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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 30, Issue 12C - Dec 2005
Volume 30, Issue 12B - Dec 2005
Volume 30, Issue 12A - Dec 2005
Volume 30, Issue 11C - Nov 2005
Volume 30, Issue 11B - Nov 2005
Volume 30, Issue 11A - Nov 2005
Volume 30, Issue 10C - Oct 2005
Volume 30, Issue 10B - Oct 2005
Volume 30, Issue 10A - Oct 2005
Volume 30, Issue 9C - Sep 2005
Volume 30, Issue 9B - Sep 2005
Volume 30, Issue 9A - Sep 2005
Volume 30, Issue 8C - Aug 2005
Volume 30, Issue 8B - Aug 2005
Volume 30, Issue 8A - Aug 2005
Volume 30, Issue 7C - Jul 2005
Volume 30, Issue 7B - Jul 2005
Volume 30, Issue 7A - Jul 2005
Volume 30, Issue 6C - Jun 2005
Volume 30, Issue 6B - Jun 2005
Volume 30, Issue 6A - Jun 2005
Volume 30, Issue 5C - May 2005
Volume 30, Issue 5B - May 2005
Volume 30, Issue 5A - May 2005
Volume 30, Issue 4C - Apr 2005
Volume 30, Issue 4B - Apr 2005
Volume 30, Issue 4A - Apr 2005
Volume 30, Issue 3C - Mar 2005
Volume 30, Issue 3B - Mar 2005
Volume 30, Issue 3A - Mar 2005
Volume 30, Issue 2C - Feb 2005
Volume 30, Issue 2B - Feb 2005
Volume 30, Issue 2A - Feb 2005
Volume 30, Issue 1C - Jan 2005
Volume 30, Issue 1B - Jan 2005
Volume 30, Issue 1A - Jan 2005
Selecting the target year
Power and Rate Adaptations in Multi-carrier DS/CDMA Communications over Rayleigh Fading Channel
Ah Heejune ; Lee Ye Hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 423~433
We present power(in frequency domain) and rate adaptation(in time domain) schemes in multicarrier (MC) direct-sequence code-division multiple-access(DS/CDMA) communications. Utilizing channel state information from the receiver, the adaptation schemes allocate power the user's sub-band with the largest channel gain. In the time domain, the transmission data rate is adapted for a desired transmission quality. In the case of single-user channels, a closed-form expression is derived for an optimal time domain power adaptation that minimizes the average bit error rate(BER). Channel inversion power adaptation is found to provide nearly optimal performance in this case, as the number of sub-bands or available average transmission power increase. Analysis and simulation results show the BER performance of the proposed power and rate adaptations with fixed average transmission power significantly improves the performance over the power allocation in the frequency domain only. Also, we compare the performance of the proposed power and rate adaptation schemes in MC-DS/CDMA systems with that of power and rate adapted single carrier DS/CDMA systems with RAKE receiver.
LDPC Decoding Algorithm for Multi-level Modulation Scheme
Lee In-Ki ; Jung Ji-Won ; Choi Duk-Gun ; Choi Ean-A ; Chang Dae-Ig ; Oh Duk-Gil ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 434~441
For LDPC decoding, received symbols are splitted bit by bit based using the received in-phase and quadrature components. The method of bit-splitting is affected on decoding performance because its method depend on distance over symbol constellation. Therefore this paper propose the bit split method using the sector information with sacrifice a little performance loss compared to Euclidean distance method. Futhermore DVB-S2 specification supports BC(Backward Compactible) mode which using the hierarchical modulation method, this paper also analyze the decoding performance according to deviation angle of 8PSK constellation for various LDPC coding rates.
