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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 28, Issue 12C - Dec 2003
Volume 28, Issue 12B - Dec 2003
Volume 28, Issue 12A - Dec 2003
Volume 28, Issue 11C - Nov 2003
Volume 28, Issue 11B - Nov 2003
Volume 28, Issue 11A - Nov 2003
Volume 28, Issue 10C - Oct 2003
Volume 28, Issue 10B - Oct 2003
Volume 28, Issue 10A - Oct 2003
Volume 28, Issue 9C - Sep 2003
Volume 28, Issue 9B - Sep 2003
Volume 28, Issue 9A - Sep 2003
Volume 28, Issue 8C - Aug 2003
Volume 28, Issue 8B - Aug 2003
Volume 28, Issue 8A - Aug 2003
Volume 28, Issue 7C - Jul 2003
Volume 28, Issue 7B - Jul 2003
Volume 28, Issue 7A - Jul 2003
Volume 28, Issue 6C - Jun 2003
Volume 28, Issue 6B - Jun 2003
Volume 28, Issue 6A - Jun 2003
Volume 28, Issue 5C - May 2003
Volume 28, Issue 5B - May 2003
Volume 28, Issue 5A - May 2003
Volume 28, Issue 4C - Apr 2003
Volume 28, Issue 4B - Apr 2003
Volume 28, Issue 4A - Apr 2003
Volume 28, Issue 3C - Mar 2003
Volume 28, Issue 3B - Mar 2003
Volume 28, Issue 3A - Mar 2003
Volume 28, Issue 2C - Feb 2003
Volume 28, Issue 2B - Feb 2003
Volume 28, Issue 2A - Feb 2003
Volume 28, Issue 1C - Jan 2003
Volume 28, Issue 1B - Jan 2003
Volume 28, Issue 1A - Jan 2003
Volume 28, Issue 9 - 00 2003
Volume 28, Issue 8 - 00 2003
Volume 28, Issue 7 - 00 2003
Volume 28, Issue 6 - 00 2003
Volume 28, Issue 5 - 00 2003
Volume 28, Issue 3 - 00 2003
Volume 28, Issue 2 - 00 2003
Volume 28, Issue 1 - 00 2003
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Design and Implementation of a High-Performance Index Manager in a Main Memory DBMS
김상욱 ; 이경태 ; 최완 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 605~605
The main memory DBMS(MMDBMS) efficiently supports various database applications that require high performance since it employs main memory rather than disk as a primary storage. In this paper, we discuss the index manager of the Tachyon, a next-generation MMDBMS. Recently, the gap between the CPU processing and main memory access times is becoming much wider due to rapid advance of CPU technology. By devising data structures and algorithms that utilize the behavior of the cache in CPU, we are able to enhance the overall performance of MMDBMSs considerably. In this paper, we address the practical implementation issues and our solutions for them obtained in developing the cache-conscious index manager of the Tachyon. The main issues touched are (1) consideration of the cache behavior, (2) compact representation of the index entry and the index node, (3) support of variable-length keys, (4) support of multiple-attribute keys, (5) support of duplicated keys, (6) definition of the system catalog for indexes, (7) definition of external APIs, (8) concurrency control, and (9) backup and recovery. We also show the effectiveness of our approach through extensive experiments.
Cyclic Polling-Based Dynamic Bandwidth Allocation for Differentiated Classes of Service in Ethernet Passive Optical Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 620~620
Ethernet passive optical networks (EPONs) are an emerging access network technology that provide a low-cost method of deploying optical access lines between a carrier's central office and customer sites. Dynamic bandwidth allocation (DBA) provides statistical multiplexing between the optical network units for efficient upstream channel utilization. To support dynamic bandwidth distribution, 1 propose an cyclic polling-based DBA algorithm for differentiated classes of service in EPONs. And, I show that an interleaved polling scheme severely decreases downstream channel capacity for user traffics when the upstream network load is low. To obtain realistic simulation results, I used synthetic traffic that exhibits the properties of self-similarity and long-range dependence I then analyzed the network performance under various loads, specifically focusing on packet delays for different classes of traffic.
A Dynamic Transmission Rate Allocation Algorithm for Multiplexing Delay-sensitive VBR-coded Streams
김진수 ; 유국열 ; 이문노 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 628~628
This paper describes a novel multiplexing scheme for delay-sensitive multiple VBR-coded bit streams in live multimedia service offered to high-speed networks. The primary goal of multiplexing in this paper is to keep delay limits of each bit streams and to enhance network resource utilization when they no multiplexed and transmitted over network. For this aim, this paper presents a dynamical control scheme which does not cause violation of any delay constraints to each bit steam. The scheme is based on the assumption that recent behavior of the each bit scream has high correlation with near-term future behavior. Such property is used to make as flat as possible by both temporal averaging on a stream-by-stream and spatial averaging is introduced when multiple VBR-coded bit streams are multiplexed. The effectiveness of the scheme is evaluated by several simulation using an MPEG-coded video trace of Star_wars and it is shown that the proposed scheme can effectively reduce the feat rate and coefficient of variation of the multiplexed transmission rate.
