• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.3
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• pp.517-524
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• 2018

This Paper presents the real time things control method through Web browser that has no limited by time and place. To design and realize the system that not only makes it possible to communicate with other protocols but also reinforces the advantages of each protocol, the real time communication environment, based on the WebSocket technology of HTML5 whose international standardization has recently been completed, is realized. Also, the message communication environment in the low electricity and limited communication environment is realized using MQTT(Message Queue Telemetry Transport) protocol which is in the spotlight as the optimum protocol in the IoT environment. And by designing intuitive and simple hardware and realizing the responsive web interface which is not limited by the user's contact devices, the interactive system in which the user receives real time data from the hardware and reversely the user controls the things is designed and realized.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1089-1096
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• 2019

Recently, small-scale IoT services using a small amount of information through low-performance computing have been spread. It requires low cost, low-power, and long-distance communication technologies with wide communication radius, relatively low power consumption. This paper proposes a MAC layer and routing protocol that supports multi-hop transmission in small-scale IoT environment distributed over a large area based on LoRa communication and delivering a small amount of sensing data. The terminal node is mobile and the communication type provides bidirectional transmission between the terminal node and the network application server. By applying the proposed protocol, a production line monitoring system for smart factory was implemented. It was confirmed that the basic monitoring functions are normally performed.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.67-72
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• 2020

Satellite communication is not used by many people like mobile communication, but it is a necessary technology for public service and communication services, such as providing the Internet in military, disaster, remote education and medical services, island areas, and infrastructure vulnerable areas. However, on ships and aircraft, mobile communications requiring base stations are either unavailable or restricted in their use. In this paper, we used a Raspberry Pi board as the terminal device to communicate network through satellite modem and PPP protocol, and implemented two-way data link using the text message of the modem to connect to the Thuraya geo-stationary orbit network. In addition, I/O devices were connected to the controller of the terminal equipment to design and implement an IoT device system for ships that can remotely access the system under control and control I/Os and transmit measured data through various sensors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.359-364
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• 2016

As cable TV networks have a media feature that is a broadband wire network, they can provide not only TV broadcasting services but also communication services. Accordingly, the cable TV network is mentioned as the optimal network for convergence of broadcasting and communication services. Recently, Available frequencies of the cable TV network have become insufficient as enhancement of video quality, increment of VoD service, and growth of high-speed internet service. This paper presents a new implementation method of switched digital video (SDV) technology that is introduced for obtaining additional frequency band. In the SDV system, only TV channels requested from viewer are sent and non-requested channels are dropped. The presented SDV uses a sharing method of TV broadcasting and communication service in a same frequency band. This method shows increase of spectrum efficient from switching of TV service channels without building a complex system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.735-738
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• 2005

The phase error in the digital transmission system are generated by random phase noise and tracking phase error due to doppler phenomenon. In the mobile satellite communication system that generates the doppler frequency, which is a system with a movement, the proper system phase noise spectrum should be designed based on analyses for phase noise and static phase error effects. Based on the analyses of the doppler frequency and the phase error for bilateral satellite communication system providing an asynchronous service, the phase noise spectrums for the mobile satellite communication are designed in this paper. Also, the available transmission services under the less doppler effect are proposed and the proper signal source units for a required transmission system can be designed under the proposed system phase noise spectrum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12C
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• pp.208-217
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• 2001

In mobile Internet environment, providing multicast requires much more complex mechanism comparing with the unicast Mobile IP routing protocol. This is because multicast datagrams are sent to a group address that do not belong to a specific network. The IETF Mobile IP suggested two approaches for mobile multicasting, namely remote subscription and hi-directional tunneling. In remote subscription, a mobile node may join a group via a local multicast router on the visited subnet. Therefore remote subscription may cause much datagram loss while reconstructing the delivery tee. In bi-directional tunneling, a mobile node may join a group via a hi-directional tunnel to its home agent. Bi-directional tunneling may suffer from inefficient routing. In this paper, we proposed a new mobile multicasting protocol, Mobile If Multicast using Local Broadcast(MIMLB) which can receive multicast datagrams as fast as possible and optimize routing path for multicast delivery. The MIMLB protocol uses hi-directional tunneling to receive multicast datagrams. And the MIMLB protocol can resolve datagram duplicated problem and optimize routing path by using local broadcast. Simulation results show that MIMLB reduces delivery path length and optimizes multicast routing path when a mobile nod? moves into a foreign network.

