• 대한전기학회논문지:전력기술부문A
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• 제48권5호
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• pp.508-516
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• 1999

This paper presents a method for constructing composite power system effective load duration curves(CMELDC) at load points by Monte Carlo method. The concept of effective load duration curves(ELDC) in power system planning is useful and important in both HLII. CMELDC can be obtained from convolution integral processing of the probability function of unsupplied power and the load duration curve at each load point. This concept is analogy to the ELEC in HLI. And, the reliability indices (LOLP, EDNS) for composite power system are evaluated using CMELDC. Differences in reliability levels between HLI and HLII come from considering with the uncertainty associated with the outages of the transmission system. It is expected that the CMELDC can be applied usefully to areas such as reliability evaluation, probabilistic production cost simulation and analytical outage cost assessment, etc. in HLII, DC load flow and Monte Carlo method are used for this study. The characteristics and effectiveness of thes methodology are illustrated by a case study of the IEEE RTS.

• 한국정보통신학회논문지
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• 제2권1호
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• pp.53-58
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• 1998

IS-95를 기본 규격으로 채택한 이동통신시스템에서, 트래픽이 각 셀마다 비균일하게 분포한 실제 시스템의 성능을 향상시키기 위한 하나의 방법으로서 새로운 소프트 핸드오프 알고리즘을 제안한다. 제안된 소프트 핸드오프 알고리즘은 소프트 핸드오프 Threshold값( 즉 T_ADD, TDROP)이 각 셀의 트래픽 조건에 따라 동적으로 변화된다. 각 셀의 트래픽 조건은 사용된 순방향 링크의 트래픽량에 의해서 결정된다. 또한 제안된 알고리즘의 성능을 평가하기 위하여, 동적으로 변화되는 Threshold값을 가지는 소프트 핸드오프 알고리즘을 적용한 시스템의 성능은 고정된 Threshold값을 갖는 전통적인 소프트 핸드오프 알고리즘을 적용한 시스템의 성능보다 우수하다는 것이 시뮬레이션 결과에 의해서 보여준다.

• 한국통신학회논문지
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• 제41권10호
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• pp.1186-1189
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• 2016

셀룰러 단말의 에너지 효율을 높이기 위하여 플로킹(flocking) 모델을 기반으로 상향링크 송신전력 제어 알고리즘을 제안한다. 플로킹 모델에서 각각의 새가 주변 새들의 평균 속도로 자신의 속도를 맞추어 나가는 것처럼, 각 셀의 단말은 주변 셀 동일 채널 단말들의 상향링크 전송률의 평균값과 자신의 상향링크 전송률이 같도록 송신 파워를 분산적으로 제어한다. 모의실험 결과 제안한 상향링크 송신전력제어 방법은 낮은 아웃티지 확률을 유지하면서 단말의 전력소비를 효과적으로 낮추어 단말의 에너지 효율을 향상시킨다.

• 조명전기설비학회논문지
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• 제23권12호
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• pp.162-168
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• 2009

본 논문은 이미 표준 절연설계 값으로 건설되어 운전중인 송전선로의 절연거리를 과전압분석결과, 뇌사고 및 오손 고장 확률과 특성을 고려하여 재설계하고 소요 애자수량을 결정하기 위하여 수행된 연구결과이다. 송전선로의 절연성능을 훼손하지 않으면서 적절한 절연거리를 확보하기 위하여 EMTP 모델을 이용하여 선로에서 발생 가능한 최대 과전압을 계산하고, 뇌 고장실적 및 뇌사고율 예측계산결과와 오손 고장 확률을 조사 분석하였다. 분석결과로부터 고장 특성을 고려한 소요 애자수량의 결정방법을 제시한다.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.869-877
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• 2016

Necessity has compelled man to improve upon the art of tapping wind energy for power generation; an apt reliever of strain exerted on the non-renewable fossil fuel. The power generation in a Wind Farm (WF) depends on site and wind velocity which varies with time and season which in turn determine wind power modeling. It implies, the development of an accurate wind speed model to predict wind power fluctuations at a particular site is significant. In this paper, Box-Jenkins ARIMA (Auto Regressive Integrated Moving Average) time series model for wind speed is developed for a 99MW wind farm in the southern region of India. Because of the uncertainty in wind power developed, the economic viability and reliability of power generation is significant. Life Cycle Costing (LCC) method is used to determine the economic viability of WF generated power. Reliability models of WF are developed with the help of load curve of the utility grid and Capacity Outage Probability Table (COPT). ARIMA wind speed model is used for developing COPT. The values of annual reliability indices and variations of risk index of the WF with system peak load are calculated. Such reliability models of large WF can be used in generation system planning.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권5호
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• pp.2009-2028
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• 2018

