• Title/Summary/Keyword: Time synchronization

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A Compensation Method of Timing Signals for Communications Networks Synchronization by using Loran Signals (Loran 신호 이용 통신망 동기를 위한 타이밍 신호 보상 방안)

  • Lee, Young-Kyu;Lee, Chang-Bok;Yang, Sung-Hoon;Lee, Jong-Gu;Kong, Hyun-Dong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.11A
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    • pp.882-890
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    • 2009
  • In this paper, we describe a compensation method that can be used for the situation where Loran receivers lose their phase lock to the received Loran signals when Loran signals are employed for the synchronization of national infrastructures such as telecommunication networks, electric power distribution and so on. In losing the phase lock to the received signals in a Loran receiver, the inner oscillator of the receiver starts free-running and the performance of the timing synchronization signals which are locked to the oscillator's phase is very severly degraded, so the timing accuracy under 1 us for a Primary Reference Clock (PRC) required in the International Telecommunications Union (ITU) G.811 standard can not be satisfied in the situation. Therefore, in this paper, we propose a method which can compensate the phase jump by using a compensation algorithm when a Loran receiver loses its phase lock and the performance evaluation of the proposed algorithm is achieved by the Maximum Time Interval Error (MTIE) of the measured data. From the performance evaluation results, it is observed that the requirement under 1 us for a PRC can be easily achieved by using the proposed algorithm showing about 0.6 us with under 30 minutes mean interval of smoothing with 1 hour period when the loss of phase lock occurs.

A Technical Guide to Operational Regional Ocean Forecasting Systems in the Korea Hydrographic and Oceanographic Agency (I): Continuous Operation Strategy, Downloading External Data, and Error Notification (국립해양조사원 해양예측시스템 소개 (I): 현업 운영 전략, 외부 해양·기상 자료 내려 받기 및 오류 알림 기능)

  • BYUN, DO-SEONG;SEO, GWANG-HO;PARK, SE-YOUNG;JEONG, KWANG-YEONG;LEE, JOO YOUNG;CHOI, WON-JIN;SHIN, JAE-AM;CHOI, BYOUNG-JU
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.22 no.3
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    • pp.103-117
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    • 2017
  • This note provides technical guide on three issues associated with establishing and automatically running regional ocean forecasting systems: (1) a strategy for continuous production of hourly-interval three-day ocean forecast data, (2) the daily download of ocean and atmospheric forecasting data (i.e., HYCOM and NOAA/NCEP GFS data), which are provided by outside institutions and used as initial condition, surface forcing, and boundary data for regional ocean models, and (3) error notifications to numerical model managers through the Short Message Service (SMS). Guidance on dealing with these three issues is illustrated via solutions implemented by the Korea Hydrographic and Oceanographic Agency, since in embarking on this project we found that this procedural information was not readily available elsewhere. This technical guide is based on our experiences and lessons learned during the process of establishing and operating regional ocean forecasting systems for the East Sea and the Yellow and East China Seas over the 5 year period of 2012-2016. The fundamental approach and techniques outlined in this guide are of use to anyone wanting to establish an automatic regional and coastal ocean forecasting system.

A CDMA Network-based Wireless System for Measuring Lap Time on a Ski Slope (CDMA 망에 기반한 스키장 슬로프의 무선 구간 기록 측정 시스템)

  • Lee, Hyung-Bong;Park, Lae-Jeong;Moon, Jung-Ho;Chung, Tae-Yun
    • The KIPS Transactions:PartD
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    • v.16D no.1
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    • pp.133-138
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    • 2009
  • This paper introduces a pilot CDMA network-based wireless lap time measurement system set up on a ski slope of Yongpyong Ski Resort. The wireless lap time measurement system is one output of U-Sports Project of Gangwon Province, which is intendended for promoting local strategic business and preparation for hosting 2018 Winter Olympic Games at Pyeongchang. A pair of laser sensors is installed at the entry and exit points of a section requiring lap time measurement on a ski slope. Each laser sensor is connected to a sensor node via wire so that the sensor node can detect the time when a skier enters or exits the section. Also each sensor node is connected to a CDMA network via a modem and receives a standard time from a NTP server. Each node executes the NTP algorithm to synchronize its local time to the received server time. As a result of the time synchronization, the sensor nodes maintain its local time within a resolution of at least 10 miliseconds and transmit the time of detection to a central control center. While the wireless lap time measurement system introduced in the paper does not need expensive measurement equipment, the system allows the central control center to provide lap time records in a more convenient manner compared to conventional manual lap time measuremnt methods.

