Results for "Kai-Kit Wong"

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Analysis of Compressed Sensing with Spatially-Coupled Orthogonal MatricesFeb 13 2014Recent development in compressed sensing (CS) has revealed that the use of a special design of measurement matrix, namely the spatially-coupled matrix, can achieve the information-theoretic limit of CS. In this paper, we consider the measurement matrix ... More
Self-Optimized OFDMA via Multiple Stackelberg Leader EquilibriumAug 23 2011The challenge of self-optimization for orthogonal frequency-division multiple-access (OFDMA) interference channels is that users inherently compete harmfully and simultaneous water-filling (WF) would lead to a Pareto-inefficient equilibrium. To overcome ... More
Sum Rate and Fairness Analysis for the MU-MIMO Downlink under PSK Signalling: Interference Suppression vs ExploitationDec 06 2018In this paper, we analyze the sum rate performance of multi-user multiple-input multiple-output (MU-MIMO) systems, with a finite constellation phase-shift keying (PSK) input alphabet. We analytically calculate and compare the achievable sum rate in three ... More
One- and Two-Way Relay Optimization for MIMO Interference NetworksMar 27 2017This paper considers multiple-input multiple-output (MIMO) relay communication in multi-cellular (interference) systems in which MIMO source-destination pairs communicate simultaneously. It is assumed that due to severe attenuation and/or shadowing effects, ... More
UAV-Assisted Relaying and Edge Computing: Scheduling and Trajectory OptimizationDec 06 2018In this paper, we study an unmanned aerial vehicle (UAV)-assisted mobile edge computing (MEC) architecture, in which a UAV roaming around the area may serve as a computing server to help user equipment (UEs) compute their tasks or act as a relay for further ... More
Cooperative Cognitive Networks: Optimal, Distributed and Low-Complexity AlgorithmsApr 12 2012This paper considers the cooperation between a cognitive system and a primary system where multiple cognitive base stations (CBSs) relay the primary user's (PU) signals in exchange for more opportunity to transmit their own signals. The CBSs use amplify-and-forward ... More
Constructive Interference Based Secure Precoding: A New Dimension in Physical Layer SecurityDec 27 2016Conventionally, interference and noise are treated as catastrophic elements in wireless communications. However, it has been shown recently that exploiting known interference constructively can even contribute to signal detection ability at the receiving ... More
Ergodic Capacity Analysis of Amplify-and-Forward MIMO Dual-Hop SystemsNov 27 2008This paper presents an analytical characterization of the ergodic capacity of amplify-and-forward (AF) MIMO dual-hop relay channels, assuming that the channel state information is available at the destination terminal only. In contrast to prior results, ... More
To Harvest and Jam: A Paradigm of Self-Sustaining Friendly Jammers for Secure AF RelayingFeb 25 2015Oct 21 2015This paper studies the use of multi-antenna harvest-and-jam (HJ) helpers in a multi-antenna amplify-and-forward (AF) relay wiretap channel assuming that the direct link between the source and destination is broken. Our objective is to maximize the secrecy ... More
Secure Two-Way Transmission via Wireless-Powered Untrusted Relay and External JammerAug 21 2017Mar 01 2018In this paper, we propose a two-way secure communication scheme where two transceivers exchange confidential messages via a wireless powered untrusted amplify-and-forward (AF) relay in the presence of an external jammer. We take into account both friendly ... More
Energy Harvesting Enabled MIMO Relaying through Time SwitchingApr 10 2017This letter considers simultaneous wireless information and power transfer (SWIPT) for a multiple-input multiple-output (MIMO) relay system. The relay is powered by harvesting energy from the source via time switching (TS) and utilizes the harvested energy ... More
Energy Harvesting Enabled MIMO Relaying through PSMar 30 2017This paper considers a multiple-input multiple-output (MIMO) relay system with an energy harvesting relay node. All nodes are equipped with multiple antennas, and the relay node depends on the harvested energy from the received signal to support information ... More
