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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 21, Issue 12 - Dec 1996
Volume 21, Issue 11 - Nov 1996
Volume 21, Issue 10 - Oct 1996
Volume 21, Issue 9 - Sep 1996
Volume 21, Issue 8 - Aug 1996
Volume 21, Issue 7 - Jul 1996
Volume 21, Issue 6 - Jun 1996
Volume 21, Issue 5 - May 1996
Volume 21, Issue 4 - Apr 1996
Volume 21, Issue 3 - Mar 1996
Volume 21, Issue 2 - Feb 1996
Volume 21, Issue 1 - Jan 1996
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Nonlinear hierarchical motion estimation method based on decompositionof the functional domain
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 807~821
In this paper, we proposed a nonlinear hierarchical mtion estimation method. Generally, the conventional hierarchical motion estimation methods have been proposed for fast convergence and detection of large motions. But they have a common drawback that large error in motion estimation is propapated across motion discontinuities. This artifiact is due to the constriaint of motion continuity and the linear interpolation of motion vectors between hierarchical levels. In this paper, we propose an effective hierarchical motion estimation mechod that is robust to motion discontinuities. The proposed algorithm is based on the decomposition of the functional domain for optimizing the intra-level motion estimation functional. Also, we propose an inter-level nonlinear motion estimation equation rather than using the conventional linearprojection scheme of motion field. computer simulations with several test sequences show tht the proposed algorithm performs better than several conventional methods.
Video coding based on wavelet transform for very low bitrate channel
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 822~833
The video coding for very low bit rate has recently received considerable attention, but conventional block based transform coding schemes suffer from the blocking effect for the constraints of bit rates. In this paper, we present a video coding sysem suing multi-resolution motion estimation/compensation with variable size block(VMRME/C) and multi-resolution vector quantization(MRVQ) in wavelet transform domain for very low bit rate coding. It is shown that the presented scheme has better performance in the peak signal-to-nose ratio(RSNR) by 0.2-0.6 dB as well as subjective quality than that of conventional block based transform video coding techniques(especially, H. 263 which is DCT based video coding).
Selective coding scheme using global/local motion information
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 834~847
A selective coding scheme is proposed that describes a method for coding image sequences distinguishing bits between background and target region. The suggested method initially estimates global motion parameters and local motion vectors. Then segmentation is performed with a hierarchical clustering scheme and a quadtree algorithm in order to divide the processing image into the backgraound and target region. Finally image coding is done by assigning more bits to the target region and less bits to background so that the target region may be reconstructed with high quality. Simulations show that the suggested algorithm performs well especially in the circumstances where background changes and target regionis small enough compared with that of background.
Color image quantization considering distortion measure of local region block on RGB space
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 848~854
Many image display devices allow only a limited number of colors to be simultaneously displayed. in disphaying of natural color image using color palette, it is necessary to construct an optimal color palette and the optimal mapping of each pixed of the original image to a color from the palette. In this paper, we proposed the clustering algorithm using local region block centered one color cluster in the prequantized 3-D histogram. Cluster pairs which have the least distortion error are merged by considering distortion measure. The clustering process is continued until to obtain the desired number of colors. The same as the clustering process, original color value. The proposed algorithm incroporated with a spatial activity weighting value which is reflected sensitivity of HVS quantization errors in smoothing region. This method produces high quality display images and considerably reduces computation time.
Similar and rotation invariant optical pattern recognition characteristics of SA-MPOF
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 855~868
In this paper, multiplhase only filter(MPOFs) are designed using simulated annealing algorithm. These filters have excellent recognition characteristics for similar patterns or rotated patterns and enhance optical efficiency as well as spatial-bandwidth product by deleting mirror image. As the result of computer simulation to certify recogntion characteristics of similar patterns, simulated annealing-MPOF(SA-MPOF) has superior discrimination and higher correlation peak values than cosine binary phase only filters(CBPOF) and simpulated annealing-BPOF (SA-BPOF). THe filter having training process for rotated patterns of arbitraty possible angle can overcome that phase only filter(POF) and CBPOF can't recognize rotated input patterns.
Determination of threshold values for color image segmentation
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 869~875
This paper investigates a method for dtermining a threshold value based on the probability distribution function for color image segmentation. Principal components of normalized color is nalyzed and found that there are effective color transforms for outdoor scents. We esplain the functional relationship of the treshold and the probability of a regiona detection, asuming bivarate Gaussian probability density function. Experimental results show that the probability of detection is proportional to the segmented area.
