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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 18, Issue 12 - Dec 1993
Volume 18, Issue 11 - Nov 1993
Volume 18, Issue 10 - Oct 1993
Volume 18, Issue 9 - Sep 1993
Volume 18, Issue 8 - Aug 1993
Volume 18, Issue 7 - Jul 1993
Volume 18, Issue 6 - Jun 1993
Volume 18, Issue 5 - May 1993
Volume 18, Issue 4 - Apr 1993
Volume 18, Issue 3 - Mar 1993
Volume 18, Issue 2 - Feb 1993
Volume 18, Issue 1 - Jan 1993
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A Study on "A Public Key Cryptosystem for Computer Communication Networks"
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1051~1058
This paper points out some weakpoints in the "A Study on Public Key Cryptosystem for Computer Communication Networks" proposed by Gi Jun Ku at KICS 92-22('92-3 Vol.17 No.3) . This public key cryptosystem based on polynomials over finite rings is not strong against cipertext-only-attack. This paper indicate the insecureness of the proposed a public key cryptosystem.ptosystem.
The Analysis of Arbitrarily Shaped Microstrip Patch Antennas using the MPIE
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1059~1068
We will put the emphasis on the analysis of arbitrarily shaped microstrip antennas. The most general and rigorous treatment of microstrip antennas is given by the electric field integral equation(EFIE), usally formulated in the spectral domain. In this paper, we use a modification of EFIE, called the mixed potential integral equation(MPIE) , and we solve it in the space domain. This technique uses Green's functions associated with the scalar and vector potential which are calculated by using stratified media theory and are expressed as Sommerfeld integrals. The integral equation is solved by a moment's method using rooftop subsectional basis function. Thus, microstrip patches of any shape can be analysed at any frequency and for any substrate. Numerical results for a rectangular patch and for a L-shaped patch are given and compared with measured values.
Video Data Compression using the MPEG-2 Video Algorithm
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1069~1082
The International Organization for Standardization(ISO) has undertaken an effort to develop a standard for video and associated audio on digital storage media. This effort is known by the name of the expert group that started if : MPEG-Moving Picture Experts Group Is currently part of the ISO-I EC/J TC1/SC2/WG11. The promise of MPEG-2 is that a video signal and its associated audio can be compressed to a bit rate of about 10 Mbits/s with an acceptable quality. In this paper, the implementation of a video compression simulator based on MPEG-2 Video Test Model 2(TM2) is described and analyzed according to the simulation results. The implemented simulator is also applied to code HDTV sequences at the several bit rates. Some computer simulation results using the MPEG and the HDTV test sequences are given. In addition, some techniques which can improve the coding efficiency of the implemented video compression simulator are also suggested.
Design and Implementation of Group Management System for Multicast Services
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1083~1093
Recently, some applications require the multicast service that transmit messages to multiple destinations in computer communication network enviroment. Multicast service is to send messages to the group which consists of a number of processes. A multicast group is a collection of processes which are destinations of the transmitted messages and these processes may run on one or more hosts. Therefore, it is important to manage each member of process groups in order to provide efficient multicast services. In this paper, we design and implement group management system to support multicast services. Group Management System was designed with Process Group Management System(PGMS) and Host Group Management System(HGMS). We have implemented basic primitives of PGMS, HGMS. Also, membership tree management algorithm is designed and implemented. Membership tree provides the relation of the members of multicast groups and routing Informations.
Noise Eliminations by Median filtering in BDPCM Image
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1094~1101
We show that image compression possibilities of BDPCM which reduces information and increases correlation with signal-blurring. Under the same quantization steps, signal flow at the coder is analyzed and complete signal reconstruction properties are shown. Dynamic range characteristics of the differences by the conventional DPCM predictor are analyzed. In order to improve the median filter reduces impulse noise with blurring, adaptive filtering for the differences is proposed. By means of the difference range, transmission impulse noises are detected and corrected by the filtering. Therefore, low bit rate image codec with noise eliminations is proposed.
Microwave Dielectric Properties of CaTiO
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1102~1107
Microwave dielectric properties of CaTiO3 and CaTiO3-TiO2 ceramics for the composition range between 40 and 50 mol% CaO in CaO-TiO2 binary system were investigated. CaTiO3 ceramics with50 mol% CaO showed the dielectric constant (e,) of 178, the temperature coefficient of resonant frequency(c,) of+1000 ppm/'c and the qualify factor Q of 2760 (f0=2.7 GHz ). Dielectric constant and temperature coefficient of resonant frequency of ceramics with dual phases of CaTiO3 and TiO2 decreased gradually from those of CaTiO3 as the CaO content decreased. Q value and density were found to have minimum at the composition of 47 mol% CaO. The degradation of Q value and density in dual phase ceramics seems to be caused by the large pores at grain boundaries and/or within grains remained after rapid growth of CaTiO3 grains as TiO2 Phase decreased.