Wireless Information and Power Transfer Design for Energy Cooperation Distributed Antenna SystemsJun 15 2016Distributed antenna systems (DAS) have been widely implemented in state-of-the-art cellular communication systems to cover dead spots. Recent studies have also indicated that DAS have advantages in wireless energy transfer (WET). In this paper, we study ... More
Task and Bandwidth Allocation for UAV-Assisted Mobile Edge Computing with Trajectory DesignJul 08 2019In this paper, we investigate a mobile edge computing (MEC) architecture with the assistance of an unmanned aerial vehicle (UAV). The UAV acts as a computing server to help the user equipment (UEs) compute their tasks as well as a relay to further offload ... More
Covert Communications Versus Physical Layer SecurityMar 18 2018This letter studies and compares the physical-layer security approach and the covert communication approach for a wiretap channel with a transmitter, an intended receiver and an eavesdropper. In order to make the comparison, we investigate the power allocation ... More
Robust Physical Layer Security for Power Domain Non-orthogonal Multiple Access-Based HetNets and HUDNs, SIC Avoidance at EavesdroppersJun 06 2018In this paper, we investigate the physical layer security in downlink of Power Domain Non Orthogonal Multiple Access based heterogeneous cellular network in presence of multiple eavesdroppers. Our aim is to maximize the sum secrecy rate of the network. ... More
Secure Full-Duplex Device-to-Device CommunicationSep 07 2017This paper considers full-duplex (FD) device-to-device (D2D) communications in a downlink MISO cellular system in the presence of multiple eavesdroppers. The D2D pair communicate sharing the same frequency band allocated to the cellular users (CUs). Since ... More
Truth-Telling Mechanism for Secure Two-Way Relay Communications with Energy-Harvesting RevenueMar 20 2017Mar 21 2017This paper brings the novel idea of paying the utility to the winning agents in terms of some physical entity in cooperative communications. Our setting is a secret two-way communication channel where two transmitters exchange information in the presence ... More
Wireless Information and Power Transfer in Full-Duplex Communication SystemsMar 07 2016This paper considers the problem of maximizing the sum-rate for simultaneous wireless information and power transfer (SWIPT) in a full-duplex bi-directional communication system subject to energy harvesting and transmit power constraints at both nodes. ... More
Two-way relay beamforming optimization for full-duplex SWIPT systemsJun 28 2016Mar 21 2017In this paper, we investigate the problem of two-way relay beamforming optimization to maximize the achievable sum-rate of a simultaneous wireless information and power transfer (SWIPT) system with a full-duplex (FD) multiple-input multiple-output (MIMO) ... More
A Data-Aided Channel Estimation Scheme for Decoupled Systems in Heterogeneous NetworksMay 03 2018Uplink/downlink (UL/DL) decoupling promises more flexible cell association and higher throughput in heterogeneous networks (HetNets), however, it hampers the acquisition of DL channel state information (CSI) in time-division-duplex (TDD) systems due to ... More
Efficient Downlink Channel Reconstruction for FDD Multi-Antenna SystemsMay 18 2018In this paper, we propose an efficient downlink channel reconstruction scheme for a frequency-division-duplex multi-antenna system by utilizing uplink channel state information combined with limited feedback. Based on the spatial reciprocity in a wireless ... More
Joint Channel-and-Data Estimation for Large-MIMO Systems with Low-Precision ADCsJan 22 2015The use of low precision (e.g., 1-3 bits) analog-to-digital convenors (ADCs) in very large multiple-input multiple-output (MIMO) systems is a technique to reduce cost and power consumption. In this context, nevertheless, it has been shown that the training ... More
A Deterministic Equivalent for the Analysis of Non-Gaussian Correlated MIMO Multiple Access ChannelsAug 20 2011Large dimensional random matrix theory (RMT) has provided an efficient analytical tool to understand multiple-input multiple-output (MIMO) channels and to aid the design of MIMO wireless communication systems. However, previous studies based on large ... More
