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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 22, Issue 12 - Dec 1997
Volume 22, Issue 11 - Nov 1997
Volume 22, Issue 10 - Oct 1997
Volume 22, Issue 9 - Sep 1997
Volume 22, Issue 8 - Aug 1997
Volume 22, Issue 7 - Jul 1997
Volume 22, Issue 6 - Jun 1997
Volume 22, Issue 5 - May 1997
Volume 22, Issue 4 - Apr 1997
Volume 22, Issue 3 - Mar 1997
Volume 22, Issue 2 - Feb 1997
Volume 22, Issue 1 - Jan 1997
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Performance analysis of cellular CDMA networks with power control error in nakagami fading channel
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 1~11
We examine the DS/SSMA system which is employing coherent BPSK with RAKE receiver. We adop Nakagami m-distribution as a multipath fading model. First, we analyze the performances of the system in the single cell environment and obtain the other-cell interference according to power control error. And considering the other-cell interference into the analysis of single cell system, we examine the cellular CDMA network. The average BER and outage probability are the figures of merit that characterize the system performance. The required BER, 1E-3, and required outage probability are the figures of merit that characterize the system performance. The requeired BER, 1E-3, and required outage probability, 1% for the voice transmission is considered to acquire the capacity of system.
SPICE models of PCB traces in high-speed systems
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 12~20
Physical interconnect such as Printed Circuit Board(PCB) traces introduces new challenges for parameter extraction and delay calculation for high-speed system design. PCB traces are dominated by frequency dependent LC propagation which makes precharacterization difficult for all possible configurations. Moreover, simulating the transient behavior of the trace for noise and delay analysis requries the combined used of a variety of models and techniques for efficiently handling lossy, low-loss, frequency dependent, and coupled transmission lines together with lumped elements. In this paper we explain how the frequency dependence caused by ground plane proximity and skin effects can be modeled using the adstracted models. These abstracted (lumped) models are SPICE-compatible and can be simulated in time-domain, along with precharacterized lumped parasitic elements and nonlinear driver and load models.
Implementation of manual/automatic complex redundancy control method for modulation system of a paging earth station in reduntancy structure
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 21~29
This paper describes implementation contents contents of manual/automatic complex redundancy control mothod for control of a modulation system of a Paging earth station in redundancy stracture. The existed redundancy control method usually is a automatic local control method in which the redundancy switching, including display or alarm beeping through operation of display devices or audio devices, is performed by the co-action of components or modules when the abnormal status is occurred in a modulation system. However, this method introduced in here is designed to enable use of three control modes;1) Manual mode by an operator, 2) Auto-remote mode by the Network Maagement System, through implementation of the redundancy control system composed of the redundancy control board and the redundancy switching circuit.
Multi-symbol detection for biorthogonal signals over rayleigh fading channels
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 30~39
In this paper, a new practical coherent detection scheme for biorthogonal signals, which uses multi-symbol observation interval, is proposed and its performances are analyzed and simulated. The technique jointly estimates both the demondulated data and the channel from received signal only while reducing computation complexity by an approximate maximum-likelihood sequence estimation rather than symbol-by-symbol detection as in previous noncoherent detection. The scheme achieves performance close to that of ideal coherent detection with perfect channel estimates when select the appropriate observation symbol interval N in the given symbol alphabet wize M. What is particularly interesting is that the requeired average signal-to-noise ratio per bit
can be reducedd by as much as 1.4dB and the capacity can be increase by as much as 38% when we use this system in the CDMA cellular reverse link.
An adaptive data precompensator for compensation of nonlinear distortion in OFDM systems
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 40~52
It has been known that the OFDM-based terrestrial broadcasting systems are significantly more sensitive to nonlinear distortion in high-power amplifiers (HPA's) than the broadcasting systems using single-carrier modulation technique. In this paper, an adaptive precompensator which can compensate the nonlinear effect of the HPA for OEDM systems is proposed. The proposed precompensator consists of a compensation table, realized by memory (RAM), and an adaptive algorithm which can update the values of the compensation table more efficiently using a
A new macroblock-based bit allocation algorithm in multiple MPEG-1 video encoders system
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 53~63
In this paper, we present a new macroblock-based bit allocation scheme in multiple MPEG-1 video encoders system and a single multiplexer over a single channel. The proposed scheme models the relations between fate(Bits/MB) and distortion(MSE/MB), rate and quantizer parameter(QP), distortion and quantizer parameter, respectively, in the same form. By using these relations, we minimize the Larangian cost function to obtain a bit allocation scheme based on macroblock unit. Experimental results show that the proposed scheme can reduce MSE compared to other conventional buffer-based rate control methods, i.e. independent buffer control method and shared common buffer control one. And we confirmed, through computer simulation, that the proposed scheme can be effectively modified to maintain the objective quality of a specific video service at a constant level.
