• 대한전자공학회논문지
• /
• 제25권1호
• /
• pp.42-48
• /
• 1988

MM(multimode) PWM(pulse width modulation) Suitable for high performance and harmonic effects minimization of VSI (voltabge source invertetr)-IM (induction motor)drive system is proposed. The approximated optimal, suboptimal and optimal PWM are implemented in the low frequency range, while square wave operation is realized in the hibh frequency range. The pulse width Modulator is capable of generating control signals to a transistorized inverter operating at about 1KHz. All functions except digital comparison have been implemented in softyware making the scheme economical, flexible and reliable. Pulse width modulator is built and tested experimentally. In order to confirm the effectiveness and the reliability of the theoretical proposition, this scheme is applied to 1Hp, Three phase IM. As results, it is concluded that the scheme of MM PWM is superior to other conventional switching scheme through the discussions or analysis carried out on the items such as line-to-line voltage, current and spectrum of current harmonic components observed at the output terminal of inverter, noise level of motor.

• 제어로봇시스템학회논문지
• /
• 제20권7호
• /
• pp.767-773
• /
• 2014

The carrier-to-noise power ratio is a key parameter for determining the reliability of PVT (Position, Velocity, and Time) solutions which are obtained by a GNSS (Global Navigation Satellite System) receiver. It is also used for locking a tracking loop, deciding the re-acquisition process, and processing advanced navigation in the receiver subsystem. The representative carrier-to-noise power ratio estimation schemes are the narrowband-wideband power ratio method (NW), the MM (Moment Method), and Beaulieu's method (BL). The NW scheme is the most classical one for commercial GNSS receivers. It is often used as an authoritative benchmark for assessing carrier-to-noise power estimation schemes. The MM scheme is the least biased solution among them, and the BL scheme is a simpler scheme than the MM scheme. This paper focuses on the less biased estimation with low complexity when the residual phase noise remains, then proposes a novel carrier-to-noise power ratio estimation scheme with low complexity for GNSS receivers. The asymptotic bias of the proposed scheme is derived and compared with others, and the simulation results demonstrate that the complexity of the proposed scheme is lowest among them, while the estimation performance of the proposed scheme is similar to those of the BL and MM schemes in normal and high gained reception environments.

• 한국콘텐츠학회논문지
• /
• 제11권9호
• /
• pp.54-62
• /
• 2011

본 논문은 차세대네트워크에서 끊김없는 서비스를 위한 로컬 및 글로벌 이동성 지원 방안을 제안한다. 제안방안은 MPLS LSP(Label Switch Path)를 통한 2.5계층 스위칭을 이용하여 핸드오버 시그널링을 처리하는 기존 MPLS-MOB(Multi Protocol Label Switching-based Mobility Management)에 로컬 이동성 관리 절차를 추가 한다. 제안방안에 의한 성능 향상을 검증하기 위해 M/M/1 수식을 이용하여 기존방안인 MIP, PMIP과 MIP 연동 시나리오 그리고 MPLS 기반 마이크로 이동성 관리 방안들과 제안방안의 핸드오버 지연을 분석하고 비교하였다. 그 결과 제안방안이 기존방안들 보다 더 나은 성능을 보임을 확인하였다.

• International Journal of Advanced Culture Technology
• /
• 제6권3호
• /
• pp.178-186
• /
• 2018

