• Journal of Internet Computing and Services
• /
• v.10 no.5
• /
• pp.49-63
• /
• 2009

The performance of spatio-temporal moving pattern mining depends on how to analyze and process the huge set of spatio-temporal data due to the nature of it. The several method was presented in order to solve the problems in which existing spatio-temporal moving pattern mining methods[1-10] have, such as increasing execution time and required memory size during the pattern mining, but they did not solve properly yet. Thus, we proposed the STMP/MST method[11] as a preceding research in order to extract effectively sequential and/or periodical frequent occurrence moving patterns from the huge set of spatio-temporal moving data. The proposed method reduces patterns mining execution time, using the moving sequence tree based on hash tree. And also, to minimize the required memory space, it generalizes detailed historical data including spatio-temporal attributes into the real world scopes of space and time by using spatio-temporal concept hierarchy. In this paper, in order to verify the effectiveness of the STMP/MST method, we compared and analyzed performance with existing spatio-temporal moving pattern mining methods based on the quantity of mining data and minimum support factor.

• The KIPS Transactions:PartC
• /
• v.13C no.3 s.106
• /
• pp.345-352
• /
• 2006

In the integrated wired/wireless network which consists of the Internet and moving networks, multiple wireless links are used to connect a fixed host(FH) in the Internet to a mobile host(MH) in the moving network. For use in such an environment, we propose a scheme to overcome the TCP performance degradation due to the packet losses over the wireless links without losing the end-to-end TCP semantics. The proposed scheme in each mobile router(MR) allows to obtain the information regarding packet losses over the upstream wireless links based on the received packet sequence number and the ACK number. This information is delivered to the upstream router, which enables the upstream access router(AR) or MR to quickly retransmit the lost packets. The proposed scheme has the feature to quickly recover the packet losses incurred over the upstream wireless links and the performance of the proposed scheme is evaluated through simulation. It is shown that the significant performance gain can be obtained using the proposed scheme compared with the snoop mechanism which maintains end-to-end TCP semantics and does not require any additional features at the source and/or destination nodes.

• KIPS Transactions on Computer and Communication Systems
• /
• v.9 no.11
• /
• pp.256-264
• /
• 2020

Industrial Wireless Sensor Networks (IWSNs) is exploited to achieve various objectives such as improving productivity and reducing cost in the diversity of industrial application, and it has requirements such as low-delay and high reliability packet transmission. To accomplish the requirement, the network manager performs graph construction and resource allocation about network topology, and determines the transmission cycle and path of each node in advance. However, this network management scheme cannot treat mobile devices that cause continuous topology changes because graph reconstruction and resource reallocation should be performed as network topology changes. That is, despite the growing need of mobile devices in many industries, existing scheme cannot adequately respond to path failure caused by movement of mobile device and packet loss in the process of path recovery. To solve this problem, a network management scheme is required to prevent packet loss caused by mobile devices. Thus, we analyse the location and movement cycle of mobile devices over time using machine learning for predicting the mobility pattern. In the proposed scheme, the network manager could prevent the problems caused by mobile devices through performing graph construction and resource allocation for the predicted network topology based on the movement pattern. Performance evaluation results show a prediction rate of about 86% compared with actual movement pattern, and a higher packet delivery ratio and a lower resource share compared to existing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.4A
• /
• pp.370-377
• /
• 2004

In this paper, we present an adaptive modulation technique for orthogonal frequency division multiplexing (OFDM) for broadband wireless communications. Also, using improved channel prediction, we enhance the performance of adaptive OFDM in high mobility environments. Adaptive modulation technique has been shown to achieve reliable high-rate data transmission over frequency-selective fading channel when OFDM is employed. This scheme requires the accurate channel information between two stations for a better performance. In an outdoor high mobility environment, most of adaptive OFDM systems have to be given the channel information transmitted from the receiver. Even if it is possible, there is some delay. Moreover, the channel impulse response between two stations is very rapidly varied. If the channel information is obsolete at the time of transmission, then poor system performance will result. In order to solve this problem, we propose adaptive OFDM with improved channel predictor. The proposed bit allocation algorithm has a lower complexity and the proposed scheme mitigates the effect of channel delay. Robust approach is less sensitive to outdated channel information. Performance results show that the proposed scheme can achieve considerable performance enhancement.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.6
• /
• pp.1395-1401
• /
• 2005

Mobile manipulator is a robot that has mobility and manipulability with the combination of the task robot and mobile robot. One of the most important feature of the Mobile Manipulator is redundant freedom. Using the redundant freedom, Mobile Manipulator can move various mode, perform dexterous motion. It can have the wider workspace and better performance in avoidance of singularity and obstacle than the fixed base structured robot. Cooperation control using the Mobile Manipulator improves the performance of the robot with redundant freedom in workspace. In this paper, configuration control of the Mobile Manipulator has been studied using Task Segment and TOMM(Task-Oriented Manipulability Measure). For verifying the proposed algorithm, we implemented a mobile manipulator, PURL-II, which is composed of a mobile robot with 3DOF and a task robot with SDOF.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.4
• /
• pp.1032-1044
• /
• 1999