A study on nonlinear channel equalization using RBF network
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 64~71
Digital communication channels are imparied by linear effects such as dispersion, ISI(intersymbol Interference), fading phenomenon etc. But, the practical channel equalization system is required to design for compensating the nonlinear distortion caused by harmonic distortion etc. This paper is a study on the performance of nonlinear channel equalization using RBF(Radial Basis Funclion) network, which has the equivalent structure to the optimal Basian filter. Expecially, the variance of RBF network is modifiedby nonlinear polynomial filters to compare the convergence characteristic of nonlinear channel equalization. Experimental results show that the modified RBF network achieves the faster convergence property than conventional RBF network. Moreover, the RBF network ofhigher order variance modified represents the better performance than that of lower order variance in the bandpass channels and second/third order polynomial channels.
Development of 750MHz CATV amplifier module using PHEMTs
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 72~80
A 750 MHz CATV amplifier module has been designed and fabricated using PHEMT chips on alumina board. Developed 2-stage push-pull amplifier using wire bounded PHEMT chips shows 19dB gain, 15dB return loss and 4. 2dB noise figure over 50-750MHz frequency range. These results are superior to the characteristics of the commer-cially abailable 750MHz amplifier module. In this paper, brief background of the amplifier design, the circuit diagram and the test result have been presented.
Narrowband tunable wavelength filters with asymmetrical directional coupler structure
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 81~88
Wavelength tunable, narrowbandwidth wvelength filters in compound semiconductor have been modeled, fabricated, and characterized. In order to obtain a narrow bandpass characteristics at 1.55.
m, a highly asymmertrical directional coupler structure composed of a strongly guided ridge waveguide and a weakly guided strip-loaded waveguide was used. The optimized filter structure modeling has been obtained by using the spectral index method, effective index method, and the coupled mode theory. Operation at a center wavelength a 1.537.mu.m with a bandwidth of 1.8nm and transfer efficiency of 50-70% is experimentally achieved. For the purpose of center wavelength tuning, the carrier injection in p-n diode structure has been theoretically investigated. It has been found that the tuning range of nanometer can be easily obtained by moderate amount carrier injection. We also found that the bandwidth becomes broad as the center wavelength tuning increases.
Wide-band design of X-cut
optcal modulator employing a ridge waveguide
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 89~95
optical modulator is analyzed by finite element calculation. the purpose of this trial is the design of wide-bandwidth x-cut
optical modulator with ridge wave guide, which was only applied to z-cut
optical modulator. the simulation tool is examined by the comparison between our results and Becker's. And we consider the optimum position of optical waveguide to electrodes for decreasing the driving voltage. The calculated driving-voltage, characteristic impedance and microwave effective index at
optical wavelength are 18 V.cm,
and 2.168, respectively.
Development of 2.5Gb/s x 4channels WDM link prototype and it experiments
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 96~103
We developed the prototype of 4-channel WDM link with erbium-doped fiber amplifiers. Bit rate of each channel was 2.5Gb/s. The unrepeatered transmission over 120km with DSF was achieved and the transmission length was extended to 240km using two EDFAs.
Code acquisition and demodulation performance of the RAKE receiver in the DS/CDMA mobile communication systems
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 104~115
This paper investigates PN code acquistion algorithm and demodulation performance of the RAKE receiver in the DS/CDMA(direct sequence code division multiple access) sysytems under a multipath fading channel with multiusers. To speed up the acquisition process, PN matched filter is applied and postdetection integration technique comable withthe dynamic threshold set method is proposed. the Maximum-Likelihood algorithmin serial fashion is able to find PN code delay estimates for the RAKE branches using sliding window in a multipath fading channel. The correct acquistion probability and mean acquistion time are used as a performance measure of the system using the Monte Carlo method. The performance of the RAKEreceiver, afte the code acquisition is achieved is the CDMA systems, is also investigated for three major combining techniques.
Digital demodulator design and characteristics of AM and FM signals by undersampling scheme
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 116~126
As the digital system with high sampling rates is required to process numerous data, it is difficult to realize the real time processing for this system. By using the nonlinear energy tracking signal operator, in this paper four kinds of AM/FM demodulators are proposed and designed by the undersampling scheme of decreasing the sampling rate. Particularly, the undersampling frequency and 3dB bandwidth are controllable of these systems and their conditions are respectively. Through the analysis of the designed detectors, useful results are obtained in respect to characteristics and errors.
An efficient buffer control scheme using HOL algorithm with jump coefficient in ATM networks
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 127~138
In this paper, we study new HOL-LJ scheme to guarantee the QoW of low priority cell with simple hardware which is not realizable in previously proposed HOL and HOL-PJ. the performance of the proposed scheme is evaluated by analysing an equivalent /M/M/1/N queuing system. In case of using the proposed scheme, we confirmed that good performance compared with HOL-PJ through simpulation and mathematical analysis. We also applied HOL-LJ algorithm to convetional Dual Buffer and Partial Buffer, and we analyzed the performance through computer simulation.