Duty Cycle Scheduling considering Delay Time Constraints in Wireless Sensor Networks (무선네트워크에서의 지연시간제약을 고려한 듀티사이클 스케쥴링)

  • Vu, Duy Son;Yoon, Seokhoon
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.2
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    • pp.169-176
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    • 2018
  • In this paper, we consider duty-cycled wireless sensor networks (WSNs) in which sensor nodes are periodically dormant in order to reduce energy consumption. In such networks, as the duty cycle interval increases, the energy consumption decreases. However, a higher duty cycle interval leads to the increase in the end-to-end (E2E) delay. Many applications of WSNs are delay-sensitive and require packets to be delivered from the sensr nodes to the sink with delay requirements. Most of existing studies focus on only reducing the E2E delay, rather than considering the delay bound requirement, which makes hard to achieve the balanced performance between E2E delay and energy consumption. A few study that considered delay bound requirement require time synchronization between neighboring nodes or a specific distribution of deployed nodes. In order to address limitations of existing works, we propose a duty-cycle scheduling algorithm that aims to achieve low energy consumption, while satisfying the delay requirements. To that end, we first estimate the probability distribution for the E2E delay. Then, by using the obtained distribution we determine the maximal duty cycle interval that still satisfies the delay constraint. Simulation results show that the proposed design can satisfy the given delay bound requirements while achieving low energy consumption.

The DEVS-based Detailed Implementation Method of the Command and Fire Control System for the Underwater Vehicle DEVS-HLA Simulation in the Engagement Level (교전급 수중운동체 DEVS-HLA 시뮬레이션을 위한 전술통제체계의 DEVS 기반 상세 구현 방법)

  • Son, Myeong-Jo;Cha, Ju-Hwan;Kim, Tae-Wan;Lee, Kyu-Yeul;Nah, Young-In
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.4
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    • pp.628-645
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    • 2010
  • To perform the engagement level simulation between the underwater vehicle model and the surface model those are constituted with various systems/ sub-systems, we implemented four different federates as a federation according to the IEEE 1516 HLA (High Level Architecture) protocol that is the international standard in the distributed simulation. Those are CFCS (Command and Fire Control System) federate, motion federate, external entities (torpedos, countermeasure and surfaceship) federate, and visualization federate that interacts with OSG (Open Scene Graph)-based visualization rendering module. In this paper, we present the detailed method about the model constitution for discrete event simulation in the distributed environment. For the sake of this purpose, we introduce the DEVS (Discrete Event System Specification)-HLA-based modeling method of the CFCS federate that reflects not only the interations between models, but also commands from user and tactics manager that is separated from the model. The CFCS federate makes decisions in various missions such as the normal diving, the barrier misision, the target motion analysis, the torpedo launch, and the torpedo evasion. In the perspective of DEVS modeling, the CFCS federate is the coupled model that has the tactical data process model, command model and fire control model as an atomic model. The message passing and time synchronization with other three federates are settled by the $m\ddot{a}k$ RTI (Runtime Infrastructure) that supports IEEE 1516. In this paper, we provides the detailed modeling method of the complicated model that has hierarchical relationship such as the CFCS system in the submarine and that satisfies both of DEVS modeling method for the discrete event simulation and HLA modeling method for the distributed simulation.

Development of a Chameleonic Pin-Art Equipment for Generating Realistic Solid Shapes (실감 입체 형상 생성을 위한 카멜레온형 핀아트 장치 개발)

  • Kwon, Ohung;Kim, Jinyoung;Lee, Sulhee;Kim, Juhea;Lee, Sang-won;Cho, Jayang;Kim, Hyungtae
    • Journal of Broadcast Engineering
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    • v.25 no.4
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    • pp.497-506
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    • 2020
  • A chameleonic surface proposed in this study was a pin-art and 3D display device for generating arbitrary shapes. A smooth and continuous surface was formed using slim telescopic actuators and high-elasticity composite material. Realistic 3D shapes were continuously generated by projecting dynamic mapping images on the surface. A slim telescopic actuator was designed to show long strokes and minimize area for staking. A 3D shape was formed by thrusting and extruding the high-elasticity material using multiple telescopic actuators. This structure was advantageous for generating arbitrary continuous surface, projecting dynamic images and lightening weight. Because of real-time synchronization, a distributed controller based on EtherCAT was applied to operate hundreds of telescopic actuators smoothly. Integrated operating software consecutively generated realistic scenes by coordinating extruded shapes and projecting 3D image from multiple projectors. An opera content was optimized for the chameleon surface and showed to an audience in an actual concert.