A Speculative Study on 6GFeb 18 2019While 5G is being tested worldwide and anticipated to be rolled out gradually in 2019, researchers around the world are beginning to turn their attention to what 6G might be in 10+ years time, and there are already initiatives in various countries focusing ... More
Secure Full-Duplex Two-Way Relaying for SWIPTSep 24 2017This letter studies bi-directional secure information exchange in a simultaneous wireless information and power transfer (SWIPT) system enabled by a full-duplex (FD) multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay. The AF relay injects ... More
State of the Art, Taxonomy, and Open Issues on Cognitive Radio Networks with NOMAJan 06 2018The explosive growth of mobile devices and the rapid increase of wideband wireless services call for advanced communication techniques that can achieve high spectral efficiency and meet the massive connectivity requirement. Cognitive radio (CR) and non-orthogonal ... More
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access NetworksJan 06 2018Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be promising in the fifth generation (5G) wireless networks. H-CRANs enable users to enjoy diverse services with high energy efficiency, high spectral efficiency, and low-cost operation, ... More
Joint Antenna Selection and Spatial Switching for Energy Efficient MIMO SWIPT SystemNov 01 2016In this paper, we investigate joint antenna selection and spatial switching (SS) for quality-of-service (QoS)-constrained energy efficiency (EE) optimization in a multiple-input multiple-output (MIMO) simultaneous wireless information and power transfer ... More
Learning the Wireless V2I Channels Using Deep Neural NetworksJul 10 2019For high data rate wireless communication systems, developing an efficient channel estimation approach is extremely vital for channel detection and signal recovery. With the trend of high-mobility wireless communications between vehicles and vehicles-to-infrastructure ... More
Secrecy and Energy Efficiency in Massive MIMO Aided Heterogeneous C-RAN: A New Look at InterferenceJul 12 2016In this paper, we investigate the potential benefits of the massive multiple-input multiple-output (MIMO) enabled heterogeneous cloud radio access network (C-RAN) in terms of the secrecy and energy efficiency (EE). In this network, both remote radio heads ... More
Energy Efficiency Optimization with Simultaneous Wireless Information and Power Transfer in MIMO Broadcast ChannelsNov 01 2016Oct 23 2017Simultaneous wireless information and power transfer (SWIPT) is anticipated to have great applications in fifth-generation (5G) and beyond communication systems. In this paper, we address the energy efficiency (EE) optimization problem for SWIPT multiple-input ... More
Massive MIMO-Enabled Full-Duplex Cellular NetworksNov 11 2016Mar 04 2017In this paper, we provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the self-interference (SI) channels follow the Rician distribution and other channels ... More
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges AheadJan 16 2018Physical layer security which safeguards data confidentiality based on the information-theoretic approaches has received significant research interest recently. The key idea behind physical layer security is to utilize the intrinsic randomness of the ... More
Simultaneous Wireless Information and Power Transfer in MISO Full-Duplex SystemsMar 16 2017This paper investigates a multiuser multiple-input single-output (MISO) full-duplex (FD) system for simultaneous wireless information and power transfer (SWIPT), in which a multi-antenna base station (BS) simultaneously sends wirelessly information and ... More
Deep Neural Network Based Resource Allocation for V2X CommunicationsJun 24 2019This paper focuses on optimal transmit power allocation to maximize the overall system throughput in a vehicle-to-everything (V2X) communication system. We propose two methods for solving the power allocation problem namely the weighted minimum mean square ... More
Joint Transmit Power and Relay Two-Way Beamforming Optimization for Energy-Harvesting Full-Duplex CommunicationsOct 12 2016This paper studies the joint optimization problem of two-way relay beamforming, the receiver power splitting (PS) ratio as well as the transmit power at the sources to maximize the achievable sum-rate of a simultaneous wireless information and power transfer ... More
