Sungchul Kim

There is an explosive growth in the market of wireless communications services in urban areas. New regulatory environments as well as competition in the communications industry require that these systems be deployed quickly and at low cost. Computer-based radio propagation prediction tools are strong candidates for this goal. We introduce an outdoor radio propagation prediction tool using a ray tracing technique in two dimensions (2-D) and three dimensions (3-D). We have compared the predicted a

The growing use of unlicensed wireless systems has spurred interest in the 2.4-GHz ISM band. In order to facilitate the design of such systems, measurements of the pulse response characteristics have been made inside commercial buildings. From the measured pulse response, the statistical properties of the amplitude variation for individual pulses was determined, in addition to the path loss, mean excess delay, root mean square (RMS) delay spread, and the coherence bandwidth of the indoor channel

This paper reports the results of extensive wideband
\nchannel measurements conducted on in-house outlets
\nat 10~30MHz. Two kinds of measurements were
\nperformed: impulse response measurements and noise
\nmeasurements. Impulse responses were obtained in
\ntwo different time scales: 50 impulse responses taken
\nfor 1 minute to see short term variation and for 6
\nmilliseconds to see very short term variation. Noise
\nmeasurements were carried out to measure
\

In this article, we propose a novel harmonic clutter recognition and suppression method to overcome the deterioration of a target- or vehicle-detection performance due to harmonic clutters. Although several studies have been performed on the reflection and diffraction on road surfaces for automotive radar sensors, most of them did not consider the case where metallic structures such as iron tunnels with greater reflection are densely distributed. The proposed method measures the periodicity of h

In this paper, we present an energy efficient priority-based MAC (EEP-MAC) protocol for energy harvesting Wireless Sensor Networks (WSNs). To provide priority-based data transmission the EEP-MAC uses the modified IEEE 802.15.4 beacon frame. A receiver node periodically wakes up, receives sender beacon frames from its neighbors, and broadcasts a beacon frame containing the selected sender's address. A receiver node selects sender node according to sender's data priority. Under EEP-MAC protocol, n

This article presents a 24 Gb/s/pin single-ended capacitively driven transceiver that employs four-level pulse amplitude modulation (PAM-4), tailored for high-density die-to-die (D2D) interfaces. To fulfill the high-throughput demand in D2D interfaces, a PAM-based crosstalk cancellation (XTC) technique capable of improving the channel density is proposed along with a doubled per-pin data rate using PAM-4 signaling. Remarkably, the proposed XTC technique only requires a single capacitor at the ou

남중국해 분쟁을 둘러싼 베트남의 대중정책은 헤징으로 특징된다. 베트남은 중국과의 거듭되는 분쟁에도 불구하고 2013년 필리핀의 상설중재재판소의 제소에동참하지 않았고 독자 제소도 하지 않았다. 또 2016년 재판소가 중국의 “구단선” 의 법적근거 없음을 결정하여 베트남의 대중국 외교공세 여건이 마련됐음에도 불구하고 하노이 당국은 소극적인 정책 대안인 헤징을 택했다. 베트남의 대중국 헤징을 인과의 깔때기(funnel of causality) 관점에서, 역사에 근거한 정세인식, 안보 및경제의 역량, 해당이슈관련 파트너의 코미트먼트의 순서로 파악할 필요가 있다. 본 논문은 남중국해 분쟁의 배경과 성격, 상설중재재판소 결정에의 대중국 헤징내용을 살펴본 후, 그 요인으로 (1) 냉전종식 후 역사적 교훈에 근거한 협력-갈등의중첩적 국제정세 인식, (2) 안보 역량을 위한 외교다변화, 군사협력 강화, (3) 경제적으로 중국에의 비의존적 협력 강화, (4) ASEAN, 미국의 코미트먼트 한계로 인한

This brief presents a single-ended (SE) receiver (RX) with a self-referenced (SR) technique using sample and hold (S&H) circuits. The proposed RX does not require a reference voltage (VREF) for data recovery by comparing the present data with previous data. The RX was implemented as half-rate architecture to halve the clock frequency and facilitate the S&H operation. Moreover, the proposed decision feedback equalizer (DFE) is suitable for SR RX and improves the reliability of RX by eliminating i

지금까지 많은 연구가 북한의 핵개발 동기와 의도, 그리고 비핵화를 위한 협상과정을 분석했던 반면, 본 논문은 북한의 핵억제론 자체에 관한 연구로서, 핵억제 교리(또는 핵교리), 미국 안보전략과의 관계, 핵전략과 한계, 핵운용 유형 등을 규명한다. 북한은 2003년 6월 최초로 “핵억제”를 주창한 이후 국가주권 보호와 전쟁방지가 목적이며 핵이 협상대상이 아니라고 일관해왔다. 핵억제 주장은 “핵의 평화적 이용”이라는 과거의 수사에서 크게 선회한 것으로서, 핵억제 필요의 근거로 9.11 이후 미국이 채택한 선제공격론을 들고 있다. 북한의 핵교리는 2013년 4월 핵보유법제화와 여타의 정부 성명 및 매체들을 통해 구체적인 실체를 드러냈다. 북한의 핵억제는 핵능력의 비대칭성으로 미국의 확장억제에 비교되지 않아 억제력의 효용은 제한된 반면, 모호성을 통한 위협의 고저조절, 합리적 비합리성의 연출 등으로 일정한 효과를 노리고 있다. 북한의 핵운용은 핵군축협상 주장과 군사적 균형 변화 추구 등으로

In this paper, we propose a hybrid localization algorithm to boost the accuracy of range-based localization by improving the ranging accuracy under indoor non-line-of-sight (NLOS) conditions. We replaced the ranging part of the rule-based localization method with a deep regression model that uses data-driven learning with dual-band received signal strength (RSS). The ranging error caused by the NLOS conditions was effectively reduced by using the deep regression method. As a consequence, the pos

The empirical channel model of power line is obtained through impulse response measurements
\nusing the pseudo-noise (PN) correlation method. The BER performance for QPSK is also reported as a result of
\ncomputer simulation with the proposed channel model. Simulation results show that effective mitigation
\nmethods are required to support high speed data communication over power line with the acceptable BER.

Acceleration of ion rotation is observed during internal reconnection events (IREs) in the versatile experiment spherical torus. Two IRE discharges with opposite torques, i.e. acceleration or deceleration of ohmic plasmas with intrinsic, counter-Ip rotation, can be generated using different wall conditionings method. When an IRE occurs, acceleration and deceleration of impurity ion rotation as well as well-known ion heating are observed globally via ion Doppler spectroscopy with multiple channel

Entertainment robots, a subset of social robots designed to engage users, constitute a crucial dimension of human–robot interaction. However, current research predominantly focuses on technical advancements, leaving non-technical aspects, such as user experience and emotional engagement, underexplored. This study examines the research trends and gaps in the field of entertainment robots through a bibliometric analysis of 237 academic works published between 1998 and 2024 and a systematic literat