• ETRI Journal
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• 제36권5호
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• pp.783-790
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• 2014

In this paper, we first analyze carrier-to-interference ratio performance of the space-frequency block coded orthogonal frequency-division multiplexing (SFBC-OFDM) system in the presence of phase noise (PHN) and residual carrier frequency offset (RCFO). From the analysis, we observe that conventional SFBC-OFDM systems suffer severely in the presence of PHN and RCFO. Therefore, we propose a new inter-carrier interference (ICI) self-cancellation method - namely, ISC - for SFBC-OFDM systems to reduce the ICI caused by PHN and RCFO. Through the simulation results, we show that the proposed scheme compensates the ICI caused by PHN and RCFO in Alamouti SFBC-OFDM systems and has a better performance than conventional schemes.

• Journal of Communications and Networks
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• 제14권3호
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• pp.273-279
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• 2012

In this paper, we propose an iterative interstream interference cancellation technique for system with frequency selective multiple-input multiple-output (MIMO) channel. Our method is inspired by the fact that the cancellation of the interstream interference can be regarded as a reduction in the magnitude of the interfering channel. We show that, as iteration goes on, the channel experienced by the equalizer gets close to the single input multiple output (SIMO) channel and, therefore, the proposed SIMO-like equalizer achieves improved equalization performance in terms of normalized mean square error. From simulations on downlink communications of $2{\times}2$ MIMO systems in high speed packet access universal mobile telecommunications system standard, we show that the proposed method provides substantial performance gain over the conventional receiver algorithms.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.127-134
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• 2017

Vortex Induced Vibration (VIV) is a typical flow-structure interference phenomenon which causes an unsteady flow pattern due to vortex shedding at or near the structure's natural frequency leading to resonant vibrations. VIV may cause premature fatigue failure of marine risers and pipelines. A test model was carried out to investigate the role of a stationary fairing by varying the caudal horn angle to suppress riser VIV taking into account the effect of wake interference. The test results show significant reduction of VIV for risers disposed in tandem and side-by-side. In general, fairing with a caudal horn of $45^{\circ}$ and $60^{\circ}$ are efficient in quelling VIV in risers. The results also reveal fairing can reduce the drag load of risers arranged side-by-side. For the tandem configuration, a fairing can reduce the drag load of an upstream riser, but will enlarge the drag force of the downstream riser.

• IEIE Transactions on Smart Processing and Computing
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• 제1권2호
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• pp.117-124
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• 2012

A client collaboration (CC) system is proposed for a user relay system. The proposed scheme focuses on the management of transmit power and leakage interference. In the proposed CC system, edge users transmit signals to the masters considered as user relays. The masters relay the signals of the edge users to the base station using the resource blocks (RBs) that are assigned to the edge users. The leakage interference and power consumption were analyzed in the CC system. In addition, an optimal master location problem was formulated based on the signal-to-leakage-plus-noise ratio (SLNR). Because the optimal master location problem is quite complex, a sub-optimal master location problem was proposed and a closed-form sub-optimal master location was obtained. The edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC. The numerical results showed that the edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC, and the average throughput increases.

• 인지과학
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• 제17권1호
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• pp.29-52
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• 2006

이 연구는 Weissman과 Banich(1999)가 제안했던 반구 간의 상호작용보다도 표적자극과 방해자극의 반구 간 분리처리가 간섭을 감소시키는 데 더 효과적이라는 것을 밝히기 위해 수행되었다. 이를 위해 사각형의 색과 단어가 의미하는 색을 비교하는 세 개의 실험이 수행되었다. 실험 1에서는 표적자극 중의 하나인 단어의 색 차원이, 실험 2와 3에서는 단어의 글자 색이 검정색으로 고정된 상태에서 제 3의 자극인 원의 색이 방해자극으로 사용되었다. 실험 결과 두 표적자극의 비교를 위해 반구간 상호작용이 요구되는 반구간 비교조건에서, 반구간 상호작용은 요구하지 않지만 방해자극이 표적자극과 다른 반구로 투사된 반구내 비교 조건보다 더 큰 간섭효과가 관찰되었다. 이 결과는 반구간 상호작용보다도 표적과 방해자극의 반구간 분리가 간섭 감소에 더 효과적임을 시사한다. 실험 3에서는 원이 단어나 사각형과 분리되어 다른 반구에 제시될 때 주변단서를 이용하여 원의 위치로 주의를 유도하면 방해자극의 반구간 분리 효과가 사라지면서 반구간 비교와 반구내 비교 조건의 간섭효과가 유사해지는 것을 보여 주었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권12호
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• pp.2272-2293
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• 2011

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

• 한국소음진동공학회논문집
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• 제12권5호
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• pp.374-379
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• 2002

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 하계종합학술대회논문집
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• pp.37-40
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• 2000

This paper represented the analytic results of outage probability, considering the effect of Rician fading, Interference and Interference-reduction techniques and simulated, when cellular system was constructed by using Stratospheric platform, one of the next generation wireless communication infras which provides high speed multimedia services.

• 방송공학회논문지
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• 제18권3호
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• pp.474-480
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• 2013

OFDM 시스템에서 수신기가 고속으로 이동하는 경우에는 채널의 급속한 변화로 인해 반송파 간 직교성이 파괴되고 반송파 간 간섭(ICI)이 발생하여 수신기의 성능을 떨어뜨린다. 기존의 수신기에서는 ICI 를 추정한 후 이를 수신 신호로부터 상쇄시켜 성능을 개선한다. 본 논문에서는 수신 신호를 시간 영역에서 마스킹하고 더하여 발생하는 ICI의 크기를 줄여 수신기의 성능을 개선하는 방법을 제안하고 이를 DVB-T 수신기에 적용하여 도플러 이동 수신 성능을 검증한다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.219-224
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• 1995

The adaptive wall test section has distinct advantage over the other devices for reduction of wall interference in the wind tunnel testing. For two-dimensional steady flows the wall adaption strategy has been well established and, in some extent, has been effectively applied to three-dimensional steady flows. For unsteady testing, the wall adaptation is conceptually possible but has never been realized in the wind tunnel experiment. In this study, relatively simple adaptive wall models have been proposed and evaluated through numerical tests. The effect of Mach number, frequency, and amplitude of pitching oscillation on the wall interference reduction has been also studied.