• Journal of the Institute of Electronics Engineers of Korea TC
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• 제49권8호
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• pp.39-45
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• 2012

This paper investigates the capacity for the secondary user with the primary full duplex relay (FDR) network in spectrum sharing systems. For sharing the spectrum of the primary user, sharing scheme under the various primary network should be investigated. However, the conventional works only consider the point-to-point primary communication system. When the FDR node is used for the primary networks, both primary relay and destination suffer the interference from the secondary transmitter simultaneously. Thus, the strict interference constraint should be considered to share the spectrum of the primary user. Therefore, we investigate the capacity of the secondary user with the primary FDR network under the average and peak received-power constraints. In addition, we analyze the performance degradation by the selection of the worst interference channels to consider interference constraint in this system. Through the numerical results, the capacities of the primary and secondary users under the average received-power is superior to the that under the peak received-power constraint.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제30권7A호
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• pp.578-586
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• 2005

We propose a random frequency hopping orthogonal frequency division multiple access (RFH-OFDMA) system based on statistical multiplexing for improving downlink user capacity. User capacity is defined as the maximum number of users served with a given basic data-rate in a cell. We compare the downlink user capacity of the proposed RFH-OFDMA system with that of the conventional frequency hopping OFDMA (FH-OFDMA) systems in the worst case where all users are located at the cell boundary. User capacity is limited by either the number of subcarriers or other-cell interference (OCI). Simulation results show that the proposed RFH-OFDMA system can accommodate 262 users in a 3-sectored cell, while the conventional FH-OFDMA systems can accommodate 51 users, when the user channel activity and the required Eb/I0 are 0.1 and 6 dB, respectively, and all users are assumed to be located at the cell boundary.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제36권1C호
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• pp.22-27
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• 2011

This paper proposes an efficient user selection algorithm that provides a maximum 셀 용량 based Multi-user MIMO system based on zero-forcing criterion. The proposed scheme forms a primary group of users whose channel power exceeds a predetermined threshold. Through computer simulations, we have found that the proposed method outperforms the conventional scheme yielding a sum rate that is 0.33 bps/Hz higher when the total numbers of users and transmit antennas in the cell are 100 and 4, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제35권3A호
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• pp.238-244
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• 2010

We propose a user selection method in multi-cell multiuser uplink system with the subspace interference alignment to maintain the high sum-rate capacity. The proposed method selects users whose interference to adjacent cells are strong and apply the subspace interference alignment to the users. The proposed method provides that the number of users performing the interference alignment reduces and the high total sum-rate is maintained. Simulation results exhibit the proposed method reduces the number of users who would decompose the channel for the subspace interference alignment by 50% when the required sum-rate is 90% of the maximal achievable sum-rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제38A권8호
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• pp.724-732
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• 2013

In this paper, we analyze a performance of multiuser massive multiple-input and multiple-output (MIMO) system. We derive the ergodic cell capacity based on a downlink frame structure and analyze the ergodic cell capacity with respect to the number of base station (BS) antennas and the number of users. This paper shows that the ergodic cell capacity is a concave function with respect to the number of BS antennas and the number of users, and also derives the optimal numbers of BS antennas and users for the maximum cell capacity. The simulation results verify the derived analyses and show that the derived numbers of BS antennas and users provide the maximum cell capacity.

• Journal of Satellite, Information and Communications
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• 제6권1호
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• pp.19-27
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• 2011

In this paper, we propose the data stream allocation algorithms for maximizing sum capacity of downlink multiuser MIMO (Multiple-input Multiple-output) systems with BD (Block Diagonalization). The conventional BD precoding algorithms maximize the capacity by controlling power against channel gain of each user. In multiuser MIMO systems, however, the number of data streams for each user can be used to as another control parameter, which determines the capacity. This paper proposes the data stream allocation algorithm of BD for increasing capacity in multiuser MIMO systems. The proposed algorithm allocates unequal bit stream to each user based on channel matrix of each user for maximizing sum capacity. It is proved that proposed algorithm can achieve the significantly improved sum capacity by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제34권12A호
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• pp.1006-1013
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• 2009

This paper proposes a data stream allocation technique for fair capacity performance in multiuser multiple-input multiple-output (MIMO) systems using block diagonalization (BD) algorithm. Conventional studies have been focused on maximum sum capacity. Thus, there is a very large difference of capacity among users, since user capacity unfairly distributed according to each user channel environment. In additional, poor channel user has very small capacity, since base station allocates the power by using water-filling technique. Also, almost studies limited itself to obtain the additional gain by using the same number of data streams for all users. In this paper, we propose the technique for maximizing sum capacity under the fair performance constraint by allocating data stream according to user channel environment. Also, proposed algorithm has more gain of sum capacity and transmit power than conventional equal allocation via computer simulation.

