• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.6-11
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• 2016

In this paper, we have analyzed the effects of co-channel, adjacent-channel, and the human shield(Body Blockage) for wideband WLAN based on the IEEE802.11n 40MHz channel bandwidth required for high speed digital signage service. Simulation results show that wideband WLAN can be operated with 78 interferers over 63m distance in co- channel, 80 interferer over 61m distance in adjacent channel. By applying the mitigation method for reducing the interference, we have confirmed that protection distance is improved to 51m using beamforming, and 40m using cognitive radio in co-channel interference. Also body blockage interference is reduced using adaptive channel bandwidth, C/I ratio, beamforming, power control mitigation methodology.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.415-419
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• 2018

This paper predicts and measures the C/N ratio of a beacon signal transmitted from geostationary orbit satellite KorSat 5A ($113^{\circ}E$) at a ground station located in Kimpo. Based on the ground stations, we compared the rain attenuation of the zone K of ITU-R and the rain attenuation which analyzed the domestic weather information. In ITU-R, the Korean rainfall characteristics are classified into zone K, but forecasting the rainfall intensity and attenuation of three adjacent cities based on the cumulative rainfall data per minute from 2013 to 2017. The calculation of rainfall path and attenuation is based on ITU-R recommendations. The change of the C/N according to the rainfall amount was confirmed through the 2 week satellite beacon signal C/N measurement. The predicted critical C/N was decreased to 12 dB at $A_{0.3}$. During the experiment, it was confirmed that it decreased up to 8 dB according to the concentrated rainfall.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.174-180
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• 2004

The World Radiocommunication Conference in year of 2000 adopted new Plans as well as Lists for BSS and its feeder-link in the Regions 1 and 3, based on the new technical criteria such as small size of antenna and low satellite power. Since the new Plans and Lists were based on new technical criteria, ITU was requested to review the relevant regulatory procedures and sharing criteria of broadcasting satellite networks contained in Appendices 30 and 30A of Radio Regulations. Korean BSS network at 116$^{\circ}$E was chosen for the study and ITU S/W (MSPACEG) was used. We analyzed the interference effects from adjacent BSS networks to Korean BSS network using parameters of an antenna diameter and polarization of receiving earth station. The analysis shows that it is difficult to co-operate BSS networks both at 116$^{\circ}$E and 113$^{\circ}$E, however, it is possible to use small antenna (i.e. 45cm) in frequency sharing among BSS networks with 6$^{\circ}$ orbital separation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.757-766
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• 2014

To compensate signal loss due to the channel blockage in satellite communication link, we propose a cooperative communication scheme for OTM(On-The-Move) terminal in next generation satellite communication systems. The proposed scheme configures cooperation subnet with adjacent OTM terminal with the help of ground communication equipment. Shared data is spread by orthogonal spreading code, then the spread sequences are transmitted simultaneously. The receiver combines the power of received signals by EGC(Equal gain combining). The OTM terminal blockage channel is modeled by 2-state Markov chain. We evaluate the bit error rate according to the blockage channel of the channel state for the performance analysis of the proposed scheme. As a result, the proposed scheme shows better BER performance than traditional scheme with the help of subset members. In particular, the proposed scheme shows superior performance as the channel block probability is higher. However, as the number of subset members is increasing, there is a constraint because of the higher multiple access interference.

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.312-318
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• 2006

WRC-2000 allowed HAPS to provide IMT-2000 service in the bands 1885-1980 MHz, 2010-2025 MHz and 2110-2170 MHz which have been utilized by the conventional terrestrial IMT-2000 service. In this paper, we analyze the interference effects from HAPS into terrestrial IMT-2000 system in adjacent band. To do this, in this paper, we have analyzed the interference and the sharing criteria between HAPS and the conventional terrestrial/satellite mobile system by considering the service and system requirements, the specification of system and developing the interference scenarios and the analysis algorithms.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.32-36
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• 2011

In this paper, we propose a cancellation scheme of multiple access interference (MAI), which is caused by carrier frequency offset, for the receiver of an interleaved orthogonal frequency division multiple access (IFDMA) uplink system. In the IFDMA systems, carrier frequency offsets introduce adjacent channel interference from other users' subcarriers, which results in performance degradation. In the proposed method, we compensate the carrier frequency offset in time domain and then eliminate MAI by using parallel interference cancellation in frequency domain. Simulation results show that the proposed method is effective in removing the MAI especially when the number of users are large and the MAI severely degrades the system performance.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.29-32
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• 2015

It has been a big trend of the convergence technologies about communication systems and vehicular industry to improve safety and convenience. To achieve a number of infotainment vehicular applications, vehicles should transmit information with high reliability. A robust and accurate channel estimation scheme is of great importance to achieve the goal. In this paper, we present a novel enhanced decision-directed channel estimation scheme called FADP (Frequency Averaging Data Pilot) for dynamic time-varying vehicular channels in IEEE 802.11p. We use linear averaging filtering in frequency domain, and utilize the correlation characteristic of the channels between the adjacent two data symbols, update the CR in time domain to get more accuracy. Finally, analysis and simulation results reveal that compared with exist schemes, the proposed scheme has a good performance in mean square error (MSE) and bit error rate (BER).

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.130-136
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• 2015

In this paper, we analyzed the adjacent channel interference of the LTE band 40 defined by 3GPP on the WLAN system based on the Monte-Carlo method, and found the guard band required for compatibility between the two systems. This study have a difference compared to the previous studies about cell radius was determined using Extended Hata Model considering practical environment, interference protection distance related to guard band, and the spectrum emission mask improvement effect for minimizing the interference. Simulation results, for no channel interference compatibility of LTE and WLAN for mobile satellite wireless package system, we can find the need 15MHz guard band at specified spectrum emission mask and 10MHz guard band at assumed spectrum emission mask.

• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.41-48
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• 2021

In this paper, we will discuss techniques that can increase the resolution by 1.4 times without distortion or performance degradation of the original image, using diagonal information of the image. The applied method is to use the image information of 4 adjacent points without actual rotating the image by 45 degrees and enlarge and rearrange it according to the characteristics of the camera, so that the same physical concept as the actual 45 degrees can be applied. This is a concrete realization method that can improve the resolution by 1.4 times without deterioration of performance and a demonstration of this result.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.417-425
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• 2006

This Paper Proposes a method of building a panoramic video from several videos captured from adjacent cameras. The panoramic image which constructed from adjacent and overlapped images is used for photogrammetry, satellite photo or many computer graphic applications. The perspective transformation, which is estimated from the appropriate corresponding pairs of images, can be used to construct the panoramic image without unwarranted distortion and its quality is decided by how to find the features needed for transform estimation. We used the corner points for the corresponding features, and morphological structures were utilized for fast and robust corner detection. We used the criterion of the corner strength, which guarantees the robust detection of the corner in most situations. For the transformation, 8 parameters were estimated from perspective equations which use matched points of adjacent images, and bilinear color blending was used to construct a soapless panoramic video. The experiments showed that the proposed method yields fast results with good quality under various conditions.