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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 19, Issue 12 - Dec 1994
Volume 19, Issue 11 - Nov 1994
Volume 19, Issue 10 - Oct 1994
Volume 19, Issue 9 - Sep 1994
Volume 19, Issue 8 - Aug 1994
Volume 19, Issue 7 - Jul 1994
Volume 19, Issue 6 - Jun 1994
Volume 19, Issue 5 - May 1994
Volume 19, Issue 4 - Apr 1994
Volume 19, Issue 3 - Mar 1994
Volume 19, Issue 2 - Feb 1994
Volume 19, Issue 1 - Jan 1994
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Performance Enhancement of An Optimal Network Protocol for High-Speed Communication
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1641~1647
This paper describes an optimal communication protocol for high-speed networks. This scheme can support multimedia services and provide fast data transmission using the distributed gueue scheme and the dynamic bandwidth allocation architecture, based on ATM(Asynchronous Transfer Mode). Performance analyses and simulation results are presented to illustrate the effectiveness of the proposed scheme in a variety of communication environments.
Implementation and compatibility Test of KAX. 25 Link Layer Protocol for Microsatellite Packet Communications
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1648~1657
This paper is concerned with the development of a packet communication protocol KAX. 25 to be used on the KITSAT microsatellite. As a part of the KAX, 25 protocol, an interrupt driven I/O driver, I/O handler and an AX. 25 radio communication protocol are implemented in the KASCOM that will be used as On-Board Computer in the next missions. The implemented protocol is applied to the enginnering model of the KITSAT-2 satellite in the test configuration simulating the link between the satellite and the ground station and the compatibility of the data link layer protocol is tested.
A Channel Assignment by Graph Coloring Problem in Cellular Mobile Communication Control System
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1658~1667
In a cellular mobile communication control system, assignment channel for a call in a cell so as to achieve high spectral efficience is an important problem within limited frequence bandwidth. The spectral efficiency is related to the coloring problem of graph theory in a cellular mobile communication control system. In this paper, we propose channel offset scheme using a graph theory of cellular mobile communication control system and formulate chromatic bandwidth of channel offset system which is related graph coloring problem. From formulated channel assignment problem, we investgate an optimal channel offset scheme of more efficent frequence spectrum and cell design according to channel constitution and give and upper and lower bound for overall srectral bandwidth.
Cochannel Interference Probability of Cellular Mobile Radio Systems in the Environments of Noise and Nakagami Fading plus Lognormal Shadowing
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1668~1679
The cochannel interference probability has been estimated both in the environment of Nakagami fading and Gasussian noise and in the environments of Gaussian noise and Nakagami fading plus log-normal shadowing. In noise and Nakagami fading environments, a theoretical analysis has been performed in order to calculate the cochannel interference probability in addition to computer simulation. In the environments of noise and Nakagami fading plus shadowing, only a simulation technique is used due to complexity in analysis. The spectrum efficiency is discussed on each case.
An Extended Hypertext Data Model based on Object-Oriented Praradigm
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1680~1691
We propose an extended hypertext data model based on object oriented paradigm that can easily the real world and semantics. We use the BNF notation to formalize the model. In our model, We introduce conceptional navigation by associating semantics on links and drive intelligent navigation using weights on links to alleviate user disorientation problem which is currently somewhat vague. We functionally classify the hypertext node into three types:Indexing node, Content node, Extract node and likewise classify the link into Alink type, Rlink type, Slink type. We believe that the typed node and typed link approach accommodate efficient query/search in hypertext.
A Study on the Phase Locked Loop Macromodel for PSPICE
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1692~1701
Macromodeling technology is useful to simulate and analyze the performance of new elements and complicated circuits or systems without any changes in today's general simulator, PSPICE. In this paper, Phase Locked Loop(PLL) is designed using macromodeling technique. The PLL macromodel has two basic sub-macromodels of the phase detector and the voltage controlled oscillator(VCO). The PLL macromodel has two open terminals for inserting RC low pass filter. The PLL macromodel is simulated using simulation parameters of LM565CN manufactured in the National company. At a free-running frequency, 2500Hz, upper lock range and lower capture range was 437Hz, 563Hz, respectively. Also, experimental results and simulation results of LM565CN PLL show good agreement.
