• 한국정보과학회논문지:정보통신
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• 제29권5호
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• pp.573-582
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• 2002

본 논문에서는 라우팅 도메인 내의 모든 라우터들을 대신하여 라우트 서버가 QoS 경로 결정을 담당하도록 하는 중앙 집중적인 QoS 라우팅 구조를 제안한다. 라우트 서버는 QoS 경로를 할당하고 반환 받는 작업을 통해 스스로 QoS 경로 계산에 필요한 동적인 링크 QoS 상태 정보를 파악하고 유지한다. 따라서, 제안하는 QoS 라우팅 구조에서는 동적 네트워크 상태 정보 교환으로 인한 프로토콜 오버헤드를 제거하였다. 또한, 이와 같은 방식으로 네트워크 상태 정보를 유지함으로써 정확한 네트워크 상태 정보를 이용하여 경로 계산을 수행할 수 있기 때문에 라우팅 성능 또한 크게 향상시킬 수 있다. 본 논문에서는 라우트 서버의 경로 계산 오버헤드를 감소시키기 위한 경로 캐슁 스킴들을 제안하고, 시뮬레이션을 통해 그 성능을 평가하였다. 시뮬레이션 결과, 제안하는 캐슁 스킴을 통해 라우트 서버의 오버헤드가 크게 줄어드는 것을 확인할 수 있었다. 뿐만 아니라 기존에 제안된 다양한 분산 QoS 라우팅 스킴들과도 성능을 비교하였는데, 그 결과 제안하는 서버 기반 QoS 라우팅 스킴이 라우팅 성능을 크게 향상시킬 뿐 아니라, 라우팅 오버헤드 측면에서도 우수함을 볼 수 있었다.

• 대한전자공학회논문지TC
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• 제42권2호
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• pp.61-74
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• 2005

디지털 멀티미디어 방송(DMB)은 대용량의 멀티미디어 정보를 무선환경의 이동체에 전송하기 위해 제안된 방식이다. 이러한 멀티미디어 서비스를 제공하기 위해 DM시스템은 COFDM 변조방식을 사용하여 다중 경로 페이딩 현상을 극복하고, 동시에 강력한 채널오류 정정 능력을 필요로 한다. DMB 수신기를 위한 비터비 디코더(구속장 7, code rate 1/4)는 가변 부호화된 데이터의 복호화를 수행해야 하고, 방송시스템이므로 실시간으로 동작하기 위해서 효율적인 구조를 가져야 한다. 따라서 DMB 시스템을 위한 비터비 디코더를 구현하기 위해서는 복호화 과정을 고속으로 수행할 수 있는 별도의 전용 하드웨어 모듈을 설계하는 것이 바람직하다. 본 논문에서는 많은 연산량을 효율적으로 줄일 수 있는 결합된 Add-Compare-Select(ACS)와 Path Metric Normalization(PMN)구조를 새롭게 제안하고자 한다. PMN구조에서의 단점인 comparison tree에 의한 임계 경로(critical path)의 문제를 고정치(fixed value)에 의한 선택 알고리즘을 적용함으로써 고속 동작이 가능하게 하였고, ACS구조에서는 분할 기법(decomposition method)과 선계산(pre-computation)을 이용하여 덧셈기, 비교기, 표준화기의 복잡도를 줄일 수 있도록 하였다. 시뮬레이션 결과 펑처드 비터비 디코더는 일반적인 구조를 적용했을 때 보다 면적 $3.78\%$, 전력소모 $12.22\%$, 최대 게이트 지연 $23.80\%$의 감소율을 보였다.

• 한국항공운항학회지
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• 제24권1호
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• pp.1-9
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• 2016

In this paper, we integrate three degree of freedom(3DOF) point-mass model for aircraft and three-dimensional path generation algorithms using dubins curve and nonlinear path tracking law. Through this integration, we apply the path generation algorithm to the path planning, and verify tracking performance and feasibility of using the aircraft 3DOF point-mass model for air traffic management. The accuracy of modeling 6DOF aircraft is more accurate than that of 3DOF model, but the complexity of the calculation would be raised, in turn the rate of computation is more likely to be slow due to the increase of degree of freedom. These obstacles make the 6DOF model difficult to be applied to simulation requiring real-time path planning. Therefore, the 3DOF point-mass model is also sufficient for simulation, and real-time path planning is possible because complexity can be reduced, compared to those of the 6DOF. Dubins curve used for generating the optimal path has advantage of being directly available to apply path planning. However, we use the algorithm which extends 2D path to 3D path since dubins curve handles the two dimensional path problems. Control law for the path tracking uses the nonlinear path tracking laws. Then we present these concomitant simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.84-88
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• 2001

This paper proposes a method of solving a unit commitment problem using parallel tabu search (PTS). The TS is efficient optimization method using meta-heuristic. In this paper, to reduce the computation time for evaluating the neighborhoods, an evaluating method only on changed part and a path relinking method as diversification strategy are proposed. To show the usefulness of the proposed method, we simulated for 10 units system and 110 units system. Numerical results show improvements in the generation costs and the computation time compared with conventional methods. Numerical results show improvements in the generation cost and the computation time compared to previously obtained results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.49.3-49
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• 2001

In 1994 Adelman´s pioneer work demonstrated that deoxyribonucleic acid (DNA) could be used as a medium for computation to solve mathematical problems. He described the use of DNA based computational approach to solve the Hamiltonian Path Problem (HPP). Since then a number of combinatorial problems have been analyzed by DNA computation approaches including, for example: Maximum Independent Set (MIS), Maximal Clique and Satisfaction (SAT) Problems. In the present paper we propose a method of solving another classic combinatorial optimization problem - the eraph Coloring Problem (GCP), using specifically designed circular DNA plasmids as a computation tool. The task of the analysis is to color the graph so that no two nodes ...

