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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 22, Issue 12 - Dec 1997
Volume 22, Issue 11 - Nov 1997
Volume 22, Issue 10 - Oct 1997
Volume 22, Issue 9 - Sep 1997
Volume 22, Issue 8 - Aug 1997
Volume 22, Issue 7 - Jul 1997
Volume 22, Issue 6 - Jun 1997
Volume 22, Issue 5 - May 1997
Volume 22, Issue 4 - Apr 1997
Volume 22, Issue 3 - Mar 1997
Volume 22, Issue 2 - Feb 1997
Volume 22, Issue 1 - Jan 1997
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Design of cache mechanism in distributed directory environment
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 205~214
In this paper, we suggest a cache mechanism to improve the speed fo query processing in distributed directory environment. For this, request and result and result about objects in remote site are store in the cache of local site. A cache mechanism developed through six phases; 1) Cached information which stored in distributed directory system is classified as application data, system data and meta data. 2) Cache system architecture is designed according to classified information. 3) Cache schema are designed for each cache information. 4) Least-TTL algorithms which use the weighted value of geograpical information and access frquency for replacements are developed for datacaches(application cache, system cache). 5) Operational algorithms are developed for meta data cache which has meta data tree. This tree is based on the information of past queries and improves the speed ofquery processing by reducing the scope of search space. 6) Finally, performance evaluations are performed by comparing with proposed cache mechanism and other mechanisms.
Vertical class fragmentation in distributed object-oriented databases
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 215~224
This paper addresses the vertical class fragmentation in distributed object-oriented databases. In the proposed vertical fragmentation, after producing the attribute fragment by partitioning attributes, then the method fragment is produced by gathering methods referring the attribute in each fragment. For partitioning attributes, we define query access matrix(QAM) and method access matrix(MAM) to express attributes that method refers, and extend QAM, MAM and attribute usage matrix(AUM) to universal class environment for representing relationship among other classes through class hierarchy and class composite hierarchy.
A study on the establishment of model of multual recognition for type approval system of telecommunications terminal equipments
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 225~240
With the lanuch of the World Trade Organization(WTO) system, National and international trends toward more liberalized regulation of telecommunications terminal equipments drive the globalization of the telecommunications market. Despite of such trends, most countries have long viewed the type approval system as a major hindrance to overseas maketing because of a hodgepodge of diverse type approval system of telecommunications terminal equipments in each country. But, recently, many countries under these situations try to make a better understanding of respective requeirements of each country's many countries under these situations try to make a better understanding of respective requirements of each country'stype approval system, and where possible to strengthen commonalities, through referred to as "multual recognitio" system for the purpose of the development of procedures for hamonization oftype approval system in "one world, one market". Thus, this paper covers the definition, considerations and the case studies of mutual recognition between countries. Also, this paper suggests the desirable and general model of mutual recognition to be applied all the countries, which are being preparing and processing it.g and processing it.
On the Generation of Synchronizable Conformance Test Sequences Using the Duplex Digraph and Distinguishing Sequences
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 241~249
In this paper, a new technique is proposed for generating a minimum-length synchronizable test sequence that can be applied in the distributed test architecture where both external synchtonization and input/output operation costs are taken into consideration. the method defines a set of transformation rules that constructs a duplex digraph from a given finite state machine representation of a protocol specification rules that constructs a duplex digraph from a given finite state machine representation of a protocol specificatio such that a rural chinese postman tour of the duplex digraph can be used to generate a minimum-length synchronizable test sequence using synchronizable distinguishing sequences as the state identification sequence for each state of the given finite state machine. The method provides an elegant solution to the synchronization problem that arises during the application of a predetermined test sequence in some protocol test architectures that utilize remote testers.
Modified IPRMA protocol using priority scheme in wireless LAN
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 250~258
A modified IPRMA protocol using priority scheme is proposed to increase the number of maximum users, which prevents the collision between the voice and data traffic. A simple decentralized traffic control scheme is presented for the proposed protocol. The improvement in performance over conventional IPRMA is shown through simulation, and EPA(Equilibrium Point Analysis) is used to evaluate system performance.
An implementation of the dynamic rate leaky bucket algorithm combined with a neural network based prediction
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 259~267
The advent of B-ISDN using ATM(asynchronous transfer mode) made possible a variety of new multimedia services, however it also created a problem of congestion control due to bursty nature of various traffic sources. To tackle this problem, UPC/NPC(user parameter control/network parameter control) have been actively studied and DRLB(dynamic rate leaky bucket) algorithm, in which the token generation rate is changed according to states of data source andbuffer occupancy, is a good example of the UPC/NPC. However, the DRLB algorithm has drawbacks of low efficiency and difficult real-time implementation for bursty traffic sources because the determination of token generation rate in the algorithm is based on the present state of network. In this paper, we propose a more plastic and effective congestion control algorithm by combining the DRLB algorithm and neural network based prediction to remedy the drawbacks of the DRLB algorithm, and verify the efficacy of the proposed method by computer simulations.
