• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1134-1140
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• 2004

In this paper, we investigated the effect of cross phase modulation(XPM) on compensation for WDM channel distortion due to chromatic dispersion, self phase modulation and XPM as a function of fiber dispersion coefficient and modulation format in 320 Gbps WDM systems. The considered WDM transmission system is based on mid-span spectral inversion(MSSI) compensation method, which has highly nonlinear dispersion shifted fiber(HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that the maximum channel input power resulting 1 dB eye opening penalty is reduced due to XPM effect on channel distortion, even if MSSI method was applied to WDM system. But, we confirmed that the effect of XPM on channel distortion becomes decrease as fiber dispersion coefficient of WDM system becomes larger. Futhermore, we confirmed that NRZ is better than RZ as a modulation format for similarly compensating overall WDM channels in WDM system with large fiber dispersion coefficient in order to minimize the effect of the XPM on channel distortion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.719-726
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• 2004

In this paper, compensation characteristics of distorted WDM channel due to both chromatic dispersion and self phase modulation (SPM) is numerically investigated under the assumptions of non-uniformly distributed fiber dispersion, in order to inspect the application of mid-span spectral inversion (MSSI) to any exact transmission links. The MSSI is compensation method used in this approach. This method has an optical phase conjugator (OPC) placed in mid-way of total transmission length to compensate distorted WDM channels. It is confirmed that MSSI will become applicable to long-haul WDM systems by controlling input light power of transmission channels, when the averaged dispersion of both fiber sections with respect OPC was varied and distributed unequally each other. Applying MSSI to long-haul WDM system, it is possible to remove all in-line compensator, consequently it will be expected to reducing system cost.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1A
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• pp.1-9
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• 2005

We have studied the dispersion properties of a 40 channel x 10 Gbit/s wavelength division multiplexer(WDM) transmission link using standard single mode fiber with all EDFA amplification over 30 x 100 km spans. The dispersion map of the link was investigated by adding fiber sections with positive or negative dispersion at the transmitter, within each amplifier span, and at the receiver. Optimum combinations of these dispersive fiber lengths were attained to significantly enhance the overall transmission performance.

• The KIPS Transactions:PartB
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• v.11B no.3
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• pp.345-352
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• 2004

This paper deals a method to deliver more realistic sound by cancelling the cross-talk which is inherent to the 5.1 channel speaker system. The acoustical model for cross-talk cancellation is the free field model. This model minimizes distortion of sound. 1 used the bark scale sound quality compensation which based on psycho-acoustic. For the surround channels, band-limited sound quality compensation is performed in the frequency domain. I also performed the sound qualify assessment test on the traditional 2 channel stereo and 5.1 channel system. This test is performed in the tort chamber which satisfies the ITU-R specifications. 1 uses the IACC(Inter-Aural Cross-Correlation) to determine the preferences of the amateur and the golden ear experts to asses the trans-aural filter. According to the result from the proposed method, I got more the 38dB separation rates with the Dolby standard speaker array. The results on the diffusion by the subjective test with the experts shows 0.4∼0.5 point Increased then before.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.1025-1033
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• 2002

This paper presents temperature-compensation circuits of Ku-band amplifiers for satellite payload. After carefully investigating design specifications of Ku-band amplifiers for satellite payload, we designed three types or temperature-compensation circuits, which are an active bias circuit, an attenuator control, and an ALC loop circuit. Our design technique demonstrates good agreement between measured and predicted results. These temperature-compensation circuits are suitable for Ku-band satellite payload active components, such as channel amplifiers, LNA and IF amplifiers.