High Speed Turbo Product Code Decoding Algorithm
Choi Duk-Gun ; Lee In-Ki ; Jung Ji-Won ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 442~449
In this paper, we introduce three kinds of simplified high-speed decoding algorithms for turbo product decoder. First, A parallel decoder structure, the row and column decoders operate in parallel, is proposed. Second, HAD(Hard Decision Aided) algorithm is used for early-stopping algorithm. Lastly, P-Parallel TPC decoder is a parallel decoding scheme, processing P rows and P columns in parallel instead of decoding one by one as that in the original scheme.
An FPGA Design of High-Speed Turbo Decoder
Jung Ji-Won ; Jung Jin-Hee ; Choi Duk-Gun ; Lee In-Ki ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 450~456
In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.
Efficient Traffic Management Scheme for Fast Authenticated Handover in IEEE 802.16e Network
Choi Jae Woo ; Kang Jeon il ; Nyang Dae Hun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 457~464
Recently, Portable Internet being standardized provides fast movement with wider service range than wireless LAN does. If Portable Internet service starts, many people will use Portable Internet and thus wireless traffic is going to increase. In Portable Internet, it is important to reduce handover latency to provide user with satisfactory service when handover occurs. In IEEE 802.16e, MSS sends its own security context information to one Base Station which it will move to reduce handover latency. But this is not suitable in the situation that the BS doesn't know the security context. To reduce handover latency of proactive caching method that is to send security context information to adjacency Base Stations in advance has been proposed by. In this paper we propose effective traffic management algorithm to reduce signaling network traffic caused by proactive caching method.
Directional Interpolation of Lost Block Using Difference of DC values and Similarity of AC Coefficients
Lee Hong Yub ; Eom Il Kyu ; Kim Yoo Shin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 465~474
In this paper, a directional reconstruction of lost block in image over noisy channel is presented. DCT coefficients or pixel values in the lost blocks are recovered by using the linear interpolation with available neighboring blocks that are adaptively selected by the directional measure that are composed of the DDC (Difference of DC opposite blocks)and SAC(Similarity of AC opposite blocks) between opposite blocks around lost blocks. The proposed directional recovery method is effective for the strong edge and texture regions because we do not make use of the fixed 4-neighboring blocks but exploit the varying neighboring blocks adaptively by the directional information in the local image. In this paper, we describe the novel directional measure(CDS: Combination of DDC and SAC) composed of the DDC and the SAC and select the usable block to recover the lost block with the directional measure. The proposed method shows about 0.6dB PSNR improvement in average compared to the conventional methods.
SNR-independent Methods for Estimating Maximum Doppler Frequency
Yu Hyun-kyu ; Park Goo-hyun ; Oh Seong-Mok ; Kang Chang-eon ; Hong Dae-sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 475~480
Information of the maximum Doppler frequency enable to optimize many channel-adaptive techniques and radio resource management methods for mobile radio communication systems. In this paper, we propose two maximum Doppler frequency estimators which are based on the level crossing rate(LCR) and the covariance function (COV). To eliminate the effect of additive noise, we analyze the conditions for the estimators independent of the signal-to-noise ratio(SNR) and implement the conditions with a simple downsampling process. The proposed methods achieve good SNR-independent performance.
Efficient Training Sequence Structure for Adaptive Linear Multiuser Detectors in Space-Time Block Coded Multiuser Systems
Hwang Hyeon Chyeol ; Shin Seung Hoon ; Seok Hyun Taek ; Lee Hyung Ki ; Yoo Dong Kwan ; Kwak Kyung Sup ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 481~489
In this letter, we propose an efficient training sequence structure for adaptive linear multiuser detectors in space-time block coded multiuser systems, by exploiting a particular property of the minimum mean square error multiuser detectors used in these systems. The proposed structure wastes less overall system capacity than the straightforward training structure, without any corresponding loss of performance, as confirmed by the simulation results.
