• 한국통신학회논문지
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• 제27권6B호
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• pp.593-600
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• 2002

The reverse link signal power required for multimedia traffic in multipath faded single-code (SC-) and multi-code CDMA (MC-CDMA) systems is investigated. The effect of orthogonality loss among multiple spreading code channels is herein characterized by the orthogonality factor. The required signal power in both the CDMA systems is then analyzed in terms of the relative required signal power ratio of data to voice traffic. The effect of varying system parameters including spreading bandwidth, the of orthogonality factor, and the number of spreading codes are examined. Analytical results show that MC-CDMA users transmitting only a single traffic type require significantly more power than SC-CDMA users with only a single traffic type. On the other hand, MC-CDMA users transmitting multimedia traffic require power levels approximately identical to SC-CDMA users with multimedia traffic. The results can be used in the design of radio resource management (e.g., power allocation) scheme for wireless multimedia services.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 2004년도 추계학술대회
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• pp.323-330
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• 2004

As mobile market grows more and more fast, the mobile contents market, especially music contents for mobile phones have recorded remarkable growth. In spite of this rapid growth, mobile web users experience high levels of frustration to search the desired music. New musics are very profitable to the content providers, but the existing collaborative filtering (CF) system can't recommend them. To solve these problems, we propose an extended CF system to reflect the user's real preference by representing the characteristics of users and musics in the feature space. We represent the musics using the music contents based acoustic features in multi-dimensional feature space, and then select a neighborhood with the distance based function. Furthermore, this paper suggests a recommendation for procedure for new music by matching new music with other users' preference. The suggested procedure is explained step by step with an illustration example.

• 한국조경학회지
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• 제24권4호
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• pp.39-58
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• 1997

This study aims to find out differences between designer's design guidelines and user's actual behavior about play facilities of children playground in multifamily housing site by using the method of Post-Occupancy Evaluation. Korea National Housing Cooperation developed the 18 play facilities and constructed them into children' playground of Bun-dong and Junggae-dong housing site in Seoul. The results are as follows: First, user's behaviors which differed from designer's guidelines were influenced by mechanical and technical problems rather than design. Second, users adjusted their brahvior to play facilities which have a little operational problems. Third. users tried to make dangrous activity instead of designer's guidelines based on the safety. It infers that users want to make creative activities from play facilities. Fourth. designers should have developed play facilities for infants and youth. Fifth. users liked to play more complicated play facilities rather than single facility.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 추계학술발표대회
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• pp.759-762
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• 2015

Many applications require users to log-in, some applications can allow users to use the same account is active on multiple devices at the same time. On location-based application that serves to record the movement of the position, account is active on multiple devices could not be permitted because it causes a different location data from multiple devices, so the location of the users become ambiguous. This paper describes a simple protocol to prevent users from using their accounts on multiple devices at the same time. This Protocol will turn off one account on a device when the account log-in on new devices.

• Journal of Communications and Networks
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• 제11권2호
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• pp.134-147
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• 2009

Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.889-906
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• 2020

Analysis of multi-physics systems and the visualization of simulation data are crucial and difficult in computational science and engineering. In Korea, Korea Institute of Science and Technology Information KISTI developed EDISON, a web-based computational science simulation platform, and it is now the ninth year since the service started. Hitherto, the EDISON platform has focused on providing a robust simulation environment and various computational science analysis tools. However, owing to the increasing issues in collaborative research, data format standardization has become more important. In addition, as the visualization of simulation data becomes more important for users to understand, the necessity of analyzing input / output data information for each software is increased. Therefore, it is necessary to organize the data format and metadata for the representative software provided by EDISON. In this paper, we analyzed computational fluid dynamics (CFD) and computational structural dynamics (CSD) simulation software in the field of mechanical engineering where several physical phenomena (fluids, solids, etc.) are complex. Additionally, in order to visualize various simulation result data, we used existing web visualization tools developed by third parties. In conclusion, based on the analysis of these data formats, it is possible to provide a foundation of multi-physics and a web-based visualization environment, which will enable users to focus on simulation more conveniently.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2009년 춘계학술발표대회 논문집
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• pp.217-221
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• 2009

