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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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Continuous digits recognition using spatio-temporal neural network
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1605~1612
In this paper, a new approach for continuous digits recognition using the Spatio-Temporal Neural Network (STNN) is reported. The continuous seven digits are gargeted to recognize, and our initial recognition rate was 28%. In this paper, to increase the recognition rate, two methods are proposed. In the first method, to compensated the STNN's own defect as well as to emphasize the Korean digits' phonic characteristics, the starting point ofeach digit is detected using the energy and zero-crossing rate, but the ending point is detectedonly using the energy value. In this case, the seven digits recognition reate increased to 61%. Furthermore, in the second method, considering the fact that a same digit could be pronounced differently in continuously spoken environment, the number of STNNs used to represent each digit is increased from one to five. Consequently, the same digit but pronounced differently could be handled well in the new system. As a result of that, the continuously spoken seven digits recognition rate increased to 89%.
Quadtree image compression using isolated wavelet coefficients removal
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1613~1623
In this paper, an image coding scheme using removal of isolated coefficients and quadtree structure in wavelet transformed domain, is suggested. The number of significant coefficients can be reduced by quantizing in different stages according to the weights of the each band. The quadtree structure preseves the location information while significantly reducing the number of bits required to represent the locality of an image. To increase the efficienty of the wavelet transformed images using quadtree, the energy of the isolated coefficients is analyzed and those with low energy are eliminated. Furthermore, to control the bit rate the entropy of each block is sorted according to its energy concentration and the number of bits required for encoding, and the blocks with low energy are removed to achieve the desired compression rate.
An efficient block wavelet transform using variable filter length
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1624~1632
Wavelet transform is widely used for high compression ratio image compression. It requeires a large memory when it is implemented by a hardware. Therefore, it is efficient to divide the entire image into blocks. Because the wavelet transform for divided blocks causes losses, pixels of the adjacent blocks are used. In the case of color image compression, the image is decomposed into brightness and color components, and then color components are downsampled. When the wavelet transform is performed by using pixels of adjacentblocks, the number of necessary pixels are doubled due to downsampling of color components. In this paper, we propose an efficient block wavelet transform using variablefilter length for brightness and color components. By using the proposed method, the number of pixels of adjacent blocks is optimized. We show the degradation of image quality due to the reduction of filter length for color components is negligible through simulations.
Estimation of surface reflectance properties and 3D shape recovery using photometric matching
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1633~1641
In this paper we propose a new method for anlayzing the properties of surface reflectance and reconstructing the shape of object using estimated reflectance parameters. We have investigated the hybrid reflectance surface which has specularreflection and diffuse reflection, which can be explained by Torrance-Sparrow model. Sample sphere made on one maerial is used to estimate the reflectance properties by using LMS algorithm. We can make the reference image which consists of surface normal and brightness value using estimated reflectance parameters, and thenarbitrary shape object made of the same material as sample can be reconstructed by matching with reference image. Photometric matching method proposed in this paper is robust because it mateches object image with the reference imageconsidering its neighbor brightness distribution. Also, in this paper plate diffuse illumination is used to remove intensity disparity with simple scheme. It is expected that the proposed algorithm can be applied to 3D recognition, vision inspection system and other fields.
Customised feature set selection for automatic signature verification
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1642~1653
This paper covers feature extraction for automatic handwritten signature verification. Several major feature selection techniques are investigated from a practical perspective to realise an optimal signature verification system, and customised feature set selection based on set-on-set distance measurement is presented. The experimental results have proved the proposed methods to be efficient, offering considerably improved verification performance compared to conventional methods. Also, they dramatically reduce the processing complexity in the verification system.
Fractal image compression based on discrete wavelet transform domain
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1654~1667
The conventional fractal image compression methods have high computational complexity at encoding reduce PSNR at low bit rate and havehighly visible blocking effects in a reconstructed image. In this paper we propose a fractal image compression method based on disctete wavelet transform domain, which takes the absolute value of discrete wavelet transform coefficient, and assembles the discrete wavelet tranform coefficients of different highpass subbands corresponding to the same spatial block and then applies "0" encoding according to the energy of each range blocks. The proposed method improved PSNR at low bit rate and reduced computational complexity at encoding distinctly. Also, this method can achieve a blockless reconstructed image and perform hierarchical decoding without recursive constractive transformation. Computer simulations with several test images show that the proposed method shows better performance than convnetional fractal coding methods for encoding still pictures. pictures.
