• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.8
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• pp.2894-2909
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• 2015

As the number of mobile devices such as smart phones and tablets explodes, the need for new services or applications is also rapidly increasing. Smart class application is one of the emerging applications, in which most of contents are distributed to all members of a class simultaneously. It is highly required to select relay nodes to cover shadow area of radio as well as extend coverage, but existing algorithms in a smart class environment suffer from high control packet overhead and delay for exchanging topology information among all pairs of nodes to select relay nodes. In addition, the relay selection procedure should be repeated in order to adapt to the dynamic topology changes caused by link status changes or device's movement. This paper proposes the learning based relay selection algorithm to overcome aforementioned problems. The key idea is that every node keeps track of its relay quality in a fully distributed manner, where RQI (Relay Quality Indicator) is newly defined to measure both the ability of receiving packets from content source and the ability of successfully relaying them to successors. The RQI of each node is updated whenever it receives or relays broadcast packet, and the node having the higher RQI is selected as a relay node in a distributed and run-time manner. Thus, the proposed algorithm not only removes the overhead for obtaining prior knowledge to select relay nodes, but also provides the adaptability to the dynamic topology changes. The network simulation and experimental results prove that the proposed algorithm provides efficient and reliable content distribution to all members in a smart class as well adaptability against network dynamics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.157-168
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• 1999

In this paper the new channel allocation method which is important in designing mobile radio system, is proposed. If the channel is allocated by time-frequency-code sliced and using DAMA scheduler, the blocking probability is lower than TA channel allocation method. With traffic load $\rho$=0.8 and 2% of blocking probability, TFS method can allocate 36 slices compared to 11 slices in TA method. At traffic load $\rho$=0.9 and 1% of blocking probability, the maximum available slices are 13 in TA method, but in TFS method 40 slices are allocated to user, so TFS method is better frequency availability by 3.75 times than TA method. TFS method could be suitable for system planning to multirate communication users.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.80-83
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• 2016

In this paper, a simplified uplink transmission procedure is proposed for reducing energy consumption and improving lifetime of CIoT devices. In the proposed procedure, the CIoT devices register information on their service and traffic to the networks, and the networks statically allocate pre-defined amounts of radio resources when the CIoT devices have requested permission for their uplink transmissions. This paper provides details of the proposed procedure comparing with those of the current GSM procedure, and defines detailed operations of the devices and the networks for the proposed one. This shows that the proposed scheme can effectively support CIoT services on GSM networks.

• Journal of Digital Contents Society
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• v.6 no.3
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• pp.137-142
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• 2005

CDMA scheme has received a great deal of attenttion as a multiple-access method for future mobile networks. Its main advantage: are higher radio capacity and the capacity of flexible data tranmission. And CDMA scheme is a key technology in the proposals submitted to the ITU on next generation multimedia system with integrated services, namely real-time voice services and non real-time data services. In this paper, capacity evaluation of multiple-input multiple-output(MIMO) Multi-Carrier(MC)/CDMA system is considered to mitigate multiple access interference, partial-band interference and enhance system channel capacity in wireless channel. Recently, to increase the spectrum efficiency and the link reliability, MIMO-MC/CDMA scheme is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA system is evaluated according to Eb/No. Mc, p and B. From the results, in order to inappropriate spacing and the signals are frequency overlapped by partial band interference, the channel capacity of MIMO-MC/CDMA system becomes substantially smaller.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.21-27
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• 2004

In an urban area telecommunication using wireless system, the accurate prediction and analysis of wave propagation characteristics are very important to determine the service area optimized selection of base station, and eel design, etc. In the stage of these analyses, we have to present the propagation prediction mood which is varied with the type of antenna, directional angle, and configuration of the ground in our urban area in addition we need to perform an analysis of the conventional mode which is similar to ours and dig out the parameters to evaluate the wave environment before the cell design for the selected area. In this paper, we propose a wave propagation prediction model concerning the topography and obstacles in our urban area. We extract the parameters and apply them to the proposed wave environment for the simulation analyzing the propagation characteristics. Throughout these analyzing procedure, we extracted the essential parameters such as the position of the base station, the height of topography, and adequate type and height of the antenna with our preferable cuteness.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.540-550
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• 2013

The Future Wireless Railway Communication System(FWRCS) has attracted attention for the various advantages of such a system like efficient management, precise periodicity of operation and speedy travel. Related to it, the area of bandwidth requirement estimation for the FWRCS is being researched actively because there is a great need for accurate bandwidth distribution. In this paper, sophisticated bandwidth requirement estimation method for FWRCS is proposed by modifying ITU-R M.1390. With this method, the expected frequency requirements for the present, for five years from now, and for 10 years from now can be calculated by applying the data gathered from the actual field.

• Journal of Digital Convergence
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• v.13 no.2
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• pp.291-297
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• 2015

The basic idea of IoT(Internet of Things) is interconnection and cooperation with a variety of things in real life such as Radio-Frequency Identification(RFID) tags, sensors, mobile phone, etc, through internet. IoT technologies which applied to these fields consist of sensor network technology and middleware, application. Currently, IoT technology is applied to various fields such as health care, home care, automotive, transportation, construction, agriculture, environment, food, and etc, based on its technologies. This paper focuses on discussion of the IoT development trend in game field. In order to achieve this purpose, first, the IoT technologies for game development based on sensor network technology and middleware, application is mentioned. Second, covers serious game and gamification that is expected to be a growing that is expected to be a growing, by applying IoT technologies to the game field. It can help for game developers by using IoT technologies.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.183-191
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• 2016

Most recent trend reveals broader state of provision of NFC service as NFC technology was applied on smartphones which has become core communication tools by providing integrated services such as payment, medical, and personal authentication. Moreover, with integration of original service and NFC technology, new service providers now can handle personal information of original service or can handle other personal information with transition of previous service provider to NFC service provider. Considering current state of security industry along with NFC technology and service, we would like to analyze current stage of security threats and plan the counter strategies to create NFC service structure.

• Journal of IKEEE
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• v.24 no.1
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• pp.90-96
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• 2020

As various communication services have emerged due to the development of mobile communication technology, there is a need for a wideband antenna supporting multiple communication services with one antenna. In this paper, we propose a planar slot wideband antenna that can support all the communication services of 3.1~4.99GHz, the low frequency band of 5G, in addition to the existing communication services such as WiFi, LTE 2300/2500, and WiMAX. Through the simulation, the optimized antenna design parameters were obtained, and the antenna was fabricated to implement an antenna with a frequency bandwidth of 1.96~6.01GHz (S11 <-10dB) and presented the radiation pattern and gain of the antenna. The proposed antenna is a multi-band antenna that can provide all the services of LTE, Wifi, WiMAX, and 5G low frequency bands. It can be used as a repeater antenna in radio shadow area such as buildings, dense areas, and ships.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.529-534
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• 2002

It was recommended for all ship engaged in international voyages to carry the dedicated Digital Selective Calling receiver, DSC equipment, VHF transceiver, etc according to Global Maritime Distress & Safety System. Also International Maritime Organization recommended for navigation and communication equipments to applicate the EMC regulations, therefore most of electronic equipments using in the vessel to be faced with problems to cope with new regulations. This study has applied and analyzed the EMC for an equipment integrated with Ch.70 dedicated DSC receiver, DSC equipment, VHF transceiver and groped for solutions to cope with. The test has applied the electromagnetic interference such as the measurement for unwanted emissions from conductive & radio emission and the electromagnetic susceptibility such as the immunity from voltage, frequency variation and electro static discharge, hence comes to be understand the problems related with the power and the earth.