• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4618-4639
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• 2018

One of the most innovative paradigms for the next-generation of wireless cellular networks is the cloud-radio access networks (C-RANs). In C-RANs, base station functions are distributed between the remote radio heads (RHHs) and base band unit (BBU) pool, and a communication link is defined between them which is referred as the fronthaul. This leveraging link is expected to reduce the CAPEX (capital expenditure) and OPEX (operating expense) of envisioned cellular architectures as well as improves the spectral and energy efficiencies, provides the high scalability, and efficient mobility management capabilities. The fronthaul link carries the baseband signals between the RRHs and BBU pool using the digital radio over fiber (RoF) based common public radio interface (CPRI). CPRI based optical links imposed stringent synchronization, latency and throughput requirements on the fronthaul. As a result, fronthaul becomes a hinder in commercial deployments of C-RANs and is seen as one of a major bottleneck for backbone networks. The optimization of fronthaul is still a challenging issue and requires further exploration at industrial and academic levels. This paper comprehensively summarized the current challenges and requirements of fronthaul networks, and discusses the recently proposed system architectures, virtualization techniques, key transport technologies and compression schemes to carry the time-sensitive traffic in fronthaul networks.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.2
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• pp.82-94
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• 2007

Wireless sensor networking technology is one of the basic infrastructures for ubiquitous environment. It enables us to gather various sensory data such as temperature, humidity, gas leakage, and speed from the remote sensor devices. To support these networking functions, IEEE WPAN working group makes standards for PHY and MAC, while ZigBee Alliance defines the standards for the network, security, and applications. The low-rate WPAN was emerged to have the characteristics of network resilience, low cost, and low power consumption. It has a broad range of applications including, but not limit to industrial control and monitoring, home automation, disaster forecast and monitoring, health care. In order to provide more intelligent and robust services, users want voice-based solutions to accommodate to low-rate WPAN. In this paper, we have evaluated voice quality of an IEEE 802.15.4 standard compliant voice node. Specifically, it includes the design of a voice node and experiments based on the prediction of voice quality using the E-model suggested by ITU-T G.107, and the network communication mechanisms considering beacon-enabled and nonbeacon-enabled networks for real-time voice communications.

• International journal of advanced smart convergence
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• v.9 no.1
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• pp.109-112
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• 2020

Many devices are connected on the internet to give functionalities for interconnected services. In 2020', The number of devices connected to the internet will be reached 5.8 billion. Moreover, many connected service provider such as Google and Amazon, suggests edge computing and mesh networks to cope with this situation which the many devices completely connected on their networks. This paper introduces the current state of the introduction of the wireless mesh network and edge cloud in order to efficiently manage a large number of nodes in the exploding Internet of Things (IoT) network and introduces the existing Network Time Protocol (NTP). On the basis of this, we propose a relatively accurate time synchronization method, especially in heterogeneous mesh networks. Using this NTP, multiple time coordinators can be placed in a mesh network to find the delay error using the average delay time and the delay time of the time coordinator. Therefore, accurate time can be synchronized when implementing IoT, remote metering, and real-time media streaming using IoT mesh network.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.883-895
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• 2007

In this work, we present the development of a patrol robot which is intended to navigate outdoor rough terrain. Proposed mechanism consists of six legs for overcoming an obstacle, and six wheels for traveling. Also, in order to absorb vibration in rough terrain effectively, the slide-spring system and tubed type tire are adopted to each leg and each wheel. The control system of robot consists of several imbedded boards for management of lots of diverse devices such as sensors designed for rough terrain, motor controllers, camera, micro controller and so on. And the base system of the robot is designed to operate in real time and to surveille in the vicinity of the robot, and the robot system is controlled by wireless LAN connected to GUI-based remote control system, while CAN communication connects the control board and the device controllers for sensors and motor controllers. For operating this robot system efficiently, we propose the control algorithms for autonomous navigation using GPS, stabilization maintenance by posture control, obstacle-avoidance by impedance control, and obstacle-overcoming with interference-avoidance between wheels. The performance of the robot and the proposed algorithms are tested and proved by a set of experiments in outdoor rough terrain.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.1
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• pp.9-15
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• 2012

Multiple convenience features have been getting installed in recently released cars. However, the control of them has many uncomfortable matters yet. To resolve them, it is needed to study how to use easier the convenience features and control them remotely. Currently, wide range of convergence services are being released in various industries by using smartphone and smartphones with its state-of-the-art functions also are being released. In this paper, we design and implement smartphone-based applications for controling the vehicle's convenience features to control the vehicle convenience features with smartphone. To do this, we configure CAN (Controller Area Network) communication between the vehicle's various convenience features, and establish MCU (Micro Controller Unit) to control each feature. We also connect between the MCU and smartphones to make them available for the remote control. We can control lights, turn signals, audio, windows, air conditioner, and so on with the implemented smartphone-based control service of vehicle's convenience features using CAN remotely.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.84-87
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• 2008