On the application of angular spectrum for synthesizing a 3-D image from a series of 2-D images
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1668~1676
This paper presents the evaluation of an angular spectrum-based method used to calculate scattering pattern of a three-dimensional object modelled as a collection composed of vertical sectional two-dimensional images. This is done via comparing a proposed method with two existing methods, i.e., a Fresnel hologram method and a ray-tracing method, in terms of computatioal complexities and reconstructed results. Maathematical derivations for each methods are reviewed and implementing procedures are described in detail, along with the amount of computaions required from the implementation point of view, rather than from the mathematical point of view. We show simulation results in which the Fresnel holoram method dose not exhibit promising results although it requires the least computation. Moreover, it is also shown that the proposed method, even with much less computational requirement than the ray-tracing method, produces good performances asmuch as the ray-tracing method does.
Properties of stack filterand edge detector
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1677~1684
The theory of optimal stack filtering has been used in difference of estimates(DoE) approach to the detection of intensity edges in noisy image. In this approach, stack filters are applied to a noisy image to obtain local estimates of the dilated and eroded versions of the noise-free image. Thresholding the difference between these two estimates produces the estimated edge map. In this paper, the DoE approach is modified by imposing a symmetry condition of the data used to train the two stack filers. Under this condition, the stack filters obtained are duals of each other. Only one filter must therefore be trained;the other is simply its dual. They also produce statistially unbiased estimates. This new technique is called the symmetric Difference of Estimates (SDoE) approach.
Theoretical analysis of the projection of filtered data onto the quantization constraint set
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1685~1695
The postprocessing of compressed images based on the projections onto convex sets and the constrained minimization imposes several constraints on the procesed data. The quantization constraint has been commonly used in various algorithms. Quantization is many-to-one mapping, by which all the dat in a quantization region are mapped to the corresponding representative level. The basic idea behind the projection onto the QCS(quantization constraint set) is to prevent the processed data from diverging from the original quantization region in order to redue the artifacts caused by filtering in postprocessing. However, there have been few efforts to analye the POQCS(projection onto the QCS). This paper analyzed mathematically the POQCS of filtered data from the viewpoint of minimizing the mean square error. Our analysis shows that a proper filtering technique followed by the POQCS can reduce the quantization distortion. In the conventional POQCS, the outside data of each quantization region are mapped into the corresponding boundary. Our analysis also shows that mappingthe outside data to the boundary of a subregion of the quantization region yields lower distortion than does the mapping to the boundary of the original region. In addition, several examples and discussions on the theory are introduced.
The morphological edge detector by using stack filters
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1696~1705
The theory of stack filtering, which is a generalization of median filtering, is used to the detection of intensity edges in noisey images. The proposed approach, called the Difference of Estimates(DoE) approach, is a new formulation of a morphological scheme which has been very sensitive to impulse noise. In this approach, stack filters are applied to a noisy image to obtain local estimates of the dilated and eroded versions of the noise-free image. Thresholding the difference between these two estimates yields the binary edge map. We find that this approach yields results comparable to those obtained with the Canny operator for images with additive Gaussian noise, burt works much better when the noise is impulsive.
An adaptive decision feedback equalizer using error feedback
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1706~1715
The decision feedback equalizer(DFE) received recent attention since it can compensate for channels with severe intersymbol interference(ISI) without as much noise enhancement as the linear equalizer(LE). In this paper, we propose a new DFE which can icrease the performance of DFE further by using error feedback. The performance increase is achieved by reducing correlation of error signal, which cannot be reduced by the feedforward or feedback filter. Hardware complexity for the proposed approcach is minimal since it requires only additional few taps to the conventional DFE. Based on theoretical analysis and computer simulations, the proposed approach is shown to be much more effective than the conventional DFE, especially for channels with large ISI.
A high speed huffman decoder using new ternary CAM
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1716~1725
In this paper, the huffman decoder which is a part of the decoder in JPEG standard format is designed by using a new Ternary CAM. First, the 256 word * 16 bit-size new bit-word all parallel Ternary CAM system is designed and verified using SPICE and CADENCE Verilog-XL, and then the verified novel Ternary CAM is applied to the new huffman decoder architecture of JPEG. So the performnce of the designed CAM cell and it's block is verified. The new Ternary CAM has various applications because it has search data mask and storing data mask function, which enable bit-wise search and don't care state storing. When the CAM is used for huffman look-up table in huffman decoder, the CAM is partitioned according to the decoding symbol frequency. The scheme of partitioning CAM for huffman table overcomes the drawbacks of all-parallel CAM with much power and load. So operation speed and power consumption are improved.
