• Joint Scheduling and Beamforming via Cloud-Radio Access Networks Coordination

      Douik, Ahmed; Dahrouj, Hayssam; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim (2018 IEEE 88th Vehicular Technology Conference (VTC-Fall), IEEE, 2019-04-15) [Conference Paper]
      Cloud radio access network (CRAN) emerges as a promising architecture for large-scale interference management. This paper addresses the benefit of one particular type of coordinated resource allocation in CRANs through the combined effect of joint scheduling and beamforming. Consider the downlink of a CRAN where the cloud is connected to several remote radio heads (RRHs), each equipped with multiple antennas. The transmit frame of every RRH is formed by several radio resource blocks (RRBs), each capable of serving multiple single-antenna users via spatial multiplexing using beamforming. The paper focuses on the problem of maximizing the network-wide weighted sum-rate by jointly determining the set of scheduled users at each RRB, and their corresponding beamforming vectors. The main contribution of the paper is to solve such a mixed discrete-continuous optimization problem using a graph-theoretical based approach. The paper introduces the joint scheduling and beamforming graph, wherein each independent set accounts for a feasible schedule and feasible beamforming vectors. Afterward, the joint scheduling and beamforming problem is shown to be equivalent to a maximum independent set problem in the proposed graph. Simulation results suggest that the proposed joint solution provides appreciable performance improvements as compared to the classical iterative approach.
    • Reproducibility in Benchmarking Parallel Fast Fourier Transform based Applications

      Aseeri, Samar; Muite, Benson K.; Takahashi, Daisuke (Companion of the 2019 ACM/SPEC International Conference on Performance Engineering - ICPE '19, ACM Press, 2019-04-05) [Conference Paper]
      An overview of concerns observed in allowing for reproducibility in parallel applications that heavily depend on the three dimensional distributed memory fast Fourier transform are summarized. Suggestions for reproducibility categories for benchmark results are given.
    • Efficient Assimilation of Crosswell Electromagnetic Data Using Ensemble-Based History-Matching Framework

      Zhang, Yanhui; Hoteit, Ibrahim (SPE Reservoir Simulation Conference, Society of Petroleum Engineers, 2019-03-27) [Conference Paper]
      An ensemble-based history-matching framework is proposed to enhance the characterization of petroleum reservoirs through the assimilation of crosswell electromagnetic (EM) data. As one of advanced technologies in reservoir surveillance, crosswell EM tomography can provide a cross-sectional conductivity map and hence saturation profile at an interwell scale by exploiting the sharp contrast in conductivity between hydrocarbons and saline water. Incorporating this new information into reservoir simulation in combination with other available observations is therefore expected to enhance the forecasting capability of reservoir models and to lead to better quantification of uncertainty. The proposed approach applies ensemble-based data-assimilation methods to build a robust and flexible framework under which various sources of available measurements can be readily integrated. Because the assimilation of crosswell EM data can be implemented in different ways (e.g., components of EM fields or inverted conductivity), a comparative study is conducted. The first approach integrates crosswell EM data in its original form which entails establishing a forward model simulating observed EM responses. In this work, the forward model is based on Archie's law that provides a link between fluid properties and formation conductivity, and Maxwell’s equations that describe how EM fields behave given the spatial distribution of conductivity. Alternatively, formation conductivity can be used for history matching, which is obtained from the original EM data through inversion using an adjoint gradient-based optimization method. Because the inverted conductivity is usually of high dimension and very noisy, an image-oriented distance parameterization utilizing fluid front information is applied aiming to assimilate the conductivity field efficiently and robustly. Numerical experiments for different test cases with increasing complexity are carried out to examine the performance of the proposed integration schemes and potential of crosswell EM data for improving the estimation of relevant model parameters. The results demonstrate the efficiency of the developed history-matching workflow and added value of crosswell EM data in enhancing the characterization of reservoir models and reliability of model forecasts.
    • Flexible Design of Millimeter-Wave Cache Enabled Fog Networks

