publications

2024

1. ICTC

   Max-Min Fairness Precoding with Low Resolution DACs

   S. Yoo S. Bae and J. Choi^*

   ICTC, Oct 2024

   Abs DOI

   

   We propose a max-min fairness (MMF) precoding algorithm for a multi-user multiple-input multiple-output (MU-MIMO) downlink system with different user weights, considering the quantization effects of low-resolution digital-to-analog converters (DACs). To find a precoder, we first formulate a problem, which jointly considers MMF and quantization. This joint problem presents some challenges that make finding a direct solution infeasible: non-smoothness and non-convexity. To address the non-smoothness, we use LogSumExp method to approximate the problem into a smooth problem. Subsequently, we derive the first-order optimality condition and cast it as a nonlinear eigenvalue problem. Lastly, we employ a generalized power iteration method to determine the superior stationary point. Simulation result demonstrates the superiority of our MMF precoding algorithm.

2. arXiv

   Full-Duplex MU-MIMO Systems with Coarse Quantization: How Many Bits Do We Need?

   arXiv, Mar 2024

   Abs

   

   This paper investigates full-duplex (FD) multi-user multiple-input multiple-output (MU-MIMO) system design with coarse quantization. We first analyze the impact of self-interference (SI) on quantization in FD single-input single-output systems. The analysis elucidates that the minimum required number of analog-to-digital converter (ADC) bits is logarithmically proportional to the ratio of total received power to the received power of desired signals. Motivated by this, we design a FD MIMO beamforming method that effectively manages the SI. Dividing a spectral efficiency maximization beamforming problem into two sub-problems for alternating optimization, we address the first by optimizing the precoder: obtaining a generalized eigenvalue problem from the first-order optimality condition, where the principal eigenvector is the optimal stationary solution, and adopting a power iteration method to identify this eigenvector. Subsequently, a quantization-aware minimum mean square error combiner is computed for the derived precoder. Through numerical studies, we observe that the proposed beamformer reduces the minimum required number of ADC bits for achieving higher spectral efficiency than that of half-duplex (HD) systems, compared to FD benchmarks. The overall analysis shows that, unlike with quantized HD systems, more than 6 bits are required for the ADC to fully realize the potential of the quantized FD system.

2023

1. ICTC

   A Survey on Statistical Channel Modeling for Underwater Acoustic Communications

   ICTC, Oct 2023

   Abs DOI

   

   Underwater acoustic (UWA) channel is one of the common systems for wireless underwater communication. However, the underwater environment poses significant challenges to reliable and efficient communication. This paper is a survey on channel modeling for UWA communications. We investigate various UWA channel modeling approaches that incorporate both large- and small-scale fading effects and provides a comprehensive summary of the key findings.

2. ICTC

   Downlink Satellite Network Analysis with Beam Gain in Shadowing Channel

   S. Yoo S. Kim and J. Choi^*

   ICTC, Oct 2023

   Abs DOI

   

   Satellite communications offer the potential of ensuring global coverage with a substantial capacity. In this paper, we examine the coverage performance of satellite networks by considering a distance-dependent line-of-sight (LOS) and non-LOS (NLOS) channel propagation probability, which takes into account the shadowing effect. Building upon the stochastic geometry-based network analysis used for terrestrial networks, we employ a Poisson point process to model both the satellite network and its users. Through this approach, we derive a theoretical expression for the coverage probability with beam gain under a nearest satellite association rule, providing an analytical understanding of the satellite network. The accuracy of the derived expression is confirmed through simulation results. The derived expression encompasses various network parameters such as satellite density, altitude, channel fading, pathloss, LOS probability, and beam gain, offering valuable insights into satellite networks.