An adaptive IIR echo canceller with adaptive compensator
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 876~883
Adaptive FIR filters are widely used in the echo canceller. But, most of practical systems have the transfer function composed of poles and zeros. In that case, adaptive IIR filters may be more efficient rather than FIR fiters. In this paper, a recently developed C-HARF algorithm is used to implement an adaptive IIR echo canceller. The proposed convergence of the algorithm make it attractive for this application. Extensive computer simulations show that C-HARF algorithm performs better than the NLMS algorithm after convergence, although C-HARF algorithm converges more slowly.
The modified adaptive blind stop-and-go algorithm for application to multichannel environment
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 884~892
An adaptive blind equalizer is used to combat the distortions caused by a nonideal channel without resorting to a training sequence, given the received signal and statistical information of the transmitted signal. Incidentally, a multipath channel may result in a fade which produces intersymbol interference in the received signal. Therefore, a new type of algorithm which can compenste the effects of this fade is required in the multipath channel environment. In this paper, a modified form of adaptive blind equalization algorithm using stop-and-go algorithm for multichannel system is proposed. It is demonstrated via computer simulations that the performance of the proposed multichannel stop-and-go algorithm is much better than that of the conventional multichannel algorithms.
A study on random access protocol based on reservation access for WDM passive star coupler network
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 893~910
Recently, there ary many researches on local area multichannel network as WDM technology developes. An ideal media access protocol in a multichannel network is one that shows short access delay under low load and high throughput under heavy load. This paper proposed a new media access protocol for WDM passive star coupler network. The proposed one is a random access rpotocol based on reservation. Access delay is short under low load by using random access method, and high throughput is achieved under heavy load by usin greservation access. Analytic model for the performance analysis of the proposed protocol is developed and performance of the proposed protocol is compared with the previous ones. The effect on the performance of the number of the nodes and channels, and the number of transceivers in each node are analyzed.
A flexible error control model in transport layer for multimedia application
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 911~925
Emerging service classes need an error model which efficiently satisfies the requirements for each media and application. However limited flexibility in the error control has been provided. Therefore we propose a new error control model which applies error control scheme per media flexibly with respect to ETL(Error Tolerance Leverl) and delay. In order to select the error control scheme in this model, the attributes of media(i.e., ETL, isochronism), the attributes of application(i.e., delay) and environment parameters(i.e., packet loss ration, network types, connection modes of the application) are considered as effect factors.
A multicast algorithm in overlapped process group environments
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 926~938
In this paper, we proposed a new multicast algorithm which is efficiently applicable to overlapped process group environments where one process may be involved in several process groups. Unlike the esisting algorithms, the proposed one provides an efficient group communication mechanism by generating the processgroup information in two-level tree. Using this algorithm, we improved the shortcoming of the existing algorithms by reducing the overhead in passing through unnecessary processes for message ordering. We have provided the causal ordering method as well as the total ordering method in group communication environments. As a result, we allow one process to deliver message to other processes with a short delay time, and reduced the overhead required for the message ordering. Also, we logically proved the proposed causal ordering method, and compared the performance of the proposed algorithm with ones of other existing algorithms by computer simulation.
Virtual path design in ATM network
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 939~951
The previous study of virtual path design for one traffic class with ATM DCS only should be generalized to that for the multiple traffic class cases of being given neither virtual path candidate set nor end nodes o each virtual path. In this paper, a design model of virtual paths for the general case with multiple traffic classes is suggested. The model is represented as an optimization rpoblem with a special structure. It is solved by SQA algorithm, which is developed by authors in [3, 4]. The model and the algorithm are applied to a numerical example, and results are shown.
A study on the overload control of the ATM switching system
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 952~960
In this paper, a new overload control scheme is proposed for a control system in ATM switching system. The proposed control scheme includes a counter that conunts the number of accepted calls and is decreased at cach D time interval. In overload condition of call processor, the control scheme detects over load condition when the counter value reaches a certain threshold value. Under overload condition, processor utilization is measured and the value of the D is updataed according to the difference between measured processor utilization and target utilization. A new call is accepted accepted only if the value of the counter is less than the threshold value. In overflow condition of cell traffic, accept probability of new call is reduced exponetially according to the elapsed time. The results of simulation show that the proposed overload contorl scheme maintains the target utilization very well under the various processor overload conditions and reduces the cell loss probability under the cell overflow conditions.
