• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2406-2412
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• 2015

Multi-user multi-input multi-output (MU-MIMO) system has attracted the 4^th generation wireless network as one of core technique for performance enrichment. In this system rate control is a challenging problem and another problem is optimization. Proper scheduling can resolve these problems by deciding which set of user and at which rate the users send their data. This paper proposes a new multi-parameter based scheduling (MPS) for downlink multi-user multiple-input multiple-output (MU-MIMO) system under space-time block coding (STBC) transmissions. Goal of this MPS scheme is to offer improved link level performance in terms of a low average bit error rate (BER), high packet delivery ratio (PDR) with improved resource utilization and service fairness among the user. This scheme allows the set of users to send data based on their channel quality and their demand rates. Simulation compares the MPS performance with other scheduling scheme such as fair scheduling (FS), normalized priority scheduling (NPS) and threshold based fair scheduling (TFS). The results obtained prove that MPS has significant improvement in average BER performance with improved resource utilization and fairness as compared to the other scheduling scheme.

• 한국통신학회논문지
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• 제39A권12호
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• pp.774-776
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• 2014

본 논문은 가시선 (line-of-sight) 성분이 지배적인 채널 환경에서 다중 사용자로의 정보 전송을 위해 이중 편파를 이용하는 다중 안테나 시스템을 제안한다. 이 시스템은 공간 및 편파 자원을 효율적으로 활용하여 기존의 단일 편파 안테나를 이용하는 MU-MIMO(multi-user multiple input multiple output) 시스템 보다 향상된 총 전송률을 제공할 수 있음을 보인다

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.489-494
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• 1998

This paper describes a design of graphical user interface for a simulated breeding tool with multifield. The term field is used here as a population of visualized individuals that are candidates of selection. Multi-field interface enables the user to breed his/her favorite phenotypes by selection independently in each field, and he/she can copy arbitrary individual into another field. As known on genetic algorithms, a small population likely leads to premature convergence trapped by a local optimum, and migration among plural populations is useful to escape from local optimum. The multi-field user interface provides easy implementation of migration and wider diversity. We show the usefulness of multi-field user interface through an example of a breeding system of 2D CG images.

• 전기학회논문지
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• 제65권12호
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• pp.2167-2176
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• 2016

In the multi-server environment, remote user authentication has a very critical issue because it provides the authorization that enables users to access their resource or services. For this reason, numerous remote user authentication schemes have been proposed over recent years. Recently, Lin et al. have shown that the weaknesses of Baruah et al.'s three factors user authentication scheme for multi-server environment, and proposed an enhanced biometric-based remote user authentication scheme. They claimed that their scheme has many security features and can resist various well-known attacks; however, we found that Lin et al.'s scheme is still insecure. In this paper, we demonstrate that Lin et al.'s scheme is vulnerable against the outsider attack and user impersonation attack, and propose a new biometric-based scheme for authentication and key agreement that can be used in the multi-server environment. Lastly, we show that the proposed scheme is more secure and can support the security properties.

• 한국멀티미디어학회논문지
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• 제24권3호
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• pp.355-372
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• 2021

Recently, high-performance HMDs (Head-Mounted Display) are becoming wireless due to the growth of virtual reality technology. Accordingly, environmental constraints on the hardware usage are reduced, enabling multiple users to experience virtual reality within a single space simultaneously. Existing multi-user virtual reality platforms use the user's location tracking and motion sensing technology based on vision sensors and active markers. However, there is a decrease in immersion due to the problem of overlapping markers or frequent matching errors due to the reflected light. Goal of this study is to develop a multi-user virtual reality moving platform in a single space that can resolve sensing errors and user immersion decrease. In order to achieve this goal hybrid sensing technology was developed, which is the convergence of vision sensor technology for position tracking, IMU (Inertial Measurement Unit) sensor motion capture technology and gesture recognition technology based on smart gloves. In addition, integrated safety operation system was developed which does not decrease the immersion but ensures the safety of the users and supports multimodal feedback. A 6 m×6 m×2.4 m test bed was configured to verify the effectiveness of the multi-user virtual reality moving platform for four users.

