• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.678-691
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• 2015

Internet and mobile traffic continues to surge exponentially in recent years due to popularization of smart devices, the appearance of various internet services carrying large amount of traffic from richer content and applications. This phenomenon leaded to various network problems such as the congestion delay, the non-balanced traffic ratio between ISPs, the continuous network investment cost and the Internet access problems. In light of changed data-driven communication ecosystem, There are growing concerns by both academia and industry that settlement-free peering and full transit regime have the limitations such as not only difficulties in maintaining mutual benefits but also difficulties in securing investment incentives for upgrading network performance and quality. Thus, it becomes more necessary for introducing the evolved internet interconnection regime which can fulfill the All-IP network environment. This study derives core issues regarding internet interconnection regime in Korea and suggest new evolved alternatives based on three point of view(traffic optimization, cost optimization, network investment optimization) through the empirical analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.462-473
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• 2010

The RFID system has the security problem of location tracking and user privacy. In order to solve this problem, the cryptographic access method using hash function is difficult to in real applications. Because there is a limit of computing and storage capacity of Tag, but the safety is proved. The lightweight authentication methods like HB and LMAP guarantee the high efficiency, but the safety is not enough to use. In this paper, we use the AES for RFID Authentication, and solve the problem of using fixed key with key change step by step. The symmetric keys of the tag and server are changed by the random number generated by tag, reader and server successively. This could prevent the key exposure. As a result, the output of the tag and reader always changes. These key changes could make it possible to prevent eavesdropping, replay attack, location tracking and spoofing.

• Journal of Digital Contents Society
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• v.6 no.2
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• pp.101-106
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• 2005

In this paper, performance evaluation of mobile access layer for multiple-input multiple-output (MIMO) MultiCarrier(MC)/CDMA 16 QAM system is considered to mitigate multiple access interference and enhance system channel capacity in Rayleigh wireless fading channel. Traditionally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, MIMO schemes is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA 16 QAM system is evaluated according to Eb/No, Mc, p. From the results, in order to improve the channel capacity, the signals at various elements must be uncorrelated. And if the paths are correlated due to inappropriate spacing or mutual coupling effects, the channel capacity of MIMO-MC/CDMA 16 QAM system becomes substantially smaller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7A
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• pp.676-682
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• 2002

In this paper, an effective stereo image compression and reconstruction technique using a new adaptively compensated-disparity prediction scheme is proposed. That is, by adaptively predicting the mutual correlation between the stereo image using the proposed method, the bandwidth of the stereo input image can be compressed to the level of the conventional 2D image and the predicted image also can be effectively reconstructed using this transmitted reference image and disparity data in the receiver. Especially, in the proposed method, once the feature values are extracted from the input stereo image, then the matching window size for the predicted image reconstruction is adaptively selected in accordance with the magnitude of this feature values. From this adaptive disparity estimation method, reduction of the mismatching probability of the disparity vectors is expected and as a result, the image quality in the reconstructed image can be improved. In addition, from some experiments using the CCETT's stereo images of 'Fichier', 'Manege' and 'Tunnel', it is shown that the proposed method improves the PSNR of the reconstructed image to about 9.08 dB on average by comparing with that of the conventional methods. And also, it is found that there is almost no difference between the original image and the predicted image reconstructed through the proposed method by comparison to that of the conventional methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.512-519
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• 2012

To design a new Navigation Satellite System signal, we should analyze the influence of inter-system interference to existing Global Navigation Satellite Systems(GNSS). Various GNSS systems such as GSP, GALILEO, Compass use same frequence band and incur inter-system interference due to the overlapping spectrums. In this paper, we consider L2 Band for new Navigation Satellite System and propose the BOCcos(15,2.5) signal what has least Spectral Separation Coefficient with GPS L2 system. Assuming 4 stationary satellite over Korea, we simulate the effect of interference. As a result, proposed system shows very small mutual interference effect and negligible effective signal to noise ratio(SNR) loss, compared to the interferences between GNSS systems in L1 Band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.970-976
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• 2010

