• ETRI Journal
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• 제40권6호
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• pp.726-735
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• 2018

Femtocells are good examples of the ultimate networking technology, offering enhanced indoor coverage and higher data rate. However, the dense deployment of femto base stations (FBSs) and the exploitation of subcarrier reuse between macrocell base stations and FBSs result in significant co-tier and cross-tier interference, thus degrading system performance. Therefore, appropriate resource allocations are required to mitigate the interference. This paper proposes a discrete bacterial foraging optimization (DBFO) algorithm to find the optimal resource allocation in two-tier networks. The simulation results showed that DBFO outperforms the random-resource allocation and discrete particle swarm optimization (DPSO) considering the small number of steps taken by particles and bacteria.

• 한국통신학회논문지
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• 제38A권5호
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• pp.443-450
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• 2013

본 논문에서는 셀룰러 시스템 상향 링크에서 가상 여러입력 여러출력 (multiple input multiple output: MIMO)를 적용할 때 사용자 쌍 선택 및 자원 할당 문제를 고려한다. 다중 접속 방식으로 LTE (long term evolution) 시스템의 SC-FDMA (single carrier frequency division multiple access)보다 자원 할당이 유연한 DFTS-OFDMA(discrete Fourier transform spread orthogonal FDMA) 방식을 적용하고 서로 다른 제약 조건에서 전송률을 최대로 하는 사용자 쌍 및 자원 할당 최적화 문제를 공식화하였다. 이 때 비연속 부반송파 자원을 할당하고 중복 사용자 할당을 허용하는 DFTS-OFDMA 방식은 SC-FDMA보다 전달해야 할 자원 할당 제어 정보 양은 늘어나지만 최적화 해를 쉽게 얻을 수 있고 전송률을 향상시킴을 볼 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권5호
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• pp.2233-2252
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• 2018

For the problem of cross-layer joint resource allocation (JRA) in the Long-Term Evolution (LTE)-Advanced standard using carrier aggregation (CA) technology, it is difficult to obtain the optimal resource allocation scheme. This paper proposes a joint resource allocation algorithm based on the weights of user's average quality of experience (JRA-WQOE). In contrast to prevalent algorithms, the proposed method can satisfy the carrier aggregation abilities of different users and consider user fairness. An optimization model is established by considering the user quality of experience (QoE) with the aim of maximizing the total user rate. In this model, user QoE is quantified by the mean opinion score (MOS) model, where the average MOS value of users is defined as the weight factor of the optimization model. The JRA-WQOE algorithm consists of the iteration of two algorithms, a component carrier (CC) and resource block (RB) allocation algorithm called DABC-CCRBA and a subgradient power allocation algorithm called SPA. The former is used to dynamically allocate CC and RB for users with different carrier aggregation capacities, and the latter, which is based on the Lagrangian dual method, is used to optimize the power allocation process. Simulation results showed that the proposed JRA-WQOE algorithm has low computational complexity and fast convergence. Compared with existing algorithms, it affords obvious advantages such as improving the average throughput and fairness to users. With varying numbers of users and signal-to-noise ratios (SNRs), the proposed algorithm achieved higher average QoE values than prevalent algorithms.

• 한국통신학회논문지
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• 제30권7C호
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• pp.624-632
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• 2005

이 논문에서는 BICM-OFDM(Bit Interleaved Coded modulation-Orthogonal Frequency Division Multiplexing) 시스템을 위한 비트 할당 기법에 대하여 연구한다. 부채널의 상태에 따라 부반송파의 전송 매개 변수를 조절하면 OFDM 시스템의 성능을 크게 개선시킬 수 있다. 여기서는 BICM-OFDM 시스템을 위한 적응 전송 기법으로 데이터 전송률을 일정하게 유지하면서 비트 오류율이 최소가 되도록 부반송파에 비트를 할당한다. 또한, 할당하는 비트 수가 정수인 제한 조건 하에서 최적의 해를 얻기 위해 이산 라그랑지 승수 방법을 사용한다. 모의실험을 통해 제안한 비트 할당 기법의 계산량이 크지 않으며, BICM-OFDM 시스템에 제안한 기법을 사용하면 약 $2\~3$ dB의 신호대 잡음비의 이득을 얻을 수 있음을 보인다.

• 한국경영과학회지
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• 제4권1호
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• pp.59-64
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• 1979

The application of optimization techniques to the planning of industrial, economic, administrative and military activities with random technological coefficients has been extensively studied in the literature. Stochastic (linear) programs with simple recourse essentially model the allocation of scarce resources under uncertainty with linear penalties associated with shortages or surplus. This work on a problem with a discrete random resource vector, "The allocation of aircraft under uncertain demand" given in (1), is easily and efficiently handled by the application of the recently developed Wets' algorithm (8) for solving stochastic programs with simple recourse, which approves that such class of stochastic problems can be solved with the same efficiency as solving linear programs of the same size. It is known that the algorithm is also applicable to stochastic programs with continuous random demands for their approximate solutions.

