laid across the gap. The interaction between an SPP and an optical signal around the gap edge is demonstrated experimentally and numerically with polarizations of the incident optical wave. A plasmonic signal is invertedly copied from a TE-polarized optical signal incident to the optical waveguide. The symmetrically distributed charges induced from the TE-polarized optical waves on the metal gap edges of input/output SPPWs were determined to be an essential trigger of the copied plasmonic signal. The characteristics of the PSC enable creation of a plasmonic-based circuit system that is compatible with an optical-based circuit system.
    • Dual CP Polarization Diversity and Space Diversity Antennas Enabled by a Compact T-Shaped Feed Structure

      Geng, Junping; Ziolkowski, Richard W.; Wang, Kun; Zhao, Xiaonlan; Zhou, Han; Chenhu, Guanshen; Liang, Xianling; Jin, Ronghong; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-06)
      A compact T-shaped feed structure (IFS) is reported that enables the realization of two types of diversity antennas: a polarization diversity antenna (PDA) and a spatial diversity antenna (SDA). Both systems have a high potential for mobile wireless communication applications. The IFS includes four ports and two independent coaxial channels with effective isolation between them all. The PDA is a dual CP omnidirectional antenna. Its optimized prototype achieves measured impedance bandwidths of 16.4% and 15.28% in its LHCP and RHCP states, respectively, and realized gains in both between 4.8 and 6.46 dBic. The inner thin coaxial cable (ITCC) of the TFS directly drives its LHCP subsystem, facilitating its improved omnidirectional performance. This ITCC is also used to directly feed the SDA's low-profile directional planar equiangular spiral antenna and its side port drives its omnidirectional RHCP antenna. Good hemispherical coverage is realized with a measured common impedance bandwidth larger than 14.35% with more than 40-dB isolation between its two ports. The corresponding measured realized gain of the SDA is between 4 and 7.8 dBic. The measured results for both optimized prototypes confirm their simulated performance characteristics.
    • Dual-Wavelength Passively Mode-Locked Semiconductor Disk Laser

      Scheller, Maik; Baker, Caleb W.; Koch, Stephan W.; Moloney, Jerome V.; College of Optical Sciences, The University of Arizona (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016-06-15)
      A dual-wavelength mode-locked semiconductor vertical-external-cavity-surface-emitting laser is demonstrated. A semiconductor saturable absorber mirror allows for simultaneous mode locking of pulses centered at two center wavelengths with variable frequency spacing. The difference-frequency control is achieved with an intracavity etalon. Changing the finesse of the etalon enables the adjustment of the pulse duration between 6 and 35 ps. The emitted two-color pulses are modulated by a beat frequency in the terahertz range. Self-starting mode-locking with 0.8-W average output power is demonstrated.
    • Effective Wireless Communication Architecture for Resisting Jamming Attacks

      Alshawi, Amany; Satam, Pratik; Almoualem, Firas; Hariri, Salim; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-10-07)
      Over time, the use of wireless technologies has significantly increased due to bandwidth improvements, cost-effectiveness, and ease of deployment. Owing to the ease of access to the communication medium, wireless communications and technologies are inherently vulnerable to attacks. These attacks include brute force attacks such as jamming attacks and those that target the communication protocol (Wi-Fi and Bluetooth protocols). Thus, there is a need to make wireless communication resilient and secure against attacks. Existing wireless protocols and applications have attempted to address the need to improve systems security as well as privacy. They have been highly effective in addressing privacy issues, but ineffective in addressing security threats like jamming and session hijacking attacks and other types of Denial of Service Attacks. In this article, we present an "architecture for resilient wireless communications" based on the concept of Moving Target Defense. To increase the difficulty of launching successful attacks and achieve resilient operation, we changed the runtime characteristics of wireless links, such as the modulation type, network address, packet size, and channel operating frequency. The architecture reduces the overhead resulting from changing channel configurations using two communication channels, in which one is used for communication, while the other acts as a standby channel. A prototype was built using Software Defined Radio to test the performance of the architecture. Experimental evaluations showed that the approach was resilient against jamming attacks. We also present a mathematical analysis to demonstrate the difficulty of performing a successful attack against our proposed architecture.
    • Effects of Power Split Ratio and Optical Delay Phase Tuning on Stabilization of Self-Mode-Locked Quantum-Dash Lasers Subject to Dual-Loop Optical Feedback

