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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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Performance Analysis of MC-CDMA with MAI Cancellation
Park, Hyeong Geun ; Kim, Eung Bae ; Lee, Yeon U ; Eun, Do Hyeon ; Cha, Gyun Hyeon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 1~1
In this paper, the MC-CDMA(Multi-Carrier Code Division Multiple Access) receiver that employs a cochannel interference canceller for communication over multipath fading channels is proposed and analyzed. The receiver first demodulates the received signal to produce the initial data and the channel estimates. Based on these estimates, the cancellation scheme essentially creates replicas of the CCI and removes them for a second improved data decision. Using theoretical analysis and simulation, the canceller's bit error rate(BER) performance is investigated in both the absence and presence of errors in the amplitude estimates of each user's received signal. The results show the considerably large improvement in performance that can be attained by the cancellation scheme, even under partially degraded estimates.
Traffic Model Considering Mobility Characteristics in the Integrated Terrestrial and Leo Satellite Mobile Communication Networks
Kim, Byeong Gyun ; Choe, Hyeong Jin ; Lee, Bong Geun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 10~10
In this paper, we propose a teletraffic model and evaluate the performance in the terrestrial/satellite integrated mobile communication networks having hierarchical structure consisting of terrestrial microcell and satellite spot beam. Both the subscriber terminal mobility in the microcell and satellite mobility in LEO satellite spot beam are considered. Overflow traffic generated from microcell can be accommodated by the satellite spot beam and bursty overflow traffic is analyzed by IPP which is often used to analyze non-random overflow traffic. Carried traffic capacity in each layer, blocking probability, forced termination probability and non-completion probability are evaluated for different values of the number of handoff reservation channel in microcell and satellite spot beam, and reservation channel for new call generated from satellite spot beam for the integrated network.
Frequency-Hopped MUltiple-Access Communication with Nonorthogonal BFSK in Rayleigh Fading Channels
Choe, Ho Gyu ; Kim, Sang U ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 22~22
Nonorthogonal binary FSK (BFSK) is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmitted information bits per unit time per unit bandwidth (called normalized throughput) is examined in Rayleigh fading channel. The tradeoff among tone spacing, code rate and number of frequency slots in maximizing the normalized throughput is examined, when the total bandwidth is fixed. The optimal tone spacing, code rate, and number of frequency slots in terms of the number of users and
is discussed. The throughput gain attained by using the optimal tone spacing is more significant as the number of users is increased.
A Study On Optimization of Working Set Size Using the Fuzzy Controller in Variable Location Registration
Yang, Sun Seong ; Jeong, Seong Du ; Lee, Gyun Ha ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 30~30
In personal mobile communication systems, the existing location area allocation scheme generally allocates the size of location area statically without consideration given to the mobile station's mobility patterns. This scheme is efficient to operate the system because of its simplicity, but it is not adequate to provide many mobile communication users who have a various mobility patterns with service in future mobile communication systems. In this paper, we suggest a new location area allocation scheme which allocates the individual location area in different sizes according to each mobile station's mobility patterns. The size of the location area is determined by a fuzzy controller whose input parameters indicate the number of location registrations and the amount of incoming calls per hour. In the suggested scheme, which decided the location area size by using the fuzzy controller, and the existing location area allocation scheme, which assigns a fixed location area size to users, comparing the cost of the location registration to the paging, we have conclude that a suggested scheme's total cost is decreased about 32% comparing that of the existing scheme.
Performance Analysis and Compensation of the Multi-Code CDMA System with Non-linear Amplifier
Kim, Dong Gu ; An, Cheol Yong ; Gwon, Dong Seung ; Park, Han Gyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 38~38
Multi-code CDMA (MC-CDMA) was proposed technique to provide variable rate services with different quality requirements by assigning a number of codes to a user. MC-CDMA system can be integrated easily with a conventional system, and achieve good spectral efficiency and high processing gain. But it suffers from the increase of peak-to-average power ratio. In the paper, we analyzed the effect of the non-linearity of an amplifier on MC-CDMA system and verified it through simulation over the frequency flat fading and multipath fading channels. Also, it is shown that the use of adaptive predistorter can significantly reduce the effect of an amplifier. The system performance is compared when different number of codes and different values of input backoff are used.
Extraction of Terrain Features from Discrete Geographic Elevation Data
Kim, Eung Gon ; Han, Seung Jo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 46~46
In this paper, the method of extracting terrain features such as Peaks, pits, passes, ridge lines, and ravine lines from discrete geographic elevation data is presented. The feature points using the existing techniques according to the eight-neighbor method do not satisty the Euler formula. This method extracts the feature points that satisfy the Euler formula. There have been no algorithms for constructing topological graphs such as the surface network and the Reeb graph from the extracted peaks, pits, and passes. This paper presents the methods for constructing the surface network and the Reeb graph from the feature points. These algorithms were implemented with Java Applets and VRML, and can be used by all browsers that support Java and VRML on the WWW.