Platform convergence originated from the convergence of broadcast and telecommunication is making rapid progress including IT and not-IT fields in order to provide a variety of converged services, S/W eco-system construction, and so on. With the advent of convergence environment, IEEE 802.15.4-based RF4CE technology is rising because of creating momentum for the market using converged connectivity between home and office devices as well as all around located devices. In this paper, we present enhanced RF4CE key seed distribution approach in order to provide efficient connection and control between devices. The proposed approach consists of device mutual authentication, initial vector assignment, and two-phase key seed distribution. Moreover, we make a development real RF4CE test board and its key agreement simulator to verify the proposed approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.197-206
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• 2011

In the RFID system, bulk tag information is stored into the back-end database as plaintext format not ciphertext. In this case, the tags's private informations can be easily compromised by an external hacker or an insider attacker. If the private informations of tags disclosed by the attackers, it can occur serious privacy invasion problem. Recently the database(DB) security is an important issue to prevent the above DB compromised attack. However, DB security for RFID systeme has not been considered yet. If we use the DB security technique into the RFID system, the above described privacy invasion' problem can be easily prevented. Based on this motivation, this paper proposes a secure and efficient back-end database security and authentication(S-DB) scheme with XOR-based encryption/decryption algorithm. In the proposed scheme, all tag's private information is encrypted and stored by using the DB secret key to protect the DB compromised attack. As a result, the proposed S-DB scheme 'can provide stronger security and more efficiency for the secure RFID system environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.313-323
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• 2020

With the development of smart grid technologies, a user can use the secure and reliable power services in smart gird environments. However, the users are not secure against various potential attacks because the smart gird services are provided through the public channel. Therefore, a secure and lightweight authentication and key agreement scheme has become a very important security issue in smart grid in order to guarantee user's privacy. In 2019, Zhang et al. proposed a lightweight authentication scheme for smart gird communications. In this paper, we demonstrate that Zhang et al.'s scheme is vulnerable to impersonation and session key disclosure attacks, and then we propose a secure authentication and key agreement scheme for smart grid environments without tamper-resistant devices. Moreover, we perform the informal security and the BAN logic analysis to prove that our scheme is secure various attacks and provides secure mutual authentication, respectively. We also perform the performance analysis compared with related schemes. Therefore, the proposed scheme is efficiently applicable to practical smart gird environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.549-560
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• 1993

A simple closed form approximation is developed by a new approach presented in this paper for the microstrip surface dyadic Green's function which arises in the problem of an electric current point source on an infinite planar grounded dielectric substrate. This closed form approximation includes the effects of the space wave, the surface wave and their coupling within the transition region near the source, and remains accurate as near as $0.1{\pi}_1$ from the source point for a substrate thickness as large as $0.04{\pi}_1$, where, ${\pi}_1$, is the free space wavelength, This result can significantly facilitate the rigorous moment method analysis of microstrip antenna arrays on relatively this substrates of practical interest. Numerical results illustrating the accuracy of the closed form approximation are presented and CPU times associated with some mutual impedance calculations are also included.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.1 s.114
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• pp.69-80
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• 2006

The purposes of this study are to analyze the meanings of urban spaces which are the background of the Korean films, and to capture the interactions of ordinary culture and urban spaces. By reading urban spaces through films, it is possible to understand the variety of experiences that are hardly captured with direct eyes, specific and vivid urban images, and various events formed by the interactions of spaces and people. The scope of the study is the urban spaces revealed in Korean films portraying cities after the 1960's as their settings, and the total of 18 films was selected with every $4{\sim}5$ films for each time stage. With the selected films, analytical meanings were developed with considering three aspects; 1) phylogenetic meaning that simply reflects social-cultural and historical background, 2) the outer strum meaning that concerns the situation of special background and film scene, and 3) metaphorical and metanymic meaning on films. According to the appearance frequency, spatial backgrounds of film scenes are mainly alleys, main streets, railroad, loft, and riverside. And then the connection between spaces and meaning clusters was grasped, and reflected meanings were derived for every spaces. And the meaning of urban space in films was analyzed based on the meaning of developments and outer stratum. The fundamental characteristics and feelings of people in media such as films are more emphasized than in real world. Urban space is not considered as a simple visible shell, but is recognized as 'a real situation' created by people. The intension of this study was to open the possibility of the various views of urban spaces. The construction of the urban space should be approached from a perspective of creating new places at where the space and human beings interact with considerations of stories of various human lives. I hope new vistas can be opened up for the research subjects and methodologies about the hereafter study of urban spaces through the mutual communications with various adjacent regions including films.