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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 29, Issue 12C - Dec 2004
Volume 29, Issue 12B - Dec 2004
Volume 29, Issue 12A - Dec 2004
Volume 29, Issue 11C - Nov 2004
Volume 29, Issue 11B - Nov 2004
Volume 29, Issue 11A - Nov 2004
Volume 29, Issue 10C - Oct 2004
Volume 29, Issue 10B - Oct 2004
Volume 29, Issue 10A - Oct 2004
Volume 29, Issue 9C - Sep 2004
Volume 29, Issue 9B - Sep 2004
Volume 29, Issue 9A - Sep 2004
Volume 29, Issue 8C - Aug 2004
Volume 29, Issue 8B - Aug 2004
Volume 29, Issue 8A - Aug 2004
Volume 29, Issue 7C - Jul 2004
Volume 29, Issue 7B - Jul 2004
Volume 29, Issue 7A - Jul 2004
Volume 29, Issue 6C - Jun 2004
Volume 29, Issue 6B - Jun 2004
Volume 29, Issue 6A - Jun 2004
Volume 29, Issue 5C - May 2004
Volume 29, Issue 5B - May 2004
Volume 29, Issue 5A - May 2004
Volume 29, Issue 4C - Apr 2004
Volume 29, Issue 4B - Apr 2004
Volume 29, Issue 4A - Apr 2004
Volume 29, Issue 3C - Mar 2004
Volume 29, Issue 3B - Mar 2004
Volume 29, Issue 3A - Mar 2004
Volume 29, Issue 2C - Feb 2004
Volume 29, Issue 2B - Feb 2004
Volume 29, Issue 2A - Feb 2004
Volume 29, Issue 1C - Jan 2004
Volume 29, Issue 1B - Jan 2004
Volume 29, Issue 1A - Jan 2004
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Performance of an Adaptive Modulation System Using Antenna Switching
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 907~914
In this paper, we propose an application of the receiver antenna switching to an conventional adaptive modulation system and derived the optimal antenna switching threshold of the system to maximize the average transmission bit rate and analyzed its performance. Also, we compare the performances of the presented scheme with those of an adaptive modulation using the antenna selection diversity and the one with a single antenna in terms of the average number of bits per symbol and the probability of no transmission. Performance comparison results show that the proposed system has an SNR gain of 1.4 dB over the adaptive modulation using a single antenna when the average number of bits per a symbol is two and yields an SNR gain of 6 dB for maintaining the probability of no transmission at the level of 0.1.
New Polyphase Sequence with Good Nonperiodic Autocorrelation Property
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 915~920
In this paper, we propose the new polyphase sequence with the best nonperiodic autocorrelation property in the viewpoint of the merit factors, which are important criteria for a nonperiodic autocorrelation property. We propose the general implementation of a polyphase sequence generator over an integer residue ring by using a linear feedback shift register(LFSR), in addition, we analyze the linear complexities of polyphase sequences based on the proposed implementation method.
Robust Video Transmission System Employing Byte-Aligned Variable-Length Turbo Codes and Its Code-Rate Adaptation over Mobile Communication Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 921~930
In this paper, a robust video transmission system is proposed. To effectively prevent the corruption of video stream and its propagation in spatial and temporal domains, a version of turbo code, so-called as byte-aligned variable-length turbo code, is applied. Protection performance of the proposed turbo code is first evaluated by applying it to GOB-based variable-size ITU-T H.263+ video packets, where the protection level is statically controlled based on the joint source-channel criteria. This protection is then extended to support the adaptation of code ratio to best match the time-varying channel condition. The time-varying Rayleigh fading channel is modelled considering the correlation of the fading channel. The resulting performance comparison with the static turbo code as well as the conventional RCPC code clearly demonstrates the possibility of the proposed adaptation approach for the time-varying correlated Rayleigh-fading channel.
Modeling and Classification of MPEG VBR Video Data using Gradient-based Fuzzy c_means with Divergence Measure
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 931~936
GBFCM(DM), Gradient-based Fuzzy c-means with Divergence Measure, for efficient clustering of GPDF(Gaussian Probability Density Function) in MPEG VBR video data modeling is proposed in this paper. The proposed GBFCM(DM) is based on GBFCM( Gradient-based Fuzzy c-means) with the Divergence for its distance measure. In this paper, sets of real-time MPEG VBR Video traffic data are considered. Each of 12 frames MPEG VBR Video data are first transformed to 12-dimensional data for modeling and the transformed 12-dimensional data are Pass through the proposed GBFCM(DM) for classification. The GBFCM(DM) is compared with conventional FCM and GBFCM algorithms. The results show that the GBFCM(DM) gives 5∼15% improvement in False Alarm Rate over conventional algorithms such as FCM and GBFCM.
Multiple Decision Model for Image Denoising in Wavelet Transform Domain
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 937~945
A binary decision model which is used to denoising has demerits to measure the precise ratio of signal to noise because of only a binary classification. To supplement these demerits, complex statistical model and undecimated wavelet transform are generally exploited. In this paper, we propose a noise reduction method using a multi-level decision model for measuring the ratio of noise in noisy image. The propose method achieves good denoising performance with orthogonal wavelet transform because the ratio of signal to noise can be calculated to multi-valued form. In simulation results, the proposed denoising method outperforms 0.1dB in the PSNR sense than the state of art denoising algorithms using orthogonal wavelet transform.