• 한국정보통신학회논문지
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• 제22권10호
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• pp.1379-1385
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• 2018

기존의 다중사용자 중첩 전송은 순시 채널 전력의 조건에 따라 데이터 심벌의 전력 할당 계수와 사용자별 수신 신호 처리 방법을 결정한다. 그러나 순시 채널 전력의 이용은 시스템의 복잡도를 증가시킬 수 있기 때문에 본 논문에서는 평균 채널 전력을 이용하는 고정적 다중사용자 중첩 전송을 고려한다. 고정적 다중사용자 중첩 전송 기법은 시간에 따라 느리게 변화하는 평균 채널 전력의 조건을 기반으로 데이터 심벌의 전력 할당 계수와 사용자별 수신 신호 처리 방법을 결정하기 때문에 시스템 복잡도를 감소시킬 수 있다. 본 논문에서는 고정적 다중사용자 중첩 전송에 대한 평균 심벌 오차율을 분석한다. 특히, 레일레이 페이딩 채널을 가정하여 M-ary 직교 진폭 변조에 대한 평균 심벌 오차율의 표현식을 유도한다. 또한, 수치적 결과를 통하여 열악한 채널 환경에 있는 사용자에서 고정적 다중사용자 중첩전송과 기존의 다중사용자 중첩 전송의 평균 심벌 오차율 성능이 유사함을 보였다.

• 융합보안논문지
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• 제14권2호
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• pp.11-16
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• 2014

최근 스마트폰이나 태블릿 등을 통해서 사용자가 IPTV를 사용해 집에서 시청하던 멀티미디어 서비스를 지속적으로 이용할 수 있는 멀티-스크린 서비스가 급격하게 발전하고 있다. 특별히 IPTV와 스마트폰을 연동하여 멀티-스크린 서비스를 이용하고자 하는 사용자 요구는 날로 급증하고 있는 실정이다. 하지만, IPTV에 대한 보안서비스는 다소 제공되고 있지만, 스마트폰에 대한 보안서비스는 매우 부족하고, 더욱이 스마트폰과 IPTV를 연동하기 위한 보안 서비스는 전무한 실정이다. 이에 본 연구에서 사용자가 소지한 스마트폰과 집에서 시청하는 IPTV를 연동해 멀티-디바이스 연동형 사용자 인증시스템을 제안하고자 한다. 우리가 제안한 멀티-스크린 환경을 위한 사용자 인증시스템은 커베로스를 기반으로 쉽고 빠른 사용자 인증서비스를 제공할 수 있다. 우리가 제안한 멀티-스크린 서비스에 사용자 인증 서비스를 제공할 수 있는 시스템은 기존의 PKI 인증시스템 보다 처리 절차가 가볍고 보안성이 높은 것으로 판단된다. 뿐만 아니라 향후 발생할 수도 있는 보안 위협들에 대해서도 안전한 멀티-스크린 환경을 제공할 수 있을 것으로 예상된다.

• Journal of Communications and Networks
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• 제11권3호
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• pp.279-286
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• 2009

This paper proposes an adaptive mode switching algorithm between two strategies in multiple antenna cellular networks:A single-user mode and a multi-user mode for the broadcast channel. If full channel state information is available at the base station, it is known that a multi user transmission strategy would outperform all single-user transmission strategies. In the absence of full side information, it is unclear what the capacity achieving method is, and thus there are few criteria to decide which of the myriad possible methods performs best given a system configuration. We compare a single user transmission and a multi user transmission with linear receivers in this paper where the transmitter and the receivers have multiple antennas, and find that neither strategy dom inates the other. There is instead a transition point between the two strategies. Then, the mode switching point is determined both ana lytically and numerically for a multiple antenna cellular downlink with correlation between transmit antennas.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.293-294
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• 2013

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1864-1874
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• 2005

This paper describes a wearable multi-modal user interface design and its implementation for a teleoperated field robot system. Recently some teleoperated field robots are employed for hazard environment applications (e.g. rescue, explosive ordnance disposal, security). To complete these missions in outdoor environment, the robot system must have appropriate functions, accuracy and reliability. However, the more functions it has, the more difficulties occur in operation of the functions. To cope up with this problem, an effective user interface should be developed. Furthermore, the user interface is needed to be wearable for portability and prompt action. This research starts at the question: how to teleoperate the complicated slave robot easily. The main challenge is to make a simple and intuitive user interface with a wearable shape and size. This research provides multi-modalities such as visual, auditory and haptic sense. It enables an operator to control every functions of a field robot more intuitively. As a result, an EOD (explosive ordnance disposal) demonstration is conducted to verify the validity of the proposed wearable multi-modal user interface.