• 한국컴퓨터정보학회논문지
• /
• 제29권2호
• /
• pp.1-12
• /
• 2024

경로 손실(Path Loss)을 예측하는 것은 셀룰러 네트워크(Cellular Network)에서 기지국(Base Station) 의 설치 위치 선정 등 무선망 설계에 중요한 요인 중 하나다. 기존에는 기지국의 최적 설치 위치를 결정하기 위해 수많은 현장 테스트(Field Tests)를 통해 경로 손실 값을 측정했다. 따라서 측정에 많은 시간이 소요된다는 단점이 있었다. 이러한 문제를 해결하기 위해 본 연구에서는 머신러닝(Machine Learning, ML) 기반의 경로 손실 예측 방법을 제안한다. 특히, 경로 손실 예측 성능을 향상시키기 위해서 앙상블 학습(Ensemble Learning) 접근법을 적용하였다. 부트스트랩 데이터 세트(Bootstrap Dataset)을 활용하여 서로 다른 하이퍼파라미터(Hyperparameter) 구성을 갖는 모델들을 얻고, 이 모델들을 앙상블하여 최종 모델을 구축했다. 인터넷상에 공개된 경로 손실 데이터 세트를 활용하여 제안하는 앙상블 기반 경로 손실 예측 방법과 다양한 ML 기반 방법들의 성능을 평가 및 비교했다. 실험 결과, 제안하는 방법이 기존 방법들보다 우수한 성능을 달성하였으며, 경로 손실 값을 가장 정확하게 예측할 수 있다는 것을 입증하였다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
• /
• pp.283-286
• /
• 1996

This study suggests a new methodology for the fault diagnosis based on the signed digraph in developing the fault diagnosis system of a boiler plant. The suggested methodology uses the new model, fault-effect tree. The SDG has the advantage, which is simple and graphical to represent the causal relationship between process variables, and therefore is easy to understand. However, it cannot handle the broken path cases arisen from data uncertainty as it assumes consistent path. The FET is based on the SDG to utilize the advantages of the SDG, and also covers the above problem. The proposed FET model is constructed by clustering of measured variables, decomposing knowledge base and searching the fault propagation path from the possible faults. The search is performed automatically. The fault diagnosis system for a boiler plant, ENDS was constructed using the expert system shell G2 and the advantages of the presented method were confirmed through case studies.

• 전자공학회논문지S
• /
• 제34S권2호
• /
• pp.21-32
• /
• 1997

This paper proposes an elliptical world-modeling mehtrod in order to secure the safety of the mobile robot from the unreliability of ultrasonic sensors and to estimate the lateral orientation of the detected objects. This method is advnatageous because the total amount of data that the robot utilizes is reduced when historical and new data are clusterd during each sensing period and also because the objects in the environment can be almost exactly recognized. This paper also proposes a new local path planning algorithm which is divided into four different situations and gudies the robot through the safe local path using dat acollected in elliptical form. This algorithm can help the AMR navigate by allowing it to sum up the virtual vector forces made form the ellipses in order to select a safe subgoal. This local path plannin gmehtod using the elliptical world model has been proved by several navigation experiments.

• 디지털산업정보학회논문지
• /
• 제11권3호
• /
• pp.79-90
• /
• 2015

Multipath routing technique is recognized as one of the effective approaches to improve the reliability of data forwarding. However, the traditional multipath routing focuses only on how many paths are needed to ensure a desired reliability. For this purpose, the protocols construct additional paths and thus cause significant energy consumption. These problems have motivated the study for the energy-efficient and reliable data forwarding. Thus, this paper proposes an energy-efficient concurrent multipath routing protocol with a small number of paths based on interaction between paths. The interaction between paths helps to reinforce the multipath reliability by making efficient use of resources. The protocol selects several nodes located in the radio overlapped area between a pair of paths as bridge nodes for the path-interaction. In order to operate the bridge node efficiently, when the transmission failure has detected by overhearing at each path, it performs recovery transmission to recover the path failure. Simulation results show that proposed protocol is superior to the existing multipath protocols in terms of energy consumption and delivery reliability.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권5호
• /
• pp.2218-2244
• /
• 2016

In this paper, we propose a hybrid routing scheme that utilizes location information to support reliable data transmission in mobile ad hoc networks. The proposed scheme determines and maintains routing path by considering the directionality and connectivity of nodes using grid zones and information on neighbor nodes. In addition, it generates alternative paths with consideration for node distance and reliability. To show the superiority of the proposed routing scheme, a performance evaluation was conducted using simulations. The performance evaluation results show that the proposed scheme offers faster and more reliable data transmission than the existing routing schemes, and the number of messages decreases by approximately 31% compared to the existing schemes on average.