Modeling of Self-Constructed Clustering and Performance Evaluation
Ryu Jeong woong ; Kim Sung Suk ; Song Chang kyu ; Kim Sung Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 490~496
In this paper, we propose a self-constructed clustering algorithm based on inference information of the fuzzy model. This method makes it possible to automatically detect and optimize the number of cluster and parameters by using input-output data. The propose method improves the performance of clustering by extended supervised learning technique. This technique uses the output information as well as input characteristics. For effect the similarity measure in clustering, we use the TSK fuzzy model to sent the information of output. In the conceptually, we design a learning method that use to feedback the information of output to the clustering since proposed algorithm perform to separate each classes in input data space. We show effectiveness of proposed method using simulation than previous ones
An Efficient Video Watermarking Using Re-Estimation and Minimum Modification Technique of Motion Vectors
Kang Kyung-won ; Moon Kwang-seok ; Kim Jong-nam ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 497~504
We propose an efficient video watermarking scheme using re-estimation and minimum modification technique of motion vectors. Conventional methods based on motion vectors do watermarking using modification of motion vectors. However, change of motion vectors results in the degradation of video quality. Thus, our scheme minimizes the modification of the original motion vectors and replaces an original motion vector by the adjacent optimal motion vector using re-estimation of motion vectors to avoid degradation of video quality. Besides, our scheme guarantees the amount of embedded watermark data using the adaptive threshold considering for an efficient video watermarking. In addition, this is compatible with current video compression standards without changing the bitstream. Experimental result shows that the proposed scheme obtains better video quality than other previous algorithms by about
Utilizing Korean Ending Boundary Tones for Accurately Recognizing Emotions in Utterances
Jang In-Chang ; Lee Tae-Seung ; Park Mikyoung ; Kim Tae-Soo ; Jang Dong-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 505~511
Autonomic machines interacting with human should have capability to perceive the states of emotion and attitude through implicit messages for obtaining voluntary cooperation from their clients. Voice is the easiest and most natural way to exchange human messages. The automatic systems capable to understanding the states of emotion and attitude have utilized features based on pitch and energy of uttered sentences. Performance of the existing emotion recognition systems can be further improved withthe support of linguistic knowledge that specific tonal section in a sentence is related with the states of emotion and attitude. In this paper, we attempt to improve recognition rate of emotion by adopting such linguistic knowledge for Korean ending boundary tones into anautomatic system implemented using pitch-related features and multilayer perceptrons. From the results of an experiment over a Korean emotional speech database, the improvement of
An Optimal Determination of Subband-Frame Size and Mode Switching Level for Adaptive OFDM-TDD System
Shin Kil-Ho ; Lee Chang-Suk ; Kim Jung-Gon ; Kim Hyung-Myung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 512~522
In this paper, an optimal determination method of the subband-frame size and mode-switching level is proposed for adaptive OFDM-TDD systems in frequency-selective time-varying channels. The optimization problem considering frequency selectivity. user's mobility, and the signaling overhead caused by the mode change information is formulated in the maximum spectral efficiency sense satisfying the target BER. Assuming that subband-frame size is given, the mode-switching level is first optimized so that the spectral efficiency can be maximized satisfying the target BER. The subband-frame size among candidates is then determined, which maximizes the spectral efficiency. Simulation results show that the proposed scheme outperforms conventional schemes, in terms of the spectral efficiency and the BER.
Weak Signal Detection in a Moving Average Model of Impulsive Noise
Kim In Jong ; Lee Jumi ; Choi Sang Won ; Park So Ryoung ; Song Iickho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 523~531
We derive decision regions of the maximum likelihood(ML) and suboptimum ML(S-ML) detectors in the first order moving average(FOMA) of an impulsive process. The ML and S-ML detectors are compared in terms of the bit-error-rate in the antipodal signaling system. Numerical results show that the S-ML detector, despite its reduced complexity and simpler structure, exhibits practically the same performance as the optimum ML detector. It is also shown that the performance gap between detectors for FOMA and independent and identically distributed noise becomes larger as the degree of noise impulsiveness increases.