      Emara, Mostafa; ElSawy, Hesham; Sorour, Sameh; Al-Ghadhban, Samir; Alouini, Mohamed-Slim; Al-Naffouri, Tareq Y. (2018 IEEE Globecom Workshops (GC Wkshps), IEEE, 2019-03-18) [Conference Paper]
      Ultra-densification, millimeter wave (mmW) communications, and proactive network-edge caching, utilized within mmW fog networks (mmFNs), are foreseen to provide tangible gains for broadband access, network capacity, and latency. However, caching implementation in mmFN imposes high capital expenditure (CAPEX) due to the ultra-high density of base stations (BSs). For a given caching CAPEX, it may be more efficient to install higher capacity caches in a fraction of the BSs than installing smaller capacity caches in every BSs. In the former case, wireless self-backhauling of mmW systems can be exploited to share the cache contents stored in a given cache enabled BSs (CE-BSs) with other BSs in the network. In this regards, this paper develops a mathematical model, based on stochastic geometry, to study the tradeoff between the cache size and intensity of CE-BSs on the probability that requested popular contents are retrieved from the network edge, denoted as the hit probability. Assuming a power-law inverse relationship between the cache size and intensity of CE-BSs, an optimization problem is formulated and solved for the intensity of CE-BSs and probabilistic file placement in caches such that the hit probability is maximized. The results show that neither installing small caches in every BS nor having sufficiently high capacity caches (i.e., that confine all popular files) installed in small number of BSs exploit the full potential of mmFN. Instead, there exists an optimal balance between the cache size and intensity of CE-BSs, which depends on the network parameters such as the applied caching strategy, required rate, total intensity of BSs, popular content distribution, and cache size/intensity relationship.
    • An Effective Network Intrusion Detection Using Hellinger Distance-Based Monitoring Mechanism

      Bouyeddou, Benamar; Harrou, Fouzi; Sun, Ying; Kadri, Benamar (2018 International Conference on Applied Smart Systems (ICASS), IEEE, 2019-03-18) [Conference Paper]
      This paper proposes an intrusion detection scheme for Denial Of Service (DOS) and Distributed DOS (DDOS) attacks detection. We used Hellinger distance (HD), which is an effective measure to quantify the similarity between two distributions, to detect the presence of potential malicious attackers. Specifically, we applied HD-based anomaly detection mechanism to detect SYN and ICMPv6-based DOS/DDOS attacks. Here, Shewhart chart is applied to HD to set up a detection threshold. The proposed mechanism is evaluated using DARPA99 and ICMPv6 traffic datasets. Results indicate that our mechanism accomplished reliable detection of DOS/DDOS flooding attacks.
    • Ordered Sequence Detection and Robust Design for Pulse Interval Modulation

      Guo, Shuaishuai; Park, Kihong; Alouini, Mohamed-Slim (2018 IEEE Globecom Workshops (GC Wkshps), IEEE, 2019-03-18) [Conference Paper]
      This paper proposes an ordered sequence detection (OSD) for digital pulse interval modulation (DPIM) applied in optical wireless communications (OWC). To detect a packet consisting of L-chips, the computational complexity of OSD is of the order \mathcal{O}(L\log-{2}L). Moreover, this paper also proposes a robust pulse interval modulation (RPIM) scheme based on OSD. In RPIM, the last of every K symbols is with more power to transmit information and simultaneously to provide a built-in barrier signal. In this way, error propagation is bounded in a slot of K symbols. Together with interleaver and forward error correction (FEC) codes, the bit error rate (BER) can be greatly reduced. We derive the approximate uncoded BER performance of conventional DPIM with OSD and the newly proposed RPIM with OSD based on order statistic theory. Simulations are conducted to collaborate on theoretical analysis and show that RPIM with OSD considerably outperforms existing DPIM with optimal threshold detection in either uncoded or coded systems over various channels.
    • FAST PHASE-DIFFERENCE-BASED DOA ESTIMATION USING RANDOM FERNS

      Chen, Hui; Ballal, Tarig; Al-Naffouri, Tareq Y. (2018 IEEE Global Conference on Signal and Information Processing (GlobalSIP), IEEE, 2019-03-18) [Conference Paper]
      Direction of arrival (DOA) information of a signal is important in communications, localization, object tracking and so on. Frequency-domain-based time-delay estimation is capable of achieving DOA in subsample accuracy; however, it suffers from the phase wrapping problem. In this paper, a frequency-diversity based method is proposed to overcome the phase wrapping problem. Inspired by the machine learning technique of random ferns, an algorithm is proposed to speed up the search procedure. The performance of the algorithm is evaluated based on three different signal models using both simulations and experimental tests. The results show that using random ferns can reduce search time to 1/6 of the search time of the exhaustive method while maintaining the same accuracy. The proposed search approach outperforms a benchmark frequency-diversity based algorithm by offering lower DOA estimation error.
    • Indoor Localization Using Three Dimensional Multi-PDs Receiver Based on RSS

