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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Communications and Information Sciences
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The Korean Institute of Communications and Information Sciences
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Volume & Issues
Volume 34, Issue 12C - Dec 2009
Volume 34, Issue 12B - Dec 2009
Volume 34, Issue 12A - Dec 2009
Volume 34, Issue 11C - Nov 2009
Volume 34, Issue 11B - Nov 2009
Volume 34, Issue 11A - Nov 2009
Volume 34, Issue 10C - Oct 2009
Volume 34, Issue 10B - Oct 2009
Volume 34, Issue 10A - Oct 2009
Volume 34, Issue 9C - Sep 2009
Volume 34, Issue 9B - Sep 2009
Volume 34, Issue 9A - Sep 2009
Volume 34, Issue 8C - Aug 2009
Volume 34, Issue 8B - Aug 2009
Volume 34, Issue 8A - Aug 2009
Volume 34, Issue 7C - Jul 2009
Volume 34, Issue 7B - Jul 2009
Volume 34, Issue 7A - Jul 2009
Volume 34, Issue 6C - Jun 2009
Volume 34, Issue 6B - Jun 2009
Volume 34, Issue 6A - Jun 2009
Volume 34, Issue 5C - May 2009
Volume 34, Issue 5B - May 2009
Volume 34, Issue 5A - May 2009
Volume 34, Issue 4C - Apr 2009
Volume 34, Issue 4B - Apr 2009
Volume 34, Issue 4A - Apr 2009
Volume 34, Issue 3C - Mar 2009
Volume 34, Issue 3B - Mar 2009
Volume 34, Issue 3A - Mar 2009
Volume 34, Issue 2C - Feb 2009
Volume 34, Issue 2B - Feb 2009
Volume 34, Issue 2A - Feb 2009
Volume 34, Issue 1C - Jan 2009
Volume 34, Issue 1B - Jan 2009
Volume 34, Issue 1A - Jan 2009
Selecting the target year
A Grouping Technique for Synchronous Digital Duplexing Systems
Ko, Yo-Han ; Park, Chang-Hwan ; Park, Kyung-Won ; Jeon, Won-Gi ; Paik, Jong-Ho ; Lee, Seok-Pil ; Cho, Yong-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 341~348
In this paper, we propose a grouping technique for the SDD(Synchronous Digital Duplexing) based on OFDMA(Orthogonal Frequency Division Multiple Access). The SDD has advantages of increasing data efficiency and flexibility of resource since SDD can transmit uplink signals and downlink signals simultaneously by using mutual time information and mutual channel information, obtained during mutual ranging process. However, the SDD has a disadvantage of requiring additional CS to maintain orthogonality of OFDMA symbols when the sum of mutual time difference and mutual channel length between AP(access point) and SS(subscriber station) or among SSs are larger than CP length. In order to minimize the length of CS for the case of requiring additional CS in SDD, we proposes a grouping technique which controls transmit timing and receive timing of AP and SS in a cell by classifying them into groups. Performances of the proposed grouping technique are evaluated by computer simulation.
Memory Access Reduction Scheme for H.264/AVC Decoder Motion Compensation
Park, Kyoung-Oh ; Hong, You-Pyo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 349~354
In this paper, a new motion compensation scheme to reduce external memory access frequency which is one of the major bottlenecks for real-time decoding is proposed. Most H.264/AVC decoders store reference pictures in external memories due to the large size and reference blocks are read into the decoder core as needed during decoding. If the reference data access is done for each reference block in decoding sequence, the memory bandwidth can be unacceptable for real-time decoding. This paper presents a memory access scheme for motion compensation to read as many reference data as possible with reduced memory access frequency by analyzing reference data access pattern for each macroblock. Experimental results show that the proposed motion compensation scheme leads to approximately 30% improvement in memory bandwidth requirement.
A Single Field Deinterlacing Algorithm Using Edge Map in the Image Block
Kang, Kun-Hwa ; Jeon, Gwang-Gil ; Jeong, Je-Chang ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 355~362
A new intra field deinterlacing algorithm with edge map in the image block is introduced. Conventional deinterlacing methods usually employ edge-based line average algorithm within pixel-by-pixel approach. However, it is sensitive to variation of intensity. To reduce this shortcoming, we proposed edge direction vector computed by edge map, and also its interpolation technique. We first introduce an edge direction vector, which is computed by Sobel mask, so that finer resolution of the edge direction can be acquired. The proposed edge direction vector oriented deinterlacer operates by identifying small pixel variations in five orientations, while weighted averaging to estimate missing pixel. According to the edge direction of the direction vector, we calculate weights on each edge direction. These weight values multiplied by the candidate deinterlaced pixels in order to successively build approximations of the deinterlaced sequence.