A Study on Efficient Priority Control with Traffic specification in ATM
Kim, Nam Hui ; Lee, Sang Tae ; Jeon, Byeong Sil ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 53~53
In this paper, we proposed a new priority scheme that can effectively control the cell loss rate and cell delay for each QoS classes in an output queuing system. In proposed priority control method, we use two common buffers, loss sensitive traffics and delay sensitive traffic are input in each buffer. We reduced cell loss rate with respect to loss sensitive cells using proposed cell reservation scheme and cell delay rate with respect to delay sensitive cells using cell scheduling scheme by threshold in ATM output link. The evaluation results show that the proposed scheme can effectively and efficiently control multiple QoS classes.
The Efficient Data Recovery Algorithm Using the Asynchronous Checkpoint Methods in Distributed Systems
Jeong, Gyeong Hun ; Kim, Chang Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 61~61
In this paper, we propose the efficient data recovery algorithm which is not progressed multi-step rollbacks and lessen plentiful of logging data. The checkpointing algorithms ensure the process autonomy by allowing them to take checkpoints asynchronously, and use the checkpoint coordination which is based on the message passing method for the progression of the recovery line which helps bound rollback propagation during a recovery. The proposed algorithm ensures the existence of a recovery line consistent with the lastest checkpoint of any process all the time, and exploits this feature to restore the system to a state consistent with the lastest checkpoint of a failed process.
A study on new ABR traffic control mechanism in an ATM network(ASCA)
Heo, Seong ; Jin, Yong Ok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 72~72
The ABR(Available Bit Rate) service in ATM networks has been specified to allow fair and efficient support of data applications over ATM utilizing capacity left over after servicing higher priority classes. In this paper we propose and analyze the performance of an efficient ABR(Available Bit Rate) traffic control mechanism which using the signalling channel in an ATM network. We have defined and created new Bandwidth Request and Bandwidth Allocated Message for the ABR traffic control using a signalling channel, thereby producing a new message flow diagram for ABR traffic parameter negotiation.
Performance Analysis of a Hierarchically-Structured VOD Server
Im, Beom Su ; Jo, Tae Gyeong ; Choe, Myeong Ryeol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 79~79
VOD(Video On Demand) is one of the most successful services in the early broadband networks. The placement of video server is a very important issue in the design of VOD system. A hierarchically-structured VOD server has the properties such as decreased network traffic and increased efficiency of virtual server by storing the popular video programs at the local switching units. In this paper, we propose a hierarchically-structured VOD server whose architecture shares other servers in the same tier. We have analyzed and simulated the hierarchically-distributed / multitiered VOD server using M/M/n/n+N queueing model. Analysis and simulation results of the proposed model with 3~5 tiers show that the total blocking probability, the average wating time and the total bandwidth decrease as the number of tiers is increased. This proposed model can be used to determine the network bandwidth and requirements of VOD server.
A study on Enhancement of Response Time for the ABR Service in ATM Networks
Lee, Si Jeong ; Jeon, Seok Hui ; Kim, Nam ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 89~89
MMRCA_RQL and MMRCA_TR have been suggested to improve MMR CA used for the ABR service. However, it takes long round-trip time under congestion and requires additional hardware complexity to compute the total sum of incoming rate. In this paper, the enhanced family algorithm of MMR CA and MMRCA_RQL is suggested. The family algorithms are based on the Recommendation of ATM Forum that switch can optionally set RM Cell's CI value 1 to control congestions at queuing points. As a result, it is found that proposed algorithms can converge to the second fair rate 32% faster than MMRCA and MMRCA_RQL when new channels are joined.
An Effective Transaction Scheduling Policy for improving the performance of a Real-Time Database on Network Environment
An, U Yeong ; Lee, Jae Ho ; Im, Hae Cheol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 97~97
This paper studies a transaction scheduling method that permits transactions to access information in databased within their deadlines. And it improves the overall throughput of transactions in maintaining data consistency of databased, stored at different sites. It takes the performance of the high-speed network into account that has to satisfy a various services such as conventional data, video frame, graphical image and voice. The transaction scheduling methods of distributed RTDB(Real-Time DataBase) studied up to now, have been used in database systems for the purpose of improving the total throughput of a system. But they did not take the status of network into account properly, or just extended the classical database systems to RTDB operated under network environment, which still have the problems of priority inversion or deadlock. Accordingly, this paper proposes a transaction scheduling method which is suitable for making fast decision whether to process transactions or not with considering the performance of database systems in accordance with the status and the performance of a network.
