• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.419-424
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• 2020

Poroelasticity theory has been widely used for detecting cancellous bone deterioration because of the safe use for humans. The tortuosity itself is an important indicator for ultrasound detection for bone diseases. The transport properties of cancellous bone are also important in bone mechanotransduction. In this paper, two important factors, the wave velocity and attenuation are examined for permeability (or tortuosity). The theoretical calculation for the relationship between the wave velocity (and attenuation) and permeability (or tortuosity) for cancellous bone is shown in this study. It is found that the wave along the solid phase (trabecular struts) is influenced not by tortuosity, but the wave along the fluid wave (bone fluid phase) is affected by tortuosity significantly. However, the attenuation is different that the attenuation of a fast wave has less influence than that of a slow wave because the slow wave is observed by the relative motion between the solid and fluid phases.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1149-1159
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• 2008

Since the demand for radio wave due to proliferation of radio wave communication is increased rapidly, policy for efficient use of radio wave is a challenge of sustainable research for technology development in this field with focus on service supply and distribution. Therefore, this paper analyzed and reviewed radio wave related international agreements and overseas institutions and policies, and proposed the improvement method for systematic and efficient countermeasure on radio wave management policy and system according to radio wave promotion policy circumstance changes, radio wave environmental change and technology development.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.111-116
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• 2012

Vehicular communication is one of main convergence technologies which combines information and communication technology (ICT) with vehicle and road industries. In general, vehicular communication adopts IEEE 802.11p standard which is commonly referred as wireless access in vehicular environments (WAVE). In this paper, we investigate a multi-hop communication scheme for IEEE 802.11p based communication systems which support both vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) communications. First, we briefly overview the performance of IEEE 802.11p based communication systems. Then, a multi-hop communication scheme is introduced for both broadcast and unicast. The performance of proposed scheme is presented via experimental measurements.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.544-550
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• 2009

In this paper, we proposed the radio wave propagation characteristics of the next-generation ultrafast wireless communication system in millimeter-wave fading channel. For considering doppler shift and Rayleigh fading simultaneously, the fading simulator of Jakes model implemented and analyzed the performance of the next-generation wireless communication system. In addition, the error rate characteristics of DS-CDMA system analyzed in the millimeter-wave fading channel and the system performance improved by coding technique and diversity technique.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.439-443
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• 2013

A wireless optical fiber interferometer arterial pulse wave sensor system is developed for remote sensing. The wireless optical fiber sensor system consists of Zigbee communication modules and an optical fiber interferometer arterial pulse wave sensor. The optical fiber arterial pulse wave sensor is an in-line Michelson interferometer enclosed with steel reinforcement in a heat-shrinkable tube. The Zigbee communication modules are composed of an ATmega128L microprocessor and a CC2420 Zigbee chip. The arterial pulse waves detected by the optical fiber sensor were transmitted and received via the Zigbee communication modules. The experimental results show that the wireless optical fiber sensor system can be used for monitoring the arterial pulse waves remotely.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.13-21
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• 2016

Since the direct-gradient (DG) method uses the Shack-Hartmann wave front sensor (SH-WFS), based on the phase-conjugation principle, for atmospheric compensation in free-space optical (FSO) communication, it cannot effectively correct high-order aberrations. While the stochastic parallel gradient descent (SPGD) can compensate the distorted wave front, it requires more calculations, which is sometimes undesirable for an FSO system. A hybrid compensation (HC) method is proposed by properly using the DG method and SPGD algorithm to improve the performance of FSO communication. Simulations show that this method can well compensate wave-front aberrations and upgrade the coupling efficiency with few computations, preferable correction results, and rapid convergence rate.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.943-949
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• 2009

In this paper, the 5.9GHz WAVE(Wireless Access in Vehicular Environments) channel modeling is used by the Jakes channel model for the suitability of the fast wireless channel fluctuation. The performance analysed the fading signal constellation and the spectrum in the IEEE 802.11p spectrum mask, the Doppler effect, the modulation scheme. In addition, the vehicular speed, exactly the performance analysis the WAVE communication systems follow the Doppler effect.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.8-14
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• 2020

According to the statistics provided by Korean Maritime Safety Tribunal for the year 2018, the majority of marine accidents in the past four years have occurred in fishing boats and small-sized boats. Negligent behavior resulting from not looking outside and non-compliance with navigation laws are the primary reasons behind ship collisions. Although safety education and training are reinforced to prevent such accidents, they still occur frequently. Hence, technical methods are continuously being developed to reduce ship collisions caused by human cause. The objective of this study is to reduce ship collisions by employing the WAVE communication system, which has short transmitting and receiving periods that can be incorporated for high-speed small-sized vessels. In this study, the suitability of the communication range was examined, and the appropriate range and timing for avoidance motion were accordingly selected, and a control algorithm based on the same was thereby designed. Consequently normal operation of the collision avoidance system was verified by connecting and simulating the proposed WAVE communication router-controller-steering equipment.

• Smart Structures and Systems
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• v.15 no.1
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• pp.135-150
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• 2015

Large concrete structures are prone to cracks and damages over time from human usage, weathers, and other environmental attacks such as flood, earthquakes, and hurricanes. The health of the concrete structures should be monitored regularly to ensure safety. A reliable method of real time communications can facilitate more frequent structural health monitoring (SHM) updates from hard to reach positions, enabling crack detections of embedded concrete structures as they occur to avoid catastrophic failures. By implementing an unconventional mode of communication that utilizes guided stress waves traveling along the concrete structure itself, we may be able to free structural health monitoring from costly (re-)installation of communication wires. In stress-wave communications, piezoelectric transducers can act as actuators and sensors to send and receive modulated signals carrying concrete status information. The new generation of lead zirconate titanate (PZT) based smart aggregates cause multipath propagation in the homogeneous concrete channel, which presents both an opportunity and a challenge for multiple sensors communication. We propose a time reversal based pulse position modulation (TR-PPM) communication for stress wave communication within the concrete structure to combat multipath channel dispersion. Experimental results demonstrate successful transmission and recovery of TR-PPM using stress waves. Compared with PPM, we can achieve higher data rate and longer link distance via TR-PPM. Furthermore, TR-PPM remains effective under low signal-to-noise (SNR) ratio. This work also lays the foundation for implementing multiple-input multiple-output (MIMO) stress wave communication networks in concrete channels.

• ETRI Journal
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• v.45 no.5
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• pp.781-794
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• 2023

Uncrewed aerial vehicles (UAVs) have become a vital element in nonterrestrial networks, especially with respect to 5G communication systems and beyond. The use of UAVs in support of 4G/5G base station (uncrewed aerial vehicle base station [UAV-BS]) has proven to be a practical solution for extending cellular network services to areas where conventional infrastructures are unavailable. In this study, we introduce a UAV-BS system that utilizes a high-capacity wireless backhaul operating in millimeter-wave frequency bands. This system can achieve a maximum throughput of 1.3 Gbps while delivering data at a rate of 300 Mbps, even at distances of 10 km. We also present the details of our testbed implementation alongside the performance results obtained from field tests.