• Journal of Satellite, Information and Communications
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• v.4 no.1
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• pp.28-35
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• 2009

We investigate the adaptive channel attenuation compensation of satellite OFDMA downlink users for minimum PAR (Peak to Average power Ratio), which is one of the main challenging issues in satellite OFDMA application. First, we analyze and compare PAR performances of two main different channel attenuation compensation schemes for OFDMA, i.e., PC-OFDMA (power control OFDMA) and AMC-OFDMA (Adaptive Modulation and Coding). While AMC-OFDMA maintains the constant transmission powers through entire user data subcarriers, PC-OFDMA has non-uniform subcarrier transmission powers because subcarrier powers are separately controlled to compensate each user's sub-channel attenuation. We newly found the fact that non-uniform subcarrier power in PC-OFDMA achieves rather reduced PAR compared to AMC-OFDMA and the amount of reduction becomes larger as the power differences among subcarriers increase. Also, there is an additional PAR reduction in PC-OFDMA by optimizing subcarrier grouping scheme for user's sub-channelization.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.187-195
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• 2007

In this paper, the optimal values of optical phase conjugator (OPC) position and dispersion coefficients of fiber sections depending on the extinction ratio of WDM channel signals are numerically induced in WDM system with OPC used to compensate the distorted signals due to nonlinearities and chromatic dispersion. The considered WDM system consist of 16 channels with 40 Gbps data rate and each channel is assumed to be NRZ format with the extinction ration of 5 dB, 10 dB, or 20 dB. It is confirmed that the only one parameter among two considered parameters is used to effectively compensate overall WDM channels, and each optimal value of these parameters independent on the extinction ratio. That is, overall WDM channels are excellently transmitted within 2 dB power penalty whether by positioning OPC into 496 km or by setting dispersion coefficient difference between two fiber sections to 0.055 ps/nm/km, these optimal values are not dependence on the extinction ratio.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.49-52
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• 2004

본 논문에서는 켑스트럼 기반의 후두질환 음성의 자동감별시, 훈련 및 테스트 마이크 불일치로 인한 채널 왜곡을 보상하기 위한 방법에 대해 연구를 하였다. 특징벡터 영역에서의 채널보상 방법으로 기존의 Cepstral Mean Subtraction (CMS) 방법과 Pole Filtering CMS (FPCMS) 방법을 이용하였다 실험결과 FPCMS를 적용한 경우 기존의 CMS에 비해 우수한 성능을 보이고, $40\%$의 인식 오류 감소를 얻었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.299-302
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• 2011

분산비디오압축(DVC, Distributed Video Coding) 기술은 부호화기의 복잡한 과정을 복호화기로 이동시킴으로써 경량화 비디오 부호화를 위한 새로운 방법으로 주목 받고 있다. 하지만 복호화기에서 채널 복호 과정과 움직임 추정/보상 과정이 수행됨으로써 복호화기의 복잡도가 상당히 증가하게 되며, 이에 복호화기 채널 복호 과정을 고속화하기 위한 방법이 지속적으로 제안되고 있다. 그러나 채널 복호 과정이 고속화될수록 움직임 추정/보상에 소요되는 계산량이 상대적으로 증가하게 되어, 이에 대한 연구가 필요하다. 따라서 본 논문에서는 상대적으로 증가하는 움직임 추정/보상 과정에 적응적 탐색 영역 방법을 적용하여 DVC 복호화기를 고속화하는 알고리즘을 제안한다. 제안 방법은 고정된 탐색 영역을 사용한 보조 정보 생성 방법과 비교하여 평균 76%의 시간절감이 가능하며, 성능저하는 BDBR이 약 0.31% 증가하는 정도로 크지 않다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.127-128
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• 2018

본 논문에서는 채널추정에러가 존재하는 셀룰라시스템 환경에서 D2D 통신을 위한 전력제어 알고리즘 운용방안을 제안한다. 전력제어의 목적은 요구하는 SIR 값을 유지하는 것이다. 하지만, 채널 추정에러 환경에서의 SIR 성능은 확률적 분포를 가지게 된다. 이러한 확률적 SIR 성능 분포를 고려하여, 채널추정에러를 보상하는 가변적인 SIR 적용과 재전송 기법을 복합하여 D2D 통신을 위한 전력제어 기법을 제안하도록 한다.