An Efficient Image Interpolation Algorithm using Edges Extracted Edges From Binary Image
Lee, Sang-Hoon ; Kim, Sung-Geun ; Lee, Dong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 363~370
Image interpolation addresses the problem of generating a high-resolution image from its low-resolution version. Classical linear interpolation algorithms are simple and popular, but they produce interpolated image with blurred edges and annoying artifacts, Thus, many edge-based interpolation algorithms have been proposed to improve the subjective quality of the interpolated image, especially around edges on the image. In this paper, we propose a new interpolation algorithm which uses edges extracted from binary image. The proposed algorithm is applied to the image after interpolating using 6-Tap FIR filter. The values of interpolation pixels on edges extracted from binary image are modified using neighborhood pixels on the same edge. Experimental results for various images show that the proposed method provides better performance than existing methods.
Intensity Gradient filter and Median Filter based Video Sequence Deinterlacing Using Texture Detection
Kang, Kun-Hwa ; Ku, Su-Il ; Jeong, Je-Chang ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 371~379
In this paper, we proposed new de-interlacing algorithm for video data using intensity gradient filter and median filter with texture detection in the image block. We first introduce the texture detection. According to texture detection, the current region is determined into smooth region or texture region. In case that the smooth region interpolated by median filter. In addition, in case of the texture region, we calculate missing pixel value using intensity gradient filter. Therefore, we analyze the local region feature using the texture detection and classify each missing pixel into two categories. And then, based on the classification result, a different de-interlacing algorithm is activated in order to obtain the best performance. Experimental results show that the proposed algorithm performs well with a variety of moving sequences compared with conventional intra-field method in the literature.
Novel Optical Image Encryption using Integral Unaging and Random Pixel-scrambling Schemes
Piao, Yong-Ri ; Kim, Seok-Tae ; Kim, Eun-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 380~387
In this paper, optical image encryption using integral imaging and pixel-scrambling technologies is proposed. In the encryption process, we use pixel scrambling to change the order of subsections into which the cover image is divided, and the utilize the integral imaging scheme to obtain the elemental image from the scrambled image. In order to achieve higher security, we reuse pixel scrambling to the elemental image. In the decryption process, we employ optical integral imaging reconstruction technique and inverse pixel scrambling methode. Computer simulation results prove the feasibility of the proposed method and robustness against data loss and noise.
Fire-Smoke Detection Based on Video using Dynamic Bayesian Networks
Lee, In-Gyu ; Ko, Byung-Chul ; Nam, Jae-Yeol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 388~396
This paper proposes a new fire-smoke detection method by using extracted features from camera images and pattern recognition technique. First, moving regions are detected by analyzing the frame difference between two consecutive images and generate candidate smoke regions by applying smoke color model. A smoke region generally has a few characteristics such as similar color, simple texture and upward motion. From these characteristics, we extract brightness, wavelet high frequency and motion vector as features. Also probability density functions of three features are generated using training data. Probabilistic models of smoke region are then applied to observation nodes of our proposed Dynamic Bayesian Networks (DBN) for considering time continuity. The proposed algorithm was successfully applied to various fire-smoke tasks not only forest smokes but also real-world smokes and showed better detection performance than previous method.
A Novel Expectation-Maximization based Channel Estimation for OFDM Systems
Kim, Nam-Kyeom ; Sohn, In-Soo ; Shin, Jae-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 397~402
Accurate estimation of time-selective fading channel is a difficult problem in OFDM(Orthogonal Frequency Division Multiplexing) system. There are many channel estimation algorithms that are very weak in noisy channel. For solving this problem, we use EM (Expectation-Maximization) algorithm for iterative optimization of the data. We propose an EM-LPC algorithm to estimate the time-selective fading. The proposed algorithm improves of the BER performance compared to EM based channel estimation algorithm and reduces the iteration number of the EM loop. We simulated the uncoded system. If coded system use the EM-LPC algorithm, the performance are enhanced because of the coding gain. The EM-LPC algorithm is able to apply to another communication system, not only OFDM systems. The image processing of the medical instruments that the demand of accurate estimation can also use the proposed algorithm.