Y-branch Directional Coupler Optical Switch/Modulator
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1108~1116
Y-branch directional coupler optica1 switches with two different coupling lengths are fabricated on z-cut LiNbO3 and tested at r = 1.3 rm. The normal mode and coupled mode theories are utilized to calculate device coupling length and switching voltage. Simulation of the beam propagation method (BPM) is also performed to confirm the device coupling lengths. For dc operation, experimental results are in good agreement with the modee theories expectation.
The Design and Implementation for the Secure Protocol of MHS
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1117~1127
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1128~1135
In this paper, new binary cyclic codes (hereafter, refered to as GMW code) which are generated by using GMW sequence, g(t) = tr((trk(a))r), and its cyclic shifts are introduced. Code length of GMW codes is 2a-1, where k is composite integer, e·J. Dimension of the GMW codes is k(k/j)w-1, where w is a Hamming weight of r. Several properties of GMW codes such as designed distance, minimum distance, and weights of code words are obtained in terms of parameters of GMW sequences. And expansion of GMW sequences in terms of m-sequence and its decimation sequences are introduced and characteristic polynomials of GMW sequences are also derived.
A Study on the Channel Capacity of Fading Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1136~1145
The channel capacities of various lading channels are calculated and compared with that of Gaussian noise channel to find out the decrements of channel capacity according to each fading environment. As a result, it is confirmed that the channel capacities in Rician and m-distribution fading channels approach to that of Gaussian noise channel as direct-to-indirect power ratio in Rician fading channel and fading index m in m-distribution fading channel increases respectively. And the difference between two channel capacities of Gaussian noise channel and each fading channel which is dependent on carrier-to-noise power ratio (CNR) is found. Also the improvement of channel capacity of Rayleigh fading channel by introducing two-branch diversities is obtained. For diversity reception, predetection maximal-ratio and postdetection selective combining techniques are adopted. The results show that the improvement of channel capacity by predetection maximal-ratio combining diversity is superior to the postdetection selective combining diversitiy regardless of correlation coefficient between two diversity branches in Raylelgh fading channel. The best improvement is achieved when two branches are noncorrelative in both two diversify techniques and as correlation coefficient of two diversity branches is smaller, the improvement of channel capacity is greater.
Parallel Scrambling Techniques for SDH and ATM Transmissions
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1146~1158
In this paper, parallel scrambling techniques are considered for practical use in the SDH transmission and the ATM transmission. In the ATM transmission, there are two ways of transmitting ATM cells - the SDH-based and the cell-based - and the corresponding scrambling techniques differ accordingly. For the SDH transmission and the SDH-based ATM transmission, the FSS (frame synchronous scrambling) is applied to the STM frames : while for the cell-based ATM trans-mission, the DSS(distributed sample scrambling) is used on the ATM cell stream. The parallel scrambling techniques are examined for the FSS and the DSS, and applied to achieve the parallel FSSs for use in the SDH and the SDH-based ATM transmission along with the parallel DSS applicable to the cell-based ATM transmission. The resulting(8, 4) PSRG(parallel shift resister generator) and (8, 16) PSRG based parallel scramblings are directly applicable for the STM-1 rate processing of the STM-4 and STM-16 scramblings, respectively. Likewise, the resulting (1, 8)PSRG and double-sampling-double-correction based parallel scrambling techniques can be practically used for a low-rate processing of the SDH-based and the cell-based ATM signal scrambling respectively.
A Study on Compensating the Errors of SCI using the Buffer Circuit
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1159~1168
The Switched-Capacitor Integrator(SCI) is a basic building block of Switched-Scpacitor Filter(SCF). But owing to the errors from the finite gain and bandwidth of op-amp on SCI, the most of SCP are limited to their applications. Although many of the compensation methods developed for active RC filters can be directly adapted to SCF, this is not true for the analysis of the effects of the op-amp dynamics on the filter response. The effect of finite op-amp gain is similar to the active RC filters. But SCF is more toter-ant of the finite op-amp bandwidth. In this paper, we have considered the errors of the finite gain and bandwidth of op-amp on SCI , and presented the simple and effective methods of compensating the errors of SCI due to the finite op-amp gain using the buffer circuit.