      Liu, Yinghao; Park, Kihong; Ooi, Boon S.; Alouini, Mohamed-Slim (2018 IEEE Globecom Workshops (GC Wkshps), IEEE, 2019-03-18) [Conference Paper]
      A novel design of three dimensional optical receiver for visible light communication (VLC) indoor positioning system has been proposed in this paper. We model the optical wireless channel and utilize modified triangulation method to obtain more robust receiver position by using at least two LEDs and one receiver consisting of nine photodetectors (PDs). The main characteristics are as follows: (1) our design of multi-PDs receiver is fully expanded into three dimensions compared with the pyramid structure (PR); (2) based on Multiple-Photodiode-based Indoor Positioning algorithm [1], we improve the indoor positioning algorithm by redefining the optimization problem of obtaining the direction from receiver to LED and using weighted triangulation method to locate receiver position; (3) the improved algorithm is implemented and the simulation results are shown under our three dimensional multi-PDs structure receiver.
    • A Method to Detect DOS and DDOS Attacks based on Generalized Likelihood Ratio Test

      Harrou, Fouzi; Bouyeddou, Benamar; Sun, Ying; Kadri, Benamar (2018 International Conference on Applied Smart Systems (ICASS), IEEE, 2019-03-18) [Conference Paper]
      Denial of service (DOS) and distributed DOS (DDOS) continue to be a significant concern in internet and networking systems. This paper targets to develop an anomaly detection mechanism based on the generalized likelihood ratio (GLR) scheme to detect TCP and ICMPv6 based DOS/DDOS attacks. The anomaly detection problem is addressed as a hypothesis testing problem. The proposed approach uses GLR test to monitor internet traffic for better detecting potential cyber- attacks. The decision threshold of GLR approach has been computed non parametrically based on kernel density estimation. To evaluate the performance of this approach, two network traffic datasets have been used namely the DARPA99 and ICMPv6 datasets. Results highlight the efficiency of the proposed method.
    • Validation of High Pressure Resin Impregnation Technique for High Resolution Confocal Imaging of Geological Samples

      Hassan, Ahmed; Yutkin, M. P.; Chandra, Viswasanthi; Patzek, Tadeusz (SPE Middle East Oil and Gas Show and Conference, Society of Petroleum Engineers, 2019-03-13) [Conference Paper]
      In this paper, we present a procedure for high pressure resin impregnation of microporous rock. This procedure produces the high- quality pore casts that reveal the fine details of the complex pore space of micritic carbonates. We carefully test our resin impregnation procedure and demonstrate that it renders the high resolution, 3D confocal images of pore casts. In our work, we use silicon micromodels as a reference to validate the key parameters of high-pressure resin impregnation. We demonstrate possible artifacts and defects that might develop during rock impregnation with resin, e.g., the resin shrinkage and gas trapping. The main outcome of this paper is a robust protocol for obtaining the high-quality epoxy pore casts suitable for rock imaging with Confocal Laser Scanning Microscopy (CLSM). We have implemented this protocol and provided the high resolution, three-dimensional (3D) imagery and description of microporosity in micritic carbonates.
    • Enhancing the Near-Surface Image Using Duplex-Wave Reverse Time Migration

