• 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.

• ETRI Journal
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• v.42 no.6
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• pp.827-836
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• 2020

Measuring the diffraction loss for high frequencies, long distances, and large diffraction angles is difficult because of the high path loss. Securing a well-controlled environment to avoid reflected waves also makes long-range diffraction measurements challenging. Thus, the prediction of diffraction loss at millimeter-wave frequency bands relies on theoretical models, such as the knife-edge diffraction (KED) and geometrical theory of diffraction (GTD) models; however, these models produce different diffraction losses even under the same environment. Our observations revealed that the KED model underestimated the diffraction loss in a large Fresnel-Kirchhoff diffraction parameter environment. We collected power-delay profiles when millimeter waves propagated over a building rooftop at millimeter-wave frequency bands and calculated the diffraction losses from the measurements while eliminating the multipath effects. Comparisons between the measurements and the KED and GTD diffraction-loss models are shown. Based on the measurements, an approximation model is also proposed that provides a simple method for calculating the diffraction loss using geometrical parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.122-125
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• 2005

This study is an measurement and prediction of transmission loss through dash panel with multi-path in a vehicle. Measurement results of transmission loss are derided by sound power measured using the sound intensity method under locating a sound source in the anechoic room and reverberant room, respectively. Prediction one is decided by multi-path analysis of dash panel composed by a various part of materials and complicated shape. Finally, two results show a great agreement between measured and predicted transmission loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.410-418
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• 2000

In this paper, path losses in millimeter-wave band for different propagation environments are measured, and the results are analyzed by modeling the median, maximum, and minimum values of the measurement data for each site, which are recorded for 5 minutes, with a linear regression model. The measurement data shows that in urban and suburban environments, extra path loss must be taken into account for line-of-sight path, even in millimeter wave band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9B
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• pp.563-568
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• 2007

This paper proposes a routing establishment method for improving path stability in mobile ad-hoc networks. In mobile ad-hoc networks, the network topology is highly dynamic due to the node mobility unlike wired networks. Since the existing methods are based on the shortest path algorithm with the minimum hop count regardless of the path stability, it could lead to packet loss and path disconnection in mobile ad-hoc networks. In particular, if control packets and critical data are transmitted on the unstable path, it causes serious problems. Therefore, this paper proposes one approach in order to minimize packet loss and path disconnection by considering the node mobility. After the destination node receives multiple RREQ messages, it selects the stable path through the proposed MinMax algorithm according to the node speed.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.679-685
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• 2002

Low-frequency mono-static reverberation model for shallow-water environment is presented. It is necessary to develop the transmission loss model to calculate the sub-bottom interaction because the ray-based transmission loss model is difficult to compute the pressure accurately which penetrates the bottom medium. In this paper reverberation level is calculated using the RAM (Range dependent Acoustic Model) to augment the multi-path expansion model because it does not estimate transmission loss accurately in shallow water. The signals generated by the L-HYREV and the GSM are compared with the observed signals and it is showed that the L-HYREV model provides a closer fit to the observed signals than those obtained using the GSM.

• Journal of Convergence Society for SMB
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• v.4 no.2
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• pp.7-12
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• 2014

In this study, we present the investigation results using a 3D radio wave propagation simulator in indoor environments. Previous studies treat only the path loss between the transmitter and receiver in 2D geometry. We provide the simulation results of indoor propagation prediction based on various ITU-R Recommendations. Simulation results compared here indicate that 150MHz and 2GHz frequency bands give quite different characteristics in presented indoor geometry. Since the field intensity is affected by the loss at the wall, the transmitting power level is one of the key factor for receiving power.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.6
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• pp.1063-1079
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• 2010

Vehicle ad hoc networks (VANET) are one of the most important technologies to provide various ITS services. While VANET requires rapid and reliable transmission, packet transmission in VANET is unstable because of high mobility. Many routing protocols have been proposed and assessed to improve the efficiency of VANET. However, topology-based routing protocols generate heavy overhead and long delay, and position-based routing protocols have frequent packet loss due to inaccurate node position. In this paper, we propose a position-based routing repair algorithm to improve the efficiency of VANET. This algorithm is proposed based on the premise that AODV (-PGB) can be used effectively in VANET, if the discovery, maintenance and repair mechanism of AODV is optimized for the features of VANET. The main focus of this algorithm is that the relay node can determine whether its alternative node exits and judge whether the routing path is disconnected. If the relay node is about to swerve from the routing path in a multi-hop network, the node recognizes the possibility of path loss based on a defined critical domain. The node then transmits a handover packet to the next hop node, alternative nodes and previous node. The next node repairs the alternative path before path loss occurs to maintain connectivity and provide seamless service. We simulated protocols using both the ideal traffic model and the realistic traffic model to assess the proposed algorithm. The result shows that the protocols that include the proposed algorithm have fewer path losses, lower overhead, shorter delay and higher data throughput compared with other protocols in VANET.

• Journal of the Korea Computer Graphics Society
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• v.24 no.5
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• pp.21-30
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• 2018

In this paper, we use Sound-tracing, a 3D sound technology based on ray-tracing that uses geometric method as auditory technology to enhance realism. The Sound-tracing is costly in the sound propagation stage. In order to reduce the sound propagation cost, we propose a method to calculate the average effective frame number of previous frames using the frame coherence property and to adjust the depth according to the space based on the calculated number. Experimental results show that the path loss rate is 0.72% and the traversal & Intersection test calculation amount is decreased by 85.13% and the frame rate is increased by 4.48% when the sound source is indoors, compared with the result of the case without depth control. When the sound source was outdoors, the path loss was 0% and the traversal & Intersection test calculation amount is decreased by 25.01% and the frame rate increased by 7.85%. This allowed the rendering performance to be increased while minimizing the path loss rate.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.169-172
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• 1998

A 3D-ray tracing using triangular ray tubes for predicting propagation in indoor environments is presented. Employed ray tracing scheme needs no reception sphere often suffered from how to assign the correct radius as a touching ray on the receiver. To verify the developed codes path loss for a rectangular corridor has been computed, measured, and compared with those by image methods, all shows good agreement to each other. Discussions are made on the path loss fluctuations along the distance in a rectangular corridor having a conducting knife.