Hongkun Li

Institut d'Électronique et des Technologies du numéRique

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Christophe Bourlier

Centre National de la Recherche Scientifique

Yu Cheng

Nanyang Technological University

Joel T. Johnson

The Ohio State University

Mark Andrews

The Ohio State University

Alexandra Bringer

Gillette Children's Specialty Healthcare

Nicolás Pinel

Institut Supérieur de l'Électronique et du Numérique

Peng‐Jun Wan

Illinois Institute of Technology

Domenic Belgiovane

RTX (United States)

Kenneth C. Jezek

The Ohio State University

Giovanni Macelloni

Nello Carrara Institute of Applied Physics

Cooperative Institutions

The Ohio State University

Nantes Université

Illinois Institute of Technology

Southeast University

Institut d'Électronique et des Technologies du numéRique

Institut Supérieur de l'Électronique et du Numérique

University of Michigan–Ann Arbor

Goddard Space Flight Center

Centre National de la Recherche Scientifique

Université Nantes Angers Le Mans

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A Hybrid Relative Distance Based Cluster Scheme for Energy Efficiency in Wireless Sensor Networks

Hui Gao Hongkun Li Yu Cheng

Energy efficiency is of great importance for the wireless sensor network (WSN). A popular way to save energy is to construct clusters for data aggregation and forwarding. This paper studies the distributed cluster algorithm to improve the energy consumption efficiency. We observe that the cluster head has to lie within the transmission range of the base station (sink node) and the distance between cluster head and base station is critical for the energy consumption performance, we propose a hybrid relative distance based clustering scheme (HRDCS), which considers the relative distance to the base station and the residual energy level during the cluster head selection stage. Consequently we could better balance the chance of being cluster head for all nodes. Simulation results show that our scheme is able to result in longer network lifetime than the well-known protocol LEACH.

Sink (geography)

10.1109/glocom.2010.5683388

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Citations (8)

500–2000-MHz Brightness Temperature Spectra of the Northwestern Greenland Ice Sheet

IEEE Transactions on Geoscience and Remote Sensing (2017)

Kenneth C. Jezek Joel T. Johnson Shurun Tan Leung Tsang Mark Andrews

An ultra-wideband radiometer has been developed to measure subsurface properties of the cryosphere including ice sheets and sea ice. The radiometer measures brightness temperature spectra from 0.5 to 2 GHz using 12 channels, each of which measures scene brightness temperatures over an ~88-MHz bandwidth resolved into 0.24-MHz intervals. The instrument was flown over northwestern Greenland in September 2016 and acquired the first, wideband, low-frequency brightness temperature spectra over the ice sheet and coastal region. The results reveal strong spatial and spectral variations that correlate well with the physical properties of the surface encountered along the flight path, which started over ocean, then passed the rock near the coast, and then up onto the ablation, wet, percolation, and dry snow zones of the interior ice sheet. In particular, strong spectral responses in percolation and dry snow zones are observed and plausibly explained by varying the distribution of horizontal density layers and isolated icy bodies in the upper portion of the firn. The success of the airborne deployment of the instrument and subsequent implementation of algorithms to limit radio frequency interference in unprotected bands is motivating continued airborne investigations as well as stimulating research into the feasibility of a spaceborne instrument.

Greenland ice sheet

Firn

10.1109/tgrs.2017.2764381

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A FAST EPILE+FBSA METHOD COMBINED WITH ADAPTIVE CROSS APPROXIMATION FOR THE SCATTERING FROM A TARGET ABOVE A LARGE OCEAN-LIKE SURFACE

Progress In Electromagnetics Research M (2014)

Gildas Kubické Christophe Bourlier Sami Bellez Hongkun Li

The rigorous evaluation of the NRCS (Normalized Radar Cross Section) of an object above a one-dimensional sea surface (2D case) needs to numerically solve a set of discretized integral equations involving a large number of unknowns. Thus, the direct solution of the impedance matrix equation via LU decomposition becomes the most expensive step in the MoM (Method of Moments) procedure. So, in order to minimize the computation cost, the iterative domain decomposition method called EPILE (Extended Propagation-Inside-Layer Expansion) was used and then was combined with the FBSA (Forward-Backward with Spectral Acceleration) to calculate the local interactions on the rough sea surface. The resulting fast method is called EPILE+FBSA. In this paper, we take advantage of the rank-deflcient nature of the coupling matrices, corresponding to the object-surface interactions, to further reduce the complexity of the method by using the ACA (Adaptive Cross Approximation). Thus, the coupling matrices are strongly compressed without a loss of accuracy and the memory requirement is then strongly reduced. For a cylinder above a rough sea surface, the results show the e-ciency of the accelerated EPILE+FBSA+ACA method.

Impedance parameters

Matrix (chemical analysis)

10.2528/pierm14052503

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Shadowing function from a two-dimensional surface

Institution of Engineering and Technology eBooks (2019)

Christophe Bourlier Hongkun Li

This chapter extends the derivation of the shadowing function to a two-dimensional (2D) anisotropic random rough surface [7,25]. In polar coordinates (x = R cos φ,y = R sin φ) and the term `anisotropic' means that the statistical properties of the surface depends on the azimuthal direction φ. Typically, for a sea surface, φ stands for the wind direction. We will show that the 2D case is obtained from the one-dimensional (1D) case by making a rotation of an angle φ and next by calculating the marginal probability along this direction. First, the monostatic shadowing function is derived, and next it is generalized to the bistatic case. Unlike the 1D case [8], the latter configuration requires a special attention and needs to account for the correlation with respect to the direction φ to avoid a discontinuity when the transmitter and the receiver are not in the same plane (the azimuthal directions differ).