      Sindi, Ghada; Alkhalifah, Tariq Ali; Fei, Tong; Luo, Yi (SPE Middle East Oil and Gas Show and Conference, Society of Petroleum Engineers, 2019-03-13) [Conference Paper]
      Reverse time migration (RTM) involves zero-lag cross-correlation of forward extrapolated source function wavefields and backward extrapolated receiver wavefields. For a near surface with complex structures and velocity anomalies, forward propagating the source wavelet generates wavefields containing reflections, near-surface multiples, and scattered direct arrivals. The wavefields are recorded as upgoing arrivals contaminated by the same reflections, near-surface multiples, and scattered signals, which can be critical for imaging near-surface structures and scatterers. Here, we develop a new depth migration, duplex reverse time migration (DRTM) technique to improve imaging of complex near-surface structures. DRTM uses the direct arrival as a source to forward propagate and generate source wavefields, and reversely extrapolated recorded data in a zero-lag cross-correlation imaging condition to generate the final section. The interaction between the data components during cross- correlation can use primaries and multiples to image the near-surface structure correctly. Cross-talk artifacts may exist, but they are comparatively weak. DRTM is demonstrated on both synthetic and field data examples showing an enhanced image in areas with complex near-surface structures compared to conventional RTM imaging methods. The new algorithm can significantly enhance shallow imaging without additional computation costs compared with conventional RTM. It can produce an image with higher resolution and signal-to-noise (S/N) ratio by replacing the source wavelet with the recorded direct arrivals, which include near-surface information necessary to boost the image in areas with near-surface complexity. Since the direct arrivals are one of the most energetic events recorded, the resultant image is typically of high S/N. The wave can also illuminate shallow zones better than primaries in marine environments.
    • Application of High Performance Asynchronous Acoustic Wave Equation Stencil Solver into a Land Survey

      Abdelkhalak, Rached; Akbudak, Kadir; Etienne, Vincent; Ltaief, Hatem; Tonellot, Thierry; Keyes, David E. (SPE Middle East Oil and Gas Show and Conference, Society of Petroleum Engineers, 2019-03-13) [Conference Paper]
      This paper describes the application of high performance asynchronous stencil computations for 3D acoustic modeling on a synthetic land survey. Using the Finite-Difference Time-Domain (FDTD) method, a parallel Multicore Wavefront Diamond-tiling (MWD) stencil kernel (Malas et al. 2015, Malas et al. 2017) drives the high performance execution using temporal blocking to maximize data locality, while reducing the expensive horizontal data movement. As absorbing boundary conditions, we use Convolutional Perfectly Matched Layer (CPML), which have to be redesigned to not interrupt the asynchronous execution flow engendered by the MWD stencil kernel for the inner-domain points. The main idea consists in weakening the data dependencies by moving the CPML computations into the inner-computational loop of the MWD stencil kernel (Akbudak et al. 2019). In addition to handling the absorbing boundary conditions, applying the asynchronous MWD with CPML kernels to a realistic land survey requires the extraction of the wavefield value at each receiver position. We revisit the default extraction process and make it also compliant with the overall asynchrony of the 3D acoustic modeling. We report performance improvement up to 24% against the standard spatial blocking algorithm on Intel multicore chips using the synthetic land survey, which is representative of an area of interest in Saudi Arabia. While these results concur with previous performance campaign assessment, we can actually produce and assess the resulting 3D shot gather accuracy. To our knowledge, this is the first time the effectiveness of asynchronous MWD stencil kernel with CPML absorbing boundary conditions is demonstrated in an industrial seismic application.
    • Co-Embedding Attributed Networks

      Meng, Zaiqiao; Liang, Shangsong; Bao, Hongyan; Zhang, Xiangliang (Proceedings of the Twelfth ACM International Conference on Web Search and Data Mining - WSDM '19, ACM Press, 2019-03-11) [Conference Paper]
      Existing embedding methods for attributed networks aim at learning low-dimensional vector representations for nodes only but not for both nodes and attributes, resulting in the fact that they cannot capture the affinities between nodes and attributes. However, capturing such affinities is of great importance to the success of many real-world attributed network applications, such as attribute inference and user profiling. Accordingly, in this paper, we introduce a Co-embedding model for Attributed Networks (CAN), which learns low-dimensional representations of both attributes and nodes in the same semantic space such that the affinities between them can be effectively captured and measured. To obtain high-quality embeddings, we propose a variational auto-encoder that embeds each node and attribute with means and variances of Gaussian distributions. Experimental results on real-world networks demonstrate that our model yields excellent performance in a number of applications compared with state-of-the-art techniques.
    • Online and Batch Supervised Background Estimation Via L1 Regression