• 한국시뮬레이션학회논문지
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• 제32권4호
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• pp.41-58
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• 2023

함정 교전이 수상, 수중, 공중의 적에 대한 동시다발적인 복합전 형태로 발전함에 따라 함정의 복합전 대응을 위한 체계성능 및 전술 분석의 중요성 또한 커지고 있다. 특히, 복합전을 효과적으로 분석하기 위해서는 함정에 탑재된 탐지체계의 제한된 성능자원을 적절히 활용할 수 있는 시뮬레이션 연구가 필요하다. 본 연구는 함정의 복합전 분석을 위해 DEVS(Discrete Event Systems Specifications) 형식론 기반의 시뮬레이션 모델을 제안한다. 제안 모델은 다양한 복합전 상황을 시뮬레이션 하기 위해 전투 플랫폼과 무장 객체를 일반화한 모델을 포함한다. 또한, 제한된 탐지자원을 활용하여 임무를 수행해야 하는 복합전의 특성을 고려하여 탐지성능 할당 알고리즘을 제안하고 함정의 탐지체계 모델에 적용한다. 시뮬레이션 실험으로 수상, 공중, 육지의 적 세력에 대한 복합전 상황을 가정하여 제안 모델을 적용하였다. 탐지체계의 탐지자원 할당 강도, 적군의 규모, 아군의 출항위치를 변경한 시나리오에 대하여 복합전의 효과도 분석을 수행하였고, 자원할당 기능이 교전 시간 및 성공에 미치는 영향을 결과로 제시하였다. 제안 모델의 연구 결과가 향후 다양한 복합전 상황에 대한 함정의 전술 분석에 공학적 근거로 활용되기를 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5191-5211
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• 2016

It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.227-227
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• 2015

The Wairarapa Valley occupies a predominantly rural area in the lower North Island of New Zealand. It supports a mix of intensive farming (dairy), dry stock farming (sheep and beef cattle) and horticulture (including wine grapes). The valley floor is traversed by the Ruamahanga River, the largest river in the Wellington region with a total catchment area of 3,430 km2. Environmental, cultural and recreational values associated with this Ruamahanga River are very high. The alluvial gravel and sand aquifers of the Wairarapa Valley, support productive groundwater aquifers at depths of up to 100 metres below ground while the Ruamahanga River and its tributaries present a further source of water for users. Water is allocated to users via resource consents by Greater Wellington Regional Council (GWRC). With intensifying land use, demand from the surface and groundwater resources of the Wairarapa Valley has increased substantially in recent times and careful management is needed to ensure values are maintained. This paper describes the approach being taken to manage water resources in the Wairarapa Valley and redefine appropriate limits of sustainable water use. There are three key parts: Quantifying the groundwater resource. A FEFLOW numerical groundwater flow model was developed by GWRC. This modelling phase provided a much improved understanding of aquifer recharge and abstraction processes. It also began to reveal the extent of hydraulic connection between aquifer and river systems and the importance of moving towards an integrated (conjunctive) approach to allocating water. Development of a conjunctive management framework. The FEFLOW model was used to quantify the stream flow depletion impacts of a range of groundwater abstraction scenarios. From this, three abstraction categories (A, B and C) that describe diminishing degrees of hydraulic connection between ground and surface water resources were mapped in 3 dimensions across the Valley. Interim allocation limits have been defined for each of 17 discrete management units within the valley based on both local scale aquifer recharge and stream flow depletion criteria but also cumulative impacts at the valley-wide scale. These allocation limits are to be further refined into agreed final limits through a community-led decision making process. Community involvement in the limit setting process. Historically in New Zealand, limits for sustainable resource use have been established primarily on the basis of 'hard science' and the decision making process has been driven by regional councils. Community involvement in limit setting processes has been through consultation rather than active participation. Recent legislation in the form of a National Policy Statement on Freshwater Management (2011) is reforming this approach. In particular, collaborative consensus-based decision making with active engagement from stakeholders is now expected. With this in mind, a committee of Wairarapa local people with a wide range of backgrounds was established in 2014. The role of this committee is to make final recommendations about resource use limits (including allocation of water) that reflect the aspirations of the communities they represent. To assist the committee in taking a holistic view it is intended that the existing numerical groundwater flow models will be coupled with with surface flow, contaminant transport, biological and economic models. This will provide the basis for assessing the likely outcomes of a range of future land use and resource limit scenarios.

• Industrial Engineering and Management Systems
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• 제11권3호
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• pp.215-223
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• 2012

This paper focuses on three very similar evolutionary algorithms: genetic algorithm (GA), particle swarm optimization (PSO), and differential evolution (DE). While GA is more suitable for discrete optimization, PSO and DE are more natural for continuous optimization. The paper first gives a brief introduction to the three EA techniques to highlight the common computational procedures. The general observations on the similarities and differences among the three algorithms based on computational steps are discussed, contrasting the basic performances of algorithms. Summary of relevant literatures is given on job shop, flexible job shop, vehicle routing, location-allocation, and multimode resource constrained project scheduling problems.

• 한국인터넷방송통신학회논문지
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• 제11권5호
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• pp.101-106
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• 2011

본 연구는 이산사건 시스템인 제조 시스템에 대하여 사용자 명세서에 따라 충실하게 동작하는 제어기를 설계하는 것이 목적이다. 특히, W. M. Wonham의 감독제어 이론을 기반으로 병렬처리가 가능한 패트리 넷을 이용한 제어기를 설계하는 것이다. 또한, 패트리 넷을 이용한 설계 시 고려해야 할 문제 중 공유하는 자원의 할당에 관한 문제를 다루고자 한다. 공유자원에 대한 처리를 사용자 명세서로 제시하고 제시한 패트리 넷으로 모델링하여 합성하면 제어기가 생성된다. 이렇게 생성된 제어기는 공유하는 자원이 있는 경우에 발생가능 한 교착상태(deadlock)와 기아상태(Starvation)에 대한 제어가 가능하다. 선행연구에서는 페트리 넷의 두 모델을 합성하는 방법으로 동기식 도달성 그래프를 제안하였다. 따라서 본 연구에서는 그 결과를 이용하여 교착상태와 기아상태를 예방한 제어된 시스템을 설계하여 제시하고자 한다.