Safeguarding Massive MIMO Aided HetNets Using Physical Layer SecuritySep 09 2015This paper exploits the potential of physical layer security in massive multiple-input multiple-output (MIMO) aided two-tier heterogeneous networks (HetNets). We focus on the downlink secure transmission in the presence of multiple eavesdroppers. We first ... More
Wireless Power Transfer in Massive MIMO Aided HetNets with User AssociationJul 11 2016This paper explores the potential of wireless power transfer (WPT) in massive multiple input multiple output (MIMO) aided heterogeneous networks (HetNets), where massive MIMO is applied in the macrocells, and users aim to harvest as much energy as possible ... More
Spectral and Energy Efficiency of Uplink D2D Underlaid Massive MIMO Cellular NetworksJan 13 2017May 29 2017One of key 5G scenarios is that device-to-device (D2D) and massive multiple-input multiple-output (MIMO) will be co-existed. However, interference in the uplink D2D underlaid massive MIMO cellular networks needs to be coordinated, due to the vast cellular ... More
Joint Transmit Power and Relay Two-Way Beamforming Optimization for Energy-Harvesting Full-Duplex CommunicationsOct 12 2016Oct 18 2016This paper studies the joint optimization problem of two-way relay beamforming, the receiver power splitting (PS) ratio as well as the transmit power at the sources to maximize the achievable sum-rate of a simultaneous wireless information and power transfer ... More
Probabilistically Robust SWIPT for Secrecy MISOME SystemsAug 30 2016This paper considers simultaneous wireless information and power transfer (SWIPT) in a multiple-input single-output (MISO) downlink system consisting of one multi-antenna transmitter, one single-antenna information receiver (IR), multiple multi-antenna ... More
Distributed Multicell Beamforming Design Approaching Pareto Boundary with Max-Min FairnessMay 09 2012This paper addresses coordinated downlink beamforming optimization in multicell time-division duplex (TDD) systems where a small number of parameters are exchanged between cells but with no data sharing. With the goal to reach the point on the Pareto ... More
Optimal Power Allocation by Imperfect Hardware Analysis in Untrusted Relaying NetworksSep 05 2017By taking a variety of realistic hardware imperfections into consideration, we propose an optimal power allocation (OPA) strategy to maximize the instantaneous secrecy rate of a cooperative wireless network comprised of a source, a destination and an ... More
Edge and Central Cloud Computing: A Perfect Pairing for High Energy Efficiency and Low-latencyJun 23 2018In this paper, we study the coexistence and synergy between edge and central cloud computing in heterogeneous cellular networks (HetNets), in which multi-antenna small base stations (SBSs) empowered by clouds at the edge offer computing services for user ... More
Topology and Staggered Fermion Action ImprovementJul 04 2004It is conventional wisdom that staggered fermions do not feel gauge field topology. However, the response of staggered fermion eigenmodes to the topology of the gauge field can depend quite sensitively on the way in which the staggered fermion action ... More
Fermi liquid behavior and spin-charge separation in underdoped cupratesFeb 21 2006The Gaussian fluctuations in slave-boson mean-field theory of $t-J$ model is analyzed in this paper in the low-doping regime where the superconducting to normal (pseudo-gap phase) transition is driven by vanishing of bose-condensation amplitude. By eliminating ... More
Incorporating Features Learned by an Enhanced Deep Knowledge Tracing Model for STEM/Non-STEM Job PredictionJun 06 2018The 2017 ASSISTments Data Mining competition aims to use data from a longitudinal study for predicting a brand-new outcome of students which had never been studied before by the educational data mining research community. Specifically, it facilitates ... More
The K-Receiver Broadcast Channel with Confidential MessagesDec 19 2008The secrecy capacity region for the K-receiver degraded broadcast channel (BC) is given for confidential messages sent to the receivers and to be kept secret from an external wiretapper. Superposition coding and Wyner's random code partitioning are used ... More
The Secrecy Capacity for a 3-Receiver Broadcast Channel with Degraded Message SetsJan 19 2009Jun 11 2009This paper has been withdrawn by the author due to some errors.
