• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.16 no.1
• /
• pp.100-105
• /
• 2002

This paper represents impedance calculation of the distance relay using PSCAD/EMTDC software for transmission line involving the UPFC(Unified Power Flow Controller)device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover, depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. The presence of the UPFC in the fault loop affects both voltage and current seen by relay. Therefore, the distance relay should be taken into account the variable injected voltage of the UPFC.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39A no.10
• /
• pp.593-600
• /
• 2014

OFDMA systems solves frequency selective fading problem and provides improved performance by optimal allocation of subcarriers and transmit power. Two-way relay systems provide improved spectral efficiency compared to that of the conventional half-duplex relay using bidirectional communications. In legacy OFDMA system such as WiBro, two-way DF relay utilization causes pilot re-assignment and impossibility of channel estimation and decoding at relay nodes by self-interference. In this paper, resource allocation schemes for legacy OFDMA systems with two-way DF relay are proposed. The proposed schemes allocate subcarriers considering destinations nodes which are connected to relay nodes as individual nodes which are directly connected to a base station. Subsequently, the proposed schemes compensate bandwidth loss due to orthogonal allocations by overlapped allocating unused subcarriers at other noes. Numerical simulations show that the proposed resource allocation schemes provide improved performance compared with orthogonal allocation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.10
• /
• pp.4231-4245
• /
• 2020

Non-orthogonal multiple access (NOMA) is widely studied in both academia and industry due to its high spectral efficiency over orthogonal multiple access (OMA). To effectively improve spectrum efficiency, an amplify-and-forward (AF) cooperative NOMA system is proposed as well as a novel detection scheme is proposed, in which we first perform successive interference cancellation (SIC) twice at U1 for the two signals received from two time slots to remove interference from symbol 2, then two new signals apply max ratio combining (MRC). In addition, a closed-form upper bound approximation for the ergodic capacity of our proposed system is derived. Monte-Carlo simulations and numerical analysis illustrate that our proposed system has better ergodic capacity performance than the conventional cooperative NOMA system with decode-forward (DF) relay, the conventional cooperative NOMA system with AF relay and the proposed AF cooperative NOMA system in [16]. In addition, we can see that ergodic capacity of all NOMA cooperative systems increase with the increase of transmit SNR. Finally, simulations display that power allocation coefficients have little effect on ergodic capacity of all NOMA cooperative systems. This is due to this fact that ergodic capacity of two symbols can be complementary with changing of power allocation coefficients.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.7
• /
• pp.1214-1220
• /
• 2010

This paper proposes an efficient under frequency relay load shedding scheme for the korea power system which is more than two times than the system size and its capacity of the power system 10 years ago. The proposed method is keeping the power system stability and supports for the operating system during critical situations such as big disturbances and unstable in supply and demand. In order to determine the number of load shedding steps, the load to be shed per step, and frequency level, it is necessary to investigate and analyze maximum losses of generation due to the biggest contingency, maximum system overload, maximum keeping frequency, maximum load to be shed, and recovery frequency. The proposed method is applied to Off-peak load(25,400MW) and Peak load(62,290MW) of Korea Electric Power Corporation to demonstrate its effectiveness.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.5
• /
• pp.2177-2193
• /
• 2018

This paper studies resource allocation schemes for the relay-aided cooperative system consisting of multiple source-destination pairs and decode-forward (DF) relays. Specially, relaying selection, multisubcarrier pairing and assignment, and power allocation are investigated jointly. We consider a combinatorial optimization problem on quality of experience (QoE) and energy consumption based on relay-aided cooperative system. For providing better QoE and lower energy consumption we formulate a multi-objective optimization problem to maximize the total mean opinion score (MOS) value and minimize the total power consumption. To this end, we employ the nondominated sorting genetic algorithm version II (NSGA-II) and obtain sets of Pareto optimal solutions. Specially, two formulas are devised for the optimal solutions of the multi-objective optimization problems with and without a service priority constraint. Moreover, simulation results show that the proposed schemes are superior to the existing ones.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.9
• /
• pp.16-23
• /
• 2009

