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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Communications and Information Sciences
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Volume 24, Issue 12B - Dec 1999
Volume 24, Issue 12A - Dec 1999
Volume 24, Issue 11A - Nov 1999
Volume 24, Issue 10B - Oct 1999
Volume 24, Issue 10A - Oct 1999
Volume 24, Issue 9B - Sep 1999
Volume 24, Issue 9A - Sep 1999
Volume 24, Issue 8B - Aug 1999
Volume 24, Issue 8A - Aug 1999
Volume 24, Issue 7B - Jul 1999
Volume 24, Issue 7A - Jul 1999
Volume 24, Issue 6B - Jun 1999
Volume 24, Issue 6A - Jun 1999
Volume 24, Issue 5B - 00 1999
Volume 24, Issue 5A - 00 1999
Volume 24, Issue 4B - 00 1999
Volume 24, Issue 4A - 00 1999
Volume 24, Issue 3B - 00 1999
Volume 24, Issue 3A - 00 1999
Volume 24, Issue 2B - 00 1999
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Volume 24, Issue 11B - 00 1999
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Petri-net Based Multimedia Synchronization Model for High Quality of Service
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 997~1003
It is required that synchronization model can describe various multimedia objects flexibly in the view point of time relationship and also respond quality of service requirement about jitter which is time difference between intramedia and skew which is time difference between intermedia. es desirable quality of service requirement. Proposed model applies maximum jitter and skew values which can be allowed, and then it presents high quality of service and real applies maximum jitter and skew values which can be allowed, and then it presents high quality of service and real time characteristics. In this paper we expend Petri-net and propose new synchronization specification model and apply two analysis method of Petri-net to prove oIn this paper we suggest multimedia synchronization model that is based on the Petri-net and servicur model suggested. We compared with other models and showed high QoS.
A Dynamic Signalling Period Allocation Algorithm in Wireless ATM MAC Protocols
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1004~1014
MAC protocols in wireless ATM has to increase and maintain the system throughput performance. To achieve these purposes, this paper proposes a dynamic control algorithm called DSPA (Dynamic Signalling Period Allocation) for wireless ATM MAC protocol. The proposed DSPA algorithm consists of the following three algorithms. First, a control slot generation algorithm which generates the control slots by utilizing static and dynamic parameters from the terminals, is proposed. Second, a dynamic signalling period allocation algorithm is proposed for a base station to dynamically determine each signalling period according to current terminal states, and thus allocates the optimal signalling periods. Finally, a dynamic slot allocation algorithm is proposed to dynamically determine priorities of the terminals whenever a slot is allocated. Simulation results indicates that DSPA algorithm decreases average packet delay of the terminals by dynamic allocation of signal periods based on the system utilization, and thus increases the limitation of allowable loads that quarantee quality of services. Also the proposed algorithm is shown to maintain stable throughput even in the case of traffic variations.
Median Prefilter Based Robust Acquisition Of Direct Sequence Spread Spectrum Signals In Wideband Pulse Jamming
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1015~1023
We propose nonlinear processing schemes for robust acquisition of direct-sequence spread spectrum (DS/SS) signals in wideband pulse jamming. To mitigate the interference effect due to impulse-like wideband jamming signals, the received signal is preprocessed by using the median filter, a simple order statistic filter Since only parts of the PN sequence are used for rapid acquisition, it is indispensable for analytic design of an acquisition scheme to have an appropriate model of the partial PN signal. The partial correlation of the median filtered PN signal is approximated by a two-piecewise linear model using an approximate upper bound. The acquisition performance of the proposed schemes is compared to that of other schemes. Finally, the analytic design is verified by computer simulation.
Performance of OFDM M-ary QAM System in the presence of Carrier Frequency Offset
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1024~1031
In order to transmit high-speed wide band signals efficiently in multipath fading environments, M-ary QAM signalling combined with OFDM transmission technique is applied. In this paper, the effect of synchronization error caused by carrier frequency offset and SER(Symbol Error Rate) performance of OFDM-16QAM and OFDM-64QAM are theoretically analyzed. Our result shows that as the number of sub-carrier in OFDM system increases the frequency-offset caused inter-channel interference(ICI) increases significantly, and that an error floor occurs even at high SNR of OFDM system. For OFDM-64QAM, the error floor occurs at SER=1
10-7 when a normalized frequency-offset is 0.001, in which the SNR degradation is much greater than that of OFDM-16QAM. From this study the maximum allowable frequency-offset of OFDM-16QAM and OFDM-64QAM systems can be determined to meet the specific SER requirement.
