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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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Direction-of-Arrival Estimation : Signal Eigenvector Method(SEM)
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2303~2312
A high resolution algorithm is presented for resolving multiple narrowband plane waves that are incident on an equispaced linear array. To overcome the deleterious effects due to coherent sources, a number of noise-eigenvector-based approaches have been proposed for narrowband signal processing. For differing reasons, each f these methods provide a less than satisfactory resolution of the coherency problem. The proposed algorithm makes use of fundamental property possessed by those eigenvectors of the spatial covariance matrix that are associated with eigenvalues that are larger than the sensor noise level. This property is then used to solve the incoherent and coherent sources incident on an equispaced linear array. Simulation results are shown to illustrate the high resolution performance achieved with this new approach relative to that obtained with MUSIC and spatial smoothed MUSIC.
A Study on the Multiresolutional Coding Based on Spline Wavelet Transform
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2313~2327
As the communication environment evolves, there is an increasing need for multiresolution image coding. To meet this need, the entrophy constratined vector quantizer(ECVQ) for coding of image pyramids by spline wavelet transform is introduced in this paper. This paper proposes a new scheme for image compression taking into account psychovisual feature both in the space and frequency domains : this proposed method involves two steps. First we use spline wavelet transform in order to obtain a set of biorthogonal subclasses of images ; the original image is decomposed at different scale using a pyramidal algorithm architecture. The decomposition is along the vertical and horizontal directions and maintains constant the number of pixels required the image. Second, according to Shannon's rate distortion theory, the wavelet coefficients are vectored quantized using a multi-resolution ECVQ(entropy-constrained vector quantizer) codebook. The simulation results showed that the proposed method could achieve higher quality LENA image improved by about 2.0 dB than that of the ECVQ using other wavelet at 0.5 bpp and, by about 0.5 dB at 1.0 bpp, and reduce the block effect and the edge degradation.
An Analysis of Cell Loss Process in an ATM Network Under Partial Buffer Sharing Policy
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2328~2339
The PBS(Partial Buffer Sharing) space priority mechanism is one of priority control methods which may improve the performance of a single server queueing system when mixed traffic with different performance requirements is applied to the system. This paper analyzes the cell loss behavior of PBS assuming loss sensitive traffic and delay sensitive traffic are applied to the system. To derive the successive cell loss probabilities. which are an important performance measure of realtime traffic, we develop a recursive algorithm. Performance results show the successive cell loss probabilities obtained by our method are lager than the probabilities derived from an independent cell loss assumption. These results may indicate the limitation of PBS for realtime traffic and the increase of the admissible load with the criterion of quality of service.
Performance Analysis of SSP for Advanced Intelligent Network
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2340~2352
Under the current IN(Intelligent Network) Architecture, most of their function were performed in SSP(Service Switching point), so the provision or modification of service was limited. To over come these limitation, the structure of 'AIN(Advanced Intelligent Network)' emerged. In this paper, SSP for AIN structure is designed and its performance is evaluated. In other words, the requirements for AIN service implementation are specified on the basis of ITU-T Recommendations. From these requirments and TDX-10 Exchange architecture, the SSP for AIN structure is designed, and its performance is analyzed through the method of simulation and analytical modeling. As a conclusion of this paper, when the system is operated as a standard model, the maximum throughput is 1,270,000 BHCA for Free Phone Service and 1,190,000 BHCA for Credit Call Service. The processors in INS(Interconnection Network Subsystem) are proved to be bottleneck elements. To enhance the performance, several suggestions such as processor and link speedup, and other D_bus service policy are proposed.
