• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.2
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• pp.10-19
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• 1994

The error rate equation of Reed-Solomon/Convoutional concatenated coded MFSK signal transmitted over m-distributed fading channel with Additive White Gaussian Noise (AWGN) and re- ceived with Maximal Ratio Combining (MRC) diversity has been derived. The bit error probability has been evaluated using the derived equation and shown n figures as a function of signal to noise ratio, fading index and the number of diversity branches. From the results obtained, we have shown that the bit error probability of MFSK signal is improved by using coding technique in fading environment. The concatenated coding technique is found to be very effective. When concatenated coding and MRC diversity reception techniques are used together in fading environ- ment, the improvement of error performance attains about 6.6 dB in terms of SNR as compared with that of employing only concatenated coding case.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.11a
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• pp.104-107
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• 2018

최근 촬영 기기의 기술발전으로 인해 디지털 영상의 해상도가 증가함에 따라 선명한 디지털 영상에 대한 요구가 증가하고 있다. 이러한 요구에도 불구하고 디지털 영상 내 가우시안 잡음 (gaussian noise)은 촬영기기를 통해 영상 획득 및 처리 과정에서 발생하여 화질을 열화 시킨다. 디지털 이미지에서 발생하는 가우시안 잡음을 제거하기 위해서 기존의 저대역 통과 필터 (low-pass filter: LPF)를 사용하면 잡음은 제거되지만, 블러링 현상 (blurring phenomenon)이 나타난다. 이러한 문제점을 개선하기 위해 소벨 연산자 (sobel operator)를 사용하여 영상 내 에지 맵 (edge-map)을 생성하여 에지 영역과 동질 영역을 구분한다. 에지영역에서는 약한 저역 필터 (weak low-pass filter)를 사용하고, 그 외의 이미지 영역에서는 강한 저역 필터 (strong low-pass filter)를 사용하는 알고리듬을 제안하였다. 그리고 다양한 이미지에 대하여 기존 알고리듬과 제안한 알고리듬의 적용한 결과를 통해 주관적 화질 비교하였고 객관적 지표로 최대 신호 대 잡음비 (peak signal-to noise ratio: PSNR)와 구조 유사성 (structural similarity: SSIM)을 사용하여 성능을 평가하였다. 실험결과를 통해 제안된 알고리듬이 잡음 제거 및 외곽선 보존의 우수함을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.519-529
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• 1998

In this paper, we analyze the effects of interference canceller on the performance of multitone DS/CDMA system. Although there are various kinds of interference cancellers suggested by different researchers, we adopt a canceller used by Yoon et at.［9］. We consider three kinds of inteferences, that is, multiPath interference(MPI), interchannel interference(ICI) and multiple access interference(MPI). The equations for variances ate derived for the inteferences and thermal noise used for signal to noise ratio calculation. We also consider RAKE reception over multipath channel and three stage interference canceller used for performance improvement. We draw some conclusions that interference canceller is effective in multitone DS/CDMA system and the performance is further improved with the higer order of diversity and larger number of PN chips.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.771-779
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• 2002

A new signal model suitable for indoor wireless environments with large angle spread is proposed to improve the performance of indoor wireless communication systems. Antenna array techniques adopted for this model are discussed. It is based on the far-field signal assumption. The optimal beamforming weight vector is obtained by applying the antenna algorithm based on the maximum signal to interference noise ratio criterion to the model. The proposed model is verified using a mathematical analysis and computer simulations.

• Korean Journal of Optics and Photonics
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• v.22 no.5
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• pp.223-229
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• 2011

We present a low jitter frequency up-conversion detector based on quasi-phase matched sum frequency generation in a periodically poled $LiNbO_3$ waveguide for efficient single-photon detection at 1.5 ${\mu}m$ telecommunication wavelengths. The maximum detection efficiency and the noise count rate using the pump power of 300 mW and the pump wavelength of 974 nm are about 7% and 480 kHz, respectively. We also characterize the timing jitter of the frequency up-conversion detector by analyzing the time distribution of the detection outputs for photons generated through a picosecond pump pulsed spontaneous parametric downconversion. The minimum timing jitter was measured to be about 39.1 ps. Coincidence measurement with a narrow time window for pulsed up-conversion photons can eliminate the unwanted noise counts and maximize signal to noise ratio.

• The Journal of Korean Society for Radiation Therapy
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• v.35
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• pp.41-51
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• 2023