On-line Scheduling Algorithms for Reducing the Largest Weighted Error Incurred by Imprecise Tasks
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1032~1041
This paper proposes on-line scheduling algorithms that reduce the largest weighted error incurred by preemptive imprecise tasks running on a single processor system. The first one is a two-level algorithm. The top-level scheduling, which is executed whenever a new task arrives, determines the processing times to be allotted to tasks in such a way to minimize maximum weighted error as well as to minimize total error. The lower-level algorithm actually allocates the processor to the tasks. The second algorithm extends the on-line algorithm studied by Shih and Liu by formalizing the top-level algorithm mathematically. The numerical simulation shows that the proposed algorithm outperforms the previous works in the sense that it greatly reduces the largest weighted error
Performance of Digital Predistorter in Non-linearly Amplified Land Mobile Satellite Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1042~1047
In this paper, two kinds of digital predistorters are proposed and their performances are analyzed in order to minimize ACI and SNR degradation caused by nonlinearly amplified TC-16QAM signal and to transmit high speed data in power and bandwidth limited land mobile satellite channel. Our simulation results show that LUT predistorter reduces the out-of-band ACI more efficiently as compared to intersymbol interpolated predistorter. Regarding the reduction of in-band SNR and total power intersymbol interpolated predistorter outperforms LUT predistorter. In the simulation mobile satellite channel and nonlinear HPA are modeled by Rician channel and Fujitsu SSPA, respectively.
Study on the Network Architecture and the Wavelength Assignment Algorithm for All-Optical Transport Network
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1048~1058
This paper compares some architectures to achieve the optimized WDM architecture for all optical transport network, the comparison is presented in terms of the number of required wavelength and LT. These architecture types are PPWDM, SHWDM, DHWDM and fully optical WDM. Topology is a static ring network where the routing pattern is fixed and traffic pattern has uniform demand. This paper also proposes an algorithm for the wavelength assignment for a folly optical WDM ring network which has full mesh traffic pattern. The algorithm is based on heuristic algorithm which assigns traffic connections according to their respective shortest path. Traffic described here that is to be passed through can be routed directly within the optical layer instead of having the higher layer to handle it.
A Design of TC layer Controller for ATM-PON OLT
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1059~1067
In this paper characteristics of ATM-PON is described and a TC layer controller for ATM-PON OLT is designed. This paper proposes an algorithm of economically controlling the grant information written by CPU to dynamically allocate the upstream bandwidth on the PON among the ONUs in a fair way and of encrypting the downstream data using a lower standard of encryption, termed data churning, which is used to distinguish it from existing transmission system scramblers and higher layer encryption methods. This paper also proposes a method of allocating churning-related message into the PLOAM cell in order to synchronously change the churning key between the OLT and the ONU
Implementation of ISDN User/Network Protocol Analyzer on PC-based System
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1068~1073
On the emergence of ISDN which has been introduced in the year 1980, various services are supported. This paper presents implementation of ISDN user/network protocol analyzer based on PC-extension card. Firmware and software are loaded on the PC-extension card using PC 05. The performance analysis on D-channel signalling on this system is surveyed. The monitoring results satisfiy with ISDN BRI or PRI interfaces.
155.52 Mbps High Performance CMOS Receiver for STM-1 Application
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1074~1079
A high performance CMOS receiver for 155.52 Mbps STM-1 digital communication has been designed and fabricated. The ASIC operates properly with 155.52 MHz clock frequency in case of the data loss due to some system error such as transmission line open or data transfer fail. Also it operates properly in case the system starts after the power failure or system maintenance. The designed circuit has especially PLL based self oscillation loop which operates on abnormal environment which is added to main oscillation loop. The measured results show that the circuit operates well with 153.52 MHz clock frequency not only on normal environment but also on abnormal environment. Rms jitter of the PLL loop is about 23 ps.