QoS in Explicit Multicast Networks using End-to-End Measurement
김영한 ; 오승훈 ; 윤상균 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 638~638
In this paper, we propose a group communication approach which can provide quality of service for soft real-time applications. This proposed scheme combining the explicit multicast, end-point measure-based admission control scheme(EMBAC), and diffserv, removes the need of maintaining state information in the network, so that it would be easily deployable in real networks. We propose the scheme of node configuration to measure the quality of the diffserv network, and that of managing EMBAC over group communication environment. By simulation, we validate the QoS of the proposed multicast service network.
A Design of the IP Lookup Architecture for High-Speed Internet Router
서해준 ; 안희일 ; 조태원 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 647~647
LPM(Longest Prefix Matching)searching in If address lookup is a major bottleneck of IP packet processing in the high speed router. In the conventional lookup table for the LPM searching in CAM(Content Addressable Memory) the complexity of fast update take 0(1). In this paper, we designed pipeline architecture for fast update of 0(1) cycle of lookup table and high throughput and low area complexity on LPM searching. Lookup-table architecture was designed by CAM(Content Addressable Memory)away that uses 1bit RAM(Random Access Memory)cell. It has three pipeline stages. Its LPM searching rate is affected by both the number of key field blocks in stage 1 and stage 2, and distribution of matching Point. The RTL(Register Transistor Level) design is carried out using Verilog-HDL. The functional verification is thoroughly done at the gate level using 0.35㎛ CMOS SEC standard cell library.
Performance of 8SQAM System in a Nonlinearly Amplified Channel Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 669~669
Performance of 8SQAM System in a Nonlinearly Amplified SCPC-FDMA Channel Interference Environment
성봉훈 ; 서종수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 678~678
8SQAM(8-state Superposed Quadrature Amplitude Modulation) being a new modem technique for use in power and bandwidth limited digital communication system generates output signals which have a mか and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Also, 8SQAM signal is free of inter-symbol interference(ISI), and has a compact power spectrum. Accordingly 8SQAM, as compared with a conventional 8PSK, is influenced a little by inter-modulation(IM), inter-symbol interference(ISI) and adjacent channel interference(ACI) in a nonlinearly amplified multi-channel(SCPC-FDMA) environment. In this paper, the performance of 8SQAM system in a nonlinearly amplified multi-channel interference environment is analyzed via computer simulation The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of α = 0.3 by 2.7dB in CNR to maintain BER=1×
when input back-off(IBO) of HPA is 1dB and channel space is 41.7% of the data bit rate(i.e., spectral efficiency = 2.40b/s/Hz).
Parallel Sub-filter Searching Structure and Parameter Decision Technique in Adaptive PN Code Acquisition Systems
한명수 ; 류탁기 ; 홍대식 ; 강창언 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 688~688
In this paper, the parallel sub-filter searching structure to be adapted that divides a filter into several sub filters and the parameter decision technique to control adaptive parameters with power of received signal in the code acquisition system using adaptive filter are proposed. The numerical results for the system probabilities are derived that the code acquisition system using parallel sub-filter searching structure is statistically analyzed. Also, characteristic of the parameters in adaptive code acquisition system is analyzed by simulations and the parameter decision technique through SNRc estimation is explained. The system with parallel sub-filter searching structure outperforms by 1∼l.5 dB for 16 taps, 5∼6 dB for 64 taps. And the system with parameter decision technique works efficiently with the reasonable degree of degradation about 1 ∼2.5dB for 16 and 32 taps.
An Improved Early Detection of all-zero DCT Coefficients for Fast Video Encoding
Kim, Gyu-Yeong ; Mun, Yong-Ho ; Kim, Jae-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 696~696
In this paper, we propose an improved early detection of all-zero DCT coefficients for fast video encoding. From the experimental observation, it is shown that the performance of the conventional method is limited because of the imprecision sufficient condition. When the calculation of the SAD in motion estimation is simply modified, more precise sufficient condition is derived from the theoretical analysis. Based on this idea, DCT and the quantization stages are effectively skipped in the proposed algorithm with no image degradation. The simulation results show that the proposed algorithm achieves computational saving over 10% compared to the conventional method.
