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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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Volume & Issues
Volume 24, Issue 12B - Dec 1999
Volume 24, Issue 12A - Dec 1999
Volume 24, Issue 11A - Nov 1999
Volume 24, Issue 10B - Oct 1999
Volume 24, Issue 10A - Oct 1999
Volume 24, Issue 9B - Sep 1999
Volume 24, Issue 9A - Sep 1999
Volume 24, Issue 8B - Aug 1999
Volume 24, Issue 8A - Aug 1999
Volume 24, Issue 7B - Jul 1999
Volume 24, Issue 7A - Jul 1999
Volume 24, Issue 6B - Jun 1999
Volume 24, Issue 6A - Jun 1999
Volume 24, Issue 5B - 00 1999
Volume 24, Issue 5A - 00 1999
Volume 24, Issue 4B - 00 1999
Volume 24, Issue 4A - 00 1999
Volume 24, Issue 3B - 00 1999
Volume 24, Issue 3A - 00 1999
Volume 24, Issue 2B - 00 1999
Volume 24, Issue 2A - 00 1999
Volume 24, Issue 1B - 00 1999
Volume 24, Issue 1A - 00 1999
Volume 24, Issue 12 - 00 1999
Volume 24, Issue 11B - 00 1999
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A Study on Call Loss and Call Blocking Probabilities in Hierarchical CDMA Cellular Systems
Heo, Seon ; Park, Yu Jin ; Kim, Jong Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 161~161
Starting Time Selection Method of A New Request for Minimum and Maximum CLRs of Superposed VBR MPEG Videos and Its Applications - Part I. Scheduling
No, Byeong Hui ; Kim, Jae Gyun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 169~169
The arrangement of I-picture starting times of multiplexed variable bit rate (VBR) MPEG video sources may significantly affect the cell loss ratio (CLR) characteristics of superposed traffic. In this paper, we propose a starting time selection method of a new VBR MPEG video so that the minimum or maximum CLR is expected when it is superposed with existing stream. It is shown that the proposed starting time selection method can estimate the minimum and maximum CLR points exactly. As an application of the proposed method, we also propose an efficient scheduling method for minimum CLR in such as VOD.
Starting Time Selection Method of A New Request for Minimum and Maximum CLRs of Superposed VBR MPEG Videos and Its Application - Part II. CAC
No, Byeong Hui ; Kim, Jae Gyun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 178~178
When VBR MPEG videos are multiplexed, if connection admission control (CAC) is carried out without consideration of starting time arrangement, there exist possibilities not to gurantee quality of service (QoS) even for any accepted source. In this paper, in order to guarantee QoS, we propose a new CAC method with considerationof starting time information of superposed VBR MPEG video sources in ATM networks. For CAC, we also propose a starting time selection method that the new request can cause maximum or minimum cell loss ration of superposed traffic. Experimental results show that the proposed method can guarantee QoS and increase network utilization.
Analysis of BER Performance of 16-QAM and QPRS by Differential and Manchester Coding Schemes over Mobile Communication Channel
Kim, Tae Heon ; Ha, Deok Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 187~187
We examine bit error rate (BER) improvement systems which are almost exclusively used for spectrally efficient applications, namely, quadrature- amplitude-modulation(QAM) and quadrature-partial-response system(QPRS) over Rayleigh fadding channel. From the computer simulation the differential coded 16-QAM has better error performance than the conventional 16-QAM over Rayleigh fading channel. Manchester coding scheme is also introduced to compare performance over Rayleigh fading channel. Specifically, the spectral efficiency of differential coding scheme was better than that of manchester coding scheme. A new signal constellation of 16-QAM is devised to adapt the coding scheme.
An Adaptive Reduced-State Sequence Detection Receiver in the Mobile Satellite Channel
Song, Hyeong Gyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 195~195
This paper propose an adaptive RSSD receiver, which is a suboptimal alternative to the adaptive maximum likehood detector and is able to track the time-varying ISI channels in the mobile satellite channel. The structure of the proposed adaptive RSSD is a modified RSSD utilizing a per-survivor processing as well as the symbol-aided method and a channel estimation using the tentative data sequences with a small decision delay. The complexity and performance of the proposed adaptive RSSD are controlled by the number of system states and ISI cancelers and the inserting period of the known symbols. The simulation results show the fact that the proposed adaptive RSSD obtains excellent tracking performance over time-varying ISI channels.
A Congestion Control Algorithm Based on CCR Ratio for Efficient ABR Service in ATM Networks
O, Yun Tak ; Park, Seong Han ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 205~205
In this paper, a congestion control algorithm based on Current Cell Rate is proposed to efficiently provide ABR service in ATM network. The proposed method uses Minimum Cell Rate and Peak Cell Rate among service requirements parameter which ABR sources negotiate with ATM network at connection establishment, both CCR and Previous CCR of ABR sources are also used. If switch receives forward RM cell from ABR sources, it classfies ABR sources according to CCR ratio. On receiving backward RM cell from destination, switch performs intelligent marking in consideration of the queue length of buffer, and informs ABR sources of the congestion or not. While ATM network is in potential confgestion, intelligent marking on ABR sources is decided in accordance with CCR ratio. The CCR ratio-based congestion control algorithm proposed in this paper and the existing Enhanced Proportional Rate Control Algorithm and Generalized Max-Min methods are simulated using the same model. The simulation results demonstrate that the proposed method achieve the more fair bandwidth allocation and higher link utilization than the existing methods.