3. VTC

   Joint Precoding and Combining for Quantized Full-Duplex MU-MIMO Systems

   S. Park S. Yoo and J. Choi^*

   VTC, Jun 2023

   Abs DOI

   

   We consider a full-duplex (FD) multi-user multiple-input multiple-output (MU-MIMO) system with low-resolution quantizers at an access point (AP). In the considered FD system, there are main bottlenecks: self-interference (SI), co-channel interference (CCI), and quantization errors. In this paper, we propose a novel precoding and combining method to maximize the sum spectral efficiency (SE) by incorporating the effect of the quantization errors as well as the SI and CCI. Since the beamformers are intertwined with the quantization errors, SI, and CCI, it is highly challenging to solve the sum SE maximization problem. To address the challenges, we convert the problem into the Rayleigh quotient form. Then, we derive the first-order optimality condition with interpreting it as a generalized eigenvalue problem by leveraging the principle of the Rayleigh quotient problem. Accordingly, we adopt a power iteration method for identifying the leading eigenvector: the best local optimal precoding solution. Consequently, we propose an alternating algorithm to jointly optimize the precoder and combiner. Simulations validate the proposed algorithm.

4. KICS

   Precoder Design for Quantized Full-Duplex MU-MIMO Systems

   S. Park S. Yoo and J. Choi^*

   KICS, Jun 2023

   Bib

   @article{2023_KICS_winter,
     title = {{Precoder Design for Quantized Full-Duplex MU-MIMO Systems}},
     author = {S. Yoo, S. Park and Choi, J.},
     journal = {KICS},
     pages = {1293--1294},
     year = {2023},
     url = {https://www.dbpia.co.kr/pdf/pdfView.do?nodeId=NODE11227863}
   }

2020

1. IEIE

   A new experiment of a autonomous controlled prototype to implement the edge computing and the cloud computing useful for smart marine logistics

   IEIE, Jun 2020

   Abs Bib

   This paper is a new experiment of a autonomous controlled prototype to implement the edge computing and the cloud computing useful for smart marine logistics. At first, this paper defines the scope of project which is consisted of a ‘cargo ship’mockup and a dock of berth facility. Secondly, this paper have a new experiment of a autonomous controlled prototype to implement the edge computing to control the docking information with a show in the webpage of a smart phone and the mechanism of saving and inquiry for docking information based on the newest cloud computing of GCP (Google Cloud Platform). Finally, this paper forecasts the innovative marine logistics to use the smart ship and smart dock for all world-wide ports’ competitiveness and safety of all ships and docks.

   @article{2020_KIPS_ICT2,
     title = {{A new experiment of a autonomous controlled prototype to implement the edge computing and the cloud computing useful for smart marine logistics}},
     author = {},
     journal = {IEIE},
     pages = {659--660},
     year = {2020},
     url = {https://www.dbpia.co.kr/pdf/pdfView.do?nodeId=NODE10521888}
   }

2. KIPS

   Security Management System to Block Abnormal Symptoms Using IoT Sensors and Artificial Intelligence

   KIPS, Jun 2020

   Encouragement Award Bib

   Winning the Encouragement Award in the Free Topic Category of Hanium ICT Contest, Ministry of Science and ICT, Korea

   @article{2020_KIPS_ICT3,
     title = {{Security Management System to Block Abnormal Symptoms Using IoT Sensors and Artificial Intelligence}},
     author = {},
     journal = {KIPS},
     pages = {897--900},
     year = {2020},
     url = {https://koreascience.kr/article/CFKO202025036304332.page},
   }

3. KIPS

   A Development of the Autonomous Berth Simulator (ABS) consisting of the newest Edge Computing and Artificial Intelligence useful for Smart Offshore Logistics

   KIPS, Jun 2020

   Silver Prize Bib

   Winning the Silver Prize in the Smart Marine Logistics Category of Hanium ICT Contest, Ministry of Science and ICT, Korea

   @article{2020_KIPS_ICT1,
     title = {{A Development of the Autonomous Berth Simulator (ABS) consisting of the newest Edge Computing and Artificial Intelligence useful for Smart Offshore Logistics}},
     author = {},
     journal = {KIPS},
     pages = {589--592},
     year = {2020},
     url = {https://koreascience.or.kr/article/CFKO202025035998259.page},
   }

4. KICS

   Modeling of the Angle Deception Using Cross-PolarizationJamming Against Monopulse Radar

   B. Jo S. Yoo and S. Park^*

   KICS, Jun 2020

   Bib

   @article{2020_KICS_Radar2,
     title = {{Modeling of the Angle Deception Using Cross-PolarizationJamming Against Monopulse Radar}},
     author = {S. Yoo, B. Jo and Park, S.},
     journal = {KICS},
     pages = {1346--1347},
     year = {2020},
     url = {https://www.dbpia.co.kr/pdf/pdfView.do?nodeId=NODE10499064&googleIPSandBox=false&mark=0&ipRange=false&b2cLoginYN=false&isPDFSizeAllowed=true&accessgl=Y&language=ko_KR&hasTopBanner=true}
   }