A Design and Analysis on Network Architecture for Interactive VOD Services
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1080~1087
High-speed network resources and large storage devices on video servers are necessary to Provide interactive VOD services to subscribers, therefore, building networks for VOD services requires a huge amount of cost. A number of studies on network hierarchy for distributed tree architecture, on optimized server allocation with a given network topology, and on program caching etc, are currently in progress. In this study, given specific network resources, a cost effective network architecture including the optimal number of tree levels and the optimal number of branches at a node are designed by modeling cost functions, and some restrictions on network design are discussed. The results of this study are expected to be applied to network architecture design for interactive VOD services
CLR Performance of CBR Traffic in Wireless ATM Access Network
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1088~1097
In this paper we describe our investigation en ATM CLR(Cell Loss Rate) in the wireless ATM Networks, which consist of wireless access nodes and wireless links. A wireless access node is modelled as the ND/D/1queue. A wireless channel is modelled as channel with single and burst error characteristics, and it can be seen that the CLR degrades on a link with burst errors than on a link with single error. Because wireless channel can be approximated as the Rayleigh or Rician fading channel and wireless communication systems are power limited, it is customary that the CLR degrades on a link with burst errors than on a link with single error. So error control method should be used to improve performance degradation caused by burst errors. We consider the forward error correction(FEC) as error control scheme for CBR traffics to improve performance degradation caused by burst errors, and analyze performance of concatenated FEC scheme through the use of CLR.
Efficient Stream Distributions Algorithm for Heterogeneous Multimedia Multicast
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1098~1107
In multimedia applications, a source usually generates multiple streams. By heterogeneous multimedia multicast, we mean a recipient can receive some of them, not necessarily all of them. A recipient bids for what it wants to receive and the source gains the same amount when a connection is established. The problem of distributing streams for heterogeneous multicast to maximize the source's gain, can be solved using a 0-1 integer programming, hewn as NP-complete. In this paper, we propose efficient stream distribution algorithms in two different types of multicast models. The first restricted model assumes that the capacity for a link in the multicast tree is grater than or equal to the capacities of its descendant links. In the second unrestricted model, we drop out the restriction in the restricted model. Proposed algorithms have better time and space complexities compared with any existing one. In addition, distributed implementations are straightforward, which is very useful for large networks.
An Efficient Multicast Algorithm for ATM Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1108~1112
In this paper, we propose an efficient ABR multicast algorithm for ATM networks. In ABR multicast algorithim, the feedback consolidation is necessary to avoid excessive backward resource management (BRM) cells and to aggregate the information from BRM cells received from each branch. The proposed scheme is shown to achieve fast transient response to the congestion status on a branch as well as effectively eliminate the consolidation noise through system simulation.
A Mechanism to Support Real-Time Internet Services over the ATM Network
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1113~1122
In this paper, we propose MSS(Multicast Synchronization Server) and QCS(QoS Conversion Server) models that can support IP multicast and QoS(Quality of Service) over the ATM network more efficiently. In the MSS model, it is possible to establish shortcut VCs(Virtual Circuits) among all hosts in the ATM network and to transfer multicast data at high speed. Also the MSS model is more scalable, because the number of inter-cluster VCs needed in the MSS model is less than that of EARTH. In the QCS model, ATM switch is modified to support one QoS service and best effort service through the one point-to-multipoint VC at the same time so required network resources are reduced, and dedicated server is used for QoS conversion to accept heterogeneous receivers more efficiently. In this Paper, the proposed MSS model and QCS model have solved both efficiency problem and scalability problem. It is proved through the comparison of the VCs required in each model.
Analysis of Stepped T-Junction using Improved Three Plane Mode Matching Method and Its Application
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1123~1133
In this paper, we applied mode matching and generalized scattering matrix methods to three plane mode matching method for analyzing T-junctions. We calculated all scattering matrix elements by only three times and considered several incident modes. By proposed analysis method, we could analyze various waveguide discontinuity structures more conveniently and accurately. Using the stepped T-junction, we would be able to reduce the reflection coefficient at an input port and use it over wider band. Simulated and HFSS data of T-junctions are compared, showing good agreement for scattering matrix elements. Considering step numbers, height, length and position, we extracted for optimum dimensions and equivalent circuit parameters.
Performance Analysis of an Optical CDMA System for multi-user Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1134~1141
In this paper, we implement an optical code division multiple access(OCDMA) system and analyze the performance of the implemented system. In the implemented system, a transmitter encodes input data into optical pulses by using laser diode, and spreads the encoded pulses in an encoder which consists of 4 stage delay lines. The decoder which is the same structure as that of encoder delays and combines the spreaded pulses, and thus recovers the original data. At first, we discuss the auto- and cross-correlations of OCDMA signals under both environments of single user and multi-users, and then verify the simulation results with experimental results. We also evaluate the effect of a number of stages of delay line and code length on the system performance through computer simulations. As experimental results we can see that if the decoder have the same configuration as that of encoder, the peak auto-correlation characteristics can be achieved, and thus we can recover the original data from received data. As simulation results we can see that although bit error rate decreases as code length decreases or the number of stage of delay line increases, it is difficult to implement the system because the pulse width becomes narrow. From the results, we can apply CDMA technologies to optical communication networks
Broadband Characteristics of Asymmetirc Coupled-Line 90
Phase Shifter with Dielectric Overlay
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1142~1148
In this paper, the characteristics of frequency dependent dispersion are analyzed for the phase shifters in Ku-band phased array antenna system using full-wave method, SDA(Spectral Domain Approach).The design technique of asymmetric coupled-line phase shifter with dielectric overlay is proposed. The compared results of phase responses are shown with conventional symmetric coupled-line Schiffman phase shifter. The experimental results verify the improvement of broadband characteristics by the increasing bandwidths and the decreasing phase deviations.
