• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.211-215
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• 1997

Localized communication networks for office automation, security monitoring, environmental management of buildings, computer communications, and other applications enjoy every increasing demand. This paper proposes a direct sequence spread spectrum communication system for use in power line data transmission. Advantages of power distribution circuits include reasonably universal coverage and easy access vis a standard wall plug. Disadvantages include limited communication bandwidth, relatively high noise levels, and varying levels of impedance, noise, and attenuation. Spread spectrum signalling provides immunity to narrow-band signal impairments and multiplexing capability. Our prototype power line communication module supports completely physical and data link layers based on the international standard ISO 10368 for reliable high-speed power line communication system. Moreover it provides useful functions to compose a plant monitoring and control system. All the circuits of the communication module are included in one compact circuit. Thus a functional communication system for the power line plant monitoring and control is implemented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1884-1885
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• 2011

In the wireless sensor network (WSN) environment, the approximate point-in-triangulation (APIT) is a kind of range-free localization algorithm. This algorithm provides high precision, however, the coverage rate is somewhat poor. In this paper, we propose an improved APIT algorithm for the localization of swarm robots, which is based on the received signal strength indicator (RSSI) and the center of gravity (COG) methods.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2003년도 춘계종합학술대회논문집
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• pp.245-250
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• 2003

Of all wireless technologies for personal communications, CDMA(Code Devision Multiple Access) offers the best combination of good signal quality, high security and system reliability. CDMA2000 provides Internet and internet services for variable multimedia aplications. However, good educational CDMA web contents, which focus on the easy understability and good readability, are rare dute to the difficulties and the broad range of CDMA technologies. This content is developed based upon the following two aspects. First, a basic CDMA communication theoy, which contains much color figures and animation, is introduced combing the experimental results and corresponding explanations utilizing the information obtained by the TIMS CDMA equitments. It can improve the understabiliy virtual experience of the site visitors interested in the CDMA. Secondly, the recent CDMA coverage prediction and engineering technology is introduced using the RF plan tool C24 combined for the CDMA engineers

• Journal of Positioning, Navigation, and Timing
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• 제9권3호
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• pp.249-259
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• 2020

China has deployed BDS along with the service of SBAS by 2020. Currently, the correction information for testing BDSBAS is provided through the BDS B1I signal. Many research on SBAS other than BDSBAS has been conducted in Korea. However, studies on BDSBAS are insufficient although Korea is included in both the coverage area of MSAS and BDSBAS. Therefore, it is necessary to continuously analyze the performance of MSAS and BDSBAS. In this paper, the performance of MSAS and BDSBAS in Korea, China, and Japan is analyzed in the aspect of positioning accuracy using the GNSS RINEX data provided by IGS. A Software platform is designed to analyze the performance of GPS-only, BDS-only, GPS/MSAS and BDS/BDSBAS. From the result, it can be concluded that the accuracy enhancement can be hardly seen when using the correction information of MSAS and BDSBAS in Korea

• 한국통신학회논문지
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• 제33권4A호
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• pp.361-370
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• 2008

Cooperative relaying permits one or more relay to transmit a signal from the source to the destination, thereby increasing network coverage and spectral efficiency. The performance of cooperative relaying is often measured as outage probability. However, appropriate measure for the channel quality is outage capacity. Although the outage probability for cooperative relaying protocol has been analyzed before, very little research has been addressed for the outage capacity. This paper is the first of its kind to derive a closed-form analytical solution of outage capacity using fixed decode and forward relaying and amplify and forward relaying in dissimilar Rayleigh fading channels, considering channel coefficients known to the receiver side. The analytical results show a tradeoff between the SNR and the number of relays for specific outage capacity. A comparison between decode and forward relaying and amplify and forward relaying shows that decode and forward relaying outperforms amplify and forward relaying for a large number of relays.

• 천문학회보
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• 제42권2호
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• pp.59.2-59.2
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• 2017

The Submillimeter Array (SMA) has provided forefront capabilities for high spatial and spectral resolution observations at submillimeter wavelengths from its excellent site on Mauna Kea, Hawaii since 2004. The SMA has continuously enhanced its capability. It is now equipped with two receivers in the 1.3 mm band (Rx230/Rx240) and two in the 0.85 mm band (Rx345/Rx400). The total bandwidth available is 8+8 GHz (per receiver) in the dual band or polarization mode. To maintain a leading role in the ALMA era, the SMA project is now upgrading its receivers, IF signal transport and correlator system. The new wideband SMA - the wSMA - will provide the instantaneous coverage of 56 GHz. In this presentation, I will introduce the latest status of the SMA, upgrade plan to the w-SMA, the possible science cases with the w-SMA, and the roles of the w-SMA in the ALMA era.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.809-812
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• 1999

This paper presents the radio propagation effects in the shadow region due to the presence of obstacle, like building and tree, along the path at the B-WLL band. Using the Uniform Theory of Diffraction(UTD), the total field was obtained as the sum of contributions with diffraction ray from the each obstacle's edge, the direct ray, and the reflected rays from ground. The normalized signal level(in ㏈) is calculated with the parameters of the base station elevation and the distance between obstacle and receiver. This results are used to provide the suitable radio cell planning and coverage prediction in the area of shadow region.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4453-4468
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• 2015

This paper investigates optimization-based base station (BS) placement. An optimization model is defined and the BS placement problem is transformed to a lexicographical stratified programming (LSP) model for a given trajectory, according to different accuracy requirements. The feasible region for BS deployment is obtained from the positioning system requirement, which is also solved with signal coverage problem in BS placement. The LSP mathematical model is formulated with the average geometric dilution of precision (GDOP) as the criterion. To achieve an optimization solution, a tolerant factor based complete stratified series approach and grid searching method are utilized to obtain the possible optimal BS placement. Because of the LSP model utilization, the proposed algorithm has wider application scenarios with different accuracy requirements over different trajectory segments. Simulation results demonstrate that the proposed algorithm has better BS placement result than existing approaches for a given trajectory.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.121-124
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• 2000

In this paper, we evaluate the interference statistics between the competiting wideband CDMA systems, and optimize the frequency coordination between Wideband-CDMA systems by the Monte-Carlo methodology. We develop the simulator to analyze the radio interference between CDMA systems. It can calculate or estimate the probability of interference from adjacent frequency band, which is also power controlled. We simulate the interference effects between two Wideband CDMA systems. We present the required carrier distance and zone for two operators to meet the required coverage efficiency and outage probability of Signal to interference plus noise ration (SINR).

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.359-362
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• 2000

In this paper, we propose a test pattern generation algorithm on the basis of the identification of undetectable faults for Speed-Independent(SI) asynchronous control circuits. The proposed methodology generates tests from the specification of a target circuit, which describes the behavior of the circuit in the form of Signal Transition Graph (STG). The proposed identification method uses only topological information of a target circuit and reachability information of a fault-free circuit, which is generated in the form of Binary Decision Diagram(BDD) during pre-processing. Experimental results show that high fault coverage over single input stuck-at fault model is obtained for several synthesized SI circuits and the use of the identification process as a preprocessing decreases execution time of the proposed test generation with negligible costs.