In this paper, we propose a new distributed Alamouti space-time block coding scheme using cooperative relay system composed of one source node, three relay nodes and one destination node. The source node is assumed to be equipped with two antennas which respectively use a 2-beam array to communicate with two nodes selected from the three relay nodes. During the first time slot, the two signals which respectively were transmitted by one antenna at the source, are selected by one relay node, added, amplified, and forwarded to the destination. During the second time slot, the other two relay nodes implement the conjugate and minusconjugate operations to the two received signals, respectively, each in turn is amplified and forwarded to the destination node. This transmission scheme represents a new distributed Alamouti space-time block code that can be constructed at the relay-destination channel. Through an equivalent matrix expression of symbols, we analyze the performance of this proposed space-time block code in terms of the chernoff upper bound pairwise error probability (PEP). In addition, we evaluate the effect of the coefficient $\alpha$ ($0{\leq}{\alpha}{\leq}1$) determined by power allocation between the two antennas at the source on the received signal performance. Through computer simulation, we show that the received signals at the three relays have same variance only when the value of $\alpha$ is equal to $\frac{2}{3}$, as a consequence, a better performance is obtained at the destination. These analysis results show that the proposed scheme outperforms conventional proposed schemes in terms of diversity gain, PEP and the complexity of relay nodes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.9B
• /
• pp.876-882
• /
• 2009

In this paper, we propose a sub-cell coverage control algorithm for enhancement of the cell throughput in OFDMA based relay systems. Relay station (RS) is exploited for improved quality of the received signal in cellular communication systems, especially in shadow areas. However, since a RS requires additional radio resource consumption for the link between the base station (BS) and the RS, we have to carefully control the coverage areas if a mobile station (MS) is serviced via the BS or the RS considering the cell throughput. We consider radio resource reuse as well for the sub-cell coverage configuration by applying various reuse patterns between RSs. We also consider a time varying system by adaptively changing the threshold for coverage depending on the MSs' traffic in the cell. We initially determine the sub-cell coverage of the system depending on the ratio of received signal-interference-noise-ratio (SINR) of the MS from the BS and RSs, respectively. Then, the "sub-cell coverage threshold" varies based on the "effective transmitted bits per sub-channel" with time. Simulation result shows that the proposed "time varying coverage control algorithm" leads to throughput improvement compared to the fixed sub-cell coverage configuration.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10a
• /
• pp.311-316
• /
• 1991

This paper deals with designing the PID autotuner. The system parameters are identified using the relay control, where the unidirectional relay with hysteresis is adopted. The digital PID tuning rule on Nyquist plot is derived, and the statistical wordlength is adopted for the coefficient wordlength. The experimental results of temperature control exhibit the satisfactory performance and the validity of the derived statistical wordlength.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.1 s.343
• /
• pp.133-142
• /
• 2006

This paper suggests an efficient method of protection ratio(PR) calculation and shows some results of point-to-point radio relay system for frequency coordination. The proposed PR can be expressed as a function of C/N of modulation scheme, noise-to-interference ratio(N/I), multiple interference allowance, fade margins of multi-Path and rain attenuation and net filter discrimination. And PR calculation is performed in view of fade margin, modulation scheme, distance, and interference for actual point-to-point radio relay frequency. According to results for 6.2 GHz, 64-QAM and 60 km at BER 10-6, fade margin and co-channel Protection ratio reveal 41.1dB and 74.9 dB, respectively The merit of presented method provides a systematic and easy calculation by means of PR correction factor related with various parameters and can apply the same concept to frequency coordination of millimeter wave radio relay system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.14 no.1
• /
• pp.48-55
• /
• 2021

The 3-coil magnetic resonance wireless power transmission system was analyzed using an equivalent circuit model, and the |S21| of the system was expressed as the equation of the Q of the three coils, the coupling coefficient k between the transmitting coil and the relay coil, the relay coil and the receiving coil. It is suggested that the maximum efficiency can be obtained when the relay coil is located in the center of the transmitting and the receiving coil. When the distance between the transmitting and the receiving coil is 30 cm and the two coils are aligned, maximum efficiency of 9 % is obtained with the relay coil centered between the coils. If the transmitting coil and the receiving coil are misaligned during a wireless charging of an electric vehicle, the efficiency is expected to decrease significantly compared to the aligned case. It is expected that the efficiency can be increased by using a relay coil and by rotating the coil.