      Dutta, Aritra; Richtarik, Peter (2019 IEEE Winter Conference on Applications of Computer Vision (WACV), IEEE, 2019-03-08) [Conference Paper]
      We propose a surprisingly simple model to estimate supervised video backgrounds. Our model is based on L1 regression. As existing methods for L1 regression do not scale to high-resolution videos, we propose several simple, fast, and scalable methods including iteratively reweighted least squares, a homotopy method, and stochastic gradient descent to solve the problem. Our extensive implementations of the model and methods show that they match or outperform other state-of-the-art online and batch methods that are both supervised and unsupervised in virtually all quantitative and qualitative measures and in fractions of their execution time.
    • Local Color Mapping Combined with Color Transfer for Underwater Image Enhancement

      Protasiuk, Rafal; Bibi, Adel Aamer; Ghanem, Bernard (2019 IEEE Winter Conference on Applications of Computer Vision (WACV), IEEE, 2019-03-08) [Conference Paper]
      Color correction and color transfer methods have gained a lot of attention in the past few years to circumvent color degradation that may occur due to various sources. In this paper, we propose a novel simple yet powerful strategy to profoundly enhance color distorted underwater images. The proposed approach combines both local and global information through a simple yet powerful affine transform model. Local and global information are carried through local color mapping and color covariance mapping between an input and some reference source, respectively. Several experiments on degraded underwater images demonstrate that the proposed method performs favourably to all other methods including ones that are tailored to correcting underwater images by explicit noise modelling.
    • Polarization matched c-plane III-nitride quantum wells structure

      Yao, Hsin-Hung; Lu, Yi; Li, Kuang-Hui; Alqatari, Feras; Liao, Che-Hao; Li, Xiaohang (Light-Emitting Devices, Materials, and Applications, SPIE, 2019-03-01) [Conference Paper]
      Polarization-matched quantum wells (QWs) can lead to maximized electron-hole wave functions overlap and low efficiency droop at high current density. By using the modern theory of polarization with hexagonal reference, c-plane InAlN/InGaN QWs were explored and designed for polarization matching. The simulation results show that, even on c-plane, polarization-matched structures can be achieved by adjusting strain and material composition. The In composition of larger than 35% of InAlN was required to match the total polarization of InGaN at any given composition. Considering the bandgap’s bowing factors of III-nitride ternary alloys, In0~0.1Ga1.0-0.9N as quantum barrier (QB) provided enough potential barriers for In0.35~0.45Al0.65-0.55N to form a multiple QW (MQW) structure. The results indicated that improper resistance of MQW and the existing fixed charge between the interfaces of p-type region/MQW and n-type region/MQW could result in nonuniform carrier distributions and current leakage, respectively. Furthermore, we found that In0.41Al0.59N/In0.1Ga0.9N polarization-matched MQW had proper resistance; however, such structure produced a huge polarization fixed-charge between the junction interface. By studying the strain level of InAlN QW and GaN QB, which can be grown on AlN/GaN superlattice templates, the In0.33Al0.67N/GaN polarization-matched MQW structure has been specifically designed with small resistance and without inducing improper polarization fixed charge. By optimizing the number and thickness of QWs, the 425nm LED has relative IQE of 56% and efficiency droop of only 7% at high current density of 333 A/cm2. This study provides guidance for development of In-rich InAlN materials.
    • Study on laser-based white light sources

      Shen, Chao; Ooi, Ee-Ning; Sun, Xiaobin; Ooi, Boon S.; Ng, Tien Khee (Light-Emitting Devices, Materials, and Applications, SPIE, 2019-03-01) [Conference Paper]
      We reported on the design, demonstration, and analysis of white lighting systems based on GaN laser diodes. Compared to light-emitting-diodes (LEDs), lasers have been proposed for the development of high-power light sources for many potential advantages, including circumventing efficiency droop, reduced light emitting surface, directional beam characteristics. Laser-based white light sources are also attractive for visible light communication (VLC) applications that enabling lighting and communication dual functionalities. In this work, we detailed the color-rendering index (CRI), correlated color temperature (CCT), and luminous flux analysis of laser white light sources by using the GaN laser diode exciting color converters at various driving conditions. By using a blue-emitting laser exciting a yellow YAG phosphor crystal, a luminous flux greater than 600 lm has been achieved with a moderate CRI of 67.2. By constructing a white lighting system using phosphor crystal array based on a reflection configuration, an improved CRI of 74.4 and a luminous flux of ~400 lm with a CCT of 6425 K was obtained at 3A. Using a novel ceramic phosphor plate as color converter, the CRI for the white light source has been further improved to ~ 84.1 with a CCT of ~ 4981 K, which suggests that the laser-based white light source is capable of high-quality illumination applications. The CCT of the white laser sources can be engineered from 5000 K to 6500 K and a potential approach to use laser array for high power white lighting is discussed.
    • Laser-based visible light communications and underwater wireless optical communications: a device perspective