On the 3-Receiver Broadcast Channel with Degraded Message Sets and Confidential MessagesMar 03 2009Oct 27 2009In this paper, bounds to the rate-equivocation region for the general 3-receiver broadcast channel (BC) with degraded message sets, are presented for confidential messages to be kept secret from one of the receivers. This model is more general than the ... More
The Distributed MIMO Scenario: Can Ideal ADCs Be Replaced by Low-resolution ADCs?May 12 2017May 15 2017This letter considers the architecture of distributed antenna system, which is made up of a massive number of single-antenna remote radio heads (RRHs), some with full-resolution but others with low-resolution analog-to-digital converter (ADC) receivers. ... More
PS-FCN: A Flexible Learning Framework for Photometric StereoJul 23 2018This paper addresses the problem of photometric stereo for non-Lambertian surfaces. Existing approaches often adopt simplified reflectance models to make the problem more tractable, but this greatly hinders their applications on real-world objects. In ... More
Cascaded uncoupled dual-ring modulatorJul 22 2014We demonstrate that by coherent driving two uncoupled rings in same direction, the effective photon circulating time in the dual ring modulator is reduced, with increased modulation quality. The inter-ring detuning dependent photon dynamics, Q-factor, ... More
The Quantum Geometric Phase between Orthogonal StatesOct 07 2004We show that the geometric phase between any two states, including orthogonal states, can be computed and measured using the notion of projective measurement, and we show that a topological number can be extracted in the geometric phase change in an infinitesimal ... More
Relay-Assisted Partial Packet Recovery with IDMA Method in CDMA Wireless NetworkApr 15 2010Automatic Repeat Request (ARQ) is an effective technique for reliable transmission of packets in wireless networks. In ARQ, however, only a few erroneous bits in a packet will cause the entire packet to be discarded at the receiver. In this case, it's ... More
Probing Magnetic Configurations in Co/Cu Multilayered NanowiresJan 18 2009Magnetic configurations in heterostructures are often difficult to probe when the magnetic entities are buried inside. In this study we have captured magnetic and magnetoresistance "fingerprints" of Co nanodiscs embedded in Co/Cu multilayered nanowires ... More
Performance Analysis of Protograph LDPC Codes for Nakagami-$m$ Fading Relay ChannelsApr 24 2013In this paper, we investigate the error performance of the protograph (LDPC) codes over Nakagami-$m$ fading relay channels. We first calculate the decoding thresholds of the protograph codes over such channels with different fading depths (i.e., different ... More
Two-way beamforming optimization for full-duplex SWIPT systemsJun 28 2016In this paper, we investigate the problem of two-way relay beamforming optimization to maximize the achievable sum-rate of a simultaneous wireless information and power transfer (SWIPT) system with a full-duplex (FD) multiple-input multiple-output (MIMO) ... More
Performance of Joint Channel and Physical Network Coding Based on Alamouti STBCMay 22 2013This work considers the protograph-coded physical network coding (PNC) based on Alamouti space-time block coding (STBC) over Nakagami-fading two-way relay channels, in which both the two sources and relay possess two antennas. We first propose a novel ... More
Wireless Powered Cooperative Jamming for Secrecy Multi-AF Relaying NetworksNov 11 2015This paper studies secrecy transmission with the aid of a group of wireless energy harvesting (WEH)-enabled amplify-and-forward (AF) relays performing cooperative jamming (CJ) and relaying. The source node in the network does simultaneous wireless information ... More
Grid-Based Belief Propagation for Cooperative LocalizationSep 09 2015We present a novel parametric message representation for belief propagation (BP) that provides a novel grid-based way to address the cooperative localization problem in wireless networks. The proposed Grid-BP approach allows faster calculations than non-parametric ... More
Wireless Powered Dense Cellular Networks: How Many Small Cells Do We Need?Apr 02 2017Apr 04 2017This paper focuses on wireless powered 5G dense cellular networks, where base station (BS) delivers energy to user equipment (UE) via the microwave radiation in sub-6 GHz or millimeter wave (mmWave) frequency, and UE uses the harvested energy for uplink ... More