TDMA jammer suppression on CDMA overlay
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 961~971
The effect of inband TDMA narrow band jammers to DS-CDMA system performance and the suppression techniques are investigated using Monte Carlo simulations. TIA stantard North American Digital Cellular wea used as jammer. Levinson Dubin and conventional recursive least square algorithm were emphasized since these techniques can be implemented with a few DSPs for CDMA application. Two filter structures, i.e., complex suppression filter and real suppression filter in each inphase and quadrature channels, are investigated and their performances are compared. Complex suppression filter with Levinson Durbin algorithm of 20msec updata rate is the most promising with respect to implementation and performance poit of view. Implementation feasibility is discussed and the channel capacity lost by suppression is computed.
A frequency offset correction technique for coherent OFDM receiver on the frequency-selective fading channel
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 972~983
This paper proposes a new technique for frequency offset correction for OFDM systems on a frequency selective fading channel. Frequency offset in OFDM introduces interchannel interference among the multiple subcarriers of OFDM signal. To compensate the interference, this paper describes an algorithm with two stages:acquisition and tracking. At both stages, the proposed algorithm oversamples the received OFDM signal to obtain a couple of demodulated symbol sets. At acquisition stage the frequency offset is reduced to half or less of the intercarrier spacings by matching the sign pattern of each element of the sets. Next, at tracking stage the frequency offset is corrected with a frequency detector which is controlled by the correlation of the two sets. It is shown that the proposed algorithm can correct the frequency offset in the event of uncertainty in the initial offset that exceeds one half of the intercarrier spacing. In addition, the proposed algorithm is robust to transmitted symbols and channel characteristics by using oversampled symbol sets.
Design of a convolutional encoder and viterbi cecoder ASIC for continuous and burst mode communications
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 984~995
Data errors according to the various noises caused in the satellite communication links are corrected by the Viterbi decoding algorithm which has extreme error correcting capability. In this paper, we designed and implemented a convolutional encoder and Viterbi decoder ASIC which is used to encode the input data at the transmit side and correct the errors of the received data at the receive side for use in the VSAT communication system. And this chip may be used in any BPSK, QPSK, or OQPSK transmission system. The ambiguity resolver corrects PSK modem ambiguities by delaying, interting, and/or exchanging code symbol to restore their original sequence and polarity. In case of previous decoding system, ambiguity state(AS) of data is resolved by external control logic and extra redundancy data are needed to resolve AS. But, by adopting decoder proposed in this paper, As of data is resolved automatically by internal logic of decoder in case of continuous mode, and by external As line withoug extra redudancy data in burst mode case. So, decoding parts are simple in continuous mode and transmission efficiency is increased in bust mode. The features of this chip are full duplex operation with independent transmit and receive control and clocks, start/stop inputs for use in burst mode systems, loopback function to verify encoder and decoder, and internal or external control to resolve ambinguity state. For verification of the function and performance of a fabricated ASIC chip, we equiped this chip in the Central and Remote Earth Station of VSAT system, and did the performance test using the commerical INTELSAT VII under the real satellite link environmens. The results of test were demonstrated the superiority of performance.
Adaptive blind decision feedback equalization using constant modulus and prediction algorithm
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 996~1007
In this paper, a blind adaptation method for a decision feedback equalizer (DFE) is proposed to deal with nominimum phase channels. This equalizer is composed of a linear transversal filter and a prediction error filter which are trained separately using constant modulus and decision feedback prediction algorithms, respectively, during the learnign time. The proposed algorithm guaranetees the DFE to converge to a suboptimal point on the condition that a linear transversal of the proposed scheme is illustrated and the performance is compared with conventional blind equlization algorithms.
A study on the channel assignment using neural network in cellular radio network
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1008~1018
For assigning channel in a cellular sireless network, we purpose satisfying constraints with a related probability between cells and channels on the channel interference matrix formed by m terminals and n channels. And we purpose to get efficient channel assigning to limited channels in a wireless cell using parallelism of neural networks. In this paper, we solve the problem according to the number of requeirements when channel change with 11-533 procession elements. We demonstrate efficiency of proposed algorithm through same simulations in a specific time period.
Modulation classification for BPSK and QPSK signals over rayleigh fading channel
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1019~1026
A modulation type classifier based on statistical moments has been successfully employed to classify PSK signals. Previously, developed Classifiers were analyzed in AWGN channel only. In this paper, a moments-based modulation type classifier to classify BPSK and QPSK signals over Rayleigh fading channel is proposed and analyzed. The moments of received signal are evaluated with the exact distribution of the received signal and a moments-based classifier is proposed. The performance evaluation of the proposed classifier in terms of the misclassification probability for BPSK and QPSK is investigated under Rayleigh fading environment.