      Shen, Chao; Alkhazragi, Omar; Sun, Xiaobin; Guo, Yujian; Ng, Tien Khee; Ooi, Boon S. (Novel In-Plane Semiconductor Lasers XVIII, SPIE, 2019-03-01) [Conference Paper]
      High-speed visible light communications (VLC) has been identified at an essential part of communication technology for 5G network. VLC offers the unique advantages of unregulated and secure channels, free of EM interference. Compared with the LED-based VLC transmitter, laser-based photonic systems are promising for compact, droop-free, and high-speed white lighting and VLC applications, ideal for ultra-fast 5G network and beyond. Besides the potential for achieving high data rate free-space communication links, i.e. the Li-Fi network, laser-based VLC technology can also enable underwater wireless optical communications (UWOC) for many important applications. In this paper, the recent research progress and highlights in the fields of laser-based VLC and UWOC have been reviewed with a focused discussion on the performance of various light sources, including the modulation characteristics of GaNbased edge emitting laser diodes (EELDs), superluminescent diodes (SLDs) and vertical-cavity surface-emitting lasers (VCSELs). Apart from the utilization of discrete components for building transceiver in VLC systems, the development of III-nitride laser-based photonic integration has been featured. Such on-chip integration offers many advantages, including having a small-footprint, high-speed, and low power consumption. Finally, we discuss the considerations of wavelength selection for various VLC and UWOC applications. Comparison of infrared (IR) and visible lasers for channels with high turbulence and the study of ultraviolet (UV) and visible lasers for non-line-of-sight (NLOS) communications are presented.
    • Functional integrity and stable high-temperature operation of planarized ultraviolet-A AlxGa1−xN/AlyGa1−yN multiple-quantum-disk nanowire LEDs with charge-conduction promoting interlayer

      Alfaraj, Nasir; Alhamoud, Abdullah A.; Priante, Davide; Janjua, Bilal; Alatawi, Abdullah A.; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S. (Gallium Nitride Materials and Devices XIV, SPIE, 2019-03-01) [Conference Paper]
      Unprecedented high-temperature operational stability of interfacial silicide-free ultraviolet-A multiple-quantum- disk AlGaN nanowire-based light-emitting diodes on metal is achieved and investigated. Reasonable variations in device operational parameters across a wide range of temperatures demonstrate the high quality of the layer interfaces and efficient carrier injection. We previously presented ultraviolet-A quantum-confined AlxGa1-xN/AlyGa1-yN nanowire-based light-emitting diodes and studied their steady-state electro- and photo- luminescent characteristics at room temperature. Herein, we significantly expand the scope of our previous work by investigating the operational stability of the device across a wide range of temperatures (-50-100°C) with conformal parylene-C deposition, forming a nanowire forest as a polymer/nanowire three-dimensional composite material. This work constitutes part of a larger study into the operational stability of ultraviolet light-emitting diode chemical sensors at a wide range of temperatures for operation in harsh environments such as in downhole oil exploration.
    • Accelerated Gossip via Stochastic Heavy Ball Method

      Loizou, Nicolas; Richtarik, Peter (2018 56th Annual Allerton Conference on Communication, Control, and Computing (Allerton), IEEE, 2019-03-01) [Conference Paper]
      In this paper we show how the stochastic heavy ball method (SHB)-a popular method for solving stochastic convex and non-convex optimization problems-operates as a randomized gossip algorithm. In particular, we focus on two special cases of SHB: the Randomized Kaczmarz method with momentum and its block variant. Building upon a recent framework for the design and analysis of randomized gossip algorithms [20] we interpret the distributed nature of the proposed methods. We present novel protocols for solving the average consensus problem where in each step all nodes of the network update their values but only a subset of them exchange their private values. Numerical experiments on popular wireless sensor networks showing the benefits of our protocols are also presented.