Design and Fabrication of a Narrow-Band Orthomode Transducer for Satellite Communication
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1149~1155
This paper presents a narrow-band orthomode transducer(OMT) based on waveguide to waveguide transitions which can separate two linearly polarized orthogonal modes. This operates in the range 120Hz-13GHz frequency band. It consists of two parts, main arm and side arm. Stepped transformers are designed and an inductive post is inserted to improve the characteristics of the transmission loss and isolation. This paper also presents results from fabricated OMT These results show that the transmission loss is less than 1dB and the isolation between the ports for the OMT is above 20dB.
Implementation of Phase-Error Compensation Algorithm in Terrestrial Digital TV Modulator
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1156~1164
In this paper, we have studied the 8 YSB (8 Vestigial Side Band) method which is decided as the standard of modulators for next generation digital TV System. In developing digital TV System, one of the difficult problems is how digital signal can be transmitted to the receiver without any phase distortion. But, phase error is liable to occur by imperfect design, circumstance variation and device degradation. These characteristics result in distortion of 1,0 signal of modulator and interference in adjacent channels. In particular, the interference in modulator of a high power amplifier result in serious problems in adjacent channels. Here we analyzed problems of phase error which are occurred when 8 levels digital signals are modulated to If signal. And we suggested phase error compensation algorithm and discussed the results for adaptation of the algorithm
Traffic Modeling and Design of An All-Optical WDM Backbone Network in Korea
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1165~1173
In order to support various multimedia communication services, a well balanced backbone network should be designed using recently advanced optical communication technologies. In this paper an optimal backbone network configuration design is presented fur Korean traffic environment. A new traffic model, Population-Distance-Gross Group Products(PDG) traffic model, is devised. In Korean network traffic environment, six regional centers are selected, link capacities between the regional centers are estimated from the PDG traffic model, and the overall network configuration is designed for the all-optical backbone network in Korea. A simulation study is carried out to verify the desired performance of the designed backbone network. Simulation results show that performance of the backbone network is well balanced to support various communication services in Korea in the 2000s.
A New Vertex Coding Scheme Using The Center of the Gravity of a Triangle
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1174~1182
Recently the shape information of the visual object in the scene is more important, as the completion of the MPEG-4 standard and the progress of the MPEG-7 standard. This paper represents the study of effective coding method of vertices that are used in the polygonal approximation to represent the feature of visual object. In the proposed method, we make the centers of gravity of triangles that are made using the vertices of polygonal approximation and encode them sequentially We can get a coding gain because the centers of the gravity of triangles have narrower dynamic ranges.
An Improvement MPEG-2 Video Encoder Through Efficient Frame Memory Interface
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1183~1190
This paper presents an efficient hardware architecture to improve the frame memory interface occupying the largest hardware area together with motion estimator in implementing MPEG-2 video encoder as an ASIC chip. In this architecture, the memory size for internal data buffering and hardware area for frame memory interface control logic are reduced through the efficient memory map organization of the external SDRAM having dual bank and memory access timing optimization between the video encoder and external SDRAM. In this design, 0.5 m, CMOS, TLM (Triple Layer Metal) standard cells are used as design libraries and VHDL simulator and logic synthesis tools are used for hardware design add verification. The hardware emulator modeled by C-language is exploited for various test vector generation and functional verification. The architecture of the improved frame memory interface occupies about 58% less hardware area than the existing architecture[2-3], and it results in the total hardware area reduction up to 24.3%. Thus, the (act that the frame memory interface influences on the whole area of the video encoder severely is presented as a result.
Vehicle Detection and Classification Using Textural Similarity in Wavelet Domain
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1191~1202
We propose an efficient vehicle detection and classification algorithm for an electronic toll collection using the feature which is robust to abrupt intensity change between consecutive frames. The local correlation coefficient between wavelet transformed input and reference images is used as such a feature, which takes