Measurement of Reference Phase Offset for the Loran-C Transmitting Signal of Pohang (포항 로란-C 송신 신호의 기준위상 오프셋 측정)

  • Lee, Chang-Bok;Won, Sung-Ho;Lee, Jong-Koo;Kim, Young-Jae;Lee, Sang-Jeong;Yang, Sung-Hoon
    • Journal of Navigation and Port Research
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    • v.36 no.6
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    • pp.475-480
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    • 2012
  • In order to establish eLoran (enhanced Long Range Navigation) system, it needs the advancement of receiver, transmitter, data channel addition for Loran information, differential Loran sites for compensating Loran-c signal and ASFs (Additional Secondary Factors) database, etc. In addition, the precise synchronization of transmitting station to the UTC (Coordinated Universal Time) is essential if Loran delivers the high absolute accuracy of navigation demanded for maritime harbor entrance. For better timing synchronization to the UTC among transmitting stations, it is necessary to measure and monitor the transmission delay of the station, and the correction information of the transmitting station should be provided to the user's receivers. In this paper we presented the measurement method of absolute delay of Pohang Loran transmitting station and developed a time delay measurement system and a phase monitoring system for Loran station. We achieved -2.23 us as a result of the absolute phase delay of Pohang station and the drift of Loran pulse of the station was measured about 0.3 us for a month period. Therefore it is necessary to measure the delay offset of transmitting station and to compensate the drift of the Loran signal for the high accuracy application of PNT (Positioning, Navigation and Timing).

Inland ASF Measurement by Signal of the 9930M Station (9930M국 로란-C 신호를 이용한 내륙 ASF 측정 연구)

  • Yang, Sung-Hoon;Lee, Chang-Bok;Lee, Jong-Koo;Kim, Young-Jae;Lee, Sang-Jeong
    • Journal of Navigation and Port Research
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    • v.34 no.8
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    • pp.603-607
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    • 2010
  • The LORAN system had been used widely and it was an essential navigation aid for ships in the ocean until the GPS is adopted actively. In particular, it was essential functionality for the ships to sail the oceans. According to the advancement of industry, however, the current accuracy of traditional Loran is insufficient for the utilization of harbour approach, land navigation, and the field of survey and timing. Therefore it is necessary that the study on the improvement of the positioning accuracy of Loran. The one of the improving methods is to measure and compensate the propagation time delay between the transmitter and user's receiver, which is called as additional secondary factor (ASF). In this study, we measured the ASF between the Pohang master transmitting station (9930M) and four points where locate within 33 km apart from the transmitting station, using the measuring technique of the absolute time delay without a time of coincidence (TOC) table. As the result of measurement, the ranging error caused by the propagation delay was about 210 m at 33 km, however it can be reduced up to 40 m with ASF compensation.

Case Study of the Shallow Seismic Refraction Survey using Wave Glider (웨이브글라이더를 이용한 천해저 탄성파 굴절법 탐사 사례)

  • Kim, Young-Jun;Cheong, Snons;Koo, Nam-Hyung;Chun, Jong-Hwa;Kim, Jeong-Ki;Hwang, Kyu-Duk;Lee, Ho-Young;Heo, Sin;Moon, Ki-Don;Jeong, Cheol-Hun;Hong, Sung-Du
    • Geophysics and Geophysical Exploration
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    • v.20 no.1
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    • pp.43-48
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    • 2017
  • The applicability of refraction survey has been tested using a wave glider widely used in long-term ocean observations around the world. To record seismic refractions, a single channel streamer with metal weight and a seismic recording system were mounted on the wave glider. We used GPS precise time synchronization signal and radio frequency (RF) communication to synchronize shot and recorder triggers and to control acquired data quality in real time. When the wave glider is positioned close to the set point, a 2,000 J sparker is exploded along the designed track at 2 second intervals. Through the test survey, we were able to successfully acquire refractions from the subsurface.

A Study on Adaptive Pilot Beacon for Hard Handoff at CDMA Communication Network (CDMA 통신망의 하드핸드오프 지원을 위한 적응형 파일럿 비콘에 관한 연구)

  • Jeong Ki Hyeok;Hong Dong Ho;Hong Wan Pyo;Ra Keuk Hwawn
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.10A
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    • pp.922-929
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    • 2005
  • This paper proposes an adaptive pilot beacon equipment for mobile communication systems based on direct spread spectrum technology which generates the pilot channel for handoff between base stations by using the information acquired from the downstream wireless signal regarding the overhead channel information. Such an adaptive pilot beacon equipment will enable low power operation since among the wireless signals, only the pilot channel will be generated and transmitted. The pilot channel in the downstream link of the CDMA receiver is used to acquire time and frequency synchronization and this is used to calibrate the offset for the beacon, which implies that time synchronization using GPS is not required and any location where forward receive signal can be received can be used as the installation site. The downstream link pilot signal searching within the CDMA receiver is performed by FPGA and DSP. The FPGA is used to perform the initial synchronization for the pilot searcher and DSP is used to perform the offset correction between beacon clock and base station clock. The CDMA transmitter the adaptive pilot beacon equipment will use the timing offset information in the pilot channel acquired from the CDMA receiver and generate the downstream link pilot signal synchronized to the base station. The intermediate frequency signal is passed through the FIR filter and subsequently upconverted and amplified before being radiated through the antenna.