• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.25-26
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• 2011

사용자 의사거리 보정 잔차(UDRE)는 위성항법보정정보의 측위성능을 예측하는데 이용하는 매우 중요한 무결성 감시정보이다. 위성항법보정정보 사용자는 위성별로 제공되는 사용자 의사거리 보정 잔차 정보를 이용하여 목표로 하는 측위성능을 보장할 수 있는지 여부를 계산하고, 이 결과를 반영하여 위성항법보강시스템의 보정정보를 사용할지 아니면, 무시할지를 판단한다. 즉, 사용자 의사거리 보정 잔차는 위성별로 제공되는 보정정보를 이용하여 보정을 한 후에도 제거되지 않고 남는 위성과 사용자 수신기 간의 통계학적 거리 오차로서 가우시안 분포를 갖는다고 본다. 따라서 동일한 위성항법신호 환경이라도 위성항법보강시스템의 종류와 응용분야별로 다르게 설정되는 측위성능의 보장 수준에 따라 사용자 의사거리 보정 잔차는 다른 값을 갖게 된다. 본 논문은 위성항법보강시스템의 무결성 감시성능에 영향을 미치는 사용자 의사거리 보정 잔차 추정기법의 성능해석을 목적으로 다중 기준국 원시정보를 이용한 사용자 의사거리 보정 잔차 추정기법 구조분석과 영향력을 소개하고, 성능에 영향을 미치는 인자와 사용자 의사거리 보정 잔차 추정성능의 지표에 대해 정의한다. 그리고 마지막으로 성능해석의 방법을 제안하고, 타당성을 검증한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.678-683
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• 2003

The pseudo-noise (PN) code acquisition based on the sequential estimation (SE) proposed by Ward performs well only at relatively high chip signal-to-noise ratios (SNRs). In this paper, a seed accumulating sequential estimation (SASE) method and a PN code acquisition system based on it are proposed, which perform well at low chip SNR (of practical interest) also. Then, the mean acquisition time performance of the proposed system is investigated. Numerical results show that the system based on the SASE performs dramatically better than that based on the SE at low chip SNR, and the improvement becomes larger as the period of PN code increases.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.52-57
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• 2001

The passive ranging estimation techniques using a focused beamformer have been studied under the water. It is well known that the passive ranging estimation method using a focused beamformer is excellently evaluated. Among these, the passive ranging sonar is known to have a good performance under low signal-to-noise. ratio. However, its performance is degraded in multi-source environments. In this paper, we proposed the technique using dual focused beamformers to estimate the range. And when the sampling frequency is low, it is very difficult to steer the focused beam to the desired direction, as a result of this, the low performance occurs because of a distorted beam pattern. In this paper, we study the effect of sampling rate on passive ranging by using focused beamformer. And we verified the performance of the proposed method via computer simulation.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.53-58
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• 2012

In this paper, we evaluate and analyze representative estimation methods for the sparse channel. In order to evaluate error performance of matching pursuit(MP) and minimum mean square error(MMSE) algorithm, lower bound of MMSE is determined by Cramer-Rao bound and compared with upper bound of MP. Based on analysis of those bounds, mean square error of MP which is effective in the estimation of sparse channel can be larger than that of MMSE according to the number of estimated tap and signal-to-noise ratio. Simulation results show that the performances of both algorithm are reversed on the sparse channel with Rayleigh fading according to signal-to-noise ratio.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.763-765
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• 2023

본 논문에서는 저성능 컴퓨터나 스마트폰의 카메라를 통해 입력받은 영상을 기반으로 사용자의 포즈를 추정하고, 실시간으로 사용자의 포즈에 따라 3D 모델의 모션이 제어되어 가시화 될 수 있는 클라이어트-서버 구조의 "자세추정 및 3D 모델 모션 제어 시스템"을 제안한다. 제안 시스템은 소켓통신 기반의 클라이언트-서버구조로 구성되어, 서버에서는 실시간 자세 추정을 위한 딥러닝 모델이 수행되고, 저성능 클라이언트에서는 실시간으로 카메라 영상을 획득하여 영상을 서버에 전송하고, 서버로부터 자세 추정 정보를 받아 이를 3D 모델에 반영하고 렌더링 함으로써 사용자와 함께 3D 모델이 같은 동작을 수행하는 증강현실 화면을 생성한다. 고성능을 요구하는 객체 자세 추정 모듈은 서버에서 실행하고, 클라이언트에서는 영상 획득 및 렌더링만을 실행하기 때문에, 모바일 앱에서의 실시간 증강현실을 위한 자세 추정 및 3D 모델 모션 제어가 가능하다. 제안 시스템은 "증강현실 기반 영상 찍기 앱" 에 반영되어 사용자의 움직임을 따라하는 3D 캐릭터들의 영상을 쉽게 생성할 수 있도록 할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.38-47
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• 2006

