• The Journal of Korea Robotics Society
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• v.18 no.1
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• pp.72-81
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• 2023

We introduce tightly-coupled GNSS-LiDAR-Inertial state estimator, which is capable of SLAM (Simultaneously Localization and Mapping) and autonomous driving. Long term drift is one of the main sources of estimation error, and some LiDAR SLAM framework utilize loop closure to overcome this error. However, when loop closing event happens, one's current state could change abruptly and pose some safety issues on drivers. Directly utilizing GNSS (Global Navigation Satellite System) positioning information could help alleviating this problem, but accurate information is not always available and inaccurate vertical positioning issues still exist. We thus propose our method which tightly couples raw GNSS measurements into LiDAR-Inertial SLAM framework which can handle satellite positioning information regardless of its uncertainty. Also, with NLOS (Non-light-of-sight) satellite signal handling, we can estimate our states more smoothly and accurately. With several autonomous driving tests on AGV (Autonomous Ground Vehicle), we verified that our method can be applied to real-world problem.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.8
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• pp.948-954
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• 1999

In this paper, we propose a cooperative motion planning algorithm for two tightly-coupled mobile robots. Specifically, the considered cooperative work is that two mobile robots should transfer a long rigid object along a predefined path. To resolve the problem, we introduce a master-slave concept for two obile robots having the same structure. According to the velocity of the master robot and the positions of two robots on the path, the velocity of the slave robot is determined. The slave normally tracks the master's motion, but in case that the velocity of the slave exceeds the velocity limit, the roles of the robots should be interchanged. The effectiveness of the proposed algorithm is proved by computer simulations.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1264-1273
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• 1998

In this paper, we implemented a system which provides more effective conference control than that of video conferencing system has been used on MBone. The system provides multicast service on the non-broadcasting network. It multicasts multimedia data using several MTS(Multipoint Transport Server)s and provides a tightly coupled conference control service with a CCS(Conference Control Server). As providing a tightly coupled conference control service, we can perform effectively video conferencing using this system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.777-785
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• 1987

In this paper, a tightly-coupled multiprocessor system is implemented with four processing elements based on MC68000 CPU, a common menory (128KB), and a single time-shared bus. The multi-tasking operating system, MTOS, is modified so that the multiprocessor system can support multitasking and multiprocessing. The performance of the proposed system is evaluated by stochastic Petri Net system modeling. The efficiency and the processing power are simulated for various load factors and up to 16 PEs. By running benchmark programs, such as quicksort, FFT, and matrix-multiplication, the speed of parallel processing is compared with that of a single processor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.268-274
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• 2008

With the advances in wireless communication technologies, mobile users require to get seamless services anywhere and anytime. To relize these demands, network interworking and vertical handover are necessary between heterogeneous wireless access technologies with multi-interface mobile station. A lot of organizations are doing research on the network integration schemes based on loosely and tightly integrated architectures, and research on vertical handover schemes mainly based on Mobile IP in loosely integrated environments. But actually, the tightly integrated scheme can support more faster vertical handover because heterogeneous access networks are combined tightly. However, vertical handover schemes in tightly integrated environments are conceptually proposed without any detail signaling procedures. Therefore, this paper defines a tightly integrated architecture between UMTS and WLAN, and proposes a soft vertical handover signaling procedure. The proposed soft vertical handover scheme is evaluated by the OPNET simulator, and we confirm the proposed scheme can support seamless services.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.264-273
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• 2005

Nowadays the integration of heterogeneous wireless networks become a hot issue in communications research area. Especiall,y, 3G and WiBro interworking will be introduced soon as users can be offered the most suitable service according to service area and service providers can reduce network construction and operation expenses. In this paper, we propose an interworking scheme for fast handoff between 3G and WiBro networks. The SCI (Smoothly Coupled Integration) scheme proposed in this paper takes advantages of the existing LCI (Loosely Coupled Integration) and TCI (Tightly Coupled Integration) scheme and can offer seamless services by providing fast handoff between 3G and WiBro although each network may work independently. Through extensive computer simulations using OPNET, the efficiency of the proposed scheme has been validated.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.677-681
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• 2009

The Smoothly Coupled Integration (SCI) proposed in this paper takes only the strength of loosely coupled integration and tightly coupled integration. Furthermore, 3G network and WiBro network, which are coupled with SCI, have independent architecture which supports mobility and seamless services by fast handoff. Computer simulation with the use of OPNET marked excellence in performance of smoothly coupled integration.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.654-659
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• 2009

As web based software has developed recently, service via web has increased gradually. For this, many research organizations and reports call web is the platform of software. While web based technologies have developed, middleware of WSN and its application service has been developed from desktop based operation system. So WSN's technology reached uppermost limit of desktop application. There's difficulty in integrating, distributing and maintaining & repairing for WSN due to a tightly-coupled structure which's related closely to the hardware of sensor nod. Unlike this, web has a loosely-coupled structure and an opened system, so web service or Rich internet application (RIA) is helpful to solve the above limits. Especially, RIA is web application but can be the platform of WSN' application because it gives us various methods to communicate with user interface similar to desktop application. In this study, I suggest Message System for WSN Using RIA, expanding WSN's interconnectedness and accessibility to internet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.913-919
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• 1999

A systematic synthesis process is presented for the design of ADSL POTS splitters. It consists of a low-pass filter formed by a single-ended inductor, balanced inductor, and balance tightly coupled transformer. This three low-pass filters has been simulation. Simulation results show agreement of frequency characteristics. Therefore, POTS splitters using a commercial balance tightly coupled transformer are designed for the applications of ADSL system. The experimental results show that POTS splitter in the ADSL system has ripple decibel of less than $\pm$0.5 dB over a frequency range from 0.2 kHz to 3.4 kHz(or an audio band frequency) and delay distortion of less than 130 $mutextrm{s}$ over a frequency range from 0.6 kHz to 3.2 kHz.

• ETRI Journal
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• v.32 no.1
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• pp.112-119
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• 2010

We present a useful design for a free access mat which supports two frequency bands of 2.4 GHz and 5 GHz. The free access mat is a sheet-shaped waveguide which consists of a tightly coupled double-layered microstrip resonator array. It provides easy access for devices in short-range wireless communications. Interference is a common problem with conventional applications which use free space transmission. Our proposed wireless access system uses a subsidiary waveguide, the free access mat. Wireless devices are proximately coupled to the free access mat through which the coupled electromagnetic (EM) wave transmits. The arrival domain of the EM wave of an application is therefore limited to an area close to the free access mat. Wireless devices can be coupled to the free access mat at an arbitrary position without contact. We previously presented a free access mat for a single frequency band. This paper presents a free access mat for the two frequency bands of 2.4 GHz and 5 GHz. The free access mat uses a ring patch resonator array which is easily excited by typical antennas and is resistant to interference. These characteristics are demonstrated by numerical simulation and confirmed by experiment.