An Estimation and Forcasting on Demand of Telecommunication Service in Major Cities of Korea
Choe, Dong Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 105~105
This study is based on a theoretical model of telecommunication service demand in order to establish and expect a quantitative model of telephone service demand, and following is a summary of a expected result by using a logistic model with a growth curve model. First, according to a presumed result of telephone distribution rate model by each location, the phone charge(call price index) by each location and subscription fee bring about a negative effect to phone distribution rate, while the other explanatory variables bring ablut a positive effect. Second, according to a presumed result of the model of long distance call numbers, the flexibility of phone charge in A location(relevant location) and the flexibility between the distance of A location and B location are negative values, while the flexibility of other explanatory variables is represented in a positive value. This means that the long distance call numbers from A location to B location are in inverse proportion against th phone charge(call price index) of A location and against the distance between A location and the distance of other locations except A location, while they are in direct proportion with an average call number per minute from A location to other locations except A location, and also with subscription numbers of A location, other subscribers in locations other than A location, and the total expenditures of A location.
Accurate Resonant Frequencies of Cylindrical and Ring Dielectric Resonators Using Effective Dielectric Constants
Lee, Ju Seop ; Han, Sang Min ; Hwang, Ho Tak ; Kim, Yeong Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 115~115
In this paper, effective dielectric constants(EDCs) which can be obtained from dielectric waveguide model(DWM) method have been introduced in axial and radial attenuation constants to calculate more accurate resonant frequencies of the mode of cylindrical and ring dielectric resonators in an MIC environment. The accuracy of this new method is shown to be better than 0.5 percent error.
Adaptive Beamforming by Using Pilot Symbol for an OFDM System
Kim, Chan Gyu ; Jo, Yong Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 122~122
This paper presents an adaptive beamforming algorithm for an OFDM system with an adaptive array antenna. By employing an antenna array at the access point of an OFDM system, the performance of the OFDM system, which is known to be effective for high data rate transmission due to insensitivity to frequency-selective channel with a simple one-tap equalizer, is shown to be significantly improved. The proposed algorithm for adaptive beamforming in an OFDM system is derived by (1) calculating the error signals between pilot symbols and the corresponding received signals in the frequency domain, (2) transforming the frequency-domain error signals into time-domain error signals, and (3) updating the filter coefficients of the adaptive beamformer in the direction of minimizing the MMSE. Convergence behavior and performance improvement of the proposed approach are demodulated through computer simulation by applying it to the conventional OFDM system.
Generation Methods and Performance Analysis of a Modulated Orthogonal Sequence
Park, Seong Il ; Kim, Yun Hui ; Lee, Ju Sik ; Song, Ik Ho ; Lee, Seong Ro ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 130~130
In this paper, a new generation and an information construction methods for a modulated orthogonal sequence are suggested: with the new generation method, we can generate code sequences with only integer sums and modular techniques. The autocorrelation and cross-correlation characteristics of the sequence are investigated via a new procedure. A modified sequence also having the orthogonality and satisfying the mathematical lower bound of the cross-correlation is proposed, and the symbol error probability of the proposed sequence is investigated.
Channel Coder Design Combined with Source Coder for Mobile Communication Systems
Kim, Jong Heon ; Lee, In Seong ; Gang, Seok Bong ; Lee, Jeong Gu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 137~137
In this study, the efficient channel coding method combined with CS-ACELP is proposed. The same convolutional coder and Viterbi decoder of CDMA mobile communication system is used as channel coder. To make the best available use of limited channel coding redundancy, unequal error protection of speech packet data is performed in channel coder. The punctured convolutional coder is used for variable rate allocation. But, the overall code rate is given by 2. The performance of proposed coder is analyzed and simulated in a Rayleigh fading channel. Experimental results show that the objective and subjective speech quality of variable rate channel coding methods are superior to those of non-variable channel coding method.
Using Motion Information
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 1B, 1999, Pages 145~145
In this paper, we propose an efficient subband coding of video with selective vector quantization using motion information. The motion compensated difference image (MCDI) exhibits characteristic, that is, it has significant amplitudes in the boundaries and high contrast regions of moving objects and small amplitudes in the homogeneous or unmoved regions. Therefore, by using this characteristic we can divide the MCDI into the high energy regions and low energy regions. So that we can improve the coding efficiency by encoding only the high energy regions. Also, MCDI shows another characteristic that the high energy regions of it move according to each motion vectors. Therefore,we can predict the high energy regions in the present frame from the previous frame. By using these two characteristics of MCDI, we can reduce the bit rate needed to encode the MCDI and we can get the reconstructed images with good quality.