• Journal of Korean Society of Transportation
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• 제18권2호
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• pp.17-26
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• 2000

LOS(Level of Service), the qualitative measure describing operational condition of highway, must be evaluated as quantative index in terms of user service. So, This study is focused on developing the user cost function that user cost is measured in the variation of V/C, MOE(Measure of Effectiveness) of LOS in basic Section of highway. The user cost is calculated as the sum of accident cost, operation cost, travel time cost. The data is collected in the four basic section of Singal-Ansan and Jung bu Highway. As the result of user cost function analysis, the user cost is the lowest When V/C is 0.54. Considering the V/C ratio(0.7) of Basic Section in rural highway suggested in KHCM, We find out that the LOS suggested KHCM increase the user cost of highway.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제18권11호
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• pp.2613-2620
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• 2014

In this paper, we consider a full duplexing (FD) wireless cellular network where a central base station (BS) works in the FD mode while the downlink (DL) and uplink (UL) users work in the time division duplexing (TDD) mode. Since this FD system induces the inter-user interference from UL user to DL user, the main challenge for maximizing the system performances is user scheduling that makes a pair of DL user and UL user to use the same radio resource simultaneously. We formulate an optimization problem for user pairing to maximize the cell capacity and propose a suboptimal user scheduling algorithm with low complexity. This scheduling algorithm is designed in a way where the DL user with a better signal quality has a higher priority to choose its UL user that causes less interference. Simulation results show that the FD system using the proposed user scheduling algorithm achieves the optimal performance and significantly outperforms the conventional TDD system in terms of the cell capacity.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2021년도 학술발표회
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• pp.478-478
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• 2021

전 세계적으로 많은 나라들이 기후변화에 적응하기 위해 수자원 관리 전략을 마련하고 있으며, 수자원의 근간이 되는 빗물의 효율적 사용을 위해 우리나라에서도 빗물이용시설이 많이 도입되고 있다. 본 연구에서는 사용자 편의 환경(graphical user interface; GUI)을 갖춘 빗물이용시설의 용량 결정 프로그램(capacity design aid for rainwater harvesting; CARAH)을 개발하여 관련 연구와 업무에 활용성을 높이고자 하였다. CARAH는 저수지 질량 보존식과 python의 pyswarm package에 탑재된 메타 휴리스틱 방법 중 하나인 입자 군집 최적화(particle swarm optimization; PSO) 기법을 연계하여 빗물이용시설의 최적 용량을 짧은 시간에 결정될 수 있도록 개발되었다. 그리고, C#의 Windows Forms Application을 이용하여 사용자 편의 환경을 구현하였다. CARAH의 입력 자료는 모의 기간, 유입량, 목표공급량, 공급보장률이고, 출력 자료는 공급보장률-저류조용량, 목표공급량-실공급량-미달성량, 저류용량-유입량-실공급량이다. 빗물이용시설 계획에 필요한 여러 입력 자료를 쉽게 입력할 수 있도록 구현하였고, 그래프와 표의 형태로 계산된 결과를 화면에 직접 표출함으로써 사용자가 직관적으로 확인할 수 있도록 하였다. 한편, 입·출력 자료를 포함한 분석 결과는 파일로 관리할 수 있도록 기능을 갖추어 수정 및 보완 등의 반복적 활용이 가능하도록 하였다. 개발된 프로그램의 활용성을 검토하기 위해 실제 저류지가 설계된 인천의 청라지구 1공구를 대상으로 적용하였고, 분석 결과의 적절성을 확인하였다. 본 연구에서 개발된 CARAH는 빗물이용시설의 용량 결정에 관한 효율을 높일 수 있는 프로그램이고, 누구나 쉽고 간편하게 사용할 수 있는 프로그램으로서 향후 활용성이 높을 것으로 판단된다.