Seoul National University · Engineering
Professor Jong-Ho Lee's research lab specializes in advanced wireless communication systems and nanoscale electronic devices. The lab focuses on innovative signal processing techniques for orthogonal frequency-division multiplexing (OFDM) systems, including self-interference cancellation, channel estimation, and phase noise suppression, with an emphasis on improving spectral efficiency and system robustness. Additionally, the lab investigates emerging electronic devices such as ferroelectric tunnel junctions and field-effect transistor-based gas sensors, exploring their fundamental mechanisms and applications in neuromorphic computing and environmental sensing. The integration of novel materials and device physics with practical communication systems defines the lab’s interdisciplinary research direction.
Figures are computed from collected data and may differ slightly.
In this paper, we propose an analog self-interference cancelation scheme for full-duplex wireless orthogonal frequency-division multiplexing (OFDM) systems. Since the delay of the echo path is presented as a phase rotation of the baseband transmit signal at each subcarrier, the proposed scheme uses the rotated baseband signals to emulate self-interference signals for analog cancelation. While the conventional analog cancelation schemes are matched only to a single frequency, the proposed scheme
Recently, ferroelectric tunnel junctions (FTJs) have gained extensive attention as possible candidates for emerging memory and synaptic devices for neuromorphic computing. However, the working principles of FTJs remain controversial despite the importance of understanding them. In this study, we demonstrate a comprehensive and accurate analysis of the working principles of a metal-ferroelectric-dielectric-semiconductor stacked FTJ using low-frequency noise (LFN) spectroscopy. In contrast to resi
In this paper, we investigate the effects of charge storage engineering (CSE) on the NO<sub>2</sub> gas sensing properties such as response, recovery, and sensitivity of a FET-type gas sensor with a horizontal floating-gate (FG) having tungsten trioxide (WO<sub>3</sub>) as a sensing layer. When the FET transducer is set at an erase state (ΔV<sub>th</sub> = -2 V), the holes injected into the FG by Fowler-Nordheim (F-N) tunneling increase the electron concentration at the WO<sub>3</sub>-passivatio
A joint channel estimation and phase noise suppression scheme for orthogonal frequency-division multiplexing (OFDM) systems is proposed for a case where channel estimation is needed symbol by symbol. In the proposed scheme, channel estimation and phase noise suppression are performed iteratively via the expectation-maximization (EM) algorithm. The proposed algorithm mitigates the performance degradation due to phase noise effectively while providing an accurate channel estimate with comparativel
In this letter, we propose an iterative detection scheme in the presence of residual frequency offset (RFO) for orthogonal frequency-division multiplexing systems using an approximate application of the space-alternating generalized expectation-maximization (SAGE) algorithm. In the proposed scheme, the expectation step intends to divide the received signal into the desired signal and the interference signal. In the maximization step, the desired signal is used to estimate required parameters (i.
In this letter, we propose an efficient detection scheme for space-time block coded (STBC) orthogonal frequency-division multiplexing (OFDM) with insufficient cyclic prefix (CP). The proposed scheme employs successive interference cancellation (SIC) and cyclic prefix reconstruction (CPR) concepts. Simulation results present that the proposed scheme outperforms the conventional scheme for STBC OFDM systems.
In this paper, we consider the iterative channel estimation and decoding algorithms for quadrature amplitude modulation (QAM) modulated orthogonal frequency division multiplexing (OFDM) signals. We first describe the optimal sequence estimation based on the expectation-maximization (EM) algorithm. Using some approximations, we propose a sub-optimal iterative channel estimation and decoding algorithm, which is shown to have reduced computational complexity. The bit error rate (BER) performances o
In this paper, we propose an iterative detection \nscheme in the presence of residual frequency offset (RFO) for \northogonal frequency-division multiplexing (OFDM) system \nusing the space-alternating generalized expectation-maximization \n(SAGE) algorithm. In the proposed algorithm, the expectation \nstep intends to remove the inter-carrier interferences (ICI) due to \nRFO in the received signals. Then, the maximization step is \nutilized to estimate the required pa
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