Design and Comparison of Digital Predistorters for High Power Amplifiers
Lim, Sun-Min ; Eun, Chang-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 403~413
We compare three predistortion methods to prevent signal distortion and spectral re-growth due to the high PAPR (peak-to-average ratio) of OFDM signal and the non-linearity of high-power amplifiers. The three predistortion methods are pth order inverse, indirect learning architecture and look up table. The pth order inverse and indirect learning architecture methods requires less memory and has a fast convergence because these methods use a polynomial model that has a small number of coefficients. Nevertheless the convergence is fast due to the small number of coefficients and the simple computation that excludes manipulation of complex numbers by separate compensation for the magnitude and phase. The look up table method is easy to implement due to simple computation but has the disadvantage that large memory is required. Computer simulation result reveals that indirect learning architecture shows the best performance though the gain is less than 1 dB at
for 64-QAM. The three predistorters are adaptive to the amplifier aging and environmental changes, and can be selected to the requirements for implementation.
A Near Optimal Linear Preceding for Multiuser MIMO Throughput Maximization
Jang, Seung-Hun ; Yang, Jang-Hoon ; Jang, Kyu-Hwan ; Kim, Dong-Ku ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 414~423
This paper considers a linear precoding scheme that achieves near optimal sum rate. While the minimum mean square error (MMSE) precoding provides the better MSE performance at all signal-to-noise ratio (SNR) than the zero forcing (ZF) precoding, its sum rate shows superior performance to ZF precoding at low SNR but inferior performance to ZF precoding at high SNR, From this observation, we first propose a near optimal linear precoding scheme in terms of sum rate. The resulting precoding scheme regularizes ZF precoding to maximize the sum rate, resulting in better sum rate performance than both ZF precoding and MMSE precoding at all SNR ranges. To find regularization parameters, we propose a simple algorithm such that locally maximal sum rate is achieved. As a low complexity alternative, we also propose a simple power re-allocation scheme in the conventional regularized channel inversion scheme. Finally, the proposed scheme is tested under the presence of channel estimation error. By simulation, we show that the proposed scheme can maintain the performance gain in the presence of channel estimation error and is robust to the channel estimation error.
An Improved frequency Synchronization Method Based on Autocorrelation function with Reduced Complexity
Yang, Hyun ; Jeong, Kwang-Soo ; Lee, Kyeong-Il ; Yi, Jae-Hoon ; You, Young-Hwan ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 424~429
This paper suggests an autocorrelation function (AF) based carrier frequency offset (CFO) estimator based on a training sequence in flat fading channels. The proposed CFO estimator has the reduced computational burdens in the calculation of the AF when compared to AF-based conventional frequency estimators. The simulation results show that the proposed estimator achieves a better performance than the existing estimators. Furthermore, the performance of the proposed method has been observed to lie close to the Cramer-Rao lower bound (CRLB).
An Automatic Control of Reflective Wavelength of TFBG Using Fabry-Perot Filter
Pan, Jae-Kyung ; Kim, Ji-Do ; Jeon, Keum-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 430~436
In this paper, we propose and describe our implementation of an automatic control system for the center wavelength of a fiber Bragg grating. The proposed system consists of a Fabry-Perot filter and cantilever structure controlled by a step motor interfacing computer. We consider the change of the center wavelength and the reflective spectrum shape for a given FBG according to the translation distance of the push stick and the cantilever thickness variation. The proposed system can control the center wavelength of a FBG with a resolution of 0.01 nm by applying compression or extension to the FBG. The proposed system has characteristics that keep the desired wavelength of the FBG with a variation of environmental conditions.
One-way Short-range Communication using Channel Symbol of Color Light Signal based on USN environment
Lee, Gong ; Jeon, Young-Jun ; Shin, Seung-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 437~445
Node of USN(Ubiquitous Sensor Network) environments uses radio based communication mechanism for a delivering message. Thus the multiple hop flooding is necessary for considering limited power and communicating unknown node long-range. However if there are many unknown nodes located in users' vision, the flooding of the radio base is insufficient alternative. Thus as a flash may be used to find a key in a darkness, a more direct and short range communication system is required. This study shall resolve such question through 2 different steps. First a Two kind of code method that convert Text message to color code shall be suggested. Second a hardware module, which may deliver various LED(light-emitting diode) color signal, shall be developed. The experiment may take place by fixing the entry angle of light and distance by setting a specific element as a standard mean.