A Word Dictionary Structure for the Postprocessing of Hangul Recognition
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1702~1709
In the postprocessing of Hangul recognition system, the storage structure of contextual information is an important matter for the recognition rate and speed of the entire system. Trie in general is used to represent the context as word dictionary, but the memory space efficiency of the structure is low. Therefore we propose a new structure for word dictionary that has better space efficiency and the equivalent merits of trie. Because Hangul is a compound language, the language can be represented by phonemes or by characters. In the representation by phonemes(P-mode) the retrieval is fast, but the space efficiency is low. In the representation by characters(C-mode) the space efficiency is high, but the retrieval is slow. In this paper the two representation methods are combined to form a hybrid representation(H-mode). At first an optimal level for the combination is selected by two characteristic curves of node utilization and dispersion. Then the input words are represented with trie structure by P-mode from the first to the optimal level, and the rest are represented with sequentially linked list structure by C-mode. The experimental results for the six kinds of word set show that the proposed structure is more efficient. This result is based on the fact that the retrieval for H-mode is as fast as P-mode and the space efficiency is as good as C-mode.
Design and Fabrication of the Wide-band YIG Tuned Oscillator
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1710~1718
In this paper, a broadband tunable YIG(Yittrium Iron Garnet) oscillator is designed and fabricated. To design an YTO(YIG Tuned Oscillator), a suitable YIG resonator is selected according to the design oscillation range and its equivalent R, L, C resonant circuit parameters are obtained through the measurement of its resonance characteristic. Using the equivalent circuit, the wideband topology which suppresses the parasitic oscillation is selected and implemented. The designed circuit is simulated by HBT(Harmoic Balance Technique) using EEsof's jOMEGA. The YTO thus fabricated has the wide oscillation range from 1.4 GHz to 4 GHz, and its linearity is 0.5% in the oscillation range. The phase noise is below 105dBc at 100kHz offset.
A Study on the adaptive Connection Admission Control Method in ATM Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1719~1729
In this paper, an adaptive CAC(Connection Admission Control) method is proposed. The adaptive CAC uses traffic estimates derived from both traffic parameter specified by user and cell flow measurements. Traffic estimation using user-specified parameters is performed at every moment of connection request or connection release by recursive formula which makes real-time calculation possible. Traffic estimation using cell flow measurement is carried out when the number of connected calls does not change during a measurement reflection period-renewal period. The most import ant thing for the traffic estimation using cell flow measurement is the determination of the length of a renewal period to trace a real traffic flow with an allowable time lag and the measurement reflection ratio(MRR) both to reduce the portion of overestimation and to avoid underestimation of real traffic flow. To solve these problems, the adaptive CAC updates renewal period and MRR adaptively according to the number of connections and the elapsed time after last connection or release respectively. Performance analysis for the proposed method is evaluated in several aspects for the cases of both homogeneous and heterogeneous bursty traffic. Numerical examples show the adaptive CAC method has the better performance compared with conventional CAC method based on burst model from the both utilization and QOS point of view.
A Study on the Performance of MAC Protocols for High-Speed Mobile Data Services
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1730~1738
Broadband code division multiple access(B-CDMA)previously proposed for personal communication services(PCS) is not suitable for high-speed data services with large variations in speed, because it is designed only for low-speed voice calls with small variations in speed. Meanwhile, hybrid intra-cell TDMA/inter-cell CDMA(Hybrid TDMA/CDMA) recently proposed could accomodate high-speed services easily because of its internal use of the TDMA scheme, but there would be much inefficiency in treating variable bit rate services due to the intrinsic properties of TDMA transmission scheme, In this paper, a media access control(MAC) protocol, called Resevation TDMA/CDMA, which uses a reservation scheme similar to the one in the packet reservation multiple access(PRMA) protocol to compensate for these shortcomings is proposed. In addition, the performance of this protocol is analyzed and compared with conventional protocols by computer simulation. According to the simulation results, it has been shown that the proposed Reservation TDMA/CDMA scheme could support various transmission rates of user data traffics easily, and it could utilize the variations of the treansmission rates in each active call more efficiently.