Detection Schemes Based on Local Optimality and Sequential Criterion: 1. Threshold Analysis
Choi Sang Won ; Oh Jongho ; Kwon Hyoungmoon ; Yoon Seokho ; Bae Jinsoo ; Song Iickho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 532~540
In this paper, a sequential detection scheme is proposed as a combination of a novel weak-signal and a locally optimum(LO) detection schemes. In Part 1, we propose a novel sequential detection scheme for weak signals and show some interesting threshold properties and examples. In Part 2, the performance of the proposed sequential detection scheme is compared with that of the fixed sample size(FSS) test, sequential probability ratio test (SPRT), and truncated sequential probability ratio test(TSPRT).
Correlation Coefficients between Parametric and onparametric Test Statistics for Signal Detection Problems
Park So Ryoung ; Kwon Hyoungmoon ; Bae Jinsoo ; Choi Sang Won ; Lee Jumi ; Song Iickho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 541~550
In this paper, we address the derivation of joint distributions and correlation coefficients for four pairs of statistics used commonly in a number of signal detection schemes. The upper and lower bounds of the correlation coefficients are obtained, and interesting relationships between the correlation coefficients are derived. Explicit values of the correlation coefficients are given in the form of tables and figures for easy reference. The results in this paper should be useful in comparing various detection statistics.
Estimation of AOA Using WSF for Wireless Communications
Kim Suk Chan ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 551~559
Estimation of unknown signal parameters with sensor array measurements has been investigated quite extensively. Also, there has been in recent years an explosive increase in the number of mobile users in wireless cellular systems, thus contributing to growing levels of multi-user interference. To overcome this problem, application of adaptive antenna array techniques to further increase the channel capacity has been discussed. In this paper, a new model of locally scattered signals in the vicinity of mobiles is proposed by defining the mean steering vector and is manipulated mathematically for several distributions. Under this model an estimation method of the angle of arrival(AOA) is investigated based on a weighted subspace fitting(WSF) technique. Statistical analysis and simulations are also considered.
Transmit Antenna Selection for Spatial Multiplexing with Per Antenna Rate Control and Successive Interference Cancellation
Mun Cheol ; Jung Chang-Kyoo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 560~569
This paper proposes an algorithm for transmit antenna selection in a multi-input multi-output(MIMO) spatial multiplexing system with per antenna rate control(PARC) and an ordered successive interference cancellation (OSIC) receiver. The active antenna subset is determined at the receiver and conveyed to the transmitter using feedback information on transmission rate per antenna. We propose a serial decision procedure consisting of a successive process that tests whether antenna selection gain exists when the antenna with the lowest pre-processing signal to interference and noise ratio(SINR) is discarded at each stage. Furthermore, we show that 'reverse detection ordering', whereby the signal with the lowest SINR is decoded at each stage of successive decoding, widens the disparities among fractions of the whole capacity allocated to each individual antenna and thus maximizes a gain of antenna selection. Numerical results show that the proposed reverse detection ordering based serial antenna selection approaches the closed-loop MIMO capacity and that it induces a negligible capacity loss compared with the heuristic selection strategy even with considerably reduced complexity.
Face Pose Transformation for Pose Invariant Face Recognition
Park Hyun-Sun ; Park Jong-Il ; Kim Whoi-Yul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 570~576
Recognition of posed face is one of the most challenging problems in the field of face recognition. In this paper, as a preprocessing step for recognizing such faces, a method to transform non-frontal face images into frontal face images is proposed. The linear relationship between eigenfaces is utilized to obtain a pose transform matrix. The proposed method is verified with a well-known face recognition algorithm based on PCA/LDA. Compared to the conventional algorithm applied to the original posed face images, our experimental results indicated that the proposed method contributes to improve the recognition rate of such faces by
Design of FIR filters with Prefilter-Equalizer Structure for Narrowband Communication Systems
Oh Hyukjun ; Ahn Heejune ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 577~584
Optimal methods for designing multiplierless minimal complexity FIR filters with cascaded prefilter-equalizer structures are proposed for narrowband communication systems. Assuming that an FIR filter consists of a cyclotomic polynomial(CP) prefilter and an interpolated second order polynomial(ISOP) equalizer, in the proposed method the prefilter and equalizer are simultaneously designed using mixed integer linear programming(MILP). The resulting filter is a cascaded filter with minimal complexity. Design examples demonstrate that the proposed methods produce a more computationally efficient cascaded prefilter-equalizer than other existing filters.