In the mobile communication systems such as PCS(Personal Communication Service), several strategies have been proposed to optimize the signalling traffic load by using the characteristics of traffic and mobile patterns for effective mobility management. According to IS-41 standard, LA(Location Area) consists of static and arbitrarily-defined set of cells, which do not take into account mobility patterns of mobile stations. In this paper, we propose an improved location management mechanism which contains the neighbor cells of the LA selectively using the mobility history of a mobile station and accommodates the LA size adaptively according to the speed of the mobile station. Also, we use the paging priorities for cells in LA to improve the paging efficiency. We compare the performance of conventional mechanism with that of the proposed mechanism using numerical analysis. The analysis results show that the proposed location management mechanism is better than conventional mechanism significantly.

• Journal of Korea Multimedia Society
• /
• v.10 no.2
• /
• pp.226-235
• /
• 2007

Recently, the lETF NEMO working group on network mobility is standardizing a basic support for moving networks. We need a handover scheme for achieving the performance of transparency during the movement of mobile routers in nested mobile networks. But existing handover schemes for a mobile host are not suitable for network mobility because the packet transmission delay and traffic increase during mobile router's handover in nested mobile networks. Therefore, we propose a new seamless handover scheme using the bi-casting based on Mobile IPv6 for nested mobile networks in this paper. Compared with the handover schemes using bi-directional edge tunneling for host mobility support on simulation. And, the results show that the proposed handover scheme reduces the packet delay during a mobile router changes the point of attachment in nested mobile networks.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.6
• /
• pp.1031-1037
• /
• 2001

본 고에서는 요즘 전세계적으로 관심을 모으고 있는 정보통신 산업과 기술발전으로 인한 이동전화의 서비스 품질평가에 대한 방법을 정리하였다. 주요 내용으로는 이동전화 체감 통화품질 측정을 위한 시험조건 및 시험방법개선, 시험장비 기능 확인시험, 성능개선 요구 및 확인, 시험계획 수립 및 전국 측정 방법, 측정데이터 분석, 등급별 평가 등에 대한 내용으로, 특히 이동전화 품질평가 항목별 시험조건 및 시험방법, 이동전화 체감 품질 측정용 시험장비 성능/신뢰성 개선 그리고 전국 현장 측정 데이터분석 및 지역별 품질 산출, 등급별 평가 내용을 정리하였다. 또한 각 분야별 품질 평가 기술 방법에 패한 우리나라의 대응전략을 정리하여 산업체 기술개발에 많이 활용될 수 있을 것으로 사료된다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2001.10c
• /
• pp.127-129
• /
• 2001

이동 호스트는 무선 통신망의 낮은 대역폭과 호스트들의 이동성, 부족한 저장장치와 배터리 수명 등으로 인하여 결함 발생 가능성이 높다. 이동 호스트의 결함에 효율적으로 대처하기 위한 결함 허용 기법에 관한 연구가 많이 진행되어 왔다. 셀룰라 네트워크에서는 이동 호스트이외에도 이동 호스트를 연결시키는 기지국은 보다 높은 수준의 가용도를 요구하므로 기지국의 결함에 대한 연구도 필수적이다. 본 논문에서는 이동 호스트 결함 복구를 위한 체크포인팅 기법을 기반으로 기지국 결함 복구를 위한 체크포인팅 이중화 기법을 제안하고 성능을 분석하였다. 또한 이동 호스트의 결함 복구를 위해 체크포인트가 존재하는 기지국의 복구를 기다리는 방법과 다른 기지국의 체크포인트를 이용하는 방법의 성능을 비교 분석하였다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11b
• /
• pp.901-903
• /
• 2005

본 논문은 스테레오 카메라를 이용한 이동 카메라 환경에서 다수의 사람을 검출하여 검출된 사람을 추적하는 방법을 제안한다. 카메라가 이동하게 되면 카메라의 움직임과 검출 대상이 되는 사람의 움직임이 동시에 발생하기 때문에 카메라 움직임을 변환 모델을 사용하여 보정하고, 독립적인 움직임을 추출하여 사람을 검출 하였다. 추적은 검출된 사람 영역의 컬러 분포에 기반하여 평균 이동(Mean Shift) 알고리즘을 적용하였다. 평균 이동 알고리즘은 빠르고 안정적인 성능으로 실시간 추적에 적합하다. 그러나 객체의 컬러 정보만으로는 배경과 컬러 분포가 유사한 객체의 경우 추적에 실패할 수 있는 단점이 있다. 이점을 보완하기 위하여 본 논문에서는 변위 지도(Disparity map)를 결합하여 객체와 배경을 분리하는 깊이 마스크를 생성하였다. 변위 지도를 사용하여 다수의 사람이 등장 할 경우 발생하는 가려짐, 겹침 등 다양한 실내 환경에서 발생하는 문제도 해결 하였다. 본 논문에서 제안하는 알고리즘은 다양한 데이터에 대해서 실험한 결과 정확한 검출과 추적에 우수한 성능을 확인 할 수 있었다.