Design of a Digital Robust Control Using Observer for Manipulator
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2353~2363
This paper is concerned with the design of a robust digital controller using reduced-order observer on a robotic manipulator under the disturbance. In most cases of robotic manipulator since all state vectors are not measurable, the unmeasurable state vectors must be estimated or reconstructed. Other problems are caused by the nonlinear element like as nondifferentiable Coulomb friction, disturbance due to the gravitational pull, and the torsional spring effect of a link between the drive motor and the manipulator arm. The controller is based on feeding back the observable variables and the estimated state variables which are generated by the observer, and augmenting the system by additional discrete integrators. The feedback gain parameters are obtained by first applying the optimal control theory and then readjusting the feedback parameters to eliminate the limit cycle by using describing Function for nonlinear hybrid system.
Synthesis of Multiplexed MACE Filter for Optical Korean Character Recognition
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2364~2375
For the efficient recognition of printed Korean characters, a multiplexed minimum average correlation energy(MMACE) filter is proposed. Proposed method solved the disadvantages of the tree structure algorithm which recognition system is very huge and recognition method is sophisticated. Using only one consonant MMACE filter and one vowel one, we recognized the full Korean character. Each MMACE filter is multiplexed by 4 K-tuple MACE filters which are synthesized by 24 consonants and vowels. Hence the proposed MMACE filter and the correlation distribution plane are divided by 4 subregion. We obtained the binary codes for the Korean character recognition from each correlation distribution subplane. And the obtained codes are compared with the truth table for consonants and vowels in computer. We can recognize the full Korean characters when substitute the corresponded consonant or vowel font of the consistent code to the correlation peak place in the output correlation plane. The computer simulation and optical experiment results show that the proposed compact Korean character recognition system using the MMACE filters has high discrimination capability.
An Improvement in Intra-Slice Low Delay Video Coding for Digital TV Broadcasting
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2376~2385
In receiving the digital TV signal, both decoding delay and the channel hopping delay are very critical factors in applications. The intra-slice coding in the MPEG-2 SIMPLE PROFLE of No B-picture is one of the primary methods for short delay time in video decoding. It has the advantage of short decoding delay, but has the drawback of long channel hopping delay time. In this paper, we propose a method to reduce the channel delay with negligible loss in SNR performance. It is shown that dividing pictures into several regions of slices and adding some restriction in motion vector search for inter-frame coding. hence the random acess points are effectively increased. and the channel hopping delay is reduced.
Design of FIR Filters with Finite Precision Coefficients Using LP(Linear Programming)
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2386~2396
In this paper, an optimal algorithm for the design of 1-D FIR filters with finite precision coefficients is proposed. The algorithm is based on the observation that the frequency constraints of a sub-problems(SP) in the branch and bound algorithm, which repeatedly use LP(linear programming), are closely related with those of neighboring SPs. By using the relationship between the SPs, the proposed algorithm reduces the number of constraints required for solving each SP with Lp, whereas the conventional algorithm employs all the constraints, which are required for solving the initial problem. Thus, the overall computational load for the design of FIR filters with finite precision coefficients is significantly alleviated, compared to the conventional branch and bound algorithm. Also, a new branching scheme for the design of FIR filters with sum-of-power-of-two(SOPOT) coefficients is proposed. It is shown that the computational load for the design fo SOPT coefficient filters can be further reduced with the new branching scheme.
Adaptive Equalization for Reduction of Nonlinearity in High-Density Recording Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2397~2408
In this paper, a structure for a nonlinear adaptive equalizer is discussed to reduce nonlinearity in digital high-density recording systems. We propose a nonlinear adaptive decision feedback equalizer which can reduce the nonlinear intersymbol interference increasing with high-density recording systems, and compare its performance with the RAM-DFE which is designed to remove nonlinear intersymbol interference existing in postcursor part. By observing the output SNR of each equalizer applied to recording channels with three different densities. we confirm that the nonlinear adaptive decision feedback equalizer performs the best in the general case where nonlinear intersymbol interference exists in both precursor and postcursor parts.