Microwave Absorbing Characteristics of Ferrite-silicon carbide surface Films Produced
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1169~1175
Plasma spraying method was used to fabricated the microwave absorbing ferrite-silicon carbide on the aluminum-alloy of the fuselage of an aircraft to protect it from RADAR detection. In this paper 15[rm] instead of 34[rm], the mean size of SIC-powder for ferrite-silicon carbide surface films(I) was used. 50(Kg/h) Instead of 70(Kg/h), the powder feed and 100[mm] Instead of 80(mm), spray distance of spray parameters was used. This M/W absorbers were designed experimentally and fabricated trially, as a result of which the relative frequency bandwidth of 2.8% were obtained under the tolerance limits of the reflection coefficients lower than-10[dB], and the maximum absorption thickness becomes 0.5[mm], which is much thinner than that of the conventional ones.
A Study on the Multiple Keyword Retrieval Method under the Object-Oriented Multimedia Database Model
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1176~1189
This paper presents the Multiple Keyword Retrieval Method under the Object-Oriented Multimedia Database Model. The multiple keyword registration and retrieval algorithms are developed to reduce the partial matching problem in multimedia data retrieval. For this, proper storage structures of the lookup tables are designed. And also, in order to maintain the constant retrieval time, media data files are organized with B+ tree structure.
Performance Analysis of ATM Switch with Priority Control Mechanisms
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1190~1200
In this work, the performance of both delay sensitive traffics and loss sensitive traffics of the output buffered ATM switch with priority control mechanisms has been evaluated. We choose the partial buffer sharing mechanism as the loss priority control mechanism and the HOL(Head Of Line) priority control mechanism as the time priority control mechanism. We model loss sensitive traffics with Poisson process and delay sensitive traffics with MMPP. With loss priority control, it is confirmed that loss probability of loss sensitive traffice decreases when the loss priority control mechanism is chosen. With time priority control, it has also been confirmed that mean cell delay of delay sensitive traffics decreases when the HOL priority control mechanism is used. From this analysis, It has been confirmed that the requirements of QOS for both loss sensitive and delay sensitive traffics can be satisfied in the ATM switch by combining both the loss priority control mechanism and the HOL priority control mechanism.
The Component Extraction Using Knowledge-Base from Name-Card
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1201~1212
This paper presents the automatically extracting method of data item from name-cards using knowledge-base. In our approach, we utilize a structural information and a relational information between data items and elements with knowledge in the name-cards. To describe a hierarchical knowledge, we uses a flame structure and we propose an algorithim of domain classification to extract item and group candidate domains from the name-cards. From the experimental results, we obtain the extraction rate, 95%, for 100 samples.
Design and Implementation of a Hypermedia System for Effective Multimedia Information Retrieval
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1213~1225
Hypermedia systems have the browsing mechanism using links and provide navigation tools to retrieve and represent multimedia information. In this study we designed and implemented a hypermedia system which has the hierarchical group and local map for effective navigation. We also propose the clustering mechanism which constructs a cluster tree and uses this knowledge for navigation. The system has been designed to integrate the browsing and searching function of the hypermedia system for efficient multimedia information retrieval and user-interface. This system can be used to develop hypermedia application systems in the area of encyclopedia, reference document information, electronic dictionary and electronic book.
Design of Optimal FIR Filters for Data Transmission
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 8, 1993, Pages 1226~1237
For data transmission over strictly band-limited non-ideal channels, different types of filters with arbitrary responses are needed. In this paper. we proposed two efficient techniques for the design of such FIR filters whose response is specified in either the time or the frequency domain. In particular when a fractionally-spaced structure is used for the transceiver, these filters can be efficiently designed by making use of characteristics of oversampling. By using a minimum mean-squared error criterion, we design a fractionally-spaced FIR filter whose frequency response can be controlled without affecting the output error. With proper specification of the shape of the additive noise signals, for example, the design results in a receiver filter that can perform compromise equalization as well as phase splitting filtering for QAM demodulation. The second method ad-dresses the design of an FIR filter whose desired response can be arbitrarily specified in the frequency domain. For optimum design, we use an iterative optimization technique based on a weighted least mean square algorithm. A new adaptation algorithm for updating the weighting function is proposed for fast and stable convergence. It is shown that these two independent methods can be efficiently combined together for more complex applications.