A Study on the Feed Network for Microstrip Array Antenna
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1739~1747
This study is concerned with a feeding method of microstrip patch antennas with different widths as feeding elements in order to obtain the appropriate radiation patterns of nonuniform array antennas. We analyze a microstrip patch antenna based on the transmission line model and derive that the ratio of current is equal to that of the input impedances of array antenna elements in case that the feed-line length between elements of array antenna is equal to the integer times of
. We measure the radiation patterns of the nonuniform microstrip patch array antenna with 6 and 9 elements. The patterns measured are well agreed with the theoritically calculated patterns. Thus, this result can be utilized in the implementation of a feed network in nonuniform array antennas.
Performance of cellular CDMA system for voice/data integrated service
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1748~1758
Recently, the demand of mobile communication is rapidly increasing. Also, not only the voice service but also the nonvoice services such as data, FAX, and image service are required. Therefore, in this paper, the voice/data intergraed service methods that will be utilized as a basic core technology of the PCS systems are proposed and their performances are analyzed and compared by computer simulation. According to the simulation results, it could be seen that the performance of voice/data integrated PR-CDMA method is better than that of voice/data integrated broadband CDMA method using a dedicated terminal or a voice/data integrated terminal. The reason is that the voice/data integrated PR-CDMA method can overcome the weak points of CDMA protocol, such as a limitation of the fixed CDMA logical channel number and a falling-off in channel utilization, by using PRMA protocol as a multiple access method that the terminals to which a CDMA logical channel is assigned compete.
A Steepest-Descent Image Restoration with a Regularization Parameter
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1759~1771
We proposed the iterative image restoration method based on the method of steepest descent with a regularization constraint for restoring the noisy motion-blurred images. The conventional method proposed by Jan Biemond et al, had drawback to amplify the additive noise and make ringing effects in the restored images by determining the value of regularization parameter experimentally from the degraded image to be restored without considering local information of the restored one. The method we proposed had a merit to suppress the noise amplification and restoration error by using the regularization parameter which estimate the value of it adaptively from each pixels of the image being restored in order to reduce the noise amplification and ringing effects efficiently. Also we proposed the termination rule to stop the iteration automatically when restored results approach into or diverse from the original solution in satisfaction. Through the experiments, proposed method showed better result not only in a MSE of 196 and 453 but also in the suppression of the noise amplification in the flat region compared with those proposed by Jan Biemond et al. of which MSE of 216 and 467 respectively when we used 'Lean' and 'Jaguar' images as original images.
Implementation of the ISDN Service Node Call Control Functions for Multiparty Connection Service
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1772~1781
The concept of Service Node as the network element which can provide the multiparty multimedia services based on the ISDN was presented in last study. In this study, a multiparty connection service system(Service Node and terminals) was designed using the concepts, procedure, function, and structure of Service Node given above. Based on this, a small scale experimental model giving multiparty call connection control and voice service control function was implemented and tested, which proved the applicability of the concept and validity of the procedure of the Service Node. The experimental model of service system for 4 subscriber capacity was composed of a Service Node emulator and terminals with general S-interface card. The goal of implementation and testing was concentrated of the verification of the proposed functions and procedures of service system and the test results told us that the proposed concept is adequate.
Study on the Design and Fabrication of Traveling-Wave Ti:LiNbO
Phase Optical Modulators
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1782~1792
traveling-wave phase optical modulators at wavelength 1.3㎛ have been designed and fabricated, focusing on the optical waveguide and asymmetric coplanar electrode structure. To improve the phase-mismatch of traveling-wave ACPS electrode, the characteristic impedance, effective microwave index, and electrode loss have been presented as a function of geometric parameters including electrode and buffer layer thickness. Low-loss channel optical waveguides on
were fabricated by the Ti diffusion method with
thick electrode was successfully fabricated by double-spin image reversal process. Modulation bandwidth was limited by a resonance at 2.9 GHz and modulation bandwidth up to 2.5GHz was approxirnately measured.
