• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.688-693
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• 2022

In this paper, channel propagation path loss was measured in building corridors for frequency bands of 3.7 GHz and 28 GHz, which are used in 5G mobile communication, and compared and analyzed with CI (Close-In) and FI (Floating-Intercept) channel models. To measure the propagation path loss, the measurement was performed while moving the receiver (Rx) from the transmitter (Tx) by 10 m. As a result of the measurement, the PLE (Path Loss Exponent) values of the CI model at 3.7 GHz and 28 GHz were 1.5293 and 1.7795, respectively, and the standard deviations were analyzed as 9.1606 and 8.5803, respectively. In the FI model, 𝛼 values were 79.5269 and 70.2012, 𝛽 values were -0.6082 and 1.2517, respectively, and the standard deviations were 5.8113 and 4.4810, respectively. In the analysis results through the CI model and the FI model, the standard deviation of the FI model is smaller than that of the CI model, so it can be seen that the FI model is similar to the actual measurement result.

• ETRI Journal
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• v.38 no.6
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• pp.1031-1041
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• 2016

This paper presents millimeter-wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub-6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close-in free space model and the alpha-beta-gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.950-961
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• 2004

In this paper, we measured and analyzed propagation characteristics in a subway tunnel that is recently increasingly becoming one of the radio communication environments. The measurements are carried out in a subway tunnel with frequency bands of 2.45㎓ and 5.8㎓. The length of tunnel we used for this study is 175m of LOS (Line-of-sight) and 270m of NLOS (Non Line-of-Sight). The subway tunnel is curved and its cross section is horseshoe type. The measurement systems we employ in this study are a narrow-band system and a wide-band system. The narrow-band system is used to get path loss measurement and the wide-band system is used to figure out delay profile measurement. In particular, the wide-band system consists of 1023 length PN sequence generator using a chip rate of 80MHz based on a sliding correlation technique. The omni-directional antennas and directional antennas are used to analyze propagation characteristics for beam type of antenna. The path loss displays only pure path loss of a tunnel environment. The delay profile indicates the mean excess delay and RMS (root mean square) delay spread.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.322-325
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• 2003

In this paper, path loss characteristics in a curved subway tunnel are measured and analyzed. The measurement is carried out in the frequency bands of 2.45GHz and 5.8GHz. A directional antenna is employed for transmission and an omnidirectional antenna for reception. This measurement is performed in the subway tunnel in the vicinity of the Daejon station. The tunnel is curved and its cross section is arch-shaped. The path loss is measured with the location of the transmitter antenna fixed and the receiver antenna moving in the tunnel. The measured path loss ratio is about 0.1dBm/m. Also, the signal received from the antenna located on the outer side of curve in the tunnel experiences weaker path loss.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.736-738
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• 2014

The paper deals with the accuracy comparison between two kinds of ultrasonic paths for flow rate measurement. In the Z-path, two transducers are installed on the opposite side of each other on a pipe, and the ultrasonic waves generated of one transducer propagate and arrive at the other one only through refraction. In the V-path, two transducers are installed on one side of a pipe, and the ultrasonic waves reflected at the inner wall of the pipe are received. The backgrounds were established to select one path to fit the usage by considering the advantages and disadvantages.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.861-862
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• 2011

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.3
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• pp.123-137
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• 1993

In this paper, an integrated approach is proposed to generate gouging-free Cartesian tool paths for machining sculptured surfaces from 3D measurement data. The integrated CAD/CAM system consists of two modules : offset surface module an Carteian tool path module. The offset surface module generates an offset surface of an object from its 3D measurement data, using an offsetting method and a surface fitting method. The offsetting is based on the idea that the envelope of an inversed tool generates an offset surface without self-intersection as the center of the inversed tool moves along on the surface of an object. The surface-fitting is the process of constructing a compact representation to model the surface of an object based on a fairly large number of data points. The resulting offset surtace is a composite Bezier surface without self-intersection. When an appropriate tool-approach direction is selected, the tool path module generates the Cartesian tool paths while the deviation of the tool paths from the surface stays within the user-specified tolerance. The tool path module is a two-step process. The first step adaptively subdivides the offset surface into subpatches until the thickness of each subpatch is small enough to satisfy the user-defined tolerance. The second step generates the Cartesian tool paths by calculating the intersection of the slicing planes and the adaptively subdivided subpatches. This tool path generation approach generates the gouging-free Cartesian CL tool paths, and optimizes the cutter movements by minimizing the number of interpolated points.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.71-77
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• 1996

This paper describes the development of on the machine measuring(OMM) system which can directlry measure the three dimensional machined dimensilnal accuracy using scanning probe in milling machine. Two algolithms, continuous path(CP) measurement using UC program and CAD data assisted point to point(PTP) measurement, were developed regarding specification of scanning probe. The OMM system was contructed to verify the developed system suing the proposed algorithm, and actually measured three kinds of machined TV shadow mask molds. The developed system was evaluated it's repeatability and compared with the current measurement system of CMM(Coording Measuring Machine) in terms of relative accuracy and time reduction and productivity increase.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.539-546
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• 2004

An improved low coherence interferometer system and a new analysis method for the accurate measurement of the optical path difference error of an AWG (Arrayed-Waveguide Grating) are described. The use of software simplifies the experimental setup by eliminating the hardware (clock generator). In addition, the actual distances between the peak positions of the adjacent interference signals are calculated using interpolation methods. The wavelength transmission characteristics of the AWG are calculated assuming the measured phase errors. The calculated AWG characteristic is quite similar to the actual measurement result, confirming accuracy of the proposed measurement setup.

• IE interfaces
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• v.24 no.4
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• pp.304-313
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• 2011

An Unmanned Aerial Vehicle(UAV) is a powered pilotless aircraft, which is controlled remotely or autonomously. UAVs are currently employed in many military missions(surveillance, reconnaissance, communication relay, targeting, strike etc.) and a number of civilian applications(communication service, broadcast service, traffic control support, monitoring, measurement etc.). For accomplishing the UAV's missions, guarantee of survivability should be preceded. The main objective of this study is the path planning to maximize survivability for UAV based on 3-dimensional environment. A mathematical programming model is suggested by using MRPP(Most Reliable Path Problem) and solved by transforming MRPP into SPP(Shortest Path Problem). This study also suggests a $A^*PS$ algorithm based on 3-dimensional environment to UAV's path planning. According to comparison result of the suggested algorithm and SPP algorithms (Dijkstra, $A^*$ algorithm), the suggested algorithm gives better solution than SPP algorithms.