Pipelining of orthogonal Double-Rotation Digital Lattice Filters for High-Speed and Low-Power Implementation
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2409~2417
The ODR(orthogonal double-rotation) digital lattice filters have desirable properties for VLSI implementation such as local connection, regularity and pipelinability. These filters are also known to exhibit good numerical behavior for finite precision implementation. Although these filters can be pipelined by the cut-set localization procedure, it should be noted that the maximum sample rate obtained by this technique is limited by the feedback computations. In this paper, a pipelining method for the ODR digital lattice filter is proposed, by which the sample rate can be increased at any desired level. it is also shown that the low-power CMOS digital implementation of ODR digital lattice filters can be done successfully using our pipelining method. The pipelining method is based on the properties of the Schur algoithm, constrained filter design methods, and the polyphase decomposition technique.
Efficient Learning Algorithm using Structural Hybrid of Multilayer Neural Networks and Gaussian Potential Function Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2418~2425
Although the error backpropagation(EBP) algorithm based on the gradient descent method is a widely-used learning algorithm of neural networks, learning sometimes takes a long time to acquire accuracy. This paper develops a novel learning method to alleviate the problems of EBP algorithm such as local minima, slow speed, and size of structure and thus to improve performance by adopting other new networks. Gaussian Potential Function networks(GPFN), in parallel with multilayer neural networks. Empirical simulations show the efficacy of the proposed algorithm in function approximation, which enables us to train networks faster with the better generalization capabilities.
A Study on the Electric Circuit Model for the Direct FM Characteristics of DFB Semiconductor Lasers
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2426~2438
In this paper we present for the first time the electric circuit model for direct frequrncy modulation(FM) response of the conventional distributed-feedback(DFB) semiconductor laser diodes. Especially, in this paper, the proposed model includes not only the carrier density modulation effect, but also the temperature modulation effect determining the DFM characteristics of DFB characteristics of DFB semiconductor lasers. The DFM response due to injection current modulation was obtained as a function of modulation frequency from DC to a few GHz. The circuit model representing the temperature modulation effect is obtained from the structure of DFB LD chip and the simulation results are compared with the published experimental results. The circuit model representing the temperature modulation effect is obtained from the structure of DFB LD chip and the simulation results are compared with the published experimental results. The circuit model representing carrier density modulation effect is obtained from the rate equations of DFB lasers and the simulation results are compared with the results that were obtained by the conventional numerical analysis approach. The results showed good agreements.
A Study on the New Analysis to the Dynamics of Colpitts VCO's and Practical Implication
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2439~2447
In this paper, We analyze Colpitts type voltage contrqlled oscillator(VCO) used in personal handheld phone using a nonlinear analysis with third-order model. The resul shows the non-exponentially decaying shifting bias superimposed on the oscillator output which is different with the exponentially decaying shifting bias from the linear analysis. The stable oscillation criterion during a frequency change in a design of VOC can be also determined using proposed non-linear analysis. The theory is confirmed using PSPICE simulation and the experimental result of GaAs VCO matched very well with the theory.
A Study on Performance Evaluation for the Packet Switching in the TDX-10 Packet Handler
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2448~2457
CCITT recommendation X.25 and X.75 have been applied to the PSPDN environment for data communication of packet switching. They have also been used for packet switching in the ISDN exchanges since about the year 1980. This paper presents the throughput of the TDX-10 packet handler as simulating the performance based on memory management and flow control of the resource management algorithm designed originally.
A New Design Method for One-Dimensional and Two-Dimensional Maximally Flat FIR Filters with Zero-Phase
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2458~2467
This paper proposes a new design method for obtaining the impulse responses which satisfy the prescribed conditions designing for maximally flat FIR lowpass filters and highpass filters. The bandpass filters and band-reject filters have been directly derived from the addition and subtraction of impulse responses of a lowpass filter and a highpass filter. The two-dimensional maximally flat FIR lowpass filter, highpass filters, bandpass filters and band-reject filters with zero-phase have been designed by transforming the impulses of the one-dimensional filters designed in this research, which do not destroy lines and edges at the image signal processing.