ATTOL is a software unit testing tool produced by the ATTOL Testware SA in France. It automates the entire software unit testing process: test plan template and test program generation, test program execution, test result analysis and test report generation. ATTOL is suited for the development of embedded software as it allows programmers to operate in native and cross development environments. Particularly, it is used for the development of the flight software which is embedded in the Communication Ocean Meteorological Satellite (COMS). As the flight software is mission-critical, it requires the strict software quality and high testing constraints. The flight software of COMS is verified by ATTOL in native and cross platforms. In 2002, ATTOL was taken over by the IDM Rational Software and has been supplied with the name of Test RealTime (TestRT). The test process of TestRT becomes different from that of ATTOL as TestRT provides the new functionalities that were absent from ATTOL. TestRT provides the new features in the test script language, as well. In this paper, we compare the test process of ATTOL to TestRT With an example of COMS and explain what has been changed in the test script language.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.92-95
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• 2008

The Geostationary Ocean Color Imager (GOCI) is under development to provide a monitoring of ocean-color around the Korean Peninsula from geostationary platforms. It is planned to be loaded on Communication, Ocean, and Meteorological Satellite (COMS) of Korea. The GOCI has been designed to provide multi-spectral data to detect, monitor, quantify, and predict short term changes of coastal ocean environment for marine science research and application purpose. The target area of GOCI observation covers sea area around the Korean Peninsula. Based on the nonlinear radiometric model, the GOCI calibration method has been derived. The radiometric model of GOCI has been validated through radiometric ground test. From this ground test result, GOCI radiometric model has been changed from second order to third order. In this paper, the radiometric test performed to evaluate the radiometric nonlinearity is described and the GOCI radiometric error propagation is analyzed. The GOCI radiometric calibration is based on onboard calibration devices; solar diffuser, DAMD (Diffuser Aging Monitoring Device). The radiometric model error due to the dark current nonlinearity is considered as a systematic error. Also the offset correction error due to gain/offset instability is considered. The radiometric accuracy depends mainly on the ground characterization accuracies of solar diffuser and DAMD.

• International journal of advanced smart convergence
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• v.7 no.2
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• pp.127-134
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• 2018

This study found the digital divide of Korean elderly persons on the basis of the 2013-2017 survey data of the perception of media information adopters. The studied media were traditional ones, such as newspaper and TV. The media dependence of those in their 20s to 60s was compared and analyzed. As a result, regarding their dependence on newspaper, elderly persons in their 60s had 20.7% on average, 13.6% higher than the percentage (7.1%) of young persons. Regarding their dependence on TV, those in their 60s had 97.6% and those in their 20s had 63.7%, so that there was a wide gap of 33.9% on average. The smartphone penetration rate of those in their 60s was 61.3%(2015-2017) on average, which tended to rise. The elderly's dependence on traditional media featured Digital Divide which is found in the informatization process. Accordingly, in order to solve their digital divide, it is required to expand education in line with their knowledge level through remote online centers, develop inclusive ICT for convenience, and change philosophical policy paradigm in the dimension of quality of life.

• Journal of Ocean Engineering and Technology
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• v.34 no.4
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• pp.277-284
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• 2020

Underwater acoustics, which is the study of phenomena related to sound waves in water, has been applied mainly in research on the use of sound navigation and range (SONAR) systems for communication, target detection, investigation of marine resources and environments, and noise measurement and analysis. The main objective of underwater acoustic remote sensing is to obtain information on a target object indirectly by using acoustic data. Presently, various types of machine learning techniques are being widely used to extract information from acoustic data. The machine learning techniques typically used in underwater acoustics and their applications in passive SONAR systems were reviewed in the first two parts of this work (Yang et al., 2020a; Yang et al., 2020b). As a follow-up, this paper reviews machine learning applications in SONAR signal processing with a focus on active target detection and classification.

• Korean Journal of Health Education and Promotion
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• v.13 no.1
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• pp.45-51
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• 1996

The Korea Information Infrastructure aims at the construction of an advanced national information infrastructure, consisting of communication networks, computers, databases and multimedia terminals. In the emerging information society, a well-established national information network plays a crucial role in enhancing economic efficiency and creating national wealth. Till 2015, government plans to construct an Information Superhighway Network and to provide a telecommunication service for speedy transmission of multi-media typed information and development of various applied programs, which help government's commitment to establish nationwide infrastructure to perform a leading role as a high level information society in the 21st century. In the field of health education, the research monograph contains three main parts: health education and information, acceptability of health education; development of health education management information system. In the most remote areas, it can bring high-quality health care where none is now available. In global health care, it can enhance and standardize the quality of medical care throughout the world. Before enlarging the establishment of the health education network system, the issues from this study should be considered to improve the health status through the introduction of information technology and applications in health care.