• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.924-927
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• 2014

최근 주요 홈서비스 로봇 중 하나인 청소 로봇에 대한 수요가 증가하면서 주어진 공간을 효율적으로 처리하기 위한 높은 커버리지 성능이 주목받고 있다. 이에 따라 로봇의 커버리지 성능을 높이기 위하여 청소 로봇의 자율적인 운행을 통해 지도를 작성하고 이를 활용한 경로를 생성하여 로봇의 운행에 반영하였다. 하지만, 저가형 청소 로봇은 낮은 성능의 처리 성능을 가지고 있기 때문에 불가능하다. 이에 본 논문에서는 단순한 운행 기능만을 가지고 있는 청소 로봇의 이동 패턴을 유전 프로그래밍을 이용하여 최적의 운행 계획을 설계하는 기법을 제안한다. 또한 실험을 통해 제안 기법을 통해 생성된 이동 패턴이 기존 기법에 비해 높은 운행 효율성을 보장함을 확인 하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.15-22
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• 2019

Awireless sensor network utilizes small sensors with a low cost and low power being deployed over a wide area. They monitor the surrounding environment and gather the associated information to transmit it to a base station via multi-hop transmission. Most of the research has mainly focused on static sensors that are located in a fixed position. Unlike a wireless sensor network based on static sensors, we can exploit drone-based technologies for more efficient wireless networks in terms of coverage and energy. In this paper, we introduce a transmission power model and a video encoding power model to design the network environment. We also explain a priority mapping scheme, and deploy drones oriented for network coverage and energy consumption. Through our simulations, this research shows coverage and energy improvements in adrone-based wireless sensor network with fewer sensors, compared to astatic sensor-based wireless sensor network. Concretely, coverage increases by 30% for thedrone-based wireless sensor network with the same number of sensors. Moreover, we save an average of 25% with respect to the total energy consumption of the network while maintaining the coverage required.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.567-574
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• 2008

In this paper, we propose an optimal coverage extension scheme in the OFDMA based mobile multi-hop relay system. First, we propose an optimal frequency and time assignment scheme for maximizing system throughput and analyze the frame efficiency of schemes. Then, under the given BS capacity, we find the maximum number of relay hops that can be used to estimate the maximum coverage area of a BS in a multi-hop relay system. Analytical results show that the proposed scheme is efficient in coverage extension and throughput maximization in OFDMA based multi-hop relay system. Our work may be a rough guideline to control the parameters for multi-hop relay system optimization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6B
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• pp.403-410
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• 2008

In this paper, we investigate the performance of MMR system in Non-transparent mode. The IEEE 802.16j MMR system has two node of operation, Single-frame (in band) and Multi-frame (out band) mode. In the analysis, we assume that channel interference between MR-BS and RS, or between RSs anywhere in the given area is ignored. The performance is presented in terms of the delay and the frame efficiency by varying number of RS and BS coverage to RS coverage ratio and the maximum coverage area of a BS by varying traffic density. Analytical results show that the Single-frame is more efficient than Multi-frame in frame efficiency and coverage extension.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1547-1556
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• 2014

In this paper, we propose cost-effective device-to-device (D2D) advertisement scenario with properties of proximity and timeliness through the convergence of D2D communications and social commerce service. We numerically analyze advertisement dissemination effect of the proposed scenario according to the number of sectors, and demonstrate the performance of the normalized D2D coverage, the average number of D2D users, and the average D2D coverage per user via intensive simulations. We verify the accuracy of the results for our numerical analysis compared with the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10A
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• pp.1139-1146
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• 2004

An abrupt increase of traffic-load in cellular CDMA systems can cause overload, as a result, degrade the quality of service (QoS) and the spectrum utilization due to lacking radio resources in base stations. In this paper, we propose a joint coverage and resource management (JCRM) scheme which can improve the QoS degradation and the spectrum utilization. The JCRM scheme hands over the overloaded traffic to neighboring cells by virtually reducing overloaded cell coverage and extending neighboring cell coverage, as well the scheme allocates radio resources based on the necessary handover probability. The proposed scheme can be applied to the existing cellular CDMA systems as well as adaptive coverage management schemes for next generation mobile communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.205-214
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• 2011

In 3rd generation project partnership long term evolution, wireless multicast techniques which send the same data to multiple users under single frequency networks have attracted much attention. In the multicast system, the transmission mode needs to be selected for efficient data transfer while satisfying the multicast coverage requirement. To achieve this, users' channel state information (CSI) should be available at the transmitter. However, it requires too much uplink feedback resource if all the users are allowed to transmit their CSI at all the time. To solve this problem, in this paper, the multicast coverage prediction is suggested. In the proposed algorithm, each user measures its transition probabilities between the success and the fail state of the decoding. Then, it periodically transmits its CSI to the basestation. Using these feedbacks, the basestation can predict the multicast coverage. From the simulation results, we demonstrate that the proposed scheme can predict the multicast system coverage.

• Journal of the Korea Society of Computer and Information
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• v.13 no.3
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• pp.85-90
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• 2008

In this paper, we propose a new robot cleaning algorithm, which we call SetClean. The new algorithm cleans from the most less complex area. Sometimes, when the cleaning completion time can be longer or can not be estimated, cleaning larger area first is better than optimizing the whole time for cleaning. To do this, SetClean algorithm divides the whole area into cleanable sub-areas using Set Cover algorithm and cleans the area in the order of high efficiency that maximize the cleanable area per unit time. SetClean algorithm decides the navigation flow by considering not only the size of the area but also the distance from the current robot location to the area to be cleaned and the delay time caused by the number of turns within the area. The experimental results show the mechanism and performance of the SetClean algorithm.

• Fashion & Textile Research Journal
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• v.22 no.1
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• pp.94-101
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• 2020

This helps plus-size consumers purchase ready-made clothes and improves fitness by analyzing the upper body shapes of abdomen-obese adult males; in addition, it creates a size system based on each size interval of obesity shapes. The criteria for the 572 male subjects surveyed were over 25 kg/㎡ of the BMI, over 90 cm of waist, and over 0.85 waist hip ratio. The results were as follows. First, the higher the age group, the higher the degree of abdominal obesity in each age group. The degree of obesity decreases age increase; however, was the risk of abdominal obesity increased. Second, Compared to standard body types, the average body size of Abdomen-obese males is significantly larger, especially in the waist area than in the chest area. Third, to propose a size system for abdominal obese adult males, 16 sections with a final 2% rate of appearance were finally adopted as suit-tops size system for abdominal obese adult males by applying a 3 cm dimension gap between each designation as specified in the KS standard. The coverage ratio for the 16 sections was 72.6% and the coverage effienciency was 4.5%. The results of this study can be used in a various clothes; in addition, the activation and segmentation of the plus-size market are also believed to be significant.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.4
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• pp.67-76
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• 2002

Kerberos is designed to provide strong authentication between client and application servers which are working in distributed network environment by using symmetric-key cryptography, and supposed to trust other systems of the realm. In this paper, we design an efficient and strong authentication mechanism by introducing the public/private-key to Kerberos. In the mechanism to make a system more secure, the value of the session key is changed everytime using MAC(message authentication code) algorithm with the long-term key for user-authentication and a random number exchanged through the public key. Also, we employ a mutual authentication method, which is used on challenge-response mechanism based on digital signatures, to improve trust between realms, and present a way of reducing the number of keys by simplifying authentication steps.