• 지역사회간호학회지
• /
• 제24권3호
• /
• pp.255-263
• /
• 2013

Purpose: This study examined the fitness of a path model for the relationship among daily life stress, problem of life, social support, depression, and suicidal ideation in adolescents. Methods: The subjects consisted of 247 adolescents. Data were collected through self-report questionnaires. The data were analyzed by the SPSS and AMOS programs. Results: Daily life stress, problem of life, social support, and depression showed direct effects on suicidal ideation in adolescents, while daily life stress and problem of life showed indirect effects on suicidal ideation in adolescents. Daily life stress and problem of life showed direct effects on social support and depression in adolescents. The hypothetical path model of adolescents' suicidal ideation was proven correct. Conclusion: Based on the outcomes of this study, it is necessary to design an intervention program that emphasizes the reduction of daily life stress, problem of life, depression and enhancement social support in order to prevention adolescents' suicidal ideation.

• 산업경영시스템학회지
• /
• 제32권4호
• /
• pp.192-202
• /
• 2009

Disassembly of products at their end-of-life (EOL) is a prerequisite for recycling or remanufacturing, since most products should be disassembled before being recycled or remanufactured as secondary parts or materials. In disassembly sequence planning of EOL products, considered are the uncertainty issues, i.e., defective parts or joints in an incoming product, disassembly damage, and imprecise net profits and costs. The paper deals with the problem of determining the disassembly level and corresponding sequence, with the objective of maximizing the overall profit under uncertainties in disassembly cost and/or revenue. The solution is represented as the longest path on a directed acyclic graph where parameter (arc length) uncertainties are modeled in the form of intervals. And, a heuristic algorithm is developed to find a path with the minimum worst case regret, since the problem is NP-hard. Computational experiments are carried out to show the performance of the proposed algorithm compared with the mixed integer programming model and Conde's heuristic algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권4호
• /
• pp.1249-1265
• /
• 2022

Video streaming has become one of the most popular applications for mobile devices. The network bandwidth required for video streaming continues to exponentially increase as video quality increases and the user base grows. Multi-Path TCP (MPTCP), which allows devices to communicate simultaneously through multiple network interfaces, is one of the solutions for providing robust and reliable streaming of such high-definition video. However, mobile video streaming over MPTCP raises new concerns, e.g., power consumption and cellular data usage, since mobile device resources are constrained, and users prefer to minimize such costs. In this work, we propose a mobile video streaming framework over MPTCP (mDASH) to reduce the costs of energy and cellular data usage while preserving feasible streaming quality. Our evaluation results show that by utilizing knowledge about video behavior, mDASH can reduce energy consumption by up to around 20%, and cellular usage by 15% points, with minimal quality degradation.

• Communications for Statistical Applications and Methods
• /
• 제21권6호
• /
• pp.521-528
• /
• 2014

A stochastic Gompertz diffusion model for tumor growth is a topic of active interest as cancer is a leading cause of death in Korea. The direct maximum likelihood estimation of stochastic differential equations would be possible based on the continuous path likelihood on condition that a continuous sample path of the process is recorded over the interval. This likelihood is useful in providing a basis for the so-called continuous record or infill likelihood function and infill asymptotic. In practice, we do not have fully continuous data except a few special cases. As a result, the exact ML method is not applicable. In this paper we proposed a method of parameter estimation of stochastic Gompertz differential equation via Markov chain Monte Carlo methods that is applicable for several data structures. We compared a Markov transition data structure with a data structure that have an initial point.

• 인터넷정보학회논문지
• /
• 제22권5호
• /
• pp.9-16
• /
• 2021

Recently, the traffic volume of mobile communications increases rapidly and the small-cell is one of the solutions using two offload schemes, i.e., local IP access (LIPA) and selected IP traffic offload (SIPTO), to reduce the end-to-end delay and amount of mobile data traffic in the core network (CN). However, 3GPP describes the concept of LIPA and SIPTO and there is no decision algorithm to decide the path from source nodes (SNs) to destination nodes (DNs). Therefore, this paper proposes a dynamic mobile data traffic offload scheme using small-cells to decide the path based on the SN and DN, i.e., macro user equipment, small-cell user equipment (SUE), and multimedia server, and type of the mobile data traffic for the real-time and non-real-time. Through analytical models, it is shown that the proposed offload scheme outperforms the conventional small-cell network in terms of the delay of end-to-end mobile data communications and probability of the mobile data traffic in the CN for the heterogeneous networks.