A study on the fairness ring protocol for high-speed networks
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 139~150
For high-speed networks, a new ring protocal is proposed in this paper. A ring network combined with destination removal can achieve much higher network throughput than the channel transmission rate. However, such a network exhibits fairness problems. Over a past few years, global fairness algorithms such as ATMR and Metaring have been proposed to solve such problems. But the ring access time delay and fairness in such networks are sensitive to the network parameters such as network size and traffic distribution. In addition to guaranteeing fair ring access to all nodes, there are several other important performance aspects in such networks. The one is that fairness is enforced while node throughputs are kept as high as possible. And another performance measure is access delay and more specifically Head-Of-Line(HOL) delay, i.e., the amount of time the first cell in the transmission buffer of a node has to wait before it accesses the ring. HOL delay is a mijor component in the transmission jitter of the synchronous traffic transmission. A key idea of the proposed ring protocol is to find the nodes that have much more chances to access the ring than any other nodes in the independently distributed node architecture. Since destined by many cells need to share a part of the bandwidths with the next node for the fairness in as much as performance degradation does not become critical. To investigate the performance behavior of the proposed ring protocol for various network condition,s several performance parameters wuch as ring access time delay, and throughput are compared with those of the ATMR and Metaring protocols using simulation package, SIMAN.
Priority oriented dobule reservation probocol for very high speed wireless LANs
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 151~161
In this paper we designed a high speed wireless multiple access protocol, which is suitable for future multimedia wireless LAN systems which support high quality video teleconferencing, telephony and graphic databases. In the proposed protocol, Slotted-ALOHA protocol is used for transmitting random data packets and the packet reservation multiple access(PRMA) protocol for transmitting periodic data packets. The use of minislot is introduced for the reservation scheme. In order to measure the performance characteristic of the proposed protocol, a simulator is designed using an object oriented programming language, C++, and an exhaustive simulation study is carried out. From the simulation results, it is observed that the proposed protocol and the existing PRMA protocol have almost the same delay characteristic when network traffic is low. However, the proposed protocol is superior to the PRMA protocol when traffic becomes higher. The proposed protocol and the results can be utilized for the design of the wireless access systems and future broadband wireless LANs.
Analysis of a binary feedback switch algorithm for the ABR service in ATM networks
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 162~172
In this paper, we investigated the performance of a binary feedback switch algorithm for the ABR(Available Bit Rate) service in ATM networks. A binary feedback switch is also called EFCI(Explicit Forward Congestion Indication) switch and can be classificed into input cell processing(IP) scheme according to processing methods for the EFCI bit in data-cell header. We proposed two implementation methods for the binary feedback switch according to EFCI-bit processing schemes, and analyzed the ACR(Allowed Cell Rate) of source and the queue length of switch for each scheme in steady state. In addition, we derived the upper and lower bounds for maximum and minimum queue lengths, respectively, and investigated the impact of ABR parameters on the queue length.
Compilation management of the mobile switching software on network file system
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 173~184
As the scale of the switching software gets large, it takes much time and is hard to compile and the manage it. We implement the compilation management system for the mobile switching software on network file system and describe its structure and functions in this paper. The compilation management system distributes its task of compilation to the each network system equally to reduce the comilation time and also simplifies the management of the communications among the systems, compilation manager, and the software devedlopers.
Parameter estimation of mean field annealing technique for optimal boundary smoothing
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 185~192
We propose a method of paramete estimation using order-of-magnitude analysis for optimal boundary smoothing in Mean Field Annealing(MFA) technique in this paper. We previously proposed two boundary smoothing methods for consistent object representation in the previous paper, one is using a constratined regulaization(CR) method and the other is using a MFA method. The CR method causes unnecessary smoothing effects at corners. On the other hand, the MFA method method smooths our the noise without losing sharpness of corners. The MFA algorithm is influenced by several parameters such as standard deviation of the noise, the relativemagnitude of prior ter, initial temperature and final temperature. We propose a general parameter esimation method for optimal boundary smoothing using order-of-magnitude analysis to be used for consistent object representation in this paper. In addition, we prove the effectiveness of our parameter estimation and also show the temperature parameter sensitivities of the algorithm.
Enhancement of noisy image sequence using order statistic-adaptive weighted average hybrid filters
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 1, 1997, Pages 193~204
In this research we propose the design of the Order Statistic-Adaptive Weighted Average Hybrid(OS-AWAH) filter which can suppress noise from the corrupted image sequence effectively while preserving the image structure. The proposed filter combines the desirable properties of the order static based spatial filter which can preserve the image structure while reducing noise and the adaptive weighted average based temporal filter which can adapt the filtering weights according to the amount of motion without motion estimation. Performance characteristics of the OS-AWAH filter in noisy sequences containing moving step edges are investigated throuth computer simulations and compared with the median based filters such as 3-D WM(weighted median) filter, MMF (multistage median filter), ADCWM(adaptive directional center weighted median) filter. The visual evaluations are also carried out by applyin gthe filters to the real images. The statistical analysis and experimental reslts show that the OS-AWAH filter is effective in preserving image structures while suppressing noise effectively without motion compensation preprocessing.