• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2121-2125
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• 2003

This paper proposes a fast distributed constrained power control (FDCPC) with non-stationary relaxation factor to next power update in CDMA cellular power control system. We review unconstrained control algorithms, the distributed power control (DPC), unconstrained second order power control (USOPC) and DPC with stationary relaxation factor (DPCSRF). Under the unconstrained condition, the convergence analysis shows theoretically that the convergence rate of DPC is the fastest one. However, under the constrained control algorithms, DCPC is not the fastest one any more because of transmission power constraint. To improve the convergence speed, the DCPC with non-stationary relaxation factor (FDCPC) are proposed. Under the constrained condition, the convergence rate of FDCPC outperforms that of DCPC and CSOPC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.357-358
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• 2011

A major element in the evaluation of reliability worth is the customer cost associated with a loss of supply. This paper proposes a new methodology to estimate the IEAR(Interrupted energy assessment rate) based on expectation value of outage time by using micro approach. The case study in this paper was performed on the basis of the survey data which had been conducted in a previous research.

• 전기학회논문지
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• 제57권11호
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• pp.1905-1909
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• 2008

As catenary supply electric power directly to the railway system, it is very important to prevent an accident of a catenary for appropriate train operations. This paper analyzed the outage data for British catenary safety analysis report and Korean data to compare the reliability of the railway systems. The analyzed data were applied to Fault Tree Analysis(FTA) algorithm to calculate the reliability indices of a railway system. Failure rate of an electric railway system through FTA were calculated for each element and the entire railway system. The reliability indices can be used to determine the eqipment to be replaced for the entire system reliability improvement.

• 전기학회논문지
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• 제66권5호
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• pp.857-862
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• 2017

The management of the electric power facilities became important in accordance with the industrial development and electric power facilities were influenced by weather. Even if the same kind of electric power facilities is estimated for extracting the time-varying failure rate, the failure rate could be different depending on external effect such as climate. This research will show the data mining modeling of the weather-related outage and influence of weather on the electric power facility with recent data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2338-2353
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• 2015

In this paper, the optimal power allocation algorithm that minimizes the aggregate bit error rate (BER) of the secondary user (SU) in a downlink orthogonal frequency division multiplexing (OFDM) based cognitive radio (CR) system, while subjecting to the interference power constraint and the transmit power constraint, is investigated under the assumption that the instantaneous channel state information (CSI) of the interference links between the secondary transmitter and the primary receiver, and between the primary transmitter and the secondary receiver is perfectly known. Besides, a suboptimal algorithm with less complexity is also proposed. In order to deal with more practical situations, we further assume that only the channel distribution information (CDI) of the interference links is available and propose heuristic power allocation algorithms based on bisection search method to minimize the aggregate BER under the interference outage constraint and the transmit power constraint. Simulation results are presented to verify the effectiveness of the proposed algorithms.

• 한국멀티미디어학회논문지
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• 제18권2호
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• pp.168-177
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• 2015

To increase the overall utility and decrease the link delay and power consumption, a joint optimal cross-layer design of congestion control at the transport layer, link delay at the data link layer and power allocation at the physical layer for mobile ad hoc networks is considered in this paper. As opposed to previous work, the rate outage probability in this work is based on exactly closed-form; therefore, the proposed method can guarantee the globally optimal solutions to the underlying problem. The non-convex formulated problem is transformed into a convex one, which is solved by exploiting the duality technique. Finally, simulation results verify that our proposal achieves considerable benefits over the existing method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3171-3191
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• 2016

Due to growing demand on wireless data traffic, a large number of different types of base stations (BSs) have been installed. However, space-time dependent wireless data traffic densities can result in a significant number of idle BSs, which implies the waste of power resources. To deal with this problem, we propose an active state control algorithm based on semi-Markov decision process (SMDP) for a heterogeneous network. A MDP in discrete time domain is formulated from continuous domain with some approximation. Suboptimal on-line learning algorithm with a random policy is proposed to solve the problem. We explicitly include coverage constraint so that active cells can provide the same signal to noise ratio (SNR) coverage with a targeted outage rate. Simulation results verify that the proposed algorithm properly controls the active state depending on traffic densities without increasing the number of handovers excessively while providing average user perceived rate (UPR) in a more power efficient way than a conventional algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권12호
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• pp.4356-4371
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• 2014

When the load in a multi-cell orthogonal frequency division multiple access (OFDMA) system is allowed to excessively increase in face of frequent handover, the cell area becomes smaller than the designed size, and thus continuity of quality of service (QoS) for handover requests cannot be guaranteed. To efficiently support the mobility of a mobile terminal (MT), we should adaptively cope with the resource demand of handover calls. This paper proposes a twofold resource-reservation scheme for OFDMA systems to guarantee continuity of QoS for various mobile multimedia services during MT handover from lightly to heavily loaded cells. Our twofold scheme attempts to guarantee service continuity for handover and to maximize resource allocation efficiency. We performed a simulation to evaluate our scheme in terms of outage probability, handover failure rate, total throughput, and blocking rate.

• ETRI Journal
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• 제34권2호
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• pp.264-267
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• 2012

This letter analyzes the performance of a two-hop MIMO multiuser relay network with a fixed gain amplify-and-forward protocol and antenna selection at the transmitter and receiver. A new expression for the cumulative distribution function of the highest instantaneous end-to-end signal-to-noise ratio is derived. Based on the above result, closed-form expressions for outage probability and bit error rate are presented. Also, the diversity order of the system is determined. Finally, computer simulations are compared to the analytical results, and insights and observations are provided.

• 한국통신학회논문지
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• 제11권2호
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• pp.122-136
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• 1986

본 논문에서는 이동 무선 통신을 위한 새로운 변조 방식인 디지털 위상-주파수 혼합 변조 시스템(digital phase-frequency hybrid modulation system, PFSK)을 제안하고, 이 신호가 m~분포 페이딩 채널을 통과할 경우의 시스템의 오율 및 중단율에 관한 일반식을 구하였다. 특히 레일리 페이딩에 대해서는 다이버시트 수신 기법을 이용하였을 경우의 시스템의 오율 및 중단율에 관한 일반식을 유도하였다. 유오된 오율식에서 반송파 전력 대 잡음 전력비(CNR), 페이딩 지수, 다이버시티 branch의 수, branch사이의 상관 계수를 파라미터로 수치 계산을 하여, PFSK 시스탐과 같이 심볼 전송을 하는 QDPSK시스템의 성능을 오율 및 중단율의 측면에서 비교 평가하였다. 해석 결과, 강한 페이딩하에서는 PFSK시스템이 QDPSK 시스템에 비해 오율 특성이 우수함을 알 수 있었고, 다이버시티 기법을 사용하므로써 시스템의 성능을 크게 개선시킬 수 있음을 알 수 있었다.