Purpose: This study compares and analyzes the image quality of 3D-CBCT(Cone Beam Computed-Tomography) and Gated CBCT according to baseline changes during SBRT(Stereotactic Body RadioTherapy) in lung cancer patients to find a useful CBCT method for correcting movement due to breathing Materials and methods : Insert a solid tumor material with a diameter of 3 cm into the QUASAR^TM phantom. 4-Dimentional Computed-Tomography(4DCT) images were taken with a speed of the phantom at period 3 sec and a maximum amplitude of 20 mm. Using the contouring menu of the computerized treatment planning system Eclipse^TM Gross Tumor Volume was outlined on solid tumor material. Set-up the same as when acquiring a 4DCT image using Truebeam STx^TM, breathing patterns with baseline changes of 1 mm, 3 mm, and 5 mm were input into the phantom to obtain 3D-CBCT (Spotlight, Full) and Gated-CBCT (Spotlight, Full) images five times repeatedly. The acquired images were compared with the Signal-to-Noise Ratio(SNR), Contrast-to-Noise Ratio(CNR), Tumor Volume Length, and Motion Blurring Ratio(MBR) based on the 4DCT image. Results: The average Signal-to-Noise Ratio, Contrast-to-Noise Ratio, Tumor Volume Length and Motion Blurring Ratio of Spotlight Gated CBCT images were 13.30±0.10%, 7.78±0.16%, 3.55±0.17%, 1.18±0.06%. As a result, Spotlight Gated-CBCT images according to baseline change showed better values than Spotligtht 3D-CBCT images. Also, the average Signal-to-Noise Ratio, Contrast-to-Noise Ratio, Tumor Volume Length and Motion Blurring Ratio of Full Gated CBCT images were 12.80±0.11%, 7.60±0.11%, 3.54±0.16%, 1.18±0.05%. As a result Full GatedCBCT images according to baseline change showed better values than Full 3D-CBCT images. Conclusion : Compared to 3D-CBCT images, Gated-CBCT images had better image quality according to the baseline change, and the effect of Motion Blurring Artifacts caused by breathing was small. Therefore, it is considered useful to image guided using Gated-CBCT when a baseline change occurs due to difficulty in regular breathing during SBRT that exposes high doses in a short period of time

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.15-21
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• 2011

Cooperative diversity system can be applied to an ad-hoc network for reduction of the power consumption, for expansion of the communication range, and for improving the system performance. In a selection relay cooperative diversity system which selects the maximal SNR(Signal-to-noise ratio) relay for transmitting the source information, the selected strong relay transmits continuously under slow fading channel, consequently it reduces the network lifetime. To overcome this defect, recently the uniform power relay selection has been studied to expand the network life time. We apply the uniform power relay selection to a DOT(Double opportunistic transmit) cooperative system that select the transmit relays, of which the SNR of the transmit relays exceed both of the source-relay and the relay-destination threshold. And the performance of the system is analytically derived. The performance comparisons are made among SC(Selection combining), MRC(Maximal ratio combining), and uniform power relay selection of the cooperative diversity system. We noticed that the performance of the uniform power relay selection is inferior to that of others. It is interpreted that the uniform transmit opportunity to the selected relays for extension of the network lifetime degrades the performance.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.121-123
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• 2001

최근 이동 통신의 급격한 성장으로 인하여 동일한 통신 서비스간의 간섭 뿐 아니라 서로 다른 서비스간의 간섭 문제가 통신 서비스의 품질을 저하시키는 주된 요인으로 작용하고 있다. 특히, CDMA-based 시스템은 간섭에 의해 용량이 제한되므로 CDMA-based 시스템인 기존의 IS-95 및 PCS 서비스, 그리고 차세대 이동 통신인 IMT-2000/CDMA 시스템의 용량 개선을 위한 연구 및 효율적인 무선망 설계를 위한 연구가 필요하다. 본 연구에서는 IMT-2000/CDMA 시스템의 효율적인 링크 분석(Link Analysis)을 하는데 필요한 시스템 성능 평가와 시스템 통화용량을 산출하는 프로그램을 개발하고자 한다. 여기서, 시스템 성능을 예측하기 위해서는 신호 대 잡음 전력비 (E$_{b}$N$_{o}$ )의 개념이 요구된다. 시스템 통화용량은 잡음 특성이 매우 이상적인 상태를 기준으로 하여 역방향 최대 용량을 산정하는 Pole Capacity 산출 방식과 호차단율(B1ocking Probability)로부터의 통계적 산출 방법인 Erlang Capacity 산출 방식을 적용한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.1
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• pp.19-27
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• 1988

In the user-network interface for the parcticing ISDN, an effective phase aligned time compression multiplexing transmission system is designed and analyzed in the 2 wire passive BUS. In TCM, tha average SNR due to crosstalk from adjacent channelis 9.72(dB), and in regarding the phase aligned process, frames are designed to have maximum propagation time of 6(us) so that the connection distance is extended by 0.8(Km). Therefore, the proposed transmission system is suitable for the connection between end-subscriber and network.

• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.77-83
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• 2009

This paper proposes a new noise-biased compensation of minimum statistics(MS) method using a nonlinear function and a priori speech absence probability(SAP) for speech enhancement in non-stationary noisy environments. The minimum statistics(MS) method is well known technique for noise power estimation in non-stationary noisy environments. It tends to bias the noise estimate below that of true noise level. The proposed method is combined with an adaptive parameter based on a sigmoid function and a priori speech absence probability (SAP) for biased compensation. Specifically. we apply the adaptive parameter according to the a posteriori SNR. In addition, when the a priori SAP equals unity, the adaptive biased compensation factor separately increases ${\delta}_{max}$ each frequency bin, and vice versa. We evaluate the estimation of noise power capability in highly non-stationary and various noise environments, the improvement in the segmental signal-to-noise ratio (SNR), and the Itakura-Saito Distortion Measure (ISDM) integrated into a spectral subtraction (SS). The results shows that our proposed method is superior to the conventional MS approach.