• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.29-36
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• 2005

A key agreement protocol is the most important part to establish a secure cryptographic system and the effort to standardize the key agreement protocols is in rapid progress. Several efficient and secure key agreement protocols have been proposed so far since Diffie-Hellman proposed a public key agreement system in 1976. But, since Diffie-Hellman based key agreement protocols need a lot of computation to establish the session key, they are not suitable for wireless Internet environment. In this paper, we propose the efficient key agreement protocol using Proxy server. The Proposed Protocol gives the security equivalent to that the Diffie-Hellman based Protocol and the computation work of mobile user can be decreased using proxy server.

• The KIPS Transactions:PartC
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• v.16C no.3
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• pp.357-362
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• 2009

Summation generator can be easily made as a simple hardware or software and it's period and linear complexity are very high. So it is appropriate to mobile security system for ubiquitous environment. But it showed us the weakness by Golic's correlation attack and Meier's fast correlation attack. In this paper, we proposed a Nonlinear Summation Generator(NSG), which is improved by using LFSR and NFSR(nonlinear feedback shift register), is different from $E_0$ algorithm which use only LFSR in summation generator. It enhanced nonlinearity and is hard to decipher even though the correlation attack or fast correlation attack. We also analyzed the security aspects and the performances for the proposed algorithm.

• The Journal of the Korea Contents Association
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• v.17 no.11
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• pp.143-155
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• 2017

In the mobile-first era, plenty of mobile apps have been created so that the number of apps owned in a smartphone have been increasing as well. However, users spend most of time with only a few apps and the rest of apps are just kept in their smartphones for future usage. Thus, in order to help users find the apps quickly it is important to study how users arrange apps in a mobile phone screen and find an app. In the literature, we extracted 5 user types to organize mobile apps. We further conducted user survey with 30 subjects and finalized major 3 user types categorized by relatedness(A), aesthetic(B), and external concepts(C). We found that most of subjects took less than 2 minutes when finding frequently-used-apps. However we identified difference in times taken to find a barely-used-apps across three user types; while A type users turns out to be the most effective in finding barely-used-apps, the B type uses tend to be the least effective among three types. For the A type users, an app's name is more important than an icon image because they tend to guess the functionality from the name of the app. The B type users use the color of app icon to find the app in the smartphone. For the C type users who tend to remain the original position of an app when first downloading it in the smartphone, the visibility of an app icon is important to catch users' eyes while they scan a page. The results of this study is expected to be useful for UX designers who improve the usability of app icon usage considering the user types.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1083-1090
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• 2005

This paper presents the design of a video encoder for the device of need TV-OUT function. The designed video encoder satisfies the standard conditions of International Telecommunication Union-Radiocommunication (ITU-R) BT.470. ITU-R BT.470 can be classified as NTSC, PAL or SECAM. NTSC and PAL use Amplitude Modulation (AM) to transmit color difference signals and SECAM uses Frequency Modulation (FM). SECAM must have an antic-cloche filter but the filter recommended by ITU-R BT.470 is not easy to design due to sharpness of the frequency response. So formerly the filter was designed as analog. This paper proposes that the filter is designed as digital and the special quality of the filter is transformed easy to design. And the modulation method is modified to be identical with the result required at standard. The encoder can control power consumption by output mode to apply mobile phone, mobile devices, etc. The proposed encoder is experimentally demonstrated with ALTERA FPGA APEX20KE EP20K1000EBC652-3 device and SAMSUNG LCD-TV.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.605-612
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• 2008

This paper researches the estimating location using repeater effect adjustment method in CDMA based system. Repeaters are commonly used by commercial and amateur radio operators to extend signals in the radio frequency range from one receiver to another. The repeater signals are increasing arrival time from base station to mobile station. So if we calculates the mobile station using repeater signals, the estimating position error is increased. However nobody researched about adjusting repeater effects. This paper proposes repeater effect adjustment algorithm. For adjusting repeater effects, we make the triangle using mobile station, reference base station and neighbor base station, and then detect the repeater effects using the triangle characteristic. The proposed method system showed the improved performance in estimating parameters and locating positions by computer simulations.