CIR Performance Enhancement by Frequency Offset Estimation in OFDM System
Ko, Seong-Hui ; Choi, Jung-Hun ; Lee, Dong-Ho ; Kim, Nam ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 446~452
OFDM system has a disadvantage of sensitiveness about the effect of frequency offset caused by the discord of oscillators in the transmitter and receiver. Either, the frequency offsets in mobile radio channels distort the orthogonality between sub-carriers resulting in the inter-carrier interference(ICI). In this paper, we analyze the effect of the ICI and propose a new method using SC technique. To analyze BER(Bit Error Rate) and CIR(Carrier to Interference Ratio) performance of the proposed method. the simulation program MATLAB is used. By the simulation results, SNR performance is improved by this method. In case the frequency offset is 0.3 and 0.5, SNR gains are over 0.5dB and 1dB in the BPSK modulation and 1dB and 2dB in the QPSK modulation at BER of
respectively. In addition, CIR performance is improved over 15dB. As a result, the proposed method is more effective to improve the system performance than the conventional method.
Performance Analysis of a CSS System in the Presence of Jamming Signals
Lee, Young-Po ; Chong, Da-Hae ; Song, Chong-Han ; Song, Iick-Ho ; Yoon, Seok-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 453~459
Due to its capability to resist jamming signals, chirp spread spectrum (CSS) technique has attracted much attention in the field of wireless communications. However, there has been little rigorous analysis for the performance of CSS systems in the presence of jamming signals. In this paper, thus, we present analytic results on the performance of a CSS system: specifically, symbol error rate (SER) expressions are derived for a CSS M-ary phase shift keying (MPSK) system in the presence of broadband and tone jamming signals, respectively. The numerical results show that the empirical SER closely agree with the analytic result.
Reduced Complexity QRD-M Algorithm for Spatial Multiplexing MIMO-OFDM Systems
Mohaisen, Manar ; An, Hong-Sun ; Chang, Kyung-Hi ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 460~468
Multiple-input multiple-output (MIMO) technology applied with orthogonal frequency division multiplexing (OFDM) is considered as the ultimate solution to increase channel capacity without any additional spectral resources. At the receiver side, the challenge resides in designing low complexity detection algorithms capable of separating independent streams sent simultaneously from different antennas. In this paper, we introduce an upper-lower bounded-complexity QRD-M algorithm (ULBC QRD-M). In the proposed algorithm we solve the problem of high extreme complexity of the conventional sphere decoding by fixing the upper bound complexity to that of the conventional QRD-M. On the other hand, ULBC QRD-M intelligently cancels all unnecessary hypotheses to achieve very low computational requirements. Analyses and simulation results show that the proposed algorithm achieves the performance of conventional QRD-M with only 26% of the required computations.
A Closed-Form BER Expression for Overlap-Based CSS System Design
Yoon, Tae-Ung ; Lee, Young-Yoon ; Lee, Myung-Soo ; Song, Iick-Ho ; Yoon, Seok-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 469~475
Overlap is one of the techniques for increasing bit rate in chirp spread spectrum (CSS). More overlaps can offer higher data throughput; however, they may cause more intersymbol interference (ISI) at the same time, resulting in serious bit error rate (BER) performance degradation. Thus, the number of overlaps should be decided according to the required BER performance. In this paper, we derive a closed form expression for BER of the overlap-based CSS system, exploiting the approximated Gaussian Q function. The derived BER expression includes the number of overlaps as a parameter, and thus, would be very useful in determining the number of overlaps for a specified BER. The numerical results demonstrate that the BER derived in a closed form closely agrees with the simulated BER.
The Surface Sidelobe Clutter and the False Alarm Probability of Target Detection for the HPRF Waveform of the Microwave Seeker
Kim, Tae-Hyung ; Yi, Jae-Woong ; Byun, Young-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 4C, 2009, Pages 476~483
Tracking and detecting targets by the microwave seeker is affected by the clutter reflecting from the earth's surface. In order to detect retreating targets in look-down scenario, which appear in the sidelobe clutter (SLC) region, in the microwave seeker of high pulse repetition frequency (HPRF) mode, it is necessary to understand statistical characteristics of the surface SLC. Statistical analysis of SLC has been conducted for several kinds of the surface using data obtained by the captive flight test of the microwave seeker in the HPRF mode. The probability density function (PDF) fitting is conducted for several kinds and conditions of the surface. PDFs and PDF parameters, which best describe statistical distribution of the SLC power, are estimated. By using the estimated PDFs and PDF parameters, analyses for setting the target-detection thresholds, which give a desired level of target-detection false alarm probability, are made. These analysis materials for statistical characteristics of SLC power and the target-detection threshold can be used in various fields, such as development of a target-detection method, the constant false alarm rate processing.