A Study on the New BC-ABBM Motion Estimation Algorithm for Low Bit Rate Video Coding
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 946~953
Fast search and conventional boolean matching motion estimation algorithms reduce computational complexity and data processing time but this algorithms have disadvantages that is difficult of implementation of hardware because of high control overhead and that is less performance than Full search Algorithm(FA). This paper present new all binary block matching algorithm, called Bit Converted All Binary Block Matching(BC-ABBM). Proposed algorithm have performance closed to the FA by boolean only block matching that may be very efficiently implemented in hardware for low bit rate video communication. Simulation results show that the PSNR of the proposed algorithm is about 0.04dB loss than FA but is about 0.6 ∼ 1.4dB gain than fast search algorithm and conventional boolean matching algorithm.
STF-OFDM Transmission Scheme via Preceding in Frequency Domain
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 954~961
In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. The STF-OFDM transmission scheme that we propose in this paper is a simple transmission cheme for achieving frequency diversity gain with low complexity. Using preceding in frequency domain, we obtain frequency diversity gain and improve the SER performance of conventional ST-OFDM. The preceding scheme proposed in this paper is a very simple method that can be encoded and decoded with low complexity.
Real-time implementation of the 2.4kbps EHSX Speech Coder Using a
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 962~970
This paper presents an efficient implementation of the 2.4 kbps EHSX(Enhanced Harmonic Stochastic Excitation) speech coder on a TMS320C6701
floating-point digital signal processor. The EHSX speech codec is based on a harmonic and CELP(Code Excited Linear Prediction) modeling of the excitation signal respectively according to the frame characteristic such as a voiced speech and an unvoiced speech. In this paper, we represent the optimization methods to reduce the complexity for real-time implementation. The complexity in the filtering of a CELP algorithm that is the main part for the EHSX algorithm complexity can be reduced by converting program using floating-point variable to program using fixed-point variable. We also present the efficient optimization methods including the code allocation considering a DSP architecture and the low complexity algorithm of harmonic/pitch search in encoder part. Finally, we obtained the subjective quality of MOS 3.28 from speech quality test using the PESQ(perceptual evaluation of speech quality), ITU-T Recommendation P.862 and could get a goal of realtime operation of the EHSX codec.c.
An active intrusion-confronting method using fake session and Honeypot
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 971~984
In the coming age of information warfare, information security patterns need to be changed such as to the active approach using offensive security mechanisms rather than traditional passive approach just protecting the intrusions. In an active security environment, it is essential that, when detecting an intrusion, the immediate confrontation such as analysing the intrusion situation in realtime, protecting information from the attacks, and even tracing the intruder. This paper presents an active intrusion-confronting system using a fake session and a honeypot. Through the fake session, the attacks like Dos(Denial of Service) and port scan can be intercepted. By monitoring honeypot system, in which the intruders are migrated from the protected system and an intrusion rule manager is being activated, new intrusion rules are created and activated for confronting the next intrusions.
An Integrated Intrusion Detection System for a Large-scale Network Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 985~996
In order to solve the increasing security problems, IDSs(Intrusion Detection System) have appeared. However, local IDSs have a limit to detect various intrusions in a large-scale network environment. So there are a lot of researches in progress which organize the elements of IDS in a distributed or hierarchical manner. In this paper, we design a integrated IDS which exchanges messages between them through the standardized message format (IDMEF) and communication protocol (IDXP). We also propose a policy profile for an effective control of IDSs, and employ the PKI mechanism for mutual authentication. We implement a prototype system for the proposed IDSs communicating with Snort and analyze its performance.
A Study on Single Sign-On Authentication Model using Multi Agent
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 997~1006
The rapid expansion of the Internet has provided users with a diverse range of services. Most Internet users create many different IDs and passwords to subscribe to various Internet services. Thus, the SSO system has been proposed to supplement vulnerable security that may arise from inefficient management system where administrators and users manage a number of ms. The SSO system can provide heightened efficiency and security to users and administrators. Recently commercialized SSO systems integrate a single agent with the broker authentication model. However, this hybrid authentication system cannot resolve problems such as those involving user pre-registration and anonymous users. It likewise cannot provide non-repudiation service between joining objects. Consequently, the hybrid system causes considerable security vulnerability. Since it cannot provide security service for the agent itself, the user's private information and SSO system may have significant security vulnerability. This paper proposed an authentication model that integrates a broker authentication model, out of various authentication models of the SSO system, with a multi-agent system. The proposed method adopts a secure multi-agent system that supplements the security vulnerability of an agent applied to the existing hybrid authentication system. The method proposes an SSO authentication model that satisfies various security requirements not provided by existing broker authentication models and hybrid authentication systems.
An implementation and security analysis on H.235 for VoIP security on embedded environments
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 1007~1014
In this paper, H.235 based security mechanism for H.323 multimedia applications was implemented in embedded environment. H.235 covers authentication using HMAC-SHAI -96, authenticated Diffie-Hellman key exchange, security capability exchange, session key management for voice encryption, and encryption functions such as DES, 3DES, RC2. H.235-based mechanisms were also analyzed in terms of its security and possible attacks.
A Peer-to-Peer Key Establishment Scheme without Pre-distributing Keys in Ad-Hoc Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 7C, 2004, Pages 1015~1023
In order to protect an exchanged data, it is indispensable to establish a peer-to-peer key between the two communicating nodes. Pre-distributing keys among the nodes is unrealistic in Ad-Hoc network environment because of the dynamic nature of its network topology and the equal authority of its nodes. This paper presents a peer-to-peer key establishment scheme without pre-distributing keys in Ad-Hoc networks. The proposed scheme is based on the Diffie-Hellman key exchange protocol. Main idea is to prevent the falsification of Diffe-Hellman values using some elements of a hash chain. As a result, it is as safe as the underlying hash function against a man-in-the-middle attack. Simulation results have shown that the proposed scheme dramatically reduces the number of messages, and has relatively higher scalability, as compared with the key pre-distribution based scheme.