An Analysis of the Hybrid Finite Element Method for Scattering and Radiation by Microstrip Patch Antennas and Arrays Residing in a Cavity in a Ground Plane
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2468~2478
A hybrid finite element method is presented for a characterization of scattering an radiation properties of microstrip patch and arrays residing in a cavity recessed in a ground plane. The technique combines the finite element and boundary integral methods to formulate a system for the solution of fields at the aperture and the scattering field and radar cross sections at free space. By virture of the finite element method, the proposed technique is applicable to patch antennas and arrays residing on or embeded in a layered dielectric loss/lossless substrate and is also capable of treating various feed configuration. Several numerical results are presented demonstrating the validity, efficiency and capability of the technique.
Dynamic Excitation Modeling Scheme Applied for Variable Low Bit-Rate Homomorphic Vocoder
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2479~2488
In this paper, a new dynamic excitation modeling scheme is proposed. Based upon the proposed excitation modeling scheme, two variable bit rate homomorphic vocoders are designed, whose average bit rates are 3.8 Kbps and 4.4 Kbps. The performance of the proposed excitation modeling scheme is then evaluated through the subjective listening tests. In the tests, the performances of two speech coders designed in this paper ate compared with the one of 4.8 Kbps homomorphic vocoder designed by Chung and Schafer, in which conventional static excitation modeling scheme applied. The subjective listening tests show that proposed dynamic excitation modeling scheme improves synthesized speech quality while lowering the average bit rate of speech coders.
Realization of a 7.7~8.5GHz 10 W Solid-State Power Amplifier
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2489~2497
This paper presents the development of a 10 W solid-state hybrid power amplifier(SSPA). operating over
. The fabrication and measurement of this amplifier are performed with 3 sections, such as the front one for high gain, the middle one for driving, and high power one, to minimize the risk of failure and to increase the easiness of development. and then the final amplifier is realized by connecting 3 sections above mentioned, DC bias circuit, and temperature compensation circuit on one housing. Total small signal gain obtained is about
, the input and output return losses are 25 and 27 dB respectively. The output power measured at 1 dB gain compression point for 3 frequencies at 7.7, 8.1, and 8.5 GHz are
, which is about 10 W. and the 3rd-order harmonic powers of 2 tones test are 13.34 dBc at output power 37.5 dBm. These obtained results satisfies the initially required specification. and the realized SSPA can be installed as a subsystem of the microwave transponder for telecommunication.
Design of Doppler-Frequency Tracking System based on the Optimum Synchronization Techniques for the Digital Satellite Communication System
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2498~2507
This paper proposes the Doppler frequency tracking system by the optimum synchronization technique which compensates the frequency shifts caused by satellite movement in a coherent digital satellite communication system. A Doppler frequency shift caused by satellite movements and the design theories of the optimum synchronization system are mathematically described. Based on this theory, a Doppler frequency tracking system is implemented via digital signal processing techniques utilizing a DSP chip, RAMs, PROMs, and a 80286 microprocessor. The performance of the designed system was evaluated through the experiments with the INTELSATVA satellite.
A Study on the Power Feeding for ISDN Subscriber Loop
The Journal of Korean Institute of Communications and Information Sciences, volume 19, issue 12, 1994, Pages 2508~2519
In this thesis, two possible schemes for power feeding are considered. The first one is the network power feeding, and the other is the power feeding from the rechargeable battery. Though each scheme has its merits and demerits, the domestic network operator has proposed the latter due to the large deviation of line resistance, high power loss, and safety. This scheme, however, has several problems. The usage is limited by the life of battery leading to the failure of minimal voice service for many hours. The space occupation of that battery is another serious problem. Moreover, the network opeator should have overhead of maintenance and repair. In order to alleviate such the difficulties, the sealing current is introduced through the subscriber loop. Flowing the current into the loop prevents from rusting. This thesis designs a power controller using PEB2025 to control various amount, duration, and period of this sealing current, to achieve the optimum current supply for sealing.