• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.1C
• /
• pp.1-7
• /
• 2010

In this paper, the performance of the soft-decision-and-forward (SDF) protocol in the cooperative communication network with one source, one relay, and one destination, where each node has two transmit and receive antennas, is analyzed in terms of the bit error rate (BER) obtained from the pairwise error probability (PEP). For the slow-varying Rayleigh fading channel, the optimal and suboptimal power allocation ratios are determined without feedback. The optimal power allocation can be obtained by minimizing the average PEP. For the tractability, an alternative strategy of maximizing the product SNR of direct and relay links, which we call the suboptimal power allocation, is considered. Through the numerical analysis, we show that the performance gap between the suboptimal and the optimal power allocation is negligible in the high SNR region.

• Defense and Technology
• /
• no.9 s.259
• /
• pp.26-37
• /
• 2000

대부분의 나라들은 미래 항공력(Air Power)의 중요성을 실감하였기에 국가적으로 공군력 강화에 주안점을 두고 있는 실정이다. 한국 공군도 공군력이 국가방위의 핵심전력이라는 공군의 목표와 버금가는 전략적 접근이 필요하다고 보며 이러한 맥락에서 공군의 F-X사업도 각군간의 사업 분배의 개념이 아닌 국가안보를 위한 강력한 억제력과 미래 불특정한 주변 위협에 대해서도 억제행사를 할 수 있는 능력을 갖출 수 있도록 국가적인 전략으로 추진되어야 한다고 본다. 그래야만 대한민국은 현재 우리 앞에 펼쳐지고 있는 그리고 곧 다가오는 동북아에서 뿐만 아니라 세계 속의 중심세력 국가로 설 수 있을 것이다.

• Journal of IKEEE
• /
• v.26 no.3
• /
• pp.389-395
• /
• 2022

With the evolution of technology, cyber physical systems (CPSs) are being upgraded, and new types of cyber attacks are being discovered accordingly. There are many forms of cyber attack, and all cyber attacks are made to manipulate the target systems. A representative system among cyber physical systems is a cyber physical power system (CPPS), that is, a smart grid. Smart grid is a new type of power system that provides reliable, safe, and efficient energy transmission and distribution. In this paper, specific types of cyber attacks well known as false data injection attacks targeting state estimation and energy distribution of smart grid, and protection strategies for defense of these attacks and dynamic monitoring for detection are described.

• Proceedings of the KIEE Conference
• /
• 2005.07a
• /
• pp.256-258
• /
• 2005

최근에, 전력 시장에 경쟁 체제가 소개되면서 탈규제(deregulation)가 중요한 문제로 대두되고 있다. 시장의 탈규제에 관한 중요한 주제 중에 하나가 정확한 전송 손실의 분석이 필요한 곳에서의 지역 경쟁 체제(spot pricing)이다. 이러한 경쟁 체제에서 해결해야 할 중요한 문제 중의 하나가 다수의 독립발전사업자에 대하여 공정하고 정확한 전력 요금을 책정하는 것이다. 따라서 각 모선별 전송 손실을 배분하는 것이 매우 중요하다. 이 논문은 송전 손실을 배분하는 새로운 알고리즘을 제시한다. 각 모선의 송전 손실을 계산하는 데는 손실 감도를 이용한 적분방법이 이용된다. 송전 손실은 전체 계통의 거래 전략(transaction strategy)을 이용한 부하 비율의 계산을 통해서 증분 송전 손실(incremental transmission losses)의 방법으로 계산된다. 제안된 방법은 9모선 계통에 시험되었고 이를 통해 제안된 방법이 신뢰할 만한 알고리즘임을 보여준다.

• Transactions of the Korean hydrogen and new energy society
• /
• v.34 no.4
• /
• pp.369-380
• /
• 2023

There is no clear standard for estimating the power distribution of fuel cells and batteries to meet the required power in hydrogen electric vehicles. In this study, a hydrogen electric vehicle simulation model equipped with a vehicle electric component model including a fuel cell system was built, and a power distribution strategy between fuel cells and batteries was established. The power distribution model was operated through two control strategies using step control and fuzzy control, and each control strategy was evaluated through data derived from the simulation. As a result of evaluation through the behavior data of state of charge, fuel cell current and balance of plant, fuzzy control was evaluated as a proper strategy in terms of control stability and durability.

• Transactions of the Korean hydrogen and new energy society
• /
• v.35 no.2
• /
• pp.230-239
• /
• 2024

Efforts are being made to replace ship diesel engines with electric propulsion motors in response to emission regulations. In particular, in the case of short-range small ships, research is being conducted to replace polymer electrolyte membrane fuel cells (PEMFC) with power sources. However, PEMFC has problems such as slow dynamic response characteristics and reduced durability at high temperatures. To solve this problem, a high-precision ship model was developed with power distribution and thermal management strategies applied, and through this, the required power, heat, and power characteristics of the propulsion system according to the ship's speed profile were analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.11
• /
• pp.1410-1413
• /
• 2016

Array beamforming for anti-jamming means that jamming signals are superposed destructively, while superposing information signals constructively at a receiver. However, according to channel state variation, the anti-jamming performance of the beamforming can be degraded because of large beamwidth of the sidelobe and lower selectivity of the mainlobe. To mitigate this problem, we introduce a beamformed decoy signal which uses frequency band distinguished from the information signal to make the jammer concentrate its jamming power to a wrong target under limited feedback. In this paper, we show that the performance of the proposed scheme can approach that of optimal one with perfect feedback.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.11
• /
• pp.1615-1621
• /
• 2014

A wireless tram which runs without catenary and instead uses batteries installed in the tram has been recently researched actively. This paper presents a new method maximizing absorption of regenerative energy of a wireless tram and extending life cycle of the energy storage device in the wireless tram by applying line-optimized charging and discharging scenario. Energy efficiency and life cycle of energy storage system (ESS) are highly dependent on the characteristic of operating conditions. For example, frequent charge and discharge with high power cause the problems that decrease the battery life cycles. Hybrid energy storage system (HESS) is combination of two ESSs which have complementary characteristics to each other. HESS can provide even better functionality and performance than the battery only ESS due to the synergy effect of two ESSs. This paper also provides a power distribution strategy and driving scenarios which increase the life cycle and energy efficiency of the HESS consisting of a battery and an ultra-capacitor. The developed strategy was tested and verified by a hardware-in-the-loop-simulation (HILS) system which emulates the a wireless tram.