A Study on the Input Buffer Controller for Improvement of Cell Loss Rate using Backpressure signal in ATM Switch
Yang, U Seok ; Lee, Jae Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 214~214
In this paper, we propose the virtually shared input buffering methode with independent input buffering and this methode is not only defference existing backpressure signal drop the cells into input buffer but also compare backpressure signal and threshold level in current input buffer because of this signal(BP) and threshold level(Th)s are reference to compare dynamic buffer allocation and improve the cell loss rate(CLR) and performance enhancement of ATM switch. For this purpose, we prepare the input buffer controller using backpressure signal generator and cell counter table in front of ATM switch input buffers which is based on the new inter-processing algorithm between input buffer controller and cell counters, thus we suggest improvement of cell loss rate in variable ATM switch.
A New Multiple Access Scheme to Ensure Security in CDMA-Based Wireless LANs
Kim, Yeong Guk ; Park, Se Ung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 221~221
Wireless medium is inherently insecure due to its broadcast characteristics. Anyone in the vicinity of ongoing communication can emulate a legitimate user and try to communicate with the base station. As wireless communications become more prevalent and utilize the radio channel for transmission of critical information, the concern for security becomes an important issue. In this paper a new security enhanced multiple access scheme based on slotted CDMA is introduced. Although most of the efforts in providing security has been content with letting the attacker know which bits have been sent, the newly proposed scheme provides another layer of protection by making acquisition of the spread spectrum signals difficult for unintended receivers. The new multiple access scheme, DSS(Double Sequence Scheme), utilizes not one LFSR(Linear Feedback Shift Register) PN(pseudo-random number) generator, but two LFSR PN generators of register length R and S to create a chip sequence that is extremely resistant to attacks. The number of calculations neccessary for the attacker to exhaustively guess future chip sequence is analyzed and performance characteristics of the security-enhanced slotted CDMA protocol such as throughput and delay are examined.
Power-Efficient Cell Coverage Control in a CDMA System
Cha, Dong Wan ; Gang, Seok Yeon ; Ma, Jung Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 231~231
In the cellular wireless system, transmitted power is regulated to provide each user an acceptable connection while limiting the interference from other users. This work addresses the power budgeting problem in association with base station assignment. In the context of CDMA system, we minimize the total transmitted power subject to maintaining an individual target SNR(Signal to Noise Ratio) for each mobile and base station. We formulate the optimization model and a solution method is proposed.
Interference Canceller Employing Subband Adaptive Filter for the Spread Spectrum System with Narrowband Interference
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 238~238
2×1 Optical Buffering Switch
Seo, Chang Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 246~246
Switched Delay Lines(SDL) as all-optical switches are used in asynchronous network to handle bursty optical cells without optical/electrical nor electrical/optical conversion. SDL has many DLs(Delay Lines) and controls the total delay by providing defferent routing paths of a cell delay with 2×2 optical switches. The total delay is determined by the total length of DL's that a cell visits and this performs buffering capability of cells. This paper introduces an innovational FIFO 2×1 optical buffering switch based on current all-optical technologies, and describes its structure and control strategy. This approach not only has many useful properties like nonblocking, self-routing, but also shows the best performance such as minimum cell loss rate under binomial distribution and minimum delay. The proposed structure is a very practical network component with minimum implementation cost and minimum maintenance problem by using minimum number of optical elements that currently impose many physical constraints of size, noise, power or heat.
Qos Enhancement Mechanism in CBR HDTV Transport Stream Packet Communications over Lossy ATM Network
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 255~255
TIVRON: The Integrated Video Retrieval System based on OODBMS
Song, Yong Jun ; Park, Dong Ju ; Lee, Dong Ho ; Kim, Hyeong Ju ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 266~266
The necessity of the efficient methods for multimedia data retrieval is increasing more and more on account of various large scale multimedia applications. Especially video data has a number of practical application areas, but the current technology is not mature enough to cover the hectic characteristics of video data such as being unnormalized and complicated. We have been performing research for past several years on the issues such as the annotation-based video retrieval, the content-based mage retrieval, and the technique for storing MPEG video data using OODBMS. By both integrating and extending these results to support the complex video retrieval in addition to the existing functions, this paper proposes TIVRON as an integrated video retrieval system based on OODBMS.