Optimizing DF Cognitive Radio Networks with Full-Duplex-Enabled Energy Access PointsNov 16 2016Mar 28 2017With the recent advances in radio frequency (RF) energy harvesting (EH) technologies, wireless powered cooperative cognitive radio network (CCRN) has drawn an upsurge of interest for improving the spectrum utilization with incentive to motivate joint ... More
Optimizing DF Cognitive Radio Networks with Full-Duplex-Enabled Energy Access PointsNov 16 2016With the recent advances in radio frequency (RF) energy harvesting (EH) technologies, wireless powered cooperative cognitive radio network (CCRN) has drawn an upsurge of interest for improving the spectrum utilization with incentive to motivate joint ... More
Toward Best Practices for Explainable B2B Machine LearningJun 11 2019To design tools and data pipelines for explainable B2B machine learning (ML) systems, we need to recognize not only the immediate audience of such tools and data, but also (1) their organizational context and (2) secondary audiences. Our learnings are ... More
Performance Analysis of Optimal Single Stream Beamforming in MIMO Dual-Hop AF SystemsMay 25 2012This paper investigates the performance of optimal single stream beamforming schemes in multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) systems. Assuming channel state information is not available at the source and relay, the optimal ... More
Multi-Cell Interference Exploitation: A New Dimension in Cell CoordinationJan 13 2019In this paper, we propose a series of novel coordination schemes for multi-cell downlink communication. Starting from full base station (BS) coordination, we first propose a fully-coordinated scheme to exploit beneficial effects of both inter-cell and ... More
B spectroscopy with NRQCD and HISQNov 11 2009Using NRQCD b quarks and HISQ light, strange and charm quarks we have calculated B meson masses and B^*-B splittings. We quote results for a range of lattice spacings and sea quark masses, enabling controlled extrapolation to the physical point. Since ... More
Performance Limits of Massive MIMO Systems Based on Bayes-Optimal InferenceOct 06 2014This paper gives a replica analysis for the minimum mean square error (MSE) of a massive multiple-input multiple-output (MIMO) system by using Bayesian inference. The Bayes-optimal estimator is adopted to estimate the data symbols and the channels from ... More
Bayes-Optimal Joint Channel-and-Data Estimation for Massive MIMO with Low-Precision ADCsJul 28 2015Dec 07 2015This paper considers a multiple-input multiple-output (MIMO) receiver with very low-precision analog-to-digital convertors (ADCs) with the goal of developing massive MIMO antenna systems that require minimal cost and power. Previous studies demonstrated ... More
Chemical Structure Elucidation from Mass Spectrometry by Matching SubstructuresNov 17 2018Chemical structure elucidation is a serious bottleneck in analytical chemistry today. We address the problem of identifying an unknown chemical threat given its mass spectrum and its chemical formula, a task which might take well trained chemists several ... More
On Sparse Vector Recovery Performance in Structurally Orthogonal Matrices via LASSOOct 27 2014Oct 29 2014In this paper, we consider a compressed sensing problem of reconstructing a sparse signal from an undersampled set of noisy linear measurements. The regularized least squares or least absolute shrinkage and selection operator (LASSO) formulation is used ... More
Large System Analysis of Cooperative Multi-cell Downlink Transmission via Regularized Channel Inversion with Imperfect CSITJul 14 2013In this paper, we analyze the ergodic sum-rate of a multi-cell downlink system with base station (BS) cooperation using regularized zero-forcing (RZF) precoding. Our model assumes that the channels between BSs and users have independent spatial correlations ... More
Message Passing Algorithm for Distributed Downlink Regularized Zero-forcing Beamforming with Cooperative Base StationsMar 26 2013Base station (BS) cooperation can turn unwanted interference to useful signal energy for enhancing system performance. In the cooperative downlink, zero-forcing beamforming (ZFBF) with a simple scheduler is well known to obtain nearly the performance ... More