New Method for Predicting the 1 dB Gain Compression Point
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1793~1801
In this paper, a new method for predicting the 1 dB gain compression point of cascaded N amplifiers is proposed. With the proposed method, the transfer function of each amplifier is derived from scalar data available from the manufacturers data sheet and all transfer functions are producted with scalar in order to also derive the overall transfer function of the subsystem under the assumption that the input and output port of each amplifier are matched. Therefore, the 1 dB gain compression point of the subsystem can be predicted or estimated, reversely, utilizing the overall transfer function obtained with the proposed method. The proposed method can be used irrespective of the number of scalar data but, in this paper, it is analyzed only with two scalar data (linear power gain and 1 dB gain compression point) and three scalar data(linear power gain, 1 dB and 0.5 dB gain compression points). With two sample amplifiers operated in Ku-band, the predicted results by the proposed and previous method, respectively, and the experimental results are together presented in order to confirm its utility.
A Study on the Ku-band Corrugated Horn Antenna for Satellite Payload by using the Modal Expansion Method
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1802~1811
In this paper, the corrugated horn antenna used in the reflector feed horn of satellite is analyzed using the modal expansion method. The modal expansion method is represented by the summations of modals at each point so the exact prediction of field and phase patterns can be obtained. The least number of iterations to compute field patterns is proposed. By using this number. calculation of accurate near and far field patterns without comsuming a lot of computational effort is available. Three kinds of corrugated horn antenna is designed to verify the method and experimented. The VSWR of designed frequency is from 1.04 to 1.1. The input impedance is nearly matched to
A Study on the Algorithm for the Q-CDMA Base Station Receiver
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1812~1823
In this paper, we focus on the simulation of receiver algorithms for the Q-CDMA reverse link modem to analyze its structure and performance. Receiver algorithm is to be characterized by processing a large amount of data for reliable data transmission through poor mobile channel environment. According to Q-CDMA receiver scheme, we connect the code acqusition and code tracking models for despreading of input signals and the RAKE structure demodulator used to resolve the time diversity signal due to multipath propagation. And this connected system is under test. The bit error rates are found for an arbitrary user under the AWGN and multipath fading environments.
A New Multicasting Method in a Multiple Access Network
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1824~1837
Broadband ISDN will support advanced communication services such as multimedia conference, VOD and electronic news service. Because many of these advanced services require multimedia data delivery, future communication networks must have flexible and efficient multiparty communications capabilities. In this paper we propose a new multicasting method which uses packer filtering capabilities both in a physical network and in a logical network layers. This new scheme has potential to reduce the transmission and packet processing overheads of multicast communications. For the new multicasting method, we develop a group matching algorithm which finds a suitable set of groups that covers multiple target hosts. We show the application of the multicasting method and the group matching algorithm with two simple examoles.
The Study of Comparison between RPE-LTP and VSELP Speech Coder
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 9, 1994, Pages 1838~1847
Until recently, they decided the standard of the digital mobile communication speech coding method and competively developed the more detailed techniques in North America, Europe, Japan, etc. But, we have not yet determined. In this paper, we compared the RPE-LTP speech coding algorithm, standard in Europe, with the VSELP speech coding algorith, standard in North America, with respect to the soruce coding. We described the comprehensive verification and comparison with each speech coder, and discussed the improvement plan. Next, we also compared the number of computations which affects the real time processing seriously. Moreover, we performed the simulation with the Korean speech data, concreting the algorithm of each speech coder. Finally, we compared the performance of each speech coder with segmental SNR and 5-point MOS. The number of computations was calculated, and the result was that the number of multiplication computing times of VSELP speech encoder was the largest. With 26 speech data, the segmental SNR of VSELP was calculated larger than that of RPE-LTP. The 5-point MOS test was performed, and the result was that the basic speech quality of VSELP was equivalent or better than that of RPE-LTP.