      Asghar, Haroon; McInerney, John G.; Univ Arizona, Coll Opt Sci (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-03-30)
      In the present work, we report a path of RF stabilization versus delay subject to self-mode-locked (SML) two-section quantum-dash (QDash) lasers emitting at similar to 1.55 mu m and operating at similar to 21 GHz repetition rate using a feedback ratio controlled and optical delay phase-dependent symmetric dual-loop optical feedback. For symmetric dual-loops (equal arms of external loops), we identify the three key parameters: power-split ratio through each cavity of the external feedback loop, optical delay phase settings, and overall feedback strength back into gain section, yields jitter stabilization on integer resonance as well as on full delay range tuning. Symmetric dual-loop feedback with two optical delay phase settings (weaker cavity set to integer resonance, fine-tuning of the stronger cavity and stronger cavity set to integer resonance, fine-tuning of a weaker cavity) and four chosen combinations of feedback ratios (-19.5:-29.03 dB,-20.6:-24.3 dB,-21:-22.7 dB,-21.3:-23 dB) has been demonstrated. Based on these four chosen combinations of feedback ratios and optical delay phase settings, a path of stabilization has been identified for SML QDash lasers using symmetric dual-loop optical feedback. Our proposed dual-loop feedback schemes provide a viable path towards the stabilization of mode-locked lasers, promising for various practical applications where ultra-stable optical pulses are highly desirable.
    • Electrically Small, Broadside Radiating Huygens Source Antenna Augmented With Internal Non-Foster Elements to Increase Its Bandwidth

      Tang, Ming-Chun; Shi, Ting; Ziolkowski, Richard W.; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017)
      A broadside radiating, linearly polarized, electrically small Huygens source antenna system that has a large impedance bandwidth is reported. The bandwidth performance is facilitated by embedding non-Foster components into the near-field resonant parasitic elements of this metamaterial-inspired antenna. High-quality and stable radiation performance characteristics are achieved over the entire operational bandwidth. When the ideal non-Foster components are introduced, the simulated impedance bandwidth witnesses approximately a 17-fold enhancement over the passive case. Within this -10-dB bandwidth, its maximum realized gain, radiation efficiency, and front-to-back ratio (FTBR) are, respectively, 4.00 dB, 88%, and 26.95 dB. When the anticipated actual negative impedance convertor circuits are incorporated, the impedance bandwidth still sustains more than a 10-fold enhancement. The peak realized gain, radiation efficiency, and FTBR values are, respectively, 3.74 dB, 80%, and 28.01 dB, which are very comparable to the ideal values.
    • Employing Bessel-Gaussian Beams to Improve Physical-Layer Security in Free-Space Optical Communications

      Wang, Tyan-Lin; Gariano, John A.; Djordjevic, Ivan B.; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018-09)
      Physical-layer security in free-space optical communications channels can be compromised when an eavesdropper performs optical beam-splitting attacks over an atmospheric channel. Previous simulations have shown that Laguerre-Gaussian orbital angular momentum-carrying beams can provide higher secrecy capacities compared to that of ordinary Gaussian beams. In this paper, we determine if Bessel-Gaussian beams can provide further improvement over their corresponding Laguerre-Gaussian counterparts. Using computer simulations and experiments with spatial light modulators, an increase in secrecy capacity of 10 to 30 bits/sec/Hz in the weak to medium turbulence regimes is demonstrated. This verifies that Bessel-Gaussian beams have more resiliency to atmospheric turbulence effects than Laguerre-Gaussian beams. Furthermore, research on optimizing the quality of these beams can help to realize a practical system for more secure communications.
    • Energy-Efficient UAV Relaying Communications to Serve Ground Nodes

      Ahmed, Shakil; Chowdhury, Mostafa Zaman; Jang, Yeong Min; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-04)
      This letter studies the energy-efficient unmanned aerial vehicle (UAV) communications to support ground nodes (GNs). The system considers the UAV working as a relay while there is a base station (BS) on the ground. We analyze the UAV energy consumption model to design the energy-efficient UAV trajectory path. We formulate the energy-efficient UAV relaying communication, which considers both throughput and UAV propulsion energy consumption. We optimize joint transmit power of UAV and BS; UAV trajectory, acceleration, and flying speed to maximize the energy-efficient UAV relaying problem. We also introduce a constraint named as information causality constraint (ICC). The main idea of ICC is to guarantee that the UAV receives information from BS in any time slot and forward the only received information to GNs in remaining time slots. The formulated energy-efficiency maximization problem is not convex. Thus, we solve it sub-optimally using the iterative method. Finally, we present the simulation results to validate the efficacy of the proposed algorithm.
    • Energy-Efficient UAV-to-User Scheduling to Maximize Throughput in Wireless Networks