FDD Massive MIMO Based on Efficient Downlink Channel ReconstructionFeb 16 2019Massive multiple-input multiple-output (MIMO) systems deploying a large number of antennas at the base station considerably increase the spectrum efficiency by serving multiple users simultaneously without causing severe interference. However, the advantage ... More
On Capacity of Large-Scale MIMO Multiple Access Channels with Distributed Sets of Correlated AntennasSep 25 2012Sep 26 2012In this paper, a deterministic equivalent of ergodic sum rate and an algorithm for evaluating the capacity-achieving input covariance matrices for the uplink large-scale multiple-input multiple-output (MIMO) antenna channels are proposed. We consider ... More
Self-calibrating Deep Photometric Stereo NetworksMar 18 2019This paper proposes an uncalibrated photometric stereo method for non-Lambertian scenes based on deep learning. Unlike previous approaches that heavily rely on assumptions of specific reflectances and light source distributions, our method is able to ... More
SPSA-FSR: Simultaneous Perturbation Stochastic Approximation for Feature Selection and RankingApr 16 2018This manuscript presents the following: (1) an improved version of the Binary Simultaneous Perturbation Stochastic Approximation (SPSA) Method for feature selection in machine learning (Aksakalli and Malekipirbazari, Pattern Recognition Letters, Vol. ... More
Spatial Image Steganography Based on Generative Adversarial NetworkApr 21 2018With the recent development of deep learning on steganalysis, embedding secret information into digital images faces great challenges. In this paper, a secure steganography algorithm by using adversarial training is proposed. The architecture contain ... More
Millimeter Wave Power Transfer and Information TransmissionDec 18 2015Compared to the existing lower frequency wireless power transfer, millimeter wave (mmWave) power transfer takes advantage of the high-dimensional multi-antenna and narrow beam transmission. In this paper we introduce wireless power transfer for mmWave ... More
User Association in 5G Networks: A Survey and an OutlookSep 01 2015Jan 02 2016The fifth generation (5G) mobile networks are envisioned to support the deluge of data traffic with reduced energy consumption and improved quality of service (QoS) provision. To this end, the key enabling technologies, such as heterogeneous networks ... More
Energy-Efficient Heterogeneous Cellular Networks with Spectrum Underlay and Overlay AccessOct 30 2016In this paper, we provide joint subcarrier assignment and power allocation schemes for quality-of-service (QoS)-constrained energy-efficiency (EE) optimization in the downlink of an orthogonal frequency division multiple access (OFDMA)-based two-tier ... More
A New Look at Physical Layer Security, Caching, and Wireless Energy Harvesting for Heterogeneous Ultra-dense NetworksMay 26 2017Sep 11 2017Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small cells with different antenna configurations. Existing work has widely studied spectral and energy ... More
Stochastic Geometric Analysis of Energy-Efficient Dense Cellular NetworksOct 21 2016Dense cellular networks (DenseNets) are fast becoming a reality with the rapid deployment of base stations (BSs) aimed at meeting the explosive data traffic demand. In legacy systems however this comes with the penalties of higher network interference ... More
Content Placement in Cache-Enabled Sub-6 GHz and Millimeter-Wave Multi-antenna Dense Small Cell NetworksJan 17 2018This paper studies the performance of cache-enabled dense small cell networks consisting of multi-antenna sub-6 GHz and millimeter-wave base stations. Different from the existing works which only consider a single antenna at each base station, the optimal ... More
Self-Interference in Full-Duplex Multi-User MIMO ChannelsJan 01 2017We consider a multi-user multiple-input multiple-output (MIMO) setup where full-duplex (FD) multi-antenna nodes apply linear beamformers to simultaneously transmit and receive multiple streams over Rician fading channels. The exact first and second positive ... More