A media access protocol for high-speed WDM LAN
Baek, Seon Uk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 277~277
In this paper, we design a new media access control algorithm for star-couple WDM LAN. Each node have two slow tunable receivers and these two receivers are pipelined: while one receiver is receiving data from one channel, the other is tunned to another channel. Tuning time is configured as a subframe and each subframe consists of multiple time slots so that multiple packets are transmitted in a subframe. An efficient scheduling algorithm is designed and its delay performances are analyzed by simulation. The proposed algorithm shows efficient performance under various traffic pattern.
A Study on Dual Microstrip Electrode for Push-Pull Operation of the Polymeric Mach-Zehnder Optical Modulators
Kim, Gwang Taek ; Lee, So Yeong ; Song, Jae Won ; Kim, Seong Guk ; Gang, Sin Won ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 287~287
In this paper we proposed a novel dual microstrip electrode for push-pull operation of Mach-Zehnder(MZ) optical modulator based on electro-optic polymer. The push-pull operation may improve the bandwidth width or driving voltage of the MZ modulators. The finite element method was used to find the impedance and velocity matching condition and calculate the overlap integral of the dual microstrip electrode. The results of simulation show that the velocity matching condition can be easily achieved independent of electrode structure but there are some trade-offs between impedance matching and overlap integral. The designed electrode was fabricated on glass substrate using conventional photolithography and electroplating and then measured its microwave characteristics using a network analyzer. The return loss was less than .5㏈ up to 20㎓ and propagation loss 0.71㏈/(㎝
). From the results of both simulation and measurement dual microstrip electrode makes it possible to improve the properties of MZ type optical modulators with simple fabrication process.
Fast Adaptive Block matching Algorithm using Predictive Motion Vector
Sin, Yong Dal ; Kim, Yeong Chun ; Lee, Geon Il ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 296~296
We present a fast adaptive block matching algorithm using predictive motion vector. In the presented method, the predictive motion vector is average of motion vector of upper and left blocks for current block. The block is classified into one of four motion categories: stationary, quasi-stationary, medium-motion or large-motion block according to motion of the left and upper blocks, and then each block estimates the motion vector adaptively. By the simulation, the PSNR of our algorithm increase 0.27㏈~0.77㏈ more than that of NTSS (new three step search) method. The computational comoexity of the presented method decreased about 36%~41% more than that of NTSS method.
Block Error Detection Algorithm of Received Image in the Channel Noise of H.263 Video Codec
Choe, Se Ha ; Lee, Ju Sin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 304~304
In this paper, we proposed an algorithm to detect block error caused by channel noise in H.263 video transmission. The proposed error detection algorithm classified macro blocks to large blocks and small blocks by the variation of pixel value between two corresponded blocks in the inter frames using temporal similarity. And it was decided that the error blocks which has large variance than adjacent blocks among the larger one at first procedure, using the spatial similarity. To evaluate the performance of the proposed algorithm, we compared the detection results with existence algorithm. And we also evaluated image quality using the PSNR of the image after concealed the error block more effectively than existing algorithm and the image quality improved more than 15㏈ compared with existence error detection algorithm.
A Dual-mode Blinde Equalization with the Variable Decision Region
Gang, Seong Jin ; Gwon, Seong Rak ; Lee, Yeong Jo ; Gang, Chang Eon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 313~313
A blind equalization algorithm may be switched to a decision-directed(DD) scheme in order to speed up the convergence rate. In this paper, we propose a new blind eualization scheme that automatically switches to the DD mode. The proposed scheme operates in two mode: blind equalization mode and a DD mode. The mode is determined by the region in which the equalizer output lies, and the region varies as a function of the estimate value of the error variance. From simulation results, it is shown that this scheme can achieve faster convergence and small MSE.
A Study on Uncertainty Principle in Natural Observation Transform of Discrete Type
Kim, Tae Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 321~321
Theoretical analysis of waveform has been achieved by using Fourier analysis method. But Fourier analysis has irrational properties for the problems of time-varying waveform types in recognition problems. In order to improve the problems, the natural observation theory has been proposed. In this paper, the uncertainty principle in discrete signals is presented and the uncertainty principle of discrete natural observation transform is proved. Furthermore it is showed that the natural observation transform is minute method than the analysis using Fourier transform
A Robust Label Embedding Method using Perceptual Adaptive Watermark
Kim, Deok Ryeong ; Park, Seong Han ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 2A, 1999, Pages 328~328
We propose a new watermarking method to embed robust labels against JPEG compression without degrading the quality of image. The proposed method adaptively determines a watermark size depending on the characteristics of images using human visual system models. To embed robust label, the frequencies to be watermarked is chosen in the low frequency using a secrete key such as Pn-sequence. Then, the watermark is added to or subtracted from the absolute value of coefficients of the selected frequencies according to another Pn-sequence. Label detecting uses the mean of the absolute value of selected frequency coefficients and the number of frequency coefficients with less value than a threshold at each label block of watermarked image. The experimental results show embedding a label into an image using an invisible watermark and the robustness for JPEG compression and noise. Especially, the bit error rate for a detected labels from watermarked images after JPEG compression and decompression demonstrates the proposed algorithm is better than previous works.