Discontinuity (linguistics)

10.1049/sbra519e_ch2

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The Ultra-Wideband Software Defined Microwave Radiometer (UWBRAD) for Ice sheet subsurface temperature sensing: Calibration and campaign results

Mark Andrews Hongkun Li Joel T. Johnson Kenneth C. Jezek Alexandra Bringer

The Ultra-Wideband Microwave Radiometer is a novel pseudo-correlation radiometer design measuring scene brightness temperatures from 0.5-2 GHz created under NASA's Instrument Incubator Program. This document analyzes the design and operation of the radiometer, the accuracy and stability of the brightness temperatures it produces, and presents initial results from a field campaign conducted in Greenland in September 2016.

Microwave radiometer

Microwave Imaging

10.1109/igarss.2017.8126938

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Citations (10)

Polarized infrared emissivity of 2D sea surfaces with one surface reflection

Remote Sensing of Environment (2012)

Hongkun Li Nicolás Pinel Christophe Bourlier

Zenith

Kurtosis

Reflection

10.1016/j.rse.2012.05.021

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Citations (11)

Propagation et diffusion Radar microondes par une surface de mer en incidence rasante et dans un milieu stratifié

HAL (Le Centre pour la Communication Scientifique Directe) (2015)

Christophe Bourlier Hongkun Li Dušan Cvetković Sami Bellez Vincent Fabbro

Dans cet article, pour des incidences rasantes et aux frequences Radar microondes, le probleme de la diffusion electromagnetique par une surface de mer et de la propagation dans un milieu stratifie (conduit au-dessus de la mer) est resolu conjointement a l'aide d'une methode rigoureuse, basee sur la resolution des equations integrales par une Methode des Moments (MdM). La propagation dans un milieu atmospherique stratifie (conduit) est traitee par une fonction de Green calculee analytiquement pour un indice de refraction au carre suivant une loi affine. Puis, le probleme de diffraction par la surface de mer est resolu numeriquement en injectant cette fonction de Green dans les equations integrales. Puisque le phenomene de guidage de l'onde Radar diffusee par la surface est observe sur une longue distance (le gradient de l'indice de refraction est tres faible devant l'unite), une methode rapide iterative stationnaire est utilisee pour reduire les ressources informatiques necessaires a la resolution du systeme lineaire de grande dimension (matrice impedance a inverser de taille 200 0002 et plus). Ainsi, connaissant les courants sur la surface de mer, le champ total en tout point dans le conduit est calcule a l'aide du principe d'Huygens. Des resultats presentant les puissances diffusees coherente et incoherente sont montres puis compares avec ceux calcules par la methode PWE (Parabolic Wave Equation), resolue par la methode SSF (Split-Step Fourier).

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Propagation et diffraction des ondes électromagnétiques radar par une surface de mer rugueuse en présence d'un conduit

HAL (Le Centre pour la Communication Scientifique Directe) (2013)

Hongkun Li Christophe Bourlier

Cet article presente une methode numerique calculant le champ diffracte par une surface de mer en presence d'un conduit et pour des frequences Radar microondes. Cette methode, basee sur la methode des moments, permet de resoudre conjointement le probleme de diffusion par la mer et le probleme de propagation dans un milieu inhomogene via l'introduction de la fonction de Green caracteristique du conduit. De plus, pour inverser efficacement la matrice impedance, la methode Forward-Backward est utilisee, reduisant ainsi significativement le stockage memoire et la complexite. En effet, La complexite est de O(N2) au lieu de O(N3), si une inversion de type LU etait appliquee.

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The ultra-wideband software defined microwave radiometer (UWBRAD) for ice sheet subsurface temperature sensing: RFI algorithms and performance

Mark Andrews Hongkun Li Joel T. Johnson Alexandra Bringer

The Ultra-Wideband Microwave Radiometer observes scene brightness temperatures over the frequency range 0.5-2 GHz, which primarily includes frequency bands that are not protected for passive microwave observations. This document presents UWBRAD's RFI mitigation algorithms and examples of the RFI environment encountered during a September 2016 flight campaign that included flights in Canada and Greenland.

Microwave radiometer

Wideband

Microwave Imaging

10.1109/igarss.2017.8127190

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Citations (1)

Computing the Optimal Capacity of Multi-Radio Multi-Channel Wireless Network over Partially Overlapping Channels

Hongkun Li Ankit Srivastava Yu Cheng

Existing works designed for the multi-radio multi-channel (MR-MC) wireless network mainly rely on the orthogonal or non-overlapping channels. But in reality, the limited number of non-overlapping channels is a major issue when the network is dense. In this paper, we study the impact of partially overlapping channels (POC) on the network capacity through computing the maximum achievable capacity in the MR-MC context. We first extend our tool of multi-dimensional conflict graph (MDCG) [4] to the weighted MDCG (WMDCG) under the physical interference model, where the weight of each edge accurately indicates the amount of interference. Such a tool facilitates the theoretical analysis considering the POC. We then develop a computing methodology to calculate the optimal achievable network capacity with POC by formulating a linear programming (LP) multi-commodity flow (MCF) problem, augmented by the interference constraints based on the WMDCG. The numerical results demonstrate the effectiveness of our computing methodology.

Maximum flow problem

10.1109/glocom.2011.6134229

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