Edge Caching in Dense Heterogeneous Cellular Networks with Massive MIMO Aided Self-backhaulSep 04 2017Jul 10 2018This paper focuses on edge caching in dense heterogeneous cellular networks (HetNets), in which small base stations (SBSs) with limited cache size store the popular contents, and massive multiple-input multiple-output (MIMO) aided macro base stations ... More
Energy and Latency Control for Edge Computing in Dense V2X NetworksJul 06 2018Nov 23 2018This study focuses on edge computing in dense millimeter wave vehicle-to-everything (V2X) networks. A control problem is formulated to minimize the energy consumption under delay constraint resulting from vehicle mobility. A tractable algorithm is proposed ... More
Massive MIMO-Enabled Full-Duplex Cellular NetworksNov 11 2016In this paper, we provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the self-interference (SI) channels follow the Rician distribution and other channels ... More
Secure Communications in Millimeter Wave Ad Hoc NetworksAug 02 2016Wireless networks with directional antennas, like millimeter wave (mmWave) networks, have enhanced security. For a large-scale mmWave ad hoc network in which eavesdroppers are randomly located, however, eavesdroppers can still intercept the confidential ... More
Energy Efficiency Optimization with Simultaneous Wireless Information and Power Transfer in MIMO Broadcast ChannelsNov 01 2016Simultaneous wireless information and power transfer (SWIPT) is anticipated to have great applications in fifth-generation (5G) and beyond communication systems. In this paper, we address the energy efficiency (EE) optimization problem for SWIPT multiple-input ... More
DFT-Based Hybrid Beamforming Multiuser Systems: Rate Analysis and Beam SelectionApr 20 2018This paper considers the discrete Fourier transform (DFT) based hybrid beamforming multiuser system and studies the use of analog beam selection schemes. We first analyze the uplink ergodic achievable rates of the zero-forcing (ZF) receiver and the maximum-ratio ... More
Full-Duplex Cloud Radio Access Network: Stochastic Design and AnalysisNov 06 2017Full-duplex (FD) has emerged as a disruptive communications paradigm for enhancing the achievable spectral efficiency (SE), thanks to the recent major breakthroughs in self-interference (SI) mitigation. The FD versus half-duplex (HD) SE gain, in cellular ... More
Power Scaling of Uplink Massive MIMO Systems with Arbitrary-Rank Channel MeansMay 27 2014This paper investigates the uplink achievable rates of massive multiple-input multiple-output (MIMO) antenna systems in Ricean fading channels, using maximal-ratio combining (MRC) and zero-forcing (ZF) receivers, assuming perfect and imperfect channel ... More
Secure Communications in Millimeter Wave Ad Hoc NetworksAug 02 2016Feb 15 2017Wireless networks with directional antennas, like millimeter wave (mmWave) networks, have enhanced security. For a large-scale mmWave ad hoc network in which eavesdroppers are randomly located, however, eavesdroppers can still intercept the confidential ... More
Performance Analysis of Protograph-based LDPC Codes with Spatial DiversityAug 12 2012In wireless communications, spatial diversity techniques, such as space-time block code (STBC) and single-input multiple-output (SIMO), are employed to strengthen the robustness of the transmitted signal against channel fading. This paper studies the ... More
Ultraharmonics and Secondary Spiral Wakes Induced by a PlanetApr 29 2016We investigate the ultraharmonics response of a protoplanetary disk to an orbiting planet. We find that the multi-armed spiral structure can be excited by the higher-order forcing due to nonlinear mode-coupling. In particular, the preferential excitation ... More
Homological flips and homological flopsJul 14 2019We introduce a notion of homological flips and homological flops. The former includes the class of all flips between Gorenstein normal varieties; while the latter includes the class of all flops between Cohen-Macaulay normal varieties whose contracted ... More
Location Identification of Power Line Outages Using PMU Measurements with Bad DataFeb 20 2015The use of phasor angle measurements provided by phasor measurement units (PMUs) in fault detection is regarded as a promising method in identifying locations of power line outages. However, communication errors or system malfunctions may introduce errors ... More