• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.784-790
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• 2012

In this paper, we propose a upstream transmission method to extend coverage in visible light communication (VLC) systems. We extend transmission distance by using focused infrared(IR) light emitting diodes(LEDs). Since the focused light covers just limited area, it might have a difficulty in transmitting data if the transmitter and receiver are not properly aligned. To solve this problem, we arrange multiple IR-LEDs in different direction and select a single best performing IR-LED among multiple IR-LEDs. Also, the transmission performance is periodically checked and another IR-LED is reselected to support the required quality of service (QoS) and to minimize battery consumption required by a mobile terminal.

• Journal of The Korean Association of Information Education
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• v.14 no.4
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• pp.489-496
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• 2010

Since the specifications of public services in broadcasting-telecommunication convergence environment are not standardized, the public services should be developed and presented by each IPTV service provider, and therefore it is worried that public organizations and IPTV service providers may invest in the public services redundantly, which are managed inefficiently. To resolve those problem, in this paper, the service and network interfaces among multiple public organizations and multiple IPTV service providers and the interactive VOD-type public service providing system of one source multi-use based on ACAP-J are proposed. The proposed system can be utilized in the standard platform of the evolved new public services. And the used technologies can be utilized as a guide for the development of new services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.287-292
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• 2010

The flow gradually into the Information age to the Information age has changed, leading to the development of computer and communication technology was very important for the value. Of these the most used in computer communication using the Internet, and this proportion accounts for the development of the Internet, the information was established as a means of interaction. In this paper, to improve these problems without the constraints of time and space to allow two-way interactions using web based learning system to enable Computer Architecture were learning. Learn how Computer Architecture using Camtasia the learner, without limitation of time and place of the browser through the Internet to enable real-time learning and assessment appropriate to individual learners and teaching - learning process in conjunction with individual learners can be self-directed learning will play a role in that.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.57-62
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• 2010

Renewable energy and smart grid become the focus of attention of industry. The smart grid is an intelligent system which maximizes the efficiency of energy and it needs to monitor the amount of power generation and power consumption continuously. Remote Monitoring System(RMS) is very useful for monitoring the power generation and consumption, but mostly they are implemented on the wire communication. In this paper, we propose a wireless sensor network based remote power monitoring system. And as an application, a new anti-islanding method with the proposed RMS is presented. An experimental micro grid system is implemented to verify the proposed RMS and anti-islanding method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.71-78
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• 2013

Recently, the opportunistic incremental relaying systems have been studied to improve the system performance effectively in wireless fading channel. Most of the performance analysis of the system includes a source-destination direct link. And there are few analysis which consider source-relay-destination indirect paths only. Therefore this paper proposes a transmission protocol which relays the source information using the selected relay from the partial channel information at the first stage in an opportunistic incremental relaying system. If the transmission fails, the selected best relay from the full channel information retransmits the information to the destination incrementally. The performance of the proposed system is derived analytically and verified from Monte Carlo simulation. The derived results can be applied to the system design and the performance estimation of the mobile systems and the bidirectional TV broadcasting systems which adapt an opportunistic incremental relaying system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.815-821
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• 2013

In this paper, application layer protocol of C12.22 node, defined by ANSI C12.22 is implemented. ANSI C12.22 defines application layer only among the OSI 7 layers and recommends using the existing protocols for the 1~4 layer to transmit the information. TCP/IP which is one of the generally used protocols has been applied for the transport and network layer protocol in this paper. ANSI C12.19 defines the parameters for the watt-hour meter, and C12.22 application layer defines the network services and data structures networking the watt-hour meter parameters at a minimum. This kind of services and data structures are used for the configuration, programming, monitoring of the networked watt-hour meter or collecting information of the watt-hour meter. A embedded board has been used to implement the C12.22 application layer and a test program for the AMI application server has been developed for the functional test.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.4
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• pp.23-31
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• 2018

This paper presented the implementation and design of the 2T-2R wireless HD video streaming systems over 1.7 GHz frequency band using 3GPP LTE-TDD standard on NI USRP RIO SDR platform. The baseband of the system used USRP RIO that are stored in Xilinx Kintex-7 chip to implement LTE-TDD transceiver modem, the signal that are transmitted from USRP RIO up or down converts to 1.7 GHz by using self-designed 1.7 GHz RF transceiver modules and it is finally communicated HD video data through self-designed 2x9 sub array antennas. It is that communication method between USRP RIO and Host PC use PCI express x4 to minimize delay of data to transmit and receive. The implemented system show high error vector magnitude performance above 32 dBc and to transmit and receive HD video in experiment environment anywhere. The proposed hybrid beam forming system could be used not only in the future 5G mobile communication systems under 6 GHz frequency band but also in the systems over 6 GHz frequency band like ones in mmWave frequency bands.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.1-8
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• 2012

In this paper, we propose an algorithm to improve collision avoidance in Vehicle-to-Vehicle (V2V) networks based on IEEE 802.11p. Since IEEE 802.11p adopts CSMA/CA as a multiple access scheme and an emergency warning message (EWM) is delivered to behind vehicles in a multi-hop manner, due to transmission collision, the more vehicles in the vehicle chain results in a longer delay. The longer delay increases the possibility of a rear-end collision. In order to ensure message reception with low latency, we consider implicit acknowledgement of a broadcasted EWM message and propose an algorithm to reduce redundant message transactions, called Two-Way Implicit Acknowledgement (TWIA). By simulations, we show that our proposed algorithm can reduce the latency until the last car receives the message by 9% and the success rate every car receives the message within 0.7sec by 12% at 100 fixed-number-of-car environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1209-1216
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• 2008

In order to maximize spectrum efficiency and data rate MIMO(Multiple Input Multiple Output) is adopted to wireless system. OFDM-based WiMAX and LTE accommodate MIMO as mandatory technology. STC(Space Time Coding) and SM(Spatial Multiplexing) are used in downlink while in uplink C-MIMO(Collaborative MIMO) is used to improve data throughput. In this paper conventional pairing schemes, RPS(Random Pairing Scheduling) and DPS(Determinant Pairing Scheduling) are analyzed. From the analysis the performance of DPS algorithm is better than that of RPS because DPS measures orthogonal factor between paired users. However, there are potential problems such as hardware complexity and performance. To overcome the issues Power-Based Scheduling(PBS) algorithm is proposed for C-MIMO. PBS can provide higher performance compared to RPS and dramatically reduce hardware complexity compared to DPS

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.8
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• pp.510-517
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• 2014

Recently, Cable communications services are becoming the HDTV to 3DTV, UHDTV broadcasting and 100Mbps to 1Gbps Internet. however existing technologies are limited to provide high-quality broadband services in the HFC network. The network upgrade technologies have some problems that Up/Downsteam frequency extension, Cost of upgrading by using DOCSIS3.1, EPOC and Legacy STB compatibility, Cost of upgrading the network by RFoG, RF overlay PON. This paper propose the RF/PON based gigabit Transmission system in order to provide the 1Gbps internet without using frequency and the Multiscreen to IP devices. After the proposed RF/PON system was developed and implemented, this paper evaluate the performance of RF/PON system for simultaneously real-time braodcasting and 1Gbps internet, Multiscreen service, and so on.