• The Journal of Society for e-Business Studies
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• v.20 no.1
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• pp.117-135
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• 2015

Mobile wallet that can keep coupons and membership cards for mobile is one of rapidly growing services due to its usability and financial benefit. However, in spite of its rapid growth, the increase of users who do not use continuously it is an important consideration to service providers for making a profit. This study aims to test the effects of factors affecting the continuous use intention of mobile wallet based on VAM (Value-based Adoption Model) which can analyse them in both benefit and sacrifice aspects, so as to suggest considerations to increase the use period of mobile wallet for service providers. The research findings supported the hypotheses regarding to the effects of usefulness, value-expression, perceived security and enjoyment in the benefit aspect and technicality in the sacrifice aspect on perceived value. In addition, the causal path from perceived value to continuous use intention was significant. The study results are expected to be used in marketing or service improvement for short-term users by taking account of emotional factors as well as functional factors.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.2
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• pp.78-86
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• 2004

Recently GPS and mobile GIS technologies based on LBS(location based service) have played an important role as DSS(decision supporting system) for domestic forest fire extinguishment policies. In this study forest fire extinguishments information management system based on mobile GIS technique was designed to seize the exact location on wireless network so that it helps to guide the safe and efficient extinguishments affairs and provide the extinguishments environment toward ground fighting teams and the central forest government in real time. Moreover, possibly to operate this system, the foundation technologies by the name of '.gci' such as the spatial data compression method, the spatial data transmission method over wireless network and the spatial analysis interface on PDA should be mainly considered. Especially, in this study the spatial data compression method having high compression rate from 51% to 62% for each polygon, line, and point data, without the loss of data was developed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.41-51
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• 2001

In this paper, we presented that the performance of the TCM(Trellis Coded Modulation) using the Euclidean distance is better than that of the convolutional code using the hamming distance under the same bandwidth efficiency. And the TCM DECODER for next generation mobile communication replacing the using convolutional decoder is implemented. Also, for the implementation of the TCM DECODER, the convolutional decoder and the TCM decoder were made by C-language and simulated under AWGN channel with respect to the hard decision and the soft decision. So we proved that performance of the TCM is better than that of the convolutional code. From this result, TCM DECODER, of which constraint length is 3, 5 or 7 and which use the soft decision method, was implemented using the AHDL(Altera Hardware Description Language) and fortified using the Max+plus H version 8.2 of Altera corporation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.774-781
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• 2014

Demand for spectrum resources is increasing with the development of mobile telecommunications and so is their economic value. As a way to enhance the economic efficiency of use of spectrum resources, many countries have focused on the management of public and broadcasting spectrums which have traditionally been undercharged compared to their economic values. In this paper, we discuss the economic value valuation of the frequencies for the fisheries communications. The estimated value is the average value of the total equipment cost of the mobile communication services that their service coverage is nation-wide, and the value that adjusted the auction price for the LTE service frequencies in 2011 to the characteristics of fisheries communications.

• The KIPS Transactions:PartC
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• v.10C no.5
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• pp.585-594
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• 2003

Java card is one of promising smart card platform with java technology. Java card defines necessary packages and classes for Embedded device that have small memory such as smart card Jana card is compatible with EMV that is Industry specification standard and ISO-7816 that is international standard. However, Java card is not offers user authentication protocol. In this paper, We design and implement an user authentication protocol applicable wireless devices based on Java Card using standard 3GPP Specification (SMS), Java Card Specification (APDU), Cryptography and so on. Our Java Card user authentication techniques can possibly be applied to the area of M-Commerce, Wireless Security, E-Payment System, Mobile Internet, Global Position Service, Ubiquitous Computing and so on.