Dynamic movable boundary mechanism for bandwidth alloc ation of ABR service in ATM networks
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 268~279
In this paper, we show the movable boundary (MB) method is the effective bandwidth allocation strategy for the ABR service among existing bandwidth allocation methods. The MB method can gurantee the QOS requirement according to the service priority and improve bandwidth utilization using the characteristics of the ABR service. The threshold values of the MB, which have an important effect upon connection blocking probability(CBP) performance of each service, are obtained by simulation. The MB method with the fixed thresholds, however, may not have good performance to variation of input traffic parameters. We suggest the dynamic MB method which changes the threshold values adaptively according to the required bandwidth of input traffic. We also show that the dynamic MB method can urantee the CBP performance according to the service priority regardless of variation of input traffic parameters.
Multi-pary protocol conformance testing using concurrent TTCN
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 280~290
The Single TTCN has been broadly used to describe the ATS(Abstract Test Suite) for the protocol confronance testing. But if the single TTCN is used to test the multi-party protocol with the non-deterministic factors, then huge amount of test notations are needed and also it is hard to understand the ATS. Therefore, the concurrent TTCN was proposed to solve these problems and the study in progress. In this paper, we did investigate and compare the characteristics of esisting single TTCN with those of the concurrent TTCN. In order to develop the ATS of the Q.2971 which is B-ISDN call/connection control protocol, the testing model was defined and the concurrent factors were extracted according to that model. As a result, we could verify the usefulness of the confcurrent TTCN.
The requirements of high-speedoptical fiber studied with 2.5 Gbps
8 channel, 123 km transmission using ready-deployed optical cable
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 291~297
A 2.5 Gbp
8 channel WDM signal was transmitted using read-deployed 123 km optical cable around Daejon area. An error free transmission was achieved with
criterion, but the receiver sensitivity varied depending on channel, and some channel showed BER floor. The reans was forud to be in reflection points, and the effects of multiple reflections on the ultra high bit transmission was found to be inreflection points, and the effects of multiple reflections on the ultra high bit transmission was analyzed in this paper.
Radition characteristics of a slot antenna in a conducting cylinder convered with a moving isotropic plasma layer
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 298~305
In this paper, the radiation characteristics of a slot annenna in conduction cylinder covered with a moving isotropic plasma layer are analyzed. Integral representations of the eletromagnetic fields in the spectral domain radiated through the plasma layer are derived and converted into the fields in the spacial domain by saddle-point ingegration. Radiation null which brings about distorion in the radiation parrern is explained by the zero of integrand in an asymptotic integral as a function of plasma and velocity parameters. Numerical results for a radiation null calculated from various plasma and velocity parameters correspond to the results of planner structure.
Developement of a 3 channel digital CVSD bit-rate converter using a general purpose DSP
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 306~317
This ppaer presents a bit-rate conversion system for efficient communications between 3 channel CVSD systems with different bit-rates. The proposed conversion system is implemented in the digital domain and specially, the conversion problem between 32 Kbps and 16 Kbps CVSD systems is studied. The conventional conversion system implemented in the analog domain allows signals to be easily degraded by external noises. To overcome this problem, a digital CVSD bit-rate conversion system robust to external noises is developed. the new systemdecodes CVSD bit sequences and converts sampling rates of decoded signals, then encodes signals at target bit-rates. Since linear phase property does not matter in this application, instead of FIR filters a IIR filter is employed to reduce the system complexity. Therefore, a 3 channel digital CVSD bit-rate conversion system was successfully real-time implemented using a general purpose DSP. In addition, conversion problems with unkown time constants were experimented and good experimental results were obtained.
Analysis of chaotic with lossless time-delayed chua's circuit
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 318~324
Chua's circuit is a simple electronic network which exhibits a variety of bifurcation and attractors. The circuit consists of two capacitors, a linear resistor, and a nonlinear resistor. In this papre we analyze a circuit obtained by replacing the parallel LC resonator in the Chua's circuit by lossless transmission line. By using the method of characteristics of this circuit we show that various periodic motions and chaotic motions can the attained according to parameter variations. From Chua's circuit with a lossless transmission line a variely of chaotic attractors which are similar to those of the normal Chua's circuit are observed.