• Journal of The Korean Association of Information Education
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• v.13 no.3
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• pp.393-400
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• 2009

As one of leading media converging broadcasting and telecommunications, IPTV is required to pursuit the idea of public interest from broadcasting industry and universal service from telecommunications industry as well as satisfying industrial effect. It needs to consider both industrial effect and public benefit when vitalizing IPTV services. The project of providing IPTV-based interactive public services is expected to enhance accessibility of public services, present shape of new public service in broadcasting-telecommunication convergence environment, resolve the shortage in contents supply which is one of most important problems in IPTV services. In this research understanding the overall response such as service usage status, satisfying/dissatisfying factor, trend of preference of the customer using IPTV-based interactive public services, we analyze what the public service mean in IPTV environment and public identity of IPTV. And we have investigate effective developing method and ripple effect of IPTV-based public services on broadcasting and telecommunications converged ecosystems.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.10-15
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• 2007

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ku-band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. An array antenna consisting of 16 leaky-wave elements is showing 30 dBi of gain, 4.9 degree of beamwidth, below than -20 dB of sidelobe level, 45 degree of beam tilt angle in center frequency. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.231-231
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• 2008

최근 인터넷의 보급과 함께 고화질 및 양방향 TV, VOD 방송, 화상 전화 등의 멀티미디어 시대가 열리면서 초고속 통신 시스템에 대한 관심이 증가되고 있다. 특히 화상이나 동영상 같은 대량의 정보가 졸은 품질 및 빠른 속도로 전달될 수 있는 통신 시스템의 필요성이 대두됨에 따라 가장 효율적인 고속 전송 수단으로 광통신이 이용되고 있으며 그에 따른 광통신 능 수동 소자 개발에 관한 연구도 활발히 이루어지고 있다. 이러한 광통신 소자 중 원하는 빛을 선택적으로 투과하고 반사할 수 있는 flat-band pass(FP) filter의 역할이 중요한 부분을 차지하고 있다. 본 논문에서는 IR 영역에서 투과성이 우수한 칼코게나이드 물질을 이용해 l 차원 광자결정구조의 FP-filter를 설계, 제작하고 그에 대한 특성을 평가하였다. 시료는 5N의 순도를 갖는 As, Se, Te 물질을 준비하고 $As_xSe_yTe_z$를 조성비에 맞추어서 석영관에 진공 봉입한 후 용융 혼합하여 $As_{33}Se_{67}$과 $As_{40}Se_{25}Te_{35}$ 조성의 두 가지 비정질 벌크를 제작하였다. 제작된 시료의 굴절률은 ellipsometer을 사용하여 측정하였고, 본 연구진이 자체 개발한 계산툴에 따라 다중층막 구조를 설계하였다. 열 증착법을 이용하여 설계된 구조에 맞게 기판에 올리는 방법으로 1차원 광자결정 구조의 다중층막 샘플을 제작하였고 UV-Vis-IR Spectroscopy를 사용하여 반사도와 투과도를 측정하였다. 광통신용 L/C 밴드 주파수 범위에서 투과성이 우수한 칼코게나이드 박막의 1차원 광자결정 구조는 FP-filter등의 소자로써 유용하게 사용될 수 있다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.69-77
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• 2009

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ka band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. Especially, for the lower sidelobe level the radiation power control using a design method of the different slot width is proposed. An array antenna consisting of 32 leakywave elements is showing 34.4 dBi of gain, 3.6 degree of beamwidth, below than -25 dB of sidelobe level, 43 degree of beam tilt angle in center frequency 20.0 GHz. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.