A 3V-50MHz analog CMOS continuous time current-mode filter with a negative resistance load
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1726~1733
A 3V-50MHz analog CMOS continuous-time current-mode filter with a negative resistance load(NRL) is proposed. In order to design a current-mode current integrator, a modified basic current mirror with a NRL to increase the output resistance is employed. the inherent circuit structure of the designed NRL current integrator, which minimizes the internal circuit nodes and enhances the gain bandwidth product, is capable of making the filter operate at the high frequency. The third order Butterworth low pass filter utilizing the designed NRL current integrator is synthesized and simulated with a 1.5.mu.m CMOS n-well proess. Simulation result shows the cutoff frequency of 50MHz and power consumption of 2.4mW/pole with a 3V power supply.
A modified FDTS/DF for considering nonlinear distortion in digital magnetic recording channels
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1734~1745
In this paper, a modified fixed-delay tree search with decision feedback(FDTS/DF) for compensation of non-linear distortion in digital magnetic recording channels is discussed. Since the nonlinear distortion, which becomes significant as recording density increases, is generally well modeled by the discrete Volterra series, the proposed equlizer is composed of a nolinear feedforward filter, a linear feedback filter, and a nonlinear distorton table, the values of which are determined by considering the effect of nonlinear distortion due to future data as well as the previous and current one. At the decision stage of FDTS, a path minimizing the branch metric is chosen by using the previously detected values, current predicted value, and future predicted value. We compare the performance of the linear FDTS/DF, the previous nonlinear FDTS/DF, and the proposed nonlinear FDTS/DF by computer simulation, and confirm that the proposed one chieves the best performance at high-density recording.
A study on IWU functions interconnecting LANs via B-ISDN
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1746~1755
In this paper, we propose the protocol stact and the server functions of IWU which interconnects distributed LAN's users by using of B-ISDN. The protocol stact of interconnecting IWU under consideration users TCP/IP in upper layer. TCP/IP is popular communication protocol in interconnecting distributed LANs. The interconnecting IWU has server functions for transfering datagrams to B-ISDN such as address translation, fragment and reassembly, CL server, signalling and traffic control. We analyze the performance ofinterconnecting IWU with M/M/1/K queueing model and obtain the throughput and buffer size of interconnecting IWU.
A study on performance improvement of switch element inbanyan network for ATM
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1756~1764
In this paper, we propose a new switch element of buffered Banyan network and analysis it. The proposed switch element consists of CASO(Content ASsociated Output) buffers, its controller and 2*2 crossbar switch. This switch element increase the performance of buffered Banyan network by removing HOL blocking. Also, we analyze the proposed switch element by mathematical modelling method based on MY analysis model which is one of earier proposed models.
Transaction management in a client-server main memory DBenvironment
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1765~1776
An all-digial HDTV modem for terrestrial broadcasting
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1777~1786
This paper describes theories and implementation techniques of a digital high-definition television(HDTV) modem based on 32-QAM for terrestrial broadcasting. We proposed a digital demodulation scheme and a symbol timing recovery structure based on the band edge component maximization(BECM) method. The adaptive equalizer has 256 complex taps to remove the multipath of delays ranging from -2.mu.s~+24.mu.s with a new T/2-spaced blind equalization algorithm. computer simulation results reveal that the proposed algorithm outperforms other conventional blind equalization algorithm a digital HDTV modem with 4.91MHz symobol rate is implemented by utilizing the proposed algorithms. All processings for modem operations such as demodulation, estimation of symbol timing phase error, adaptive equalization, and carrier recovery except IF signal processing and sampling phase control part of the AD converter are done in digital domain. Especially, the carrier recovery loop can track a carrier offset of upto .+-.350KHz.
Performance analysis of FH/CPFSK system with the error-correcting code and the diversity under rayleigh fading channel with the thermal noise and the partial-band noise jamming
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1787~1802
In this paper, the performance for FH/CPFSK system with limiter-discriminator detection and integrage-and-dump post-detection filtering under thermal noie, partial-band noise jamming and rayleigh fading have been analyzed. The method of hard-decision diversity of which the transmitter repeated L times on different hops for each data symbol in a way to mutigate the effects of the jamming has been applied, and the receiver has been combined the L chips. Also, error-correcting code have been applied for improving performance of system. The thermal noise and partial-band noise jamming, intersymbol interference for all eight of the possible adjacent bit data patterns, and FM noise click for evaluating systems have been considered. Also optimum parameters to improve performance of FH/CPFSK system have been obtained and validities have been proved through computer simulation.
