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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 32, Issue 12C - Dec 2007
Volume 32, Issue 12B - Dec 2007
Volume 32, Issue 12A - Dec 2007
Volume 32, Issue 11C - Nov 2007
Volume 32, Issue 11B - Nov 2007
Volume 32, Issue 11A - Nov 2007
Volume 32, Issue 10C - Oct 2007
Volume 32, Issue 10B - Oct 2007
Volume 32, Issue 10A - Oct 2007
Volume 32, Issue 9C - Sep 2007
Volume 32, Issue 9B - Sep 2007
Volume 32, Issue 9A - Sep 2007
Volume 32, Issue 8C - Aug 2007
Volume 32, Issue 8B - Aug 2007
Volume 32, Issue 8A - Aug 2007
Volume 32, Issue 7C - Jul 2007
Volume 32, Issue 7B - Jul 2007
Volume 32, Issue 7A - Jul 2007
Volume 32, Issue 6C - Jun 2007
Volume 32, Issue 6B - Jun 2007
Volume 32, Issue 6A - Jun 2007
Volume 32, Issue 5C - May 2007
Volume 32, Issue 5B - May 2007
Volume 32, Issue 5A - May 2007
Volume 32, Issue 4C - Apr 2007
Volume 32, Issue 4B - Apr 2007
Volume 32, Issue 4A - Apr 2007
Volume 32, Issue 3C - Mar 2007
Volume 32, Issue 3B - Mar 2007
Volume 32, Issue 3A - Mar 2007
Volume 32, Issue 2C - Feb 2007
Volume 32, Issue 2B - Feb 2007
Volume 32, Issue 2A - Feb 2007
Volume 32, Issue 1C - Jan 2007
Volume 32, Issue 1B - Jan 2007
Volume 32, Issue 1A - Jan 2007
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Design of a Low-Power LDPC Decoder by Reducing Decoding Iterations
Lee, Jun-Ho ; Park, Chang-Soo ; Hwang, Sun-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 801~809
LDPC Low Density Parity Check) code, which is an error correcting code determined to be applied to the 4th generation mobile communication systems, requires a heavy computational complexity due to iterative decodings to achieve a high BER performance. This paper proposes an algorithm to reduce the number of decoding iterations to increase performance of the decoder in decoding latency and power consumption. Measuring changes between the current decoded LLR values and previous ones, the proposed algorithm predicts directions of the value changes. Based on the prediction, the algorithm inverts the sign bits of the LLR values to speed up convergence, which means parity check equation is satisfied. Simulation results show that the number of iterations has been reduced by about 33% without BER performance degradation in the proposed decoder, and the power consumption has also been decreased in proportional to the amount of the reduced decoding iterations.
Symbol Error Probability of DVB-S2 System with I/Q Unbalances
Im, In-Chul ; Won, Seung-Chan ; Yoon, Dong-Weon ; Park, Sang-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 810~819
The I/Q unbalance which is generated by non-ideal components such as a
phase shifter and I/Q filters is an inevitable physical phenomenon and leads to performance degradation when we implement a coherent two-dimensional (2-D) modulation/demodulation system. This paper provides an exact and general expression for the SEP(symbol error probability) of DVB-S2 system with I/Q phase and amplitude unbalance over AWGN channel. Coordinate rotation and shift techniques used to redefine a received signal are key mathematical tools. In conclusion, the derived result is expressed as a linear combination of the 2-D Gaussian Q-functions.
Improved Super-Orthogonal Space Time Codes for Fast Rayleigh Fading Channels
Kim, Chang-Joong ; Heo, Seo-Weon ; Lee, Ho-Kyoung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 820~825
Super-orthogonal space-time trellis code (SOTTC) uses the expanded set of the orthogonal space-time block code to obtain coding gain and diversity gain without loss of transmit rate. In SOSTTCs, signal set expansions are performed by rotating the first column of the code matrix. The rotating phases used previously were selected to avoid the signal constellation expansion rather than the performance improvement. In this paper, we make a design criterion to select the proper rotating phase to improve the performance of SOSTTCs for fast Rayleigh fading channels. In addition, we design improved SOSTTCs by using the proper rotating phase. Simulation results are also provided to confirm our SOSTTCs are superior to the previous SOSTTCs in the view of BER performance.
An Adaptive Transmission Scheme Based on Interference Temperature Cognition for Cognitive Radio Systems
Hong, Min-Ki ; Kim, Jae-Woon ; Kim, Hyun-Wook ; Shin, Yo-An ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 826~833
In this paper, we present an adaptive transmission system model to establish the baseline for wireless adaptive transmission using CR (Cognitive Radio) systems, and propose an adaptive transmission scheme based on IT (Interference Temperature) cognition for CR systems in the presented system environment. The proposed CR adaptive transmission scheme is the method that provides the CR user with the maximum transmit power in the range of not causing any interference to the incumbent user and guaranteeing the optimal throughput by applying CR-AMC (CR-Adaptive Modulation and Coding) in the given channel state. Simulation results show that in case of using the proposed CR adaptive transmission scheme, there is little degradation of BER performance, while causing no interference to the incumbent user. At the same time, the proposed scheme guarantees the optimal throughput to the CR user in the given channel state.
