• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.583-591
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• 2009

OFDM(orthogonal frequency division multiplexing) signal with high PAPR(peak to average power ratio) produces the nonlinear distortion and/or decreases down the power efficiency of HPA(high power amplifier). So, the IMD(inter-modulation distortion) reduction method was proposed to reduce the nonlinear distortion, which shows better BER(bit error rate) performance than the PAPR reduction methods. However, IMD reduction method has inherent problem which system complexity and processing time increases because the FFT(fast Fourier transform) processor is added in transmitter and decision criterion of IMD reduction method is computed in frequency domain,. In this paper, therefore, we propose a new IMD reduction method to reduce the computational complexity and structure of IMD computation. And we apply this proposed method into OFDM system using PTS(partial transmit sequence) scheme and compare the computational complexity between conventional and proposed IMD reduction method. This method can reduce the system size and computational complexity. Also, the proposed has almost same BER performance with the conventional IMD reduction method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.1051-1059
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• 2013

This paper proposes a complexity reduced list sphere decoding (LSD) scheme for joint iterative soft detection scheme for coded MIMO system. The conventional LSD scheme is based on searching the candidates with a fixed radius. However, once the candidate list is full, it is highly probable that the radius can be reduced. By reducing the radius, the complexity can be also reduced. We propose a simple and efficient radius update method for complexity reduction of list version sphere decoding and its application to iterative soft MIMO detection. We evaluate the performance of the proposed scheme with a joint soft-input-soft-ouput iterative MIMO detection in combination with turbo codes. Simulation results show that the proposed methods provide substantial complexity reduction while achieving similar bit error rate (BER) performance as the conventional LSD scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.13-23
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• 2009

In this paper, the network performance of a turbo coded optical code division multiple access (CDMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated. We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) is considered. In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical CDMA network can be substantially improved by increasing e interleaver length and e number of iterations in e decoding process. The results of this paper can be applied to implement the indoor optical wireless LANs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.31-40
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• 2010

This paper describes a LDPC decoder for IEEE 802.11n wireless LAN standard. The designed processor supports parity check matrix for block length of 1,944 and code rate of 1/2 in IEEE 802.11n standard. To reduce hardware complexity, the min-sum algorithm and layered decoding architecture are adopted. A novel memory reduction technique suitable for min-sum algorithm was devised, and our design reduces memory size to 25% of conventional method. The LDPC decoder processor synthesized with a $0.35-{\mu}m$ CMOS cell library has 200,400 gates and memory of 19,400 bits, and the estimated throughput is about 135 Mbps at 80 MHz@2.5v. The designed processor is verified by FPGA implementation and BER evaluation to validate the usefulness as a LDPC decoder.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.124-130
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• 2012

In this paper, we propose a feature point selection method for MPEG CDVS CE-7 which is processing on International Standard task. Among a large number of extracted feature points, more important feature points which is used in image matching should be selected for the compactness of image descriptor. The proposed method is that remove the feature point in the extraction phase which is filtered by nearest neighbor distance ratio matching in the matching phase. We can avoid the waste of the feature point and employ additional feature points by the proposed method. The experimental results show that our proposed method can obtain true positive rate improvement about 2.3% in pair-wise matching test compared with Test Model.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.226-233
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• 2012

In this paper, we propose a 'linear approximation method' which is an accelerated BER (Bit Error Rate) test method for high speed interfaces, based on an analytical BER model. Both the conventional 'Q-factor estimation method' and 'linear approximation method' can predict a timing margin for $10^{-13}$ BER with an error of about 0.03UI. This linear approximation method is implemented on a hardware as an accelerated Built-In Self Test (BIST) with an internal BERT (BET Tester). While a direct measurement of a timing margin in a 3Gbps interface takes about 5.6 hours with $10^{-13}$ BER requirement and 95% confidence level, the accelerated BIST estimates a timing margin within 0.6 second without a considerable loss of accuracy. The test results show that the error between the estimated timing margin and the timing margin from an actual measurement using the internal BERT is less than 0.045UI.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.239-246
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• 1998

In this paper, a new morphological details extraction algorithm is proposed. It is known that separate transmission of details and background smoothed image is a powerful technique for very low bit-rate video data transmission. Several details extraction algorithms show relatively large variation of grayscale levels in details, smoothed image, which is the difference between original and details images, provides highly distortedand complicated result. In order to remedy those pitfails, and thus to improve the coding efficiency, we propose a new algorithm using the reconstruction top-hat result as the reference image in process of obtaining details, instead of top-hat result, which is used fur existing a1gorithms. Experimental results show that details, extracted using the proposed algorithm, are much similar to original image, and thus the smoothed image is not too complicated.

• Journal of Broadcast Engineering
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• v.18 no.4
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• pp.647-650
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• 2013

HEVC RExt(High Efficiency Video Coding Range Extension) set a goal to support RGB/YUV 4:2:2 4:4:4 color sampling and over 10 bit-depth images. Unlike the previous 4:2:0 color sampling images, RGB images have the high correlation in inter-color planes. Using this characteristic, some methods which are contributed in JCT-VC standardization meetings estimate the pixel values of inter-color plane. But when we use the estimation of inter-color plane in RGB images, high frequency components of RGB images are caused to reduce the coding efficiency because they usually have the low inter-color plane correlation. Therefore, in this paper, we propose an adaptive low pass filtering method in the inter-color plane estimation. Using this method, we can improve the estimation efficiency of inter-color plane in RGB images. The experimental results with HEVC RExt RGB test sequences show that the proposed method has 0.6% BD(Bjontegaard Distortion)-rate gain and some increased complexity compared to the previous inter-color plane estimation method.

• Journal of Mushroom
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• v.9 no.1
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• pp.44-47
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• 2011

This study was carried out investigate optimal additive content of spent medium from oyster mushroom in Volvariella volvacea cultivation. The formation of spent mushroom medium from oyster mushroom consisted of 50% pine sawdust, 30% beet pulp and 20% cotton seed hull pellet. The higher amount of spent medium from oyster mushroom resulted in higher total nitrogen content and C/N ratio of medium decreased according to increasing mixing ratio of spent medium from oyster mushroom. The fruit body yield and biological efficiency of supplemented with 50% spent medium from oyster mushroom was same level of non additive medium.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.368-374
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• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.