• Journal of Positioning, Navigation, and Timing
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• v.8 no.1
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• pp.1-12
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• 2019

In this paper, we implement a navigation software of a Global Navigation Satellite System (GNSS) receiver based on a commercial purpose GNSS software receiver platform and verify its performance by performing experimental tests for various GNSS signals available in Korea region. The SX3, employed in this paper, is composed of an application program and a Radio Frequency (RF) frontend, and can capture and process multi-constellation and multi-frequency GNSS signals. All the signal processing procedure of SX3 is accessible by the receiver software designer. In particular for an easy research and development, the Application Programing Interface (API) of the SX3 has a flexible architecture to upgrade or change the existing software program, equipped with a real-time monitoring function to monitor all the API executions. Users can easily apply and experiment with the developed algorithms using a form of Dynamic Link Library (DLL) files. Thus, by utilizing this flexible architecture, the cost and effort to develop a GNSS receiver can be greatly reduced.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.80-84
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• 2007

In this paper, the introductory study of the multi input multi output (MIMO) techniques for satellite communication systems is presented. Because of the advantage of wide coverage of satellite, it has been considered for broadcasting services and fill-in services. On the other hand, state of the art multi input multi output (MIMO) techniques such as space time code (STC) and spatial multiplexing (SM) makes the terrestrial system increase link performance and their coverage, and also increase the link throughput. For these regard, in order to satisfy the requirements of the next generation communications and coexists with terrestrial systems harmoniously, the studying about satellite MIMO techniques is necessary. In this paper, we introduce some system model and scenarios to apply MIMO technique to intermediate module repeater (IMR). The possibility of these techniques and technical requirements are also considered. Especially, Space time code is used to enhance IMRs coverage and increase the link performance, and space time multiplexing is utilized to multiplex satellite broadcasting signals with local broadcasting signal in IMR cell.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.305-308
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• 2004

In this paper, we analyze system level and link level performance for MB-OFDM UWB system. we propose physical layer model of MB-OFDM UWB system in MBOA. For this analysis, Base-band channel model from IEEE 802.15 3a was adopted. we considered the channel index parameter to select any one of 100 distinct realizations provided by the IEEE working group. Our experimental results indicate BER values according to Es/No.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.573-581
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• 2004

A self-contained wall climbing robot, called MRWALLSPECT (Multi-functional Robot for WALL inSPECTion) II, is developed. It is designed for scanning external surfaces of gas or oil tanks with small curvature in order to find defects. The robot contains all the components for navigation in itself without any external tether cable. Although it takes the basic structure of the sliding body mechanism, the robot has its original characteristic features in the kinematic design with closed link mechanism, which is enabled by adopting a simple and robust gait pattern mimicking a biological system. By employing the proposed link mechanism, the number of actuators is reduced and high force-to-weight ratio is achieved. This paper describes its mechanism design and the overall features including hardware and software components. Also, the preliminary results of experiments are given for evaluating its performances.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.1
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• pp.45-54
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• 1993

Monitoring processor in a circuit switched network is considered. Monitoring processor monitors communication links offers a grade of service in each link to controller. Such an information is useful for an effective maintenance of system. Two links with asymmetric system parameters and multi-symmetric links are respectively considered. Each links is to be an independent M /M/ 1/ 1/ type. Markov modeling technique is used to represent a model of monitoring processor with FCFS steering protocol. Performance measures considered are ratio of monitored jobs in each link, availability of minitoring processor and throughput of virtual processor in each link. The value of the performance meausres are compared with existing and simulation results.

• Journal of information and communication convergence engineering
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• v.5 no.4
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• pp.328-332
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• 2007

The structure of MMSE receiver frontended by CMA array working in CDMA forward link is proposed. By using the despreaded pilot signal of forward link as a reference signal, CMA array can capture multi-path signals securely even in severely faded mobile channel. The remaining MAl (Multiple Access Interference) is cancelled by the cascaded MMSE receiver. Through computer simulation, it is proved that the proposed system shows much better BER performance than any other systems. As a mobile based spatio-temporal receiver, the proposed system also reduces implemental cost and complexity by adopting the simplest algorithm for its spatial and temporal domain processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3183-3195
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• 1996

As a method for effective utilization of the limited power and frequency resources in satellite communications, this paper develops software which can assigns the optimal power of input carrier groups inthe multi-level SCPC systems and performs evaluation to a various satellite link environment. Using the developed software, the paper presents performance according to the frequency plan of carrier groups and suggest a frequency play method for performance improvement of satellite link. A various interference and noise caused by satellite link are analyzed for reliable performance evaluation. The performance criteria for evaluation is classified into 2 categories according to the CNR of destination receiver earth station.

• Journal of Communications and Networks
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• v.18 no.6
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• pp.884-891
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• 2016

The wireless mesh network (WMN) has attracted significant interests as a broadband wireless network to provide ubiquitous wireless access for broadband services. Especially with incorporating multiple orthogonal channels and multiple directional antennas into the WMN, each node can communicate with its neighbor nodes simultaneously without interference between them. However, as we allow more freedom, we need a more sophisticated algorithm to fully utilize it and developing such an algorithm is not easy in general. In this paper, we study a joint channel assignment, link scheduling, routing, and rate control problem for the WMN with multiple orthogonal channels and multiple directional antennas. This problem is inherently hard to solve, since the problem is formulated as a mixed integer nonlinear problem (MINLP). However, despite of its inherent difficulty, we develop an algorithm to solve the problem by using the generalized Benders decomposition approach [2]. The simulation results show the proposed algorithm provides the optimal solution to maximize the network utility, which is defined as the sum of utilities of all sessions.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.46-47
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• 2015

본 논문은 태양광 발전 시스템의 차동 전력 조절 방식 중 Feed-Foward 방식을 적용한 다중 출력 플라이백 컨버터를 이용하여 DC_Link 다중 출력 전압을 균등화 하는 회로에 대한 내용이다. DC_Link가 여러 단으로 되어 있을 경우, 전압을 일정하게 맞추어 줄 필요가 있는데, 이를 차동 전력 조절기(Differential Power Processing converter)를 통해서 DC_Link 출력 전압을 균등화 할 수 있다. 스트링 컨버터인 부스트 컨버터의 스트링 전류를 제어 하여 부스트 컨버터의 전력과 DPP역할을 하는 다중 출력 플라이백 컨버터로 전달되는 전력을 조정가능하다. 이를 통하여 전압 균등화가 이루어지게 할 수 있고, 각 DPP 컨버터는 PV 전압 제어를 하여 MPPT 동작을 하게 된다. PSIM 시뮬레이션과 150W급 하드웨어 프로토타입을 제작해 실험을 통하여 검증 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.142-145
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• 2011

무기체계의 상호운용성 측면에서 전술데이터링크는 전장정보를 공유하기 위한 필수 요소이다. 또한 비용 절감을 위해 M&S 활용이 증가됨에 따라 다중 전술데이터링크 연동이 가능한 체계 시뮬레이터가 필요하다. 그래서 M&S 장비로써 전술데이터링크인 Link-11B와 ATDL-1 연동이 가능한 다중 전술데이터링크 체계 시뮬레이터를 제안한다. 이것은 Link-11B와 ATDL-1 전술데이터링크간 정보 전달을 가능하게 하며 M&S의 표준 인터페이스인 HLA/RTI와의 연동을 통해 상호운용성을 보장한다.