Automatic Superimposed Text Localization from Video Using Temporal Information
Jung, Cheol-Kon ; Kim, Joong-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 834~839
The superimposed text in video brings important semantic clues into content analysis. In this paper, we present the new and fast superimposed text localization method in video segments. We detect the superimposed text by using temporal information contained in the video. To detect the superimposed text fast, we have minimized the candidate region of localizing superimposed texts by using the difference between consecutive frames. Experimental results are presented to demonstrate the good performance of the new superimposed text localization algorithm.
Multiple Description Coding of 3-D Data
Park, Sung-Bum ; Kim, Chang-Su ; Lee, Sang-Uk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 840~848
A multiple description coding (MDC) scheme for 3-D Data is presented. First, a plane-based 3-D data is split into two descriptions, each of which has identical contribution in 3-D surface reconstruction. In order to maximize the visual quality of reconstructed 3-D data, then, plane parameters are modified according to channel error condition. Finally, these descriptions are compressed and transmitted over distinct channels. In decoder, if two descriptions are available, we reconstruct a high quality 3-D data. If only one description is transmitted, however, 3-D surface recovery scheme reduces artifacts on erroneous 3-D surface, yielding a smooth 3-D surface. Therefore, the proposed algorithm guarantees acceptable quality reconstruction of 3-D data even though one channel is totally lost.
A Macroblock-Layer Rate Control for H.264/AVC Using Quadratic Rate-Distortion Model
Son, Nam-Rae ; Lee, Guee-Sang ; Yim, Chang-Hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 849~860
Because the H.264/AVC standard adopts the variable length coding algorithm, the rate of encoded video bitstream fluctuates a lot as time flows, though its compression efficiency is superior to that of existing standards. When a video is transmitted in real-time over networks with fixed low-bandwidth, it is necessary to control the bit rate which is generated from encoder. Many existing rate control algorithms have been adopting the quadratic rate-distortion model which determines the target bits for each frame. We propose a new rate control algorithm for H.264/AVC video transmission over networks with fixed bandwidth. The proposed algorithm predicts quantization parameter adaptively to reduce video distortion using the quadratic rate-distortion model, which uses the target bit rate and the mean absolute difference for current frame considering pixel difference between macroblocks in the previous and the current frame. On video samples with high motion and scene change cases, experimental results show that (1) the proposed algorithm adapts the encoded bitstream to limited channel capacity, while existing algorithms abruptly excess the limit bit rate; (2) the proposed algorithm improves picture quality with
Centroid Neural Network with Bhattacharyya Kernel
Lee, Song-Jae ; Park, Dong-Chul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 861~866
A clustering algorithm for Gaussian Probability Distribution Function (GPDF) data called Centroid Neural Network with a Bhattacharyya Kernel (BK-CNN) is proposed in this paper. The proposed BK-CNN is based on the unsupervised competitive Centroid Neural Network (CNN) and employs a kernel method for data projection. The kernel method adopted in the proposed BK-CNN is used to project data from the low dimensional input feature space into higher dimensional feature space so as the nonlinear problems associated with input space can be solved linearly in the feature space. In order to cluster the GPDF data, the Bhattacharyya kernel is used to measure the distance between two probability distributions for data projection. With the incorporation of the kernel method, the proposed BK-CNN is capable of dealing with nonlinear separation boundaries and can successfully allocate more code vector in the region that GPDF data are densely distributed. When applied to GPDF data in an image classification probleml, the experiment results show that the proposed BK-CNN algorithm gives 1.7%-4.3% improvements in average classification accuracy over other conventional algorithm such as k-means, Self-Organizing Map (SOM) and CNN algorithms with a Bhattacharyya distance, classed as Bk-Means, B-SOM, B-CNN algorithms.
Modified Cubic Convolution Scaler for Multiformat Conversion in a Transcoder
Yoo, Young-Joe ; Seo, Ju-Heon ; Han, Jong-Ki ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 867~880
We derive a modified version of cubic convolution interpolation for the enlargement or reduction of digital images by arbitrary scaling factors. The proposed scaling scheme is used to resize various format pictures in the transcoding system, which transforms the bitstream compressed at a bit rate, such as the HD bitstream, into another bit rate stream. In many applications such as the transcoder, the resolution conversion is very important for changing the image size while the scaled image maintains high quality. We focus on the modification of the scaler kernel according to the relation between formats of the original and the resized image. In the modification, various formats defined in MPEG standards are considered. We show experimental results that demonstrate the effectiveness of the proposed interpolation method.
Automatic Summarization of Basketball Video Using the Score Information
Jung, Cheol-Kon ; Kim, Eui-Jin ; Lee, Gwang-Gook ; Kim, Whoi-Yul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 881~887
In this paper, we proposed a method for content based automatic summarization of basketball game videos. For meaningful summary, we used the score information in basketball videos. And the score information is obtained by recognizing the digits on the score caption and analyzing the variation of the score. Generally, important events of basketball are the 3-point shot, one-sided runs, the lead changes, and so on. We have detected these events using score information and made summaries and highlights of basketball video games.