In this paper, we propose a velocity-adaptive channel estimation scheme using the simple zero-forcing technique in the frequency domain. Channel estimation is performed by removing frequency components that are higher than the maximum Doppler frequency in the received signal. The proposed scheme can be extended to the combined estimation scheme for channel coefficients and mobile velocity using one FFT/IFFT module. Simulation results show that the proposed scheme outperforms conventional schemes for a wide range of mobile velocities($3{\sim}300\;Km/h$). Finally, the MSE for the proposed channel estimation scheme is analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1C
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• pp.149-156
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• 2004

In this paper, novel power-aware motion estimation is proposed for low-power multimedia communication. In the video compression, motion estimation dominates the total power consumption, where better performance usually requires more power consumption. Among several motion estimation algorithms with different performance and power, the proposed motion estimation adaptively selects the optimal algorithm during run-time, considering the trade-off between performance and power. The proposed motion estimation can be easily applied to various motion estimation algorithms with negligible computation or hardware overhead. According to simulation results, the proposed motion estimation reduces the power consumption to 1/15.7~1/5.6 without performance degradation, when compared to the conventional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.43-50
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• 2005

In this paper, we present an improved channel estimation method for orthogonal frequency division multipexing systems using pilot symbol assisted modulation(PSAM). Conventional linear minimum mean square error(LMMSE) channel estimation method uses only pilot symbols for channel estimation. So, as the fading channel varies rapidly, the system performance is degraded. The basic idea of the proposed scheme is that we firstly estimate channel coefficients at the middle point between two pilot symbols and then compute the channel attenuation by using LMMSE method. Superior performance achieved with the proposed method is illustrated by simulation experiments with the Doppler frequency of 36Hz and 185Hz in comparison with conventional LMMSE channel estimator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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• pp.746-756
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• 2013

The emitter geolocation method using the time difference of arrival (TDOA) and the frequency difference of arrival (FDOA) has more accurate performance comparing to the single TDOA or FDOA based method. The estimation performance varies with the sensor paring strategies, the deployment and velocities of the sensors. Therefore, to establish effective strategy on the electronic warfare system, it is required to analyze the relation between the estimation accuracy and the operational condition of sensors. However, in the conventional non-iterative method, the restriction of the deployment of sensors and the reference sensor exists. Therefore, we derive the emitter geolocation method based on a Gauss-Newton method which is available to apply to any various sensor pairs and the deployment and velocities of the sensors. In addition, simulation results are included to compare the performance of geolocation method according to the used measurements: the combined TDOA/FDOA, TDOA, and FDOA. Also, we present that the combined TDOA/FDOA method outperforms over single TDOA or FDOA on the estimation accuracy with the CEP plane.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.153-156
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• 2006

본 논문에서는 T-DMB 수신기의 채널추정 성능향상을 위한 잡음감소 기법을 제안한다. 일반적으로 T-DMB 수신기에서의 채널추정은 파일럿 신호 추출과 채널계수 추정에 의해 수행된다. 채널추정의 성능은 수신 SNR (Signal to Noise Ratio)과 연관되어 추정된 채널계수에 남아있는 잡음성분에 의해 결정되기 때문에, 잔존하는 잡음성분을 감소시키는 것은 매우 중요하다. 이러한 잡음성분을 감소시키기 위해, M-point 가중이동평균(weighted moving average)을 기반으로 한 잡음제거 기법을 제안한다. 전산 실험에 의하면, 제안된 방법은 등화 후 SER (Symbol Error Rate) 측면에서 기존의 방법에 비해 2-3 dB의 성능 향상을 보인다.