Estimation of an intitial image for fast fractal decoding
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 325~333
In fractral decoding procedure, the reconstructed image is obtained by iteratively applying the contractive transform to an arbitrary initial image. But this method is not suitable for the fast decoding because convergence speed depends on the selection of initial image. Therefore, the initial image to achieve fast decoding should be selected. In this paper, we propose an initial image estimation that can be applied to various decoding methods. The initial image similar to the original image is estimated by using only the compressed data so that the proposed method does not affect the compression ratio. From the simulation, the PSNR of the proposed initial image is 6dB higher han that of ones iterated output image of conventional decoding with Babaraimage. Computations in addition and multiplication are reduced about 96%. On the other hands, if we apply the proposed initial image to other decoding algorithms, the faster convergence speed is expected.
Reference white setting based on brightness of CPT and resolution
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 334~343
Reference white in color television receiver can be achieved by adjusting the RGB gun current ratio and it is necessary to provide additional gain ratio adjustment for the RGB video signal. Generally, the gun current density profile has a gaussian distribution and the gain-bandwidth product of RGB channel amplifieris constant. Therefore brightness and spatial resolution are changed with variations in reference white of receiver. In this paper, the effect of RGB gun current and channel gain ratios on brightness and resolution of CPT is analyzed. Brightness is increased with the color temperature of referenc white because of Helmholtz-kohlrausch effect. The change in ligh output is more abrupt and spatial resolution is improved with unity current ratio. For more bright and improved ressolution we also present the range of color temperature of reference white for P22 phosphors.
A conditional entropy codingscheme for tree structured vector quantization
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 344~352
This paper proposes an efficient lossless coding scheme for tree structured vector quantization (TSVQ) system which efficiently exploits inter-block correlation. The TSVQ index of the current block is adaptively arithmeticencoded depending on the indices of the previous blocks. This paper also presents a reductio method, which effectively resolve the memory problem which usually arises in many conditional entropy coding schemes. Simulation results show that the proposed scheme provides remarkable bitrate reduction by effectively exploiting not only linear but also non-linear inter-block correlation.
New RSA blocking method and its applications
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 353~360
In this paper, we propose a new blocking method in which the size of an encryption block is changed according to the size of a message block. The proposed method can be applied to multisignature scheme with no restrictio of the signing order and a multisignature anc be sent secretly to the receiver through RSA encryption. It causes expansion in block size of a multisignuture, but the length of the expanded bits is not greater than the number of signers regardless fo the bit lengths of RSA moduli.
Design of POSCAG signal decoder for operating time improvement in pager
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 361~370
In this paper, we designed POCSAG Signal Decoder to improve operating time in pager. We showed POCSAG Signal Pattern sent by transmitter and operation of this decoder. We also showed that the Pager using this decoder was equipped with Wide Area Signal Detection and designed the hardware which realizes this operation and implemented it with ASIC chip. As we inspected the function of the ASIC chip and tested the performance, we could find that the chip operated in low voltage and that power dissipation was low.
Experimental study on the optical subscriber loop transmission link utilizing shared light sources and remote modulation method
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 371~380
A lot of efforts have been made to develop low-cost and reliable broadband optical subscriber loop systems. Here we propose a new loop system with shared ligh sources and remote modulation method. This system uses an external modulation method for both directions and all the light sources are maintained inside a central office. Moreover, the ligh source is not dedicated to each subsriber link but shared among many subscriber links. We expermentally demonstrated that one shared light source could accommodate about 2, 000 deownstream links(2.5 Gb/s per link), 500 upstream links(155 Mb/s per link).
The regional information index in major cities of korea
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 381~391
This study aims at designing and calculating of the information index for efficient implementation of the regional information policy. The content and scope of this study are designing the struture of information index, measuring the informatization level in major cities of Korea and inducing rough idea for better performing of Korea information policy. Thereby we calculated tables ofinformation indexon seventy-eight cities in Korea from 1985 to 1994 and also basic strategy for better policy implementation. And we found that every citities share the benefit almost equal in the use of old media but not in that of new media. It can be expected that the bovernment will make a good use to get procedural validity in the course of designing some information policy based upon quantitative data.
Rotation and scale-invariant pattern recognition using WCHF-fSDF filter
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 2, 1997, Pages 392~400
In this paper we porposed WCHF-fSDF filter to obtain a roration and scale-invariant correlation output. WCHF-fSDF filter is synthesized by each single CHF exttracted from scale-changed and wavelet tranformed imagesfor a refereence image as tranining images. The wavelet transform is defined as the correlation of an input image with a wavelet function. Therefore two 4f optical correlation systems are needed for pattern recognition using wavelet transform. We here include the wavelet function for the input image in the process of the proposed filter design and substitute the two 4f optical correlation system with a single 4f optical correlation system. The Performances of the proposed filter are compared with conventional CHF-SDF, POCHF-SDF filters through the computer simulation. The results of computer simulation show that the proposed filter has the rotation and scale-invariant correlation output and it has better performances than thoseof the conventioanl filters.