• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.783-790
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• 2016

Since scarcity of spectrum in future mobile networks, millimeter wave frequencies from 30 GHz to 300 GHz have been proposed to be used in an important part of 5G mobile communication backhaul links to provide several giga bits services. In ITU-R has been invited to conduct and complete in time for WRC-19 the appropriate studies to determine the spectrum needs for the terrestrial component of IMT in the frequency range between 24.25 GHz and 86 GHz. Also, small cells such as a femtocell, and heterogeneous networks have been deployed through world in order to enhance the communication capacity. At this stage, it is important to develop millimeter wave frequencies to provide 5G mobile broadband services, and thus this paper proposes the effective usage of these frequencies by summarizing the FCC allocation of millimeter waves, their propagation characteristics, the required minimum path length, and the interference effect.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.79-86
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• 2007

In order to operate Low Earth Orbit(LEO) satellite on space, technical requirements and administrative procedure which are defined by the International Telecommunication Union(ITU) should be followed on satellite development. Main technical requirements to follow are purpose of use, bandwidth, Radio Frequency(RF) intensity, and constraints on new satellite network about existing satellite networks according to frequency spectrum. Such ITU's requirements are reflected and designed on system specification and space to ground interface control document. In order to have a right and protection about using the satellite network on space, the satellite network has to be registered on Master International Frequency Register(MIFR) and procedure for this has to be followed. Coordination with countries raising objection is needed in order to register. And reference and method for coordination are also needed.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.7-13
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• 2014

In this paper, an effect on a GPS receiver by spoofing signal is analyzed and a GPS spoofing signal detection algorithm for GPS L1 C/A spoofing signal is proposed. A proposed detection algorithm monitors the correlation function distortion by the spoofing signal. If detected distortion is over a detection threshold, we can determine that the spoofing signal is received. The detection threshold is calculated from the statistical characteristics of a thermal noise. For verifying the suggested algorithm, a MATLAB-based simulation platform is implemented. This platform has functionalities to track GPS signal and measure the correlation values. By using this platform, the correlation function distortion by spoofing signal is observed. Also a performance of the algorithm proposed in this paper is applied and confirm the detection of a spoofing signal.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.723-729
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• 2014

When the bluetooth technology of smartphone is applied to a remote control system, communication errors caused by wave attenuation and interference results in the shortening of communication distance, loss of the target device control and malfunctioning. In this study, we propose a method to adopt a retransmission persistence controlled S/W ARQ in bluetooth communication to minimize the effect of the communication failure and to detect and handle the state where the target device gets lost control. We implemented a motor-driven RC car equpped with a bluetooth communication module and a steering application program on smartphone to test the proposed method. The experiments are conducted in three communication environments, and have resulted in the increase of the communication distance by at least 30% when S/W ARQ is applied. Moreover, when the communication was disrupted due to environmental disturbances, the S/W ARQ based system stopped immediately any undergoing operations to avoid possible malfunction.

• Journal of Korea Water Resources Association
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• v.49 no.1
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• pp.51-60
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• 2016

The purpose of this study is to examine the control function of discharged flow due to the shape and plane arrangement of permeable submerged breakwater. For the discussion on it in detail, 3-dimensional numerical model based on PBM (Porous Body Model), which is able to simulate directly interaction of Fluid Permeable structure Seabed has been used to simulate water discharge in a NWT (Numerical Water Tank). To verify the applicability, LES-WASS-3D is analyzed comparing to the experimental result about propagation characteristics of dam-break wave through a permeable structure. Using the results obtained from numerical simulation, the effects of the shape and plane arrangement of submerged breakwater on reducing velocity and flow induction have been discussed related to the mean flow distribution and vertical distributions of horizontal velocities around ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.351-363
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• 2006

The 8-VSB modulation, the transmission standard for the terrestrial digital television(DTV) of the Advanced Television Systems Committee(ATSC), suffers from multipath fading because it conveys information on the amplitude. To solve this problem, decision feedback equalizers(DFE's) have been commonly used in terrestrial DTV receivers. However, under severe channels, such as a 0 dB ghost channel or a single frequency network (SFN) channel, the DFE shows unstable convergence due to the error propagation caused by decision errors. Instead of unstable time-domain DFE schemes, by proposing a frequency-domain direct-inversion equalization method, we try to guarantee stable equalization and achieve low symbol error rates. To secure the existence of a channel inverse, channel-matched filtering and noncausal filtering are carried out prior to equalization. Simulation results show that the proposed method performs much better than existing DFE schemes in terms of both the stability and the symbol error rate.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.6
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• pp.397-407
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• 2016

The traveling waves of the left and right of the detached breakwater are bent behind the detached breakwater by diffraction, causing phase interference, superimposed and propagated. If the direction of the waves becomes same and they head to the entrance of a port due to the geographical conditions, superimposed wave energy could influence inside of a port. In this study, we investigated the influence of the phase difference of the left and right diffraction waves generated according to the length of the detached breakwater on the wave heights in a port through numerical experiments when the detached breakwater at a port entrance is installed. From this result, it was confirmed that the wave heights in a port is increased or decreased by the influence of superimposed caused by the phase difference of the left and right diffraction waves due to the length of the detached breakwater.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1702-1707
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• 2010

As quantities of the data that transmitting by the wireless are more increased, the interest and application are extending about 802.11n that uses by combination two existing 20MHz wireless LAN Channel. 802.11n use dual band of 2.4GHz band and 5.8GHz. So this is expected in mass wireless transmission method because of interference evasion effect in compliance with the radio communication of existing 2GHz neighborhood band. Like this 802.11n uses the radio as well and transmits information there is not only a possibility of undergoing an influence in radio wave environment of circumference. Specially the interior environment and outdoor environment is a possibility of saying that will be defined with each other different modeling as affects in radio communication is different. In this paper, we'll compare the influence to RF feature (802.11n) by (Indoor/Outdoor) environment difference through compared with 802.11n RF feature and Network feature in (Indoor/Outdoor) environment and also examine the correlation between RF feature and Network feature.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1611-1622
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• 2011

The synchronization is one of the important issues for successful operation of femtocell. The synchronization of femtocell is distinctly different from that of larger wireless base stations in a number of important respects such as 1) The femtocell is located in indoor environment which may make it difficult to receive the adequate GNSS signals. 2) The backhaul of femtocell is connected to the public network which may have more PDV than private network. 3) The entire cost of femtocell needs to be very low. In our thesis, we investigate the candidate solutions including AGNSS (Assisted GNSS), NTP (Network Time Protocol), PTP (Precision Timing Protocol) and Cellular Network Listen for indoor timing solution. We propose the AGNSS-PTP Hybrid scheme which can improve time and frequency quality by selecting the better reference between AGNSS and PTP, and cover the standard status which are under discussion from IEEE, ITU-T, and IETF.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.313-322
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• 2003

In this paper, the reverse link performance of imperfect power controlled cdma2000 cellular system that using array at a base station is analyzed, when MCGM beamforming algorithm and power control error is considered in shadowing. The blocking probability of the cdma2000 cellular system based on array parameters, E$\_$b//N$\_$0/ and interference statistics is calculated, and then the system capacity is calculated at a specific blocking probability. When the blocking probability is set 1 %, PCE(power control error) is 2 dB, M=2, 4, 8, 10, the capacity of cdma2000 is increased 2.3 ∼ 2.5 times higher than IS-95.