Two New Types of Candidate Symbol Sorting Schemes for Complexity Reduction of a Sphere Decoder
Jeon, Eun-Sung ; Kim, Yo-Han ; Kim, Dong-Ku ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 888~894
The computational complexity of a sphere decoder (SD) is conventionally reduced by decoding order scheme which sorts candidate symbols in the ascending order of the Euclidean distance from the output of a zero-forcing (ZF) receiver. However, since the ZF output may not be a reliable sorting reference, we propose two types of sorting schemes to allow faster decoding. The first is to use the newly found lattice points in the previous search round instead of the ZF output (Type I). Since these lattice points are closer to the received signal than the ZF output, they can serve as a more reliable sorting reference for finding the maximum likelihood (ML) solution. The second sorting scheme is to sort candidate symbols in descending order according to the number of candidate symbols in the following layer, which are called child symbols (Type II). These two proposed sorting schemes can be combined with layer sorting for more complexity reduction. Through simulation, the Type I and Type II sorting schemes were found to provide 12% and 20% complexity reduction respectively over conventional sorting schemes. When they are combined with layer sorting, Type I and Type II provide an additional 10-15% complexity reduction while maintaining detection performance.
Study on CGM-LMS Hybrid Based Adaptive Beam Forming Algorithm for CDMA Uplink Channel
Hong, Young-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 895~904
This paper proposes a robust sub-optimal smart antenna in Code Division Multiple Access (CDMA) basestation. It makes use of the property of the Least Mean Square (LMS) algorithm and the Conjugate Gradient Method (CGM) algorithm for beamforming processes. The weight update takes place at symbol level which follows the PN correlators of receiver module under the assumption that the post correlation desired signal power is far larger than the power of each of the interfering signals. The proposed algorithm is simple and has as low computational load as five times of the number of antenna elements(O(5N)) as a whole per each snapshot. The output Signal to Interference plus Noise Ratio (SINR) of the proposed smart antenna system when the weight vector reaches the steady state has been examined. It has been observed in computer simulations that proposed beamforming algorithm improves the SINR significantly compared to the single antenna case. The convergence property of the weight vector has also been investigated to show that the proposed hybrid algorithm performs better than CGM and LMS during the initial stage of the weight update iteration. The Bit Error Rate (BER) characteristics of the proposed array has also been shown as the processor input Signal to Noise Ratio (SNR) varies.
IQ Unbalance Compensation for OPDM Based Wireless LANs
Kim, Ji-Ho ; Jung, Yun-Ho ; Kim, Jae-Seok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 905~912
This paper proposes an efficient estimation and compensation scheme of IQ imbalance for OFDM-based WLAN systems in the presence of symbol timing error. Since the conventional scheme assumes perfect time synchronization, the criterion of the scheme used to derive the estimation of IQ imbalance is inadequate in the presence of the symbol timing error and the system performance is seriously degraded. New criterion and compensation scheme considering the effect of symbol timing error are proposed. With the proposed scheme, the IQ imbalance can be almost perfectly eliminated in the presence of symbol timing error. The bit error rate performance of the proposed scheme is evaluated by the simulation. In case of 54 Mbps transmission mode in IEEE 802.11a system, the proposed scheme achieves a SNR gain of 4.3dB at
. The proposed compensation algorithm of IQ imbalance is implemented using Verilog HDL and verified. The proposed IQ imbalance compensator is composed of 74K logic gates and 6K bits memory from the synthesis result using 0.18um CMOS technology.
An Efficient Architecture Exploration Method for Optimal ASIP Design
Lee, Sung-Rae ; Hwang, Sun-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 913~921
Retargetable compiler which generates executable code for a target processor and performance profiler are required to design a processor optimized for a specific application. This paper presents an architecture exploration methodology based on ADL (Architecture Description Language). We synthesized instruction set and optimized processor structure using information extracted from application program. The information of operation sequences executed frequently and register usage are used for processor optimization. Architecture exploration has been performed for JPEG encoder to show the effectiveness of the system. The ASIP designed using the proposed method shows 1.97 times better performance.
An Approximated RLS Algorithm for Adaptive Parameter Estimation
Ahn, Bong-Man ; Hwang, Jee-Won ; Ryoo, Jung-Rae ; Cho, Ju-Phil ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 9C, 2007, Pages 922~928
This paper presents the fast adaptive algorithm which applies an approximation scheme into RLS algorithm. The proposed algorithm(D-RLS) derives a QRD RLS algorithm derivation process from RLS algorithm recursively. D-RLS has the similar pattern as the algorithm having the approximation that input signals are separated respectively. Computational complexity of D-RLS is O(N), fewer than
. To evaluate performance of proposed algorithm, we use the system identification method of FIR and Volterra system. And, finally, we can show D-RLS has an excellent performance.