• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.250-253
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• 2024

This paper proposes a low-power waveform for a long-range air-to-air data link. In the case of an air-to-air data link, data communication is performed in the air and high Doppler shift may occur depending on the flight speed, so a waveform based on the non-coherent method is suitable. In addition, since it is mounted on an aircraft, it must have low power characteristics. This paper proposes a waveform that combines a modulation technique based on frequency modulation and pulse position modulation that can turn on/off the transmission signal. As a result of the performance analysis, it was shown that the performance was suitable for air-to-air operation while showing low power characteristics.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.710-718
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• 2012

The implementation of a common control channel is one of the most challenging issues in cognitive radio networks, since a fully reliable control channel cannot be created without reserving bandwidth specifically for this purpose. In this paper, we investigate a promising solution that exploits the ultra wide band (UWB) technology to let cognitive radio nodes discover each other and exchange control information for establishing a communication link. The contribution of this paper is threefold: (i) We define the communication protocol needed to let cognitive radio nodes discover each other and exchange control information for link set up, (ii) we overcome the gap in coverage, which typically exists between UWB and long-medium range technologies, by using multi-hop communication, (iii) we evaluate the performance of our approach by adopting an accurate channel model and show its benefits with respect to an in-band signaling solution.

• Information and Communications Magazine
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• v.28 no.12
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• pp.50-60
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• 2011

Visible light communication(VLC) is one type of short-range, optical, and wireless communication system utilizing light emitting diode(LED) and laser diode(LD) as optical source. In a VLC system, visible light is used as a transmission medium and used to illuminate. Using VLC has a lot of advantages: it is harmless to human body; it transmits with high power, and it has excellent security, a high data rate, and a license free frequency band. With such a unique blend of communication and illumination in one system, the most common application would be an indoor environment. We aim at reviewing key issues in VLC network such as : FOV(field of view), priority MAC, cooperative MAC, link switching, LED-ID technique, cell site diversity, and link recovery.

• ETRI Journal
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• v.40 no.1
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• pp.89-100
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• 2018

Millimeter wave communication is one of the main disruptive technologies in upcoming 5G mobile networks. One of the first candidate applications, which will be commercially ready by 2020, is wireless backhaul links or wireless last mile communication. This paper provides an analysis of this use-case from radio engineering and implementation perspectives. Furthermore, preliminary experimental results are shown for a proof-of-concept wireless backhaul solution developed within the EU-KR 5GCHAMPION project, which will be showcased during the 2018 Winter Olympic Games in Korea. In this paper, we verify system level calculations and a theoretical link budget analysis with conductive and radiated over-the-air measurements. The results indicate that the implemented radio solution is able to achieve the target key performance indicator, namely, a 2.5 Gbps data rate on average, over a range of up to 200 m.

• Journal of the Korea Safety Management & Science
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• v.17 no.3
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• pp.377-381
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• 2015

For the first time, PLL frequency synthesizer using DDS was adapted for the data link communication system which should fast transmit and receive each other with the correct information and fast Hopping System. It is inevitable to lost the synchronization by slow lock time about PLL and no cut off the noise. This paper propose the design of PLL frequency synthesizer which can make 800MHz frequency range. The PLL frequency synthesizer has three high qualities those are frequency accuracy, fast lock time and outstanding phase noise.

• Journal of Computing Science and Engineering
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• v.4 no.3
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• pp.225-239
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• 2010

This paper introduces a new approach to modeling relative distance among nodes under a variety of communication rates, due to node's mobility in Mobile Ad-hoc Networks (MANETs). When mobile nodes move to another location, the relative distance of communicating nodes will directly affect the data rate of transmission. The larger the distance between two communicating nodes is, the lower the rate that they can use for transferring data will be. The connection certainty of a link also changes because a node may move closer to or farther away out of the communication range of other nodes. Therefore, the stability of a route is related to connection entropy. Taking into account these issues, this paper proposes a new routing metric for MANETs. The new metric considers both link weight and route stability based on connection entropy. The problem of determining the best route is subsequently formulated as the minimization of an object function formed as a linear combination of the link weight and the connection uncertainty of that link. The simulation results show that the proposed routing metric improves end-to-end throughput and reduces the percentage of link breakages and route reparations.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.640-648
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• 2018

Time division wireless communication in tactical MANET is attractive to deliver both high data rates and long-range coverage, and to provide scheduled QoS to mission participants. This paper is about the time synchronization issue of multi-mission USV in tactical MANET. As USV communication coverage becomes longer, the synchronization error also becomes higher; therefore, which results in link disconnection, and consequent failures of reconnection because base station cannot configure necessary parameters over long-distant terminal. We propose a range adaptive time synchronization method to compensate for synchronization errors. The issue of long-range time synchronization problem was identified during maritime communication tests, and we verified the proposed method through analyses of both indoor and outdoor test results.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.46-46
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• 2000

A quadruped monitoring robot is introduced. The robot has several features that poses arbitrary position thanks to a 4-wheel hive mechanism, transmits an image and command data via RF wireless communication, and moreover, the imaged date are transferred through a network communication. The robot plays a role in monitoring what is happening around the robot and covers wide range due to a moving camera operated by the 4-wheel mechanism. The robot system can be applied k versatile models based the distinguished techniques introduced in this paper

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1455-1458
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• 2002

In this paper, we propose a modified CP-AFC(Cross-Product Automatic Frequency Control) algorithm to enhance coherent signal detection for WCDMA reverse link receiver. We introduce a moving average filter at the FDD(Frequency Difference Detector) input to increase the number of cross-products, since pilot symbol in WCDMA is not transmitted continuously. We also add normalization algorithm to overcome the conventional CP-FDD's sensitivity to the variance of input signal amplitude and to increase the linear range of S- curve. For rapid frequency acquisition and tracking, we adopt a multi-stage tracking mode. We applied the proposed algorithm in the implementation of WCDMA base station modem successfully.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.250-253
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• 2014

Due to limited resource, marine communication is severely limited when compared to communications in land. Radio relay facilities, etc. based on a wired network through a long distance communication is possible. In addition, the aircraft is in the air, the ground-based network service based on long-range straight-line distance and elevation (LOS: Line of Sight) communications. On the other hand, the distance in a straight line to the sea, the sea level because communication is limited or through satellite, underwater communications relay equipment installed in the communication scheme has been investigated.. In this paper, using TCP-based real-time joint maritime security communication links were studied. Harsh marine environment, real-time communication that can provide secure communications and propose a LINK joint. In this study, more secure, and convenient communications at sea, a plan was presented to you.