• Journal of Information Processing Systems
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• 제20권2호
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• pp.226-238
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• 2024

Recently, multi-access edge computing (MEC) has emerged as a promising technology to alleviate the computing burden of vehicular terminals and efficiently facilitate vehicular applications. The vehicle can improve the quality of experience of applications by offloading their tasks to MEC servers. However, channel conditions are time-varying due to channel interference among vehicles, and path loss is time-varying due to the mobility of vehicles. The task arrival of vehicles is also stochastic. Therefore, it is difficult to determine an optimal offloading with resource allocation decision in the dynamic MEC system because offloading is affected by wireless data transmission. In this paper, we study computation offloading with resource allocation in the dynamic MEC system. The objective is to minimize power consumption and maximize throughput while meeting the delay constraints of tasks. Therefore, it allocates resources for local execution and transmission power for offloading. We define the problem as a Markov decision process, and propose an offloading method using deep reinforcement learning named deep deterministic policy gradient. Simulation shows that, compared with existing methods, the proposed method outperforms in terms of throughput and satisfaction of delay constraints.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.365-370
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• 2012

Most path planning algorithms for a marine robot in the ocean environment have been developed without considering the robot's heading angle. As a result, the robot has a difficulty in following the path correctly. In this paper, we propose a limit-cycle circle set that applies to the $Theta^*$ algorithm. The minimum turning radius of a marine robot is calculated using a limit-cycle circle set, and circles of this radius is used to generate a configuration space of an occupancy grid map. After applying $Theta^*$ to this configuration space, the limit-cycle circle set is also applied to the start and end nodes to find the appropriate path with specified heading angles. The benefit of this algorithm is its fast computation time compared to other 3-D ($x,y,{\theta}$) path planning algorithms, along with the fact that it can be applied to the 3-D kinematic state of the robot. We simulate the proposed algorithm and compare it with 3-D $A^*$ and 3-D $A^*$ with post smoothing algorithms.

• 한국군사과학기술학회지
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• 제13권2호
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• pp.180-187
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• 2010

In this paper, a global path generation method is suggested using multiple grid maps connected with the mission type of unmanned combat vehicle(UCV). In order to carry out a mission for UCV, it is essential to find a global path which is coincident with the characteristics of the mission. This can be done by considering various combat circumstances represented as grid maps such as velocity map, threat map and communication map. Cost functions of multiple grid maps are linearly combined and normalized to them simultaneously for the path generation. The proposed method is realized using $A^*$, a well known search algorithm, and cost functions are normalized in the ratio of the traverse time which is one of critical information should be provided with the operators using the velocity map. By the experiments, it is checked found global paths match with the mission type by reflecting input data of grid maps properly and the computation time is short enough to regenerate paths in real time as combat circumstances change.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.547-552
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• 2003

In mold machining, there are many concave machining regions where chatter and tool deflection occur since MRR (material removal rate) increases as curvature increases even though cutting speed and depth of cut are constant. Boolean operation between stock and tool model is widely used to compute MRR in NC milling simulation. In finish cutting, the side step is reduced to about 0.3mm and tool path length is sometimes over 300m. so Boolean operation takes long computation time and includes much error if the resolution of stock and tool model is larger than the side step. In this paper, curvature of CL(cutter location) surface and side step of tool path is used to compute the feedrate for constant MRR machining. The data structure of CL surface is Z-map generated from NC tool path. The algorithm to get local curvature from discrete data was developed and applied to compute local curvature of CL surface. The side step of tool path was computed by point density map which includes cutter location point density at each grid element. The feedrate computed from curvature and side step is inserted to new tool path to regulate MRR. The resultants wire applied to feedrate optimization system which generates new tool path with feedrate from NC codes for finish cutting. The system was applied to speaker mold machining. The finishing time was reduced to 12.6%. tool wear was reduced from 2mm to 1.1mm and chatter marks and over cut on corner were removed.

• 로봇학회논문지
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• 제16권2호
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• pp.112-121
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• 2021

Unlike a typical small-sized robot navigating in a free space, an autonomous vehicle has to travel in a designated road which has lanes to follow and traffic rules to obey. High-Definition (HD) maps, which include road markings, traffic signs, and traffic lights with high location accuracy, can help an autonomous vehicle avoid the need to detect such challenging road surroundings. With space constraints and a pre-built HD map, a new type of path planning algorithm can be conceived as a substitute for conventional grid-based path planning algorithms, which require substantial planning time to cover large-scale free space. In this paper, we propose an obstacle-avoiding, cost-based planning algorithm in a continuous space that aims to pursue a globally-planned path with the help of HD map information. Experimentally, the proposed algorithm is shown to outperform other state-of-the-art path planning algorithms in terms of computation complexity in a typical urban road setting, thereby achieving real-time performance and safe avoidance of obstacles.