Considering a dual-hop energy-harvesting (EH) relaying system, this paper advocates novel relaying protocols based on adaptive time power switching-based relaying (AR) architecture for amplify-and-forward (AF) mode. We introduce novel system model relaying network with impacts of co-channel interference (CCI) and derive analytical expressions for the average harvested energy, outage probability, and the optimal throughput of the information transmission link, taking into account the effect of CCI from neighbor cellular users. In particular, we consider such neighbor users procedure CCI both on the relay and destination nodes. Theoretical results show that, in comparison with the conventional solutions, the proposed model can achieve optimal throughput efficiency for sufficiently small threshold SNR with condition of reasonable controlling time switching fractions and power splitting fractions in concerned AR protocol. We also explore impacts of transmission distances in each hop, transmission rate, the other key parameters of AR to throughput performance for different channel models. Simulation results are presented to corroborate the proposed methodology.

• 인터넷정보학회논문지
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• 제22권5호
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• pp.1-8
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• 2021

Small-cells in heterogeneous networks are one of the important technologies to increase the coverage and capacity in 5G cellular networks. However, due to the randomly arranged small-cells, co-tier and cross-tier interference increase, deteriorating the system performance of the network. In order to manage the interference, some channel management methods use fractional frequency reuse(FFR) that divides the cell coverage into the inner region(IR) and outer region(OR) based on the distance from the macro base station(MBS). However, since it is impossible to properly measure the distance in the method with FFR, we propose a new interference aware FFR(IA-FFR) method to enhance the system performance. That is, the proposed IA-FFR method divides the MUEs and SBSs into the IR and OR groups based on the signal to interference plus noise ratio(SINR) of macro user equipments(MUEs) and received signals strength of small-cell base stations(SBSs) from the MBS, respectively, and then dynamically assigns subchannels to MUEs and small-cell user equipments. As a result, the proposed IA-FFR method outperforms other methods in terms of the system capacity and outage probability.

• 인터넷정보학회논문지
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• 제20권3호
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• pp.13-24
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• 2019

5G 네트워크의 기술 중 NOMA의 핵심은 각 노드별 파워할당계수를 할당하는 것이다. 본 연구에서는 Full Duplex NOMA 릴레이 시스템을 대상으로 성공적인 디코딩을 위한 수신단 최소 필요 신호 대 잡음비 분석을 통해 NOMA 기술의 핵심인 Uplink/Downlink 파워할당계수를 산출하는 알고리즘을 구현하였다. 이를 통해 제안된 알고리즘과 기존 파워 할당 방식과의 성능비교를 실시하였으며 에르고딕 처리용량 및 전송실패율에 관하여 우수한 성능을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.582-596
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• 2019

Considering that the existing Long Term Evolution is not suitable for the fast and frequent handovers of high-speed trains, this paper proposes a relay-assisted handover mechanism to solve the problems of long handover authentication time and vulnerable to security attacks. It can achieve mutual authentication for train-ground wireless communication, and data transmission is consistent with one-time pad at the same time. The security analysis, efficiency analysis and simulation results show that the proposed mechanism not only realizes the forward security and resists many common attacks, but also effectively reduces the computational overhead of train antenna during the secure handover process. When the running speed of a train is lower than 500km/h, the handover delay is generally lower than 50ms and the handover outage probability is less than 1.8%. When the running speed of a train is 350km/h, the throughput is higher than 16.4mbps in the process of handover. Therefore, the secure handover mechanism can improve the handover performance of high-speed trains.

• ETRI Journal
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• 제43권2호
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• pp.221-231
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• 2021

To resolve energy depletion issues in massive Internet of Things sensor networks, we developed a set of distributed energy beamforming methods with one-bit feedback and clustering for multi-node wireless energy transfer, where multiple singleantenna distributed energy transmitters (Txs) transfer their energy to multiple nodes wirelessly. Unlike previous works focusing on distributed information beamforming using a single energy receiver (Rx) node, we developed a distributed energy beamforming method for multiple Rx nodes. Additionally, we propose two clustering methods in which each Tx node chooses a suitable Rx node. Furthermore, we propose a fast distributed beamforming method based on Tx sub-clustering. Through computer simulations, we demonstrate that the proposed distributed beamforming method makes it possible to transfer wireless energy to massive numbers of sensors effectively and rapidly with small implementation complexity. We also analyze the energy harvesting outage probability of the proposed beamforming method, which provides insights into the design of wireless energy transfer networks with distributed beamforming.