5. KICS

   Effects of the Scattered Field by Terrain Bounce on Radar Angle TrackingUnder Cross-Eye Jamming

   S. Yoo H. Hwang and S. Park^*

   KICS, Jun 2020

   Bib

   @article{2020_KICS_Radar1,
     title = {{Effects of the Scattered Field by Terrain Bounce on Radar Angle TrackingUnder Cross-Eye Jamming}},
     author = {H. Hwang, S. Yoo and Park, S.},
     journal = {KICS},
     pages = {1340--1341},
     year = {2020},
     url = {https://www.dbpia.co.kr/pdf/pdfView.do?nodeId=NODE10499061&googleIPSandBox=false&mark=0&ipRange=false&b2cLoginYN=false&isPDFSizeAllowed=true&accessgl=Y&language=ko_KR&hasTopBanner=true}
   }

1967

1. Vision

   

   Letters on wave mechanics

   Albert Einstein, Erwin Schrödinger, Max Planck, and 2 more authors

   Jun 1967

   Bib

   @book{przibram1967letters,
     title = {Letters on wave mechanics},
     author = {Einstein, Albert and Schrödinger, Erwin and Planck, Max and Lorentz, Hendrik Antoon and Przibram, Karl},
     year = {1967},
     publisher = {Vision},
   }

1956

1. 

   Investigations on the Theory of the Brownian Movement

   Albert Einstein

   Jun 1956

   Bib

   @book{einstein1956investigations,
     title = {Investigations on the Theory of the Brownian Movement},
     author = {Einstein, Albert},
     year = {1956},
     publisher = {Courier Corporation},
   }

1950

1. AJP

   The meaning of relativity

   Albert Einstein and AH Taub

   American Journal of Physics, Jun 1950

   Bib

   @article{einstein1950meaning,
     title = {The meaning of relativity},
     author = {Einstein, Albert and Taub, AH},
     journal = {American Journal of Physics},
     volume = {18},
     number = {6},
     pages = {403--404},
     year = {1950},
     publisher = {American Association of Physics Teachers}
   }

1935

1. PhysRev

   Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?

   A. Einstein^*†, B. Podolsky^*, and N. Rosen^*

   Phys. Rev., New Jersey. More Information can be found here , May 1935

   Abs DOI HTML PDF Video

   

   In a complete theory there is an element corresponding to each element of reality. A sufficient condition for the reality of a physical quantity is the possibility of predicting it with certainty, without disturbing the system. In quantum mechanics in the case of two physical quantities described by non-commuting operators, the knowledge of one precludes the knowledge of the other. Then either (1) the description of reality given by the wave function in quantum mechanics is not complete or (2) these two quantities cannot have simultaneous reality. Consideration of the problem of making predictions concerning a system on the basis of measurements made on another system that had previously interacted with it leads to the result that if (1) is false then (2) is also false. One is thus led to conclude that the description of reality as given by a wave function is not complete.

1920

1. Relativity: the Special and General Theory

   Albert Einstein

   May 1920

   HTML

1905

1. Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen

   A. Einstein

   Annalen der physik, May 1905
2. Ann. Phys.

   Un the movement of small particles suspended in statiunary liquids required by the molecular-kinetic theory 0f heat

   A. Einstein

   Ann. Phys., May 1905
3. On the electrodynamics of moving bodies

   A. Einstein

   May 1905
4. Ann. Phys.

   Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt

   Albert Einstein

   Ann. Phys., May 1905

   Nobel Prize Abs DOI Bib

   Albert Einstein receveid the Nobel Prize in Physics 1921 for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect

   This is the abstract text.

   @article{einstein1905photoelectriceffect,
     title = {{{\"U}ber einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt}},
     author = {Einstein, Albert},
     journal = {Ann. Phys.},
     volume = {322},
     number = {6},
     pages = {132--148},
     year = {1905},
     doi = {10.1002/andp.19053220607},
   }