With the increase in individual income and leisure time, those urban residents who want to stay in farmland on weekend are being increased. On the contrary, rural economic situation is getting worse due to the lack of labor and income. For this, as a win-win strategy between urban and rural life, a Kleingarten(below 'KG') has been attracted by local government such as Kyunggi prefecture in Korea. This article exam the situation of KG, a weekend farm where one can stay the night in a log cabin, from the perspective of Multi-habitation. For this purpose, this study surveyed four KG areas; two cases at Yangpyung and Yeonchoen in Korea, the rest are at Kasama and Yachiyo in Japan. The findings are as following. First, a standard regulation for the application and management of users in KG should be established as soon as possible. Second, the exchange between users in KG and local residents around KG should be activated in terms of well organized exchange program. Third, a sufficient budget by public sectors or an economic scheme where private sectors can participate in this program should be arranged. Lastly, a use of post occupancy should be well managed by user themselves in KG and well monitored by supervisor of KG simultaneously.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.5100-5119
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• 2018

Most of existing privacy-preserving multi-authorities attribute-based encryption schemes (PP-MA-ABE) only considers the privacy of the user identity (ID). However, in many occasions information leakage is caused by the disclosing of his/her some sensitive attributes. In this paper, we propose a collusion-resisting ciphertext-policy PP-MA-ABE (CRPP-MACP-ABE) scheme with hiding both user's ID and attributes in the cloud storage system. We present a method to depict anonymous users and introduce a managerial role denoted by IDM for the management of user's anonymous identity certificate ($AID_{Cred}$). The scheme uses $AID_{Cred}$ to realize privacy-preserving of the user, namely, by verifying which attribute authorities (AAs) obtain the blinded public attribute keys, pseudonyms involved in the $AID_{Cred}$ and then distributes corresponding private keys for the user. We use different pseudonyms of the user to resist the collusion attack launched by viciousAAs. In addition, we utilize IDM to cooperate with multiple authorities in producing consistent private key for the user to avoid the collusion attack launched by vicious users. The proposed CRPP-MACP-ABE scheme is proved secure. Some computation and communication costs in our scheme are finished in preparation phase (i.e. user registration). Compared with the existing schemes, our scheme is more efficient.

• 한국음향학회지
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• 제19권3호
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• pp.57-62
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• 2000

본 논문은 6∼24kbit/s의 저비트율의 전송율을 지원하는 MPEG-4 CELP CODEC과 실시간 처리를 위한 효율적인 알고리즘의 최적화를 통한 인터넷 환경에서의 PC-to-PC 실시간 양방향 다자간 동시 통화 시스템을 구현하였다. 현재 구현된 시스템은 MPEG-4 CELP Mode-I을 사용하여 음성신호 압축 비트 열을 생성하고 있으며, Mode-I서 지원하는 비트율 중 18200bps 모드를 사용하고 있다. 이 경우 1프레임 당 처리하는 샘플 데이터 수는 160 샘플이고 현재 데이터 전송을 위한 데이터 package는 5 프레임이 1 package(117 byte)로 구성되어져 있으며, 동시에 4명의 용자가 접속하여 실시간으로 다자간 양방향 통신이 가능하도록 구현되었다. 개발 환경은 Windows 운영체제 하에서 Microsoft Visual C++ 6.0을 사용하였다.

• 한국산업정보학회논문지
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• 제6권1호
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• pp.15-23
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• 2001

본 논문에서는 동기 BPSK 직접확산 부호분할 다원접속(DS/CDMA)시스템에서 발생하는 다원접속 간섭을 제거할 수 있는 시스템을 제시한다. 확산부호로는 오프셋된 PN 부호와 Simplex 부호를 사용하며 임의의 순간에서는 PN 부호 또는 Simplex 부호 중 하나만을 사용하는 것으로 한다. 수신기는 기준 상관수신기를 이용하여 정보를 검출하고 다원접속간섭을 제거하도록 구성한다. 제안된 시스템을 수식적으로 해석하며 이러한 해석 결과로 제안된 시스템은 다원접속간섭을 상당히 제거함을 알 수 있다. 또한 AWGN 환경 및 나카가미 페이딩 하에서 임의의 사용자에서 발생하는 간섭을 해석하고 평균 오류확률을 분석한다.