Channel Equalization using Fuzzy-ARTMAP Neural Network
이정식 ; 김진희 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 705~705
This paper studies the application of a fuzzy-ARTMAP neural network to digital communications channel equalization. This approach provides new solutions for solving the problems, such as complexity and long training, which found when implementing the previously developed neural-basis equalizers. The proposed fuzzy-ARTMAP equalizer is fast and easy to train and includes capabilities not found in other neural network approaches; a small number of parameters, no requirements for the choice of initial weights, automatic increase of hidden units, no risk of getting trapped in local minima, and the capability of adding new data without retraining previously trained data. In simulation studies, binary signals were generated at random in a linear channel with Gaussian noise. The performance of the proposed equalizer is compared with other neural net basis equalizers, specifically MLP and RBF equalizers.
Classification of C.elegans Behavioral Phenotypes Using Shape Information
전미라 ; 나원 ; 홍승범 ; 백중환 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 712~712
C.elegans are often used to study of function of gene, but it is difficult for human observation to distinguish the mutants of C.elegans. To solve this problem, the system, which can classify the mutant types automatically using the computer vision, is now studying. In previous work［1］, we described the preprocessing method for automated-classification system. In this paper, we introduce shape features, which can be extracted from an acquisition image. We divide the feature into two categories, which are related to size and posture of the worm, and each feature is described mathematically We validate the shape information experimentally. And we use hierarchical clustering algorithm for classification. It reveals that 4 mutants of the worm, which are used in experiment, can be classified with over 90% of success rate.
Two-stage Content-based Image Retrieval Using the Dimensionality Condensation of Feature Vector
조정원 ; 최병욱 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 719~719
The content-based image retrieval system extracts features of color, shape and texture from raw images, and builds the database with those features in the indexing process. The search in the whole retrieval system is defined as a process which finds images that have large similarity to query image using the feature database. This paper proposes a new two-stage search method in the content-based image retrieval system. The method is that the features are condensed and stored by the property of Cauchy-Schwartz inequality in order to reduce the similarity computation time which takes a mostly response time from entering a query to getting retrieval results. By the extensive computer simulations, we have observed that the proposed two-stage search method successfully reduces the similarity computation time while maintaining the same retrieval relevance as the conventional exhaustive search method. We also have observed that the method is more effective as the number of images and dimensions of the feature space increase.
Motion Estimation Skipping Technique for Fast Motion Estimation
강현수 ; 박성모 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 726~726
The paper proposes a motion estimation (ME) technique to reduce computational complexity. It is achieved by skipping ME process for macro-blocks decided to be in no need of the operation. Thus, it is called ME skipping technique(MEST). In general, the ME is composed of integer pixel precision ME (IME) followed by half pixel precision ME (HME). The MEST is performed just before an IME process and makes a decision on skipping the IME process according to a criterion based on ME errors of adjacent macro-blocks (MBs) already encoded. When the IME process for a MB is decided to be skipped, which is called ME skip mode, the IME process is skipped and the integer pixel precision motion vector of the MB is just replaced by a predicted vector and used as the input of HME. On the other hands, the IME processes for MBs in ME non-skip mode are not skipped but normally performed. Accordingly, the MEST is very effective to reduce computational complexity when MBs in ME skip mode is abundant. In addition, when the MEST is applied to video encoder, it contributes to more accurate rate control and more robustness for channel errors. It is experimentally shown that the MEST has the above advantages while maintaining good reconstructed image quality.
Effective group key management protocol for secure multicast communication
이현종 ; 김진철 ; 오영환 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 733~733
Unlikely unicast transmission, there are many elements that threaten security. Thus, key management of creating and distributing group keys to authorized group members is a critical aspect of secure multicast operations. To offer security in multicast environment, the recent researches are related to most group key distribution. In this thesis, we propose a group key management protocol for efficient, scalable, and multicast operation. This proposed protocol architecture can distribute traffic centralized to the key server. since the group key rekeyed by sub-group manager. The detailed simulation compared with other group key management protocol show that the proposed group key management protocol is better for join, leave, and data latency.
Mobile Agent Protection Scheme through Execution Tracing of Agent Code and Status
정창렬 ; 고진광 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 7, 2003, Pages 743~743
With the expansion of computer technology the mobility of a mobile agent code having the flexibility in the dispersive computer situation is used to set up the applications distributed on the Internet. As it also has the ability to transmit the mobile code of a mobile agent and to receive it from a far-off host, the executive circumstances of the host system in which an agent is executed have to access to an agent code and the executive state capable of executing an agent code. Therefore, it is difficult to prevent the forgery, the alteration and the wrong execution of an agent from a malicious host. This dissertation suggests the mechanism which can protect an agent from the malicious action through the executive pursuit of a code-named mobile agent. The security of this mechanism is verified through the protective process of a mobile agent in this mechanism.