      Ahmed, Shakil; Chowdhury, Mostafa Zaman; Jang, Yeong Min; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-01-24)
      The unmanned aerial vehicle (UAV) communication is a potential technology to meet the excessive next-generation cellular users & x2019; demand due to its reliable connectivity and cost-effective deployment. However, UAV communications have to be energy efficient so that it can save energy. Thus, the UAV flies sufficiently long enough time to serve the ground users with limited on-board energy. In this paper, we investigate an energy-efficient UAV communication via designing the UAV trajectory path. We consider throughput and the UAV propulsion energy consumption jointly. We assume that the UAV flies at a fixed altitude such that it can avoid tall obstacles. A binary decision variable is assigned to schedule UAV-to-user communication. First, we derive the UAV-to-user channel model based on the line of sight and non-line of sight communication links and jointly optimize the trajectory, transmit power, and the speed of UAV; and UAV-to-user scheduling to maximize throughput. Then, we apply the UAV propulsion energy consumption, which is a function of the UAV trajectory and speed. Finally, we formulate the UAV energy-efficiency maximization problem, which is defined as the total bits of information sent to the ground users by consuming the UAV energy for a given UAV flight duration. The formulated energy-efficiency maximization problem is non-convex, fractional, and mixed-integer non-linear programming in nature. We propose an efficient algorithm based on successive convex approximation and classical Dinkelbach method to achieve the optimal solution of energy-efficient UAV. We present simulation results to validate the efficacy of our proposed algorithms. The results show a significant performance improvement compared to the benchmark methods.
    • Enhanced Grey Risk Assessment Model for Support of Cloud Service Provider

      Razaque, Abdul; Amsaad, Fathi; Hariri, Salim; Almasri, Marwah; Rizvi, Syed S.; Ben Haj Frej, Mohamed; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-04-13)
      The cloud computing environment provides easy-to-access service for private and confidential data. However, there are many threats to the leakage of private data. This paper focuses on investigating the vulnerabilities of cloud service providers (CSPs) from three risk aspects: management risks, law risks, and technology risks. Additionally, this paper presents a risk assessment model that is based on grey system theory (GST), defines indicators for assessment, and fully utilizes the analytic hierarchy process (AHP). Furthermore, we use the GST to predict the risk values by using the MATLAB platform. The GST determines the bottom evaluation sequence, while the AHP calculates the index weights. Based on the GST and the AHP, layer-based assessment values are determined for the bottom evaluation sequence and the index weights. The combination of AHP and GST aims to obtain systematic and structured well-defined procedures that are based on step-by-step processes. The AHP and GST methods are applied successfully to handle any risk assessment problem of the CSP. Furthermore, substantial challenges are encountered in determining the CSP & x2019;s response time and identifying the most suitable solution out of a specified series of solutions. This issue has been handled using two additive features: the response time and the grey incidence. The final risk values are calculated and can be used for prediction by utilizing the enhanced grey model (EGM) (1,1), which reduces the prediction error by providing direct forecast to avoid the iterative prediction shortcoming of standard GM (1,1). Thus, EGM (1,1) helps maintain the reliability on a larger scale despite utilizing more prediction periods. Based on the experimental results, we evaluate the validity, accuracy, and response time of the proposed approach. The simulation experiments were conducted to validate the suitability of the proposed model. The simulation results demonstrate that our risk assessment model contributes to reducing deviation to support CSPs with the three adopted models.
    • Error Errore Eicitur: A Stochastic Resonance Paradigm for Reliable Storage of Information on Unreliable Media

      Ivanis, Predrag; Vasic, Bane; Univ Arizona, Dept Elect & Comp Engn (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016-09)
      We give an architecture of a storage system consisting of a storage medium made of unreliable memory elements and an error correction circuit made of a combination of noisy and noiseless logic gates that is capable of retaining the stored information with the lower probability of error than a storage system with a correction circuit made completely of noiseless logic gates. Our correction circuit is based on the iterative decoding of low-density parity check codes, and uses the positive effect of errors in logic gates to correct errors in memory elements. In the spirit of Marcus Tullius Cicero's Clavus clavo eicitur (one nail drives out another), the proposed storage system operates on the principle: error errore eicitur-one error drives out another. The randomness that is present in the logic gates makes these classes of decoders superior to their noiseless counterparts. Moreover, random perturbations do not require any additional computational resources as they are inherent to unreliable hardware itself. To utilize the benefits of logic gate failures, our correction circuit relies on two key novelties: a mixture of reliable and unreliable gates and decoder rewinding. We present a method based on absorbing Markov chains for the probability of error analysis, and explain how the randomness in the variable and check node update function helps a decoder to escape to local minima associated with trapping sets.