• Journal of Korea Multimedia Society
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• v.9 no.6
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• pp.728-734
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• 2006

Carrier interferometry code is considered as a promising scheme that provides significant performance improvement via frequency diversity effect. Space-time coding is commonly employed to achieve a performance gain through space diversity. The combination of these techniques and forward error correction coding will lead to enhanced system capacity and performance. This paper presents a low-density parity check (LDPC) coded space-time orthogonal frequency division multiplexing (OFDM) transmission scheme with carrier interferometry code for high-capacity and high-performance mobile multimedia communications. Computer simulations demonstrate that the proposed mobile multimedia transmission system offers a considerable performance improvement of approximately 9dB in terms of Eb/No in the Rayleigh fading channel with relatively low delay spread, in comparison with space-time OFDM. Performance gains are further increased, comparing with traditional OFDM systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1643-1648
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• 2005

MIMO system takes advantage of the spatial diversity obtained by spatially separated antennas for high- performance and high-capacity broadband wireless access. In this paper, we propose Carrier Interferometry coded MIMO-OFDM system (MIMO-CI/OFDM) which provides frequency and spatial diversity. One combined diversity gains featly improve the performance of OFDM systems. To perform a performance analysis, we have used SPW platform that provides an easy tool to analyze the performance. The results show that the performance of MIMO-CI/OFDM shows an approximately 4dB gain over the MIMO-OFDM even in highly frequency selective fading channels.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.6-16
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• 2010

Since OFDM system suffers from high peak-to average power ratio(PAPR) drawbacks, more energy has been converted to seek for a new substitutable system which can maintain OFDM system's inherent virtues while avoid its defects. Consequently, a new multicarrier system called as CI/OFDM system has been proposed which applied carrier interferometry(CI) code to OFDM system. Due to its low PAPR advantage and orthogonal property, it has received more and more attention. Simultaneously, an old technique called single carrier(SC) system has retaken its attractions for the same purposes. This paper analyzes two cyclic prefixed transmission schemes variants of OFDM system: 1.carrier interferometry-Orthogonal Frequency-Division Multiplexing (CI/OFDM); 2. Cyclic prefixed single carrie(CP-SC) with frequency domain equalization. We compare the achievable bit rate transmission of the two systems in terms of signal to noise ratio(SNR) by mathematical derivation. We demonstrated that CI/OFDM achieves a bit higher transmission bit rate to that of the CP-SC with frequency domain equalizer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8A
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• pp.794-801
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• 2007

In this paper, in order to enhance the performance improvements of both BER and PAPR characteristic for the conventional OFDM system, both circularly polarized waves and carrier interferometry signals which shows the robustic fading reduction effect are applied to the system, and then the performance of the proposed system has been evaluated by computer simulation. From the analysis, it can be seen that the system BER performance can be improved by 2 or 3 dB. Furthermore, it can be also seen that the PAPR characteristic can be markedly reduced.

• Journal of information and communication convergence engineering
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• v.2 no.1
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• pp.5-8
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• 2004

DS-COMA is now a matured multiple access technology that utilizes spreading codes for user separation. In this paper, we attempt to improve the performance of a multiuser DS-COMA system with a unique chip shaping code called Carrier Interferometry (CI) code. The CI codes exhibit an excellent correlation property that can be used in many applications. In DS-COMA with CI codes (CI/DS-COMA), the symbols are spread by a spreading code and then the chip signals are shaped using a CI code. Due to the correlation property of the CI code, a diversity gain from the shaped chip signals is achieved and the performance of DS-COMA is significantly improved. Comparison study demonstrates that the DS-COMA with CI outperforms the conventional DS-COMA system in multiuser environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.378-383
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• 2004

Orthogonal Frequency Division Multiplexing (OFDM) transmits high-speed data by splitting the transmission bandwidth into a number of subcarriers. The bandwidth of each subcarrier is ensured to be smaller than the coherence bandwidth. This paper presents an OFDM system incorporated with the Carrier Interferometry (CI) codes to improve the performance by enhancing frequency diversity effect. The performances of CI-OFDM with multilevel modulations are investigated in highly dispersive fading channels. For the investigation of performance improvement of CI-OFDM, a simulator has been developed using a well-known SPW simulation platform. The simulation results show that the CI-OFDM provides both performance improvement and robustness against dispersive fading channel behavior. The performance of CI-OFBM with multilevel modulations demonstrates that CI-OFDM outperforms a traditional OFDM system, particularly in highly dispersive channels. With a relatively large delay spread of 151㎱ compared to the guard interval of 800㎱, CI-OFDM provides a BER of 10$^{-3}$ if sufficient signal power is present.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Korean Journal of Remote Sensing
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• v.36 no.2_2
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• pp.351-363
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• 2020

It is well known that alluvial sediment located in coastal region has been easily affected by geohazard like ground subsidence, marine or meteorological disasters which threaten invaluable lives and properties. The subsidence is a sinking of the ground due to underground material movement that mostly related to soil compaction by water extraction. Thus, continuous monitoring is essential to protect possible damage from the ground subsidence in the coastal region. Radar interferometric application has been widely used to estimate surface displacement from phase information of synthetic aperture radar (SAR). Thanks to advanced SAR technique like the Small BAseline Subset (SBAS), a time-series of surface displacement could be successfully calculated with a large amount of SAR observations (>20). Because the ALOS-2 PALSAR-2 L-band observations maintain higher coherence compared with other shorter wavelength like X- or C-band, it has been regarded as one of the best resources for Earth science. However, the number of ALOS-2 PALSAR-2 observations might be not enough for the SBAS application due to its global monitoring observation scenario. Unfortunately, the number of the ALOS-2 PALSAR-2 Stripmap images in area of our interest, Busan which located in the Southeastern Korea, is only 11 which is insufficient to apply the SBAS time-series analysis. Although it is common that the radar interferometry utilizes multiple SAR images collected from same acquisition mode, it has been reported that the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometric application could be possible under specific acquisition mode. In case that we can apply the Stripmap-ScanSAR interferometry with the other 18 ScanSAR observations over Busan, an enhanced time-series surface displacement with better temporal resolution could be estimated. In this study, we evaluated feasibility of the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometric application using Gamma software considering differences of chirp bandwidth and pulse repetition frequency (PRF) between two acquisition modes. In addition, we analyzed the interferograms with respect to spectral shift of radar carrier frequency and common band filtering. Even though it shows similar level of coherence regardless of spectral shift in the radar carrier frequency, we found periodic spectral noises in azimuth direction and significant degradation of coherence in azimuth direction after common band filtering. Therefore, the characteristics of spectral bandwidth in the range and azimuth direction should be considered cautiously for the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometry.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.168-171
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• 1991

홀로그래피 간섭무늬로부터 변형의 요철방향을 구하기 위하여 무늬반송법을 응용하였다. 변형에 의해 형성된 간섭무늬의 차수가 기준무늬를 따라 한 방향으로 증가하도록 하였으며, 디자탈 영상처리 기술을 이용하여 간섭무늬 해석을 자동화 하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.218-219
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• 2005