Frontal Face Region Extraction & Features Extraction for Ocular Inspection
Cho Dong-Uk ; Kim Sun-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 585~592
One of the most important things in the researches on diseases is to attach more importance to prevention of a disease and preservation of health than to treatment of a disease, also to foods rather than to medicines. In this context, the most significant concern in examining a patient is to find the presence of disease, and, if any, to diaguose the type of disease, after which a pharmacotherapy is followed. In this paper, various diagnosis methods of Oriental medicines are discussed. And ocular inspection, the most important method among the 4 disease diagnoses of Oriental medicines, is studied. Observing a person's shape and color has been the major method for ocular inspection, which usually has been dependent upon doctor's intuition as of these days. We are developing an automatic system which provides objective basic data for ocular inspection. As the first stage, we applied the signal processing techniques to automatic feature extraction of faces for ocular inspection. Firstly, facial regions are extracted from the point of frontal view, which was followed by extraction of their features. The experiment applied to 20 persons showed that frontal face regions are perfectly extracted, as well as their features, such as eyes, eyebrows, noses and mouths. Future work will seek to address the issues of morphological operation for a few unfinished extraction results, such as combined hair and eyebrows.
RFID Tag's Security Level Based RFID Authentication Protocol
Oh Soo-hyun ; kwak Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 593~600
Recently, RFID system is a main technology to realize ubiquitous computing environments. Because RFID system that is an automatic identification technology using radio frequency is a system to read and write the data of the entity. Therefore, many companies are interested in RFID system to reduce supply chain management and inventory control cost. However, for providing secure service, RFID authentication technology secure against tracking by an adversary is researched first. In this paper, we proposed security level based RFID authentication protocol providing reduce computational and communicational workload in the back-end database. The proposed protocol is secure against reply attack, spoofing attack, traffic analysis, and location privacy, since the proposed protocol based on the security of the hash function.
Inter-AP Security Transition Mechanism and Its FSM in WLAN AP Supporting Fast Roaming
Chung ByungHo ; Kang You Sung ; Oh KyungHee ; Kim SangHa ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 601~606
Recently with the high expectation of voice over WLAN service, to supped fast inter-AP security transition in WLAN AP is one of the most actively investigating issues. It is also very important to minimize inter-AP security transition latency, while maintaining constantly the secure association from old AP when a station transits to new AP. Hence, this paper first defines secure transition latency as a primary performance metric of AP system in WLAN supporting IEEE802.11i, 802.1x, and 802.11f, and then presents low latency inter-AP security transition mechanism and its security FSM whose objective is to minimize inter-AP transition latency. Experiment shows that the proposed scheme outperforms the legacy 802.1X AP up to
with regard to the transition latency.
Group Key Agreement Protocols for Combined Wired/Wireless Networks
Nam Junghyun ; Kim Seungjoo ; Won Dongho ; Jang Chungryong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 6C, 2005, Pages 607~615
Group key agreement protocols are designed to allow a group of parties communicating over a public network to securely establish a common secret key. Over the years, a number of solutions to this problem have been proposed with varying degrees of complexity. However, there seems to have been no previous systematic look at the growing problem of key agreement over combined wired/wireless networks, consisting of both high-performance computing machines and low-power mobile devices. In this paper we present an efficient group key agreement scheme well suited for this networking environment. Our scheme meets efficiency, scalability, and all the desired security requirements.