• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.55-68
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• 2023

In recent years, the Television White Space (TVWS) has attracted the interest of many researchers due to its propagation characteristics obtainable between 470MHz and 790MHz spectrum bands. The plenty of unused channels in the TV spectrum allows the secondary users (SUs) to use the channels for broadband services especially in rural areas. However, when the number of SUs increases in the TVWS wireless network the aggregate interference also increases. Aggregate interferences are the combined harmful interferences that can include both co-channel and adjacent interferences. The aggregate interference on the side of Primary Users (PUs) has been extensively scrutinized. Therefore, resource allocation (power and spectrum) is crucial when designing the TVWS network to avoid interferences from Secondary Users (SUs) to PUs and among SUs themselves. This paper proposes a model to improve the resource allocation for reducing the aggregate interface among SUs for broadband services in rural areas. The proposed model uses joint power and spectrum hybrid Firefly algorithm (FA), Genetic algorithm (GA), and Particle Swarm Optimization algorithm (PSO) which is considered the Co-channel interference (CCI) and Adjacent Channel Interference (ACI). The algorithm is integrated with the admission control algorithm so that; there is a possibility to remove some of the SUs in the TVWS network whenever the SINR threshold for SUs and PU are not met. We considered the infeasible system whereby all SUs and PU may not be supported simultaneously. Therefore, we proposed a joint spectrum and power allocation with an admission control algorithm whose better complexity and performance than the ones which have been proposed in the existing algorithms in the literature. The performance of the proposed algorithm is compared using the metrics such as sum throughput, PU SINR, algorithm running time and SU SINR less than threshold and the results show that the PSOFAGA with ELGR admission control algorithm has best performance compared to GA, PSO, FA, and FAGAPSO algorithms.

• Journal of IKEEE
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• v.22 no.2
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• pp.460-475
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• 2018

In the variable-speed wind energy system, to achieve maximum power point tracking (MPPT), the wind turbine should run close to its optimal angular speed according to the wind speed. Non-linear control methods that consider the dynamic behavior of wind speed are generally used to provide maximum power and improved efficiency. In this perspective, the mechanical power is estimated using Kalman filter. And then, from the estimated mechanical power, the wind speed is estimated with Newton-Raphson method to achieve maximum power without anemometer. However, the blade shape and air density get changed with time and the generator efficiency is also degraded. This results in incorrect estimation of wind speed and MPPT. It causes not only the power loss but also incorrect wind resource assessment of site. In this paper, the adaptive maximum power point tracking control algorithm for wind turbine system based on the estimation of wind speed is proposed. The proposed method applies correction factor to wind turbine system to have accurate wind speed estimation for exact MPPT. The proposed method is validated with numerical simulations and the results show an improved performance.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.235-236
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• 2008

Recently, the power load is growing larger and because of the environmental limitation of generation, the expansion of generation facilities are becoming more difficult. For that reason the importance of the demand-side resources come to be higher. One method of the demand-side resource, the DLC Program, has executed, and moreover, the loads which are available to be controlled are increasing. It should be considered of some kinds of power system components such as DLCs, because the fact that using the demand resources will be an important part of the power system. This paper considers the power factor of the load-bus which is shedded in the direct load control program. and then analyze the power system using flow sensitivity and voltage sensitivity. In this paper, we assumed two scenarios through the rank of the load power factor at each bus and to compare and evaluate each case, we used Power World for the simulation.

• Journal of Environmental Impact Assessment
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• v.20 no.4
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• pp.425-434
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• 2011

The energy produced by wind power generation is a clean energy product because it is acquired by using renewable resource. Wind power plants("wind farms), in Korea, have been built and operated as 345.6MW facilities from 2001 until now 2009. Nevertheless, environmental issues regarding construction of wind power plants have arisen. accordingly it is time to consider the environmental and social issues of wind power in accordance with the government's policy objectives of increased wind power production. In this study, we investigated the influence that noise and low frequency noise caused by Wind power plants have on neighborhood and residents. We also sought solutions to these issues. In order to analyze the issues of wind power facilities, we compared and examined precedents and the solutions for noise and low frequency noise in Europe, the United states and Japan. We intended to examine the influences of wind power facilities and propose alternative in dealing with these issues.

