• Journal of information and communication convergence engineering
• /
• v.9 no.4
• /
• pp.405-410
• /
• 2011

In this paper, a conflict-avoided resource reservation scheme for UWB (Ultra Wide Band) WPAN (Wireless Personal Area Network) with D-MAC (Distributed Medium Access Control) is proposed. Since distributed characteristic of the WiMedia D-MAC supporting DRP (Distributed Reservation Protocol) scheme may cause lots of conflicts, overall performances of the WiMedia D-MAC can be deteriorated. In addition, once a DRP conflict occurs, only one of the DRP reservations involved in that DRP conflict maintains the reserved MASs, while the other DRP reservation must be terminated and DRP negotiations for them have to be re-started. Such DRP termination and renegotiation time delays due to the DRP conflicts can be a critical problem to the mobile devices transceiving real-time QoS traffic streams. Therefore, we propose a mechanism to avoid DRP conflicts by providing a kind of path diversity using relay transmission scheme and demonstrate its performance improvements via simulation results.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.3
• /
• pp.191-199
• /
• 2020

This study aims to investigate what selection attributes of customer value are more crucial when consumers choose the dessert at convenience store, which is the fastest growing retail format in Korea recently. Factors considered to be important when customers buy dessert, such as economics, diversity, convenience, and safety were examined and also relationship between customer value and satisfaction was analyzed. The survey was conducted through online (including SNS) from April 6, 2019 to April 30, 2019. A total of 303 questionnaires were used for empirical analysis. Factor analysis was performed to verify the validity and reliability of the measured variables. And the structural equation model (SEM) was used as a statistical method for hypothesis testing. As a result, factors as 'diversity', 'safety' were revealed to significantly affect hedonic customer value, while 'convenience' was shown to affect utilitarian customer value significantly. In addition, the path that customer value leads to satisfaction was also found to be significant. The result of the study suggests that selection attributes of convenience store dessert and providing meaningful implications of related hedonic and utilitarian values when customers purchase dessert at convenience store. This study provided practical implications for managers of the fiercely competitive dessert industry.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.4
• /
• pp.553-564
• /
• 2000

In this thesis, mobile communication channel with multi-path fading which is major factor of performance degradation of DS-CDMA system has been considered. An MRC diversity and error correcting coding technique have been used to improve performance of MFSK-MDPSK/DS-CDMA system. The MFSK-MDPSK/DS-CDMA system performance has been obtained quantitatively by the numerical analysis. the modulations under consideration are noncoherent M-ary frequency shift keying(MFSK) and an MFSK based joint frequency phase modulation utilizing MFSK/DS-CDMA and MDPSK-DS-CDMA systems the MFSK-MDPSK/DS-CDMA system obtain a better performance . Also, the error performance of MFSK-MDPSK/DS-CDMA system in Nakagami fading environments is improved by increasing the number of diversity branch and coding gain.

• Journal of Satellite, Information and Communications
• /
• v.3 no.2
• /
• pp.1-6
• /
• 2008

Space-time codes (STC) can achieve the diversity gain in a multi-path environment without additional bandwidth requirement. Recent study results reported that satellite systems can also achieve this diversity gain by using space-time codes in a cooperative network with terrestrial repeaters. Due to uni-directional nature of satellite DMB services, transmit diversity can be considered as one of the most effective ways to improve the performance. In this paper, we demonstrate various simulations results of STC schemes which can contribute to improve performance of future satellite DMB services. The STC schemes introduced in this paper provides diversity gains by combing independent coded signal from the satellite as well as from the terrestrial repeaters. In addition, we discuss a few points which should be considered to develop and implement these STC schemes.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.4
• /
• pp.761-766
• /
• 2004

Rayleigh fading due to multi-path degrades the mobile service quality, especially high data rate mobile services such as 1xEVDO and W-CDMA. The field test showed that down load date rate of 1xEVDO is seriously affected by Rayleigh fading. To reduce the effect of Rayleigh fading, transmit diversity was implemented in RF repeater. In field test, transmit diversity function increased the data rate about twice comparing with no transmit diversity repeater. Recently high data rate service is getting more important, so transmit diverstiy function will be an important function in repeater.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.101-104
• /
• 2003

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the space-time code in downlink over JTC realistic channel model. We can get a diversity gain by using the space time code. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.277-280
• /
• 2003

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the reliability of communications and increase the data rate by channel coding, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve tile performance in multi-Path fading channel environment.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2008.11a
• /
• pp.1211-1214
• /
• 2008

최근 Path-diversity에 근거한 통신 방식은 다양한 P2P streaming 어플리케이션에 대역폭 고갈 현상을 해결하는 쪽으로 연구가 진행 중이다. 이 논문에서는 네트워크의 대역폭 확보와 효과적인 데이터 전송을 위해서 다소 직관적인 방법인 다중시간이론을 소개하고, 이를 P2P 네트워크에 적용할 수 있는 방법을 제시한다.

• Journal of KIISE:Software and Applications
• /
• v.34 no.11
• /
• pp.971-983
• /
• 2007

Cellular Genetic Algorithms(CGAs) are a subclass of Genetic Algorithms(GAs) in which each individuals are placed in a given geographical distribution. In general, CGAs# population space is a regular network that has relatively long characteristic path length and high clustering coefficient in the view of the Networks Theory. Long average path length makes the genetic interaction of remote nodes slow. If we have the population#s path length shorter with keeping the high clustering coefficient value, CGAs# population space will converge faster without loss of diversity. In this paper, we propose Smallest-Small-World Cellular Genetic Algorithms(SSWCGAs). In SSWCGAs, each individual lives in a population space that is highly clustered but having shorter characteristic path length, so that the SSWCGAs promote exploration of the search space with no loss of exploitation tendency that comes from being clustered. Some experiments along with four real variable functions and two GA-hard problems show that the SSWCGAs are more effective than SGAs and CGAs.

• Journal of the Korean Society for information Management
• /
• v.33 no.1
• /
• pp.7-32
• /
• 2016

This study has measured interdisciplinarity using a topic modeling, which automatically extracts sub-topics based on term information appeared in documents group unlike the traditional top-down approach employing the references and classification system as a basis. We used titles and abstracts of the articles published in top 20 journals for the past five years by the 5-year impact factor under the category of 'Information & Library Science' in JCR 2013. We applied 'Discipline Diversity' and 'Network Coherence' as factors in measuring interdisciplinarity; 'Shannon Entropy Index' and 'Stirling Diversity Index' were used as indices to gauge diversity of fields while topic network's average path length was employed as an index representing network cohesion. After classifying the types of interdisciplinarity with the diversity and cohesion indices produced, we compared the topic networks of journals that represent each type. As a result, we found that the text-based diversity index showed different ranking when compared to the reference-based diversity index. This signifies that those two indices can be utilized complimentarily. It was also confirmed that the characteristics and interconnectedness of the sub-topics dealt with in each journal can be intuitively understood through the topic networks classified by considering both the diversity and cohesion. In conclusion, the topic modeling-based measurement of interdisciplinarity that this study proposed was confirmed to be applicable serving multiple roles in showing the interdisciplinarity of the journals.