• 한국통신학회논문지
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• 제41권9호
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• pp.1001-1009
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• 2016

LTE 시스템에서 단말이 기지국에 데이터를 전송하기 위해서는 기지국이 physical downlink control channel (PDCCH)을 통해 역방향 자원 할당 제어 정보를 방송해야 한다. PDCCH 메시지의 크기 및 전송 횟수는 셀 내 단말의 수에 비례하여 증가하기 때문에 narrowband LTE (NB-LTE) 시스템의 경우 다수의 단말에 의해 발생하는 PDCCH의 오버헤드 증가 문제가 네트워크에 심각한 혼잡을 발생시킬 수 있다. 본 논문에서는 PDCCH의 오버헤드 감소를 위해, 제안하는 간소화 된 PDCCH 정보 비트 구성 방법을 사용하여 PDCCH 메시지의 크기를 줄인다. 또한, PDCCH 메시지의 전송 횟수를 감소시키는 semi-persistent scheduling (SPS) 기법을 NB-LTE 시스템에 적용하여 성능을 평가한다. 모의실험을 통해 SPS의 경우 PDCCH의 오버헤드가 감소하였으며, 시스템의 사용 효율이 높아짐을 보였다.

• 전자통신동향분석
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• 제36권6호
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• pp.36-45
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• 2021

As the global demand for satellite IoT services using small satellites increases, interest in their frequency requirements has also increased. Consequently, International Telecommunication Union Radiocommunication Sector (ITU-R) preparatory studies for WRC-23 include AI 1.18, which considers new frequency allocations for narrowband mobile satellites. This agenda item was issued in accordance with Resolution 284 (WRC-19), and contributions and reviews by government and satellite operators are underway at ITU-R SG4 WP4C with the aim of completing the study in 2023. Resolution 248 (WRC-19) considers the conditions for transmission of candidate bands and satellites and terminals for narrowband mobile satellite, and all contributions should satisfy narrowband mobile satellite system characteristics parameters within these conditions. However, among the current transmission specifications, there are several views on the exact definition of satellite e.i.r.p., and the derivation schedule of characteristic system parameters for the study is slower than that of the original work schedule. The goal of this paper is to examine the outline of WRC-23 AI 1.18 and the main content of Resolution 284 (WRC-19) and to determine the status of studies related to WRC-23 AI 1.18. The ITU-R's study on this agenda includes updating work schedules, developing the draft required spectrum and system characteristics parameter reports/recommendations, developing draft CPM reports, and examining the various views of transmission specifications in Resolution 284 (WRC-19). Focusing on candidate bands in Region 1 (Europe and Africa) and Region 2 (America), the current status of use in Korea is investigated and future countermeasures in Korea are investigated. In addition, we would like to examine the trend of narrowband mobile satellite through satellite frequency and service status and planning of satellite IoT operators, such as EchoStar, Omnispace, and Sateliot that are participating in the ITU-R study.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.189-191
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• 2022

본 논문에서는 스마트항로표지용 서비스 요구사항 및 이를 실현할 수 있는 무선 통신 후보 기술을 분석한다. 이를 기준으로 기존 통신 기술과 사물 인터넷용 통신 기술로 분류하고, 요구사항 부합도를 판정하여 스마트항로표지용 최적 통신 시스템으로 AIS, LTE-M, NB-IoT 이상 3종의 통신 방신을 제안한다.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.418-425
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• 2019

A piezoelectric ceramic fiber composite (PCFC) was successfully fabricated using $0.69Pb(Zr_{0.47}Ti_{0.53})O_3-0.31[Pb(Zn_{0.4}Ni_{0.6})_{1/3}Nb_{2/3}]O_3$ (PZT-PZNN) for use in small-scale wind energy harvesters. The PCFC was formed using an epoxy matrix material and an array of Ag/Pd-coated PZT-PZNN piezo-ceramic fibers sandwiched by Cu interdigitated electrode patterned polyethylene terephthalate film. The energy harvesting performance was evaluated in a custom-made wind tunnel while varying the wind speed and resistive load with two types of flutter wind energy harvesters. One had a five-PCFC array vertically clamped with a supporting acrylic rod while the other used the same structure but with a five-PCFC cantilever array. Stainless steel (thickness: $50{\mu}m$) was attached onto one side of the PCFC to form the PZT-PZNN cantilever. The output power, in general, increased with an increase in the wind speed from 2 m/s to 10 m/s for both energy harvesters. The highest output power of $15.1{\mu}W$ at $14k{\Omega}$ was obtained at a wind speed of 10 m/s for the flutter wind energy harvester with the PZT-PZNN cantilever array. The results presented here reveal the strong potential for wind energy harvester applications to supply sustainable power to various IoT micro-devices.