• Journal of Korea Multimedia Society
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• v.17 no.12
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• pp.1461-1472
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• 2014

Recently, smart devices has been spreaded and the definition of RFID/USN(Radio Frequency Identification/Ubiquitous Sensor Network) technology has also extended. So, originally, human is an agent of communications but now, 'the things' are also an agent of communication. That is, Internet of Things(IoT). IoT is very big IT infra technology that is based on wire-wireless network technologies such as Bluetooth and Wi-Fi. However, in reality, IoT service that can provide various meaning and integrate smoothly is not appear yet. To solve these problems of IoT, we implemented Publish/Subscribe system, which operate in Zigbee based wireless sensor network by using MQTT-SN protocol. Moreover, this system can operate with combining MQTT system that is already existed in external Internet network so, extensibility and flexibility aspect is excellent. We show that possibility of IoT services that is combined between different heterogeneous network through the MQTT-SN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1047-1055
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• 2005

One of major characteristics in wireless LAN is terminal's frequent mobility, so it makes many overheads in the process of authentications repeatedly at each handoffs. So I propose IAPP(Inter Access Point Protocol) of IEEE 802.11f, modified context block and 4 way handshake of IEEE 802.11i, in order to implement secure and rapid handoff. The context block. I proposed, doesn't makes any communication with RADIUS server at handoff period. Therefore, it guarantee higher efficiency than existing handoff mechanisms. Also it can improve security vulnerability by padding authentication field in the context block for providing in advance against Replay and DoS(Denial of Service) attacks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.557-560
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• 2004

In this paper, wireless internet services are combined with conventional wire internet service system. These system support that instrument manager can be access his instrument by use personal mobile devices and instrument manager can be take emergency action by use mobile devices. for this, error signal of local instruments are transmitted to the serial port of local server through Rf wireless communication channel. Also, The image of local instruments are transmitted to the web monitoring screen of main server. Network Camera System Supports remote monitoring functions. The interfacing of nam server with external user are possible through the mobile devices.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.33-39
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• 2018

In the Internet of Things (IoT) era, objects are connected to each other by wired and wireless networks, and information is exchanged whenever necessary. Channel and network environments change over time; thus, a carrier sensing function that identifies whether signals containing information are present in the channel is essential. The carrier sensing circuit of a wireless communication system determines the receiver sensitivity, and the receiver sensitivity is closely related to the service coverage and service quality of the system. As the receiver sensitivity decreases, the service coverage increases but it becomes sensitive to noise. However, as the receiver sensitivity increases, the service coverage decreases but it becomes insensitive to the noise. Therefore, carrier sensing design and optimization are very important from the viewpoint of the receiver sensitivity and noise sensitivity. This paper proposes an effective carrier sensing technique from the viewpoint of the receiver sensitivity for the long range IoT.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.7
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• pp.12-21
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• 2002

In this paper, we propose a new hybrid ARQ scheme to consider real-time and non real-time services in a wireless ATM network. Real-time and non-real-time services require different error control schemes according to each service characteristics. Therefore, in the next generation mobile communication environments where these service scenarios should be deployed, hybrid ARQ scheme using RCPC code with variable coding rate becomes one of the most suitable solutions. Because the variable coding rate is applied according to traits of transmitted frame and channel status, hybrid ARQ scheme using RCPC code can expect UEP effect. The UEP scheme does not apply equal error protection level to all information, but does high error protection level to more important information. In Our scheme, UEP of high error protection level is applied to real-time service, and UEP of low error protection and retransmission techniques are applied to non real-time service. We show that the proposed hybrid ARQ scheme improves channel utilization efficiency and yields high error correction behaviors.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.975-978
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• 2005

The RFID(Radio Frequency Identification) technology is a non-contact identification system which can wireless reading of information, by attaching tags on objects; various applications of the technology are feasible throughout a diversity of industries, and researches are currently under way. Recently, in connection with the wireless communication industry, application service models conveying information to the users through mobile devices with RFID readers were suggested. Such application service based on mobile RFID technology requires schema that models the form of data. Therefore, this study analyses the mobile RFID application service model that will be serviced in the mobile environment, functions and elements of the protocol, and the interface, designing a language to process the data and express contents in the said service models.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.2
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• pp.145-156
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• 2010

Now a days, the development of TV and internet like communicational technique makes IPTV service which combines internet with multimedia contents increase. But when a user gets service in specific place, the certification process and user's ID check in IPTV service is complicate so that there occurs communicational difficulty like increasing illegal users and service delay etc. This paper proposes communication security mechanism to prevent Clone attack which happens in wireless section by efficiently extracting illegal user. The proposed mechanism performs key distribution procedure, inter certification procedure, and key initiation procedure by putting security agent in RFID-USB for RFID tags users use to perform plug-and-plug function. Also, the proposed mechanism updates the hased token value by its ID and the random number which RFID-USB creates whenever a user accesses in the area of RFID-USB so that it protects reply attack and man-in-the-middle attack which happen often in the area of wireless section.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1309-1318
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• 2004

The rapid growth of the mobile Internet has enabled its application area to expand, and its users want services that require more bandwidth for multimedia services. There are limits to support the various multimedia service to mobile station provided by existing mobile communications. The wireless MAN called the IEEE 802.16 Broadband Wireless Access systems which the IEEE 802.11 wireless LAN is similar to wireline Internet service being able to supper a various contents is used and is designed to consider a handoff is studying. Especially, TG(Task Group)e of IEEE 802.16 is in progress discussion to support a handoff to higher layer using BS(Base Station) or unit of sector, to UC. Yet a scheme is not detail. This thesis proposes the network model for IEEE 802.16e to support a soft handoff between BSs to use a mobile communication network called cdma2000 Ix EV-DO network. The proposed network model supports soft handoff to add a management skill in MA of each BS for MC(Mobility Controller). The proposed network model has merits that is able to apply existing systems as it is and that is able to use a various multimedia service, when using a wireless Internet.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.1
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• pp.46-52
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• 2011

In the paper, MIMO antenna for LTE 13 band, LTE 7 band wireless communication service is proposed. The proposed antenna is designed where on the top of FR-4(${\epsilon}_r=4.4$, thickness=-.8mm). In proposed structure, two Planar Inverted F Antennas (PIFAs) using meander and folded structure are symmetrically designed for the miniaturization. The isolation between two antennas was also improved by using two slits on the ground plane. The isolation values of the fabricated antenna exhibits -18 dB, -13dB at LTE 13 and LTE 7 band, respectively. The average gain and efficiency are - 4.1 dBi, 41% on LTE 13 band, -1 dBi, 81% on LTE 7 band, respectively. Thus the proposed antenna can be applied to the LTE system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.445-450
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• 2018

AIS is the most important navigation equipment for the identification of other ships, etc. However, the AIS overload problem has been raised recently due to an increase in AIS equipped vessels. The government is planning to introduce the wireless LTE network at 100 km offshore as part of the SMART-Navigation project. Continuous development and dissemination of the services available through such platforms will be necessary to achieve major goals such as marine accident prevention and environmental protection. In this study, we applied a WAVE communication system, which could be the basis for the development of such services. As a result, reliable data transmission was confirmed for a range of communication of approx. 5 miles, although the service was limited to 1 km in road traffic. Therefore, it is expected that WAVE communication technology will be used to prevent marine accidents through such efforts as collision avoidance and the transfer of marine safety information between ships.