Threshold detection technique for code acquisition using maximum mismatched correlation value
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1803~1813
This paper describes an automatic threshold decision using a maximum mismatched correlation value in the direct sequence spread spectrum (DS-SS) system. For received PN codes with different single-to-noise ratio (SNR), this scheme is able to detect a desired threshold value in the search mode, i.e. a maximum mismstched correlation value, so that value is utilized as a threshold for the verification mode. Performance of the proposed scheme in both the additive white gaussian noise (AWGN) and frequency-selective Rayleigh fading channels is analyzed through the Monte Carlo simulation. And hardware implementation of this scheme using a DSP processor is demonstrated. The proposed acquisition shceme is compared to the conventional constant threshold (CT) scheme, and significant improvement of performance is shown. Analysis of system performance in the verification mode is presented, and key quantities such as the false alarm probability and the detection probability are derived in a AWGN channel.
Serial interface system of HDTV signal in comma free code
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1814~1819
This paper describes a dnw serial interface system which uses comma free code. Typically parallel 25 pin cable and connectors are used to transfer and receive the data between digital systems such as HDVCR, D3VTR and HDTV Receiver.The coaxial cable is more desirable for consumer product applications and also for studio applications where long signal paths and switching are requeired. This serial data trasfer technique is possible the error detection and the self synchronization, also easy edge insertion for PLL control. It is also cost effective because is does not requeire RF PLL, scrambling, and NRZI hardware.
Performance analysis of carrier recovery using pilot tone in mobile radio channel
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1820~1832
The performance of a carrier recovery is severely degraded because of amplitude fluctuations and random phases of the received signai caused by multipath fading in mobile radio channel. In this paper, we present two kinds of carrier recovery technique using pilot tone such as TCT(Tone Calibration Technique) and DTCT(Dual Tone Calibration Technique) and analyze these performance both in Rayleigh and Rician fadings. we also evaluate the BER performance of two carrier recovery systems in terms of design parameters such as pilot-to-singnal power ratio, and detection filter-to-pilot filter bandwidth ratio.
Synchronization of ALE signal for HF communication systems
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1833~1841
Recently, by emerging of the ALE techniques that make it possible to providereliable communications link automatically, high frequency communiation is newly used as emergency communication and back-up for satellite communications. ALE signal is transmitted in burst, and the received signal is subject to distortions by detrimental multipath fading channels. In the case of that channel, the performance of ALE system is highly dependent upon that of synchronization techniques. In this paper, M-ary FSK signals are detected by a bank of bandpass filter, which is implemented using recusive DFT(Discrete Fourier Transform). Also an acquisition and trancking algorithm are designed uisng parallel structure and early-late-gate methods respectively. Finally, we verify the performance ofthe proposed synchronization algorithm by the computer simulation.
Moment method analysis of the moreno directional coupler
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1842~1849
This paper presents a full-wave, moment method analysis of a Moreno directional coupler with tow crossed-slots between two crossed rectangular waveguides. the overall structure is divided into several rectangular waveguides and cavities by the use of the equivalence principle to the complex slot regions. this enables a simple and efficient analysis involving the well-known retangular waveguide/cavity Green's functions. For a numerically efficient simulation, the roof-top basis expansion and line testing is used and an acceleration technique is applied to the series summation in the Green's functions. The numerical results are compared with the measurements to verify the correctness of the present analysis.
Design of antireflection coationgs on the facets of a multilayered structure waveguide device
The Journal of Korean Institute of Communications and Information Sciences, volume 21, issue 7, 1996, Pages 1850~1860
We present the results for the design ofantireflection (AR) coatings on facets of a multilayered structure waveguide device. The method, whose results agree very well with the reusults of the rigorous method in the case of a symmetric three layer structure deveice, is extended for the design of AR coatings on the facets of a multilayered structure waveguide device. the field profile in a multilayered structure waveguide necessary for the use of the extended method is obtained from the transfer matrix method. The virtual four layered structure method (VFLM) is proposed to reduce the time for the design ofAR coatings because the time for the design of AR coatings using the extended method increases as the number of layers increases. The optimum coating parameters and tolerance mapsfor two different six layered waveguide devices in Ref.  and  are obtained using the extendedmethod and the VFLM,and for the three different cases approximated as three layered waveguide devices to compare the results of each case. The results of the VFLM are similar to those of the extended methodcompared to those of the three layered structure waveguide. The main reason for the above results is that the field profile in the device calculated usingthe VFLM is similar to that calculated using the extended method compared to that for three layered structure wavegjide. We conclude that the extended method or VFLM should be used for the design of AR coatings on facets of a deice required for the facet reflectivity less than 10
such as a semiconductor otical amplifier.