Generally, in terms of the development of irrigation scheme, the efficient water resource management that supplies the irrigation water in consideration of the required time and accurate quantity to grow the crop should be conducted. The water resource assessment should precede to supply the irrigation water efficiently. The water resources assessment is divided into the water requirement analysis and the water availability assessment. In case of Korea, the major crop is paddy rice unlike crops of Africa, such as sugarcane, maize, and cassava, etc. Because it is not familiar with the method for upland irrigation development in tropical area, it needs to know the water resources assessment for irrigation scheme development about these crops. The Natama Scheme in Chiradzulu District of the Southern Malawi was selected as study area, which has tropical climate. From the collected meteorological data, the evapotranspiration was analyzed by Penman-Monteith Method and the effective rainfall was analyzed by USDA Soil Conservation Service Method. This study displays the results that for study area, the evapotranspiration varies from 2.80 mm/day to 5.51 mm/day and the effective rainfall varied from 2.1mm to 149.0mm. According to the selected crop (Green Maize, Dry Maize), the unit water requirement (UWR) and water demand (WD) considering the irrigation efficiency, irrigation time and irrigation area were estimated to be $0.00122m^3/s/ha$ and $0.0122m^3/s$ respectively. For the water availability assessment, the runoff of Natama scheme was calculated by specific yield method. The water availability was evaluated through reviewed differences of discharge between $Q80_{intake}$ and Total WD, and the irrigation water can be supplied sufficiently in the existing 10ha of Natama scheme. As a result of reviewing the extensibility of irrigable area, total WD of scheme is $0.02313m^3/s$, and $Q80_{intake}$ is $0.02387m^3/s$ ($Q80_{intake}$ > Total WD). Therefore, Natama scheme can be extended from 10 ha to 17 ha in the dry season in consideration of the $Q80_{intake}$.

• 정보처리학회논문지C
• /
• 제16C권4호
• /
• pp.527-534
• /
• 2009

대부분의 이동통신 단말기는 사용자 간에 멀티미디어 메시지를 송수신할 수 있도록 MMS를 지원한다. MMS는 다양한 이동통신 단말기에 적합하게 설계되었고 이미 무선 환경에서 효과적으로 동작하고 있으므로 MMS를 이용한 모바일 컨텐츠 제공 방법은 효율적일 수 있다. 그러나 이동통신 사업자가 사용자에게 모바일 컨텐츠를 제공하기 위해 기존의 MMS를 그대로 이용하는 방법은 몇 가지 단점을 가진다. 본 논문은 이를 해결한 데이터 전송 및 제어 기법을 제안한다. 제안된 기법은 새로운 프로토콜 설계 없이 기존 MMS 시스템의 일부 소프트웨어적인 수정만으로 사용자들에게 보다 쉽게 모바일 컨텐츠를 제공할 수 있도록 지원하는 장점을 가진다. 또한 이동통신 사업자는 제안된 기법을 통하여 이미 제공한 모바일 컨텐츠를 관리할 수 있기 때문에 모바일 일간 뉴스, 자동 S/W 업그레이드 서비스, 모바일 광고 등 다양한 부가서비스를 제공할 수 있다. 본 논문에서는 시뮬레이션을 통해 MMS를 이용하여 이동통신 사업자 스스로 사용자에게 모바일 컨텐츠를 전송하고 제어할 수 있음을 증명하였다.

• Journal of Electrical Engineering and information Science
• /
• 제3권3호
• /
• pp.300-305
• /
• 1998

This paper describes new sense amplifier with fast sensing delay time of 0.54ns and 32kb CMOS embedded SRAM with 4.67 ns access time for a 3-V power supply. It was achieved using the sense amplifier with multiple point sensing scheme and highs peed bit-line scheme. The sense amplifier saves 25% of the power dissipation compared with the conventional one while maintaining a very short sensing delay. The SRAM uses 0.5m double-polysilicon and triple-metal CMOS process technology. A die size is 1.78${\times}$mm2.13mm.