A study on the impulse response characteristics by using the GCR proposed for korean standard
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1027~1037
This paper presents an impulse response of the multi-path channel using KS-GCR(Korean Standard Ghost Cancel Reference) signal. Using the property of the KS-GCRsignal, we can get the impulse response of the multi-path channel from circular cross correlation of the received DS-GCR signal and the orginal KS-GCR ternary sequence. Therefore impulse response of the multi-path channel can be used to design the the ghost cancellation filter if it is designed to have inverse characteristics of multi-path channel. This paper shows that the ghost occurred from the multi-path channel can be cancelled by using the impulse response and preceding ghost cancellation algorithm.
Analysis of electro encephalogram(EEG) for estimating masimum permissible exposure(MPE) of rabbit for mcirowave exposure
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1038~1047
The effect of electromagnetic wave on the biobody is to make a possibility not increasing temperature but also inducing physiological and psychological damage which is head or backbone. Generally a vital function of hean can be estimated by the measureing of Electro Encephalogram(EEG), and achieved a response of a find stimulus which can not be defected a subjective sympton and out of reaction. In this paper, the head can be modeled according to its medium and dervated the equation of SAR distritution, and the head of rabbit is approximately modeled three layers practically and the result of each SAR distribution is illustrated. Measured EEG from the nervous system of rabbit on a plane wave irradiated an be used quantitative analysis for the electrophysiogical effect of the biobody.
A study on the small duplexer using dual-mode filter for ku-band satellite communications
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1048~1058
In this paper, a small duplexer is designed and implemented using a H-plane T-junction and Transmitting/Geceiving filte with a dual mode cavity resonator for Ku-band. Transmitting(TX) filter is designed at center frequeny 12.5 GHz and Receiving(RX) filter, at center frequency 14.5 GHz. Both filters have a 100 MHz bandwidth. This duplexer is reduced to about 40% by the conventional duplexer of cavity bandpass filter structure in size. Operating characteristics of duplexer is optimized in order not to distors matching characteristics of each filter when interfaced to a H-plane T-junction. Consequently, the responses of filter with H-plane T-junction nearly coincide with that of filter itself.
Desing and fabrication of GaAs prescalar IC for frequency synthesizers
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1059~1067
A 128/129 dual-modulus prescalar IC is designed for application to frequency synthesizers in high frequency communication systems. The FET logic used in this design is SCFL(Source Coupled FET Logic), employing depletion-mode 1.mu.m gate length GaAs MESFETs with the threshold voltage of -1.5V. This circuit consists of 8 flip-flops, 3 OR gates, 2 NOR gates, a modulus control buffer and I/O buffers, which are integrated with about 440 GaAs MESFETs on dimensions of 1.8mm. For
power supply voltages 5V and -3.3V Commonly used in TTL and ECL circuits are determined, respectively. The simulation results taking into account the threshold voltage variation of .+-.0.2V and the power supply variation of .+-.1V demonstrate that the designed prescalar can operate up to 2GHz. This prescalar is fabricated using the ETRI MMIC foundary process and the measured maximum operating frquency is 621MHz.
A new continuous-time current-mode integrator for realization of low-voltage current-mode CMOS filter
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1068~1076
In this paper, a new continuous-time current-mode integrator as basic building block of the low-voltage analyog current-mode active filters is proposed. Compared to the current-mode integrator which is proposed by Zele, the proposed current-mode integrator had higher unity gain frequency and output impedance in addition to lower power dissipation. And also, a current-mode third-order lowpass active filter is designed with the proposed current-mode integrator. The designed circuits are fabricated using the ORBIT's
deouble-poly double-metal CMOS n-well process. The experimental results show that the filter has -3dB cutoff frequency at 44.5MHz and 3mW power dissipation with single 3.3V power supply and also
Analysis on power penalty due to timing jitters when considering intersymbol interference in the receivers on intensity modulation/direct detection optical communication systems
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 4, 1996, Pages 1077~1088
In this paper, we propose a new method to analyze the performance degradation by timing jitters in the receivers of intensity modulation/direct detection digital optical communication systems where pulse-shaping filters are used to minimize intersymbol interference. The results obtained from the proposed analytical method show that conventional analytical methods underestimate the influence of timing jitters on the receiver performance. Using the proposed anlaytical method, we derive an analytic equation for approximated power penalty due to timing itters and obtain an exact power penalty by numerical analyses. Assuming Gaussian or uniform probability density function for timing jitters, we also show that assumption of Gaussian distribution for timing jitters yields more performance degration than that of uniform distribution.