• Journal of IKEEE
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• v.10 no.2 s.19
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• pp.134-140
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• 2006

This paper proposed a low power resource allocation algorithm for the minimum switching activity of operators in high level synthesis. In this paper, the proposed method finds switching activity in circuit each functional unit exchange for binary sequence length and value bit are logic one value. To use the switching activity was found the allocation with minimal power consumption, the proposed method visits all control steps one by one and determines the allocation with minimal power consumption at each control step. As the existing method, the execution time can be fast according to use the number of operator and maximal control step. And it is the reduction effect from 8.5% to 9.3%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.3
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• pp.35-40
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• 2010

In this paper, we propose a hardware resource sharable camera control processor (CCP) for low-cost and low-power camera cell phones. The main idea behind the proposed architecture is that adds direct access paths in the CCP to share its hardware resources so that the baseband processor expands its capabilities and boosts its performance by utilizing CCF's hardware resources. In addition, we applied a module grain dock-gating method to reduce power dissipation. Hence, the CCP can realize low-power and low-cost camera cell phones with greater hardware efficiency. This chip was fabricated in a 0.18um CMOS process with an active area of $3.8mm\;{\times}\;3.8mm$.

• Environmental and Resource Economics Review
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• v.20 no.1
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• pp.61-98
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• 2011

This study conducts economic evaluation of alternatives for $CO_2$ reduction of thermal power plants. Two alternatives in reducing $CO_2$ emission are considered for the evaluation under the RPS(Renewable Portfolio Standard) system; one is to perform renewable energy quotas and another is to construct green thermal power plants using CCS(Carbon Capture and Sequestration). As evaluation methods, DCF(Discount Cash Flow) and ROPM(Real Options Pricing Method) are employed. At a discount rate of 7.5% applied to the Electricity Supply and Demand Plan, it is shown that green thermal power generation has economic dominance under both evaluation methods.

• Environmental and Resource Economics Review
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• v.23 no.1
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• pp.43-65
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• 2014

In this paper, we test for allocative efficiency of productive inputs including electricity and measure the divergence between the actual and optimal level of electricity for the chemical products, which is a relatively highly electricity-intensive sector in Korean manufacturing industries, by estimating a shadow cost function. Supposing cost minimization subject to market prices was achieved, we derive the price elasticities of demand for each input and simulate the impact of a 10% increase in power rate on its demand and supply price by estimating jointly a cost function with an inverse supply relation. The null hypothesis of allocative efficiency of inputs is rejected over the period 1982-2006. On average, electricity is used more than optimal level by 98% per year. The demand for electricity decreases by 11.4%, and supply price, on average, falls by 0.08%, other things being equal.

• Environmental and Resource Economics Review
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• v.25 no.4
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• pp.565-590
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• 2016

In accordance with the global efforts to reduce greenhouse gas emissions, Korean government submitted its INDC (Intended Nationally Determined Contribution) of 25.7% for domestic reduction and the total of 37% reduction by 2030 including the purchase of emission reduction permit from abroad. In this study, 25.7% reduction target is being evaluated to see its impact on domestic energy system using the integrated assessment model, GCAM (Global Change Assessment Model). Results show that electricity generation from fossil fuel technologies using coal and gas decrease by 28.0%, 13.5% while that of biomass, wind power, solar energy increase by 47.6%, 22.0% and 45.4%, respectively. It is worth noting that so called new technology such as USC (ultra supercritical power generation) does not contribute to achieving the emission reduction target and careful and quantitative analysis is required for such categorization in the future.

• Journal of Communications and Networks
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• v.13 no.6
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• pp.664-677
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• 2011

In order to control interference and improve spectrum efficiency in the femtocell and macrocell overlaid system (FMOS), we propose a joint frequency bandwidth dynamic division, clustering and power control algorithm (JFCPA) for orthogonal-frequency-division-multiple access-based downlink FMOS. The overall system bandwidth is divided into three bands, and the macro-cellular coverage is divided into two areas according to the intensity of the interference from the macro base station to the femtocells, which are dynamically determined by using the JFCPA. A cluster is taken as the unit for frequency reuse among femtocells. We map the problem of clustering to the MAX k-CUT problem with the aim of eliminating the inter-femtocell collision interference, which is solved by a graph-based heuristic algorithm. Frequency bandwidth sharing or splitting between the femtocell tier and the macrocell tier is determined by a step-migration-algorithm-based power control. Simulations conducted to demonstrate the effectiveness of our proposed algorithm showed the frequency-reuse probability of the FMOS reuse band above 97.6% and at least 70% of the frequency bandwidth available for the macrocell tier, which means that the co-tier and the cross-tier interference were effectively controlled. Thus, high spectrum efficiency was achieved. The simulation results also clarified that the planning of frequency resource allocation in FMOS should take into account both the spatial density of femtocells and the interference suffered by them. Statistical results from our simulations also provide guidelines for actual FMOS planning.