• 대기
• /
• 제15권2호
• /
• pp.91-99
• /
• 2005

This study compares the summer monsoon circulations during a heavy rainfall period over the Korean peninsular from 11 to 18 July 2004, simulated by three widely used regional models; WRF, MM5, and RSM. An identical model setup is carried out for all the experiments, except for the physical option differences in the RSM. The three models with a nominal resolution of about 50 km over Korea are nested by NCEP-DOE reanalysis data. Another RSM experiment with the same cumulus parameterization scheme as in the WRF and MM5 is designed to investigate the importance of the representation of subgrid-scale parameterized convection in reproducing monsoonal circulations in East Asia. All thee models are found to be capable of reproducing the general distribution of monsoonal precipitation, extending northeastward from south China across the Korean peninsula, to northern Japan. The results from the WRF and MM5 are similar in terms of accumulated precipitation, but a slightly better performance in the WRF than in the MM5. The RSM improves the bias for precipitation as compared to those from the WRF and MM5, but the pattern correlation is degraded due to overestimation of precipitation in northern China. In the comparison of simulated synoptic scale features, the RSM is found to reproduce the large-scale features well compared to the results from the MM5 and WRF. On the other hand, the simulated precipitation from the RSM with the convection scheme used in the MM5 and WRF is closer to that from the WRF and MM5 simulations, indicating the significant dependency of simulated precipitation in East Asia on the cumulus parameterization scheme.

• ETRI Journal
• /
• 제44권6호
• /
• pp.885-902
• /
• 2022

The mmWave cell-free massive MIMO (CFmMIMO), combining the advantages of wide bandwidth in the mmWave frequency band and the high- and uniform-spectral efficiency of CFmMIMO, has recently emerged as one of the enabling technologies for 6G. In this paper, we propose a novel framework for energy-efficient mmWave CFmMIMO systems that uses low-resolution digital-analog converters (DACs) and phase shifters (PSs) to introduce lowcomplexity hybrid precoding. Additionally, we propose a heuristic pilot allocation scheme that makes the best effort to slash some interference from copilot users. The simulation results show that the proposed hybrid precoding and pilot allocation scheme outperforms the existing schemes. Furthermore, we reveal the relationship between the energy and spectral efficiencies for the proposed mmWave CFmMIMO system by modeling the whole network power consumption and observe that the introduction of low-resolution DACs and PSs is effective in increasing the energy efficiency by compromising the spectral efficiency and the network power consumption.

• 문화기술의 융합
• /
• 제5권2호
• /
• pp.381-388
• /
• 2019

본 논문에서는 5G 이동통신 무선접속망의 프론트홀(fronthaul), 미드홀(midhaul), 백홀(backhaul) 설치 비용 효율성과 구축 용이성을 증대시키기 위해 제안된 MXN의 구조 및 동작절차를 제시하고, XDU 탐색 및 xhaul 링크 설정방식을 분석하였다. 특히 본 논문에서는 mmWave기반의 xhaul 링크 설정을 위한 여러 형태의 빔탐색 방식을 제시하고 이들 방식에 대한 성능 분석을 수행하였다. 성능 분석의 결과 제안한 임계치 기반의 탐색 혹은 획득 정보기반의 탐색은 모든 빔을 순차적으로 탐색하는 전체 빔 탐색 방식에 비해 50%이하의 짧은 탐색 지연시간을 보장함을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권5호
• /
• pp.1929-1943
• /
• 2021

Millimeter wave (mmWave) communication based on the wide bandwidth of >28 GHz is one of the key technologies for cellular-connected unmanned aerial vehicles (UAVs). The selection of mmWave beams in such cellular-connected UAVs is challenging and critical, especially when downlink transmissions toward aerial user equipment (UE) suffer from poor signal-to-interference-plus-noise ratio (SINR) more often than their terrestrial counterparts. This study proposed a coordinated mmWave beam selection scheme using fingerprint for cellular-connected UAV. The scheme comprises fingerprint database configuration and coordinated beam selection. In the fingerprint database configuration, the best beam index from the serving cell and interference beam indexes from neighboring cells are stored. In the coordinated beam selection, the best and interference beams are determined using the fingerprint database information instead of performing an exhaustive search, and the coordinated beam transmission improves the SINR for aerial UEs. System-level simulations assess the UAV effect based on the third-generation partnership project-new radio mmWave and UAV channel models. Simulation results show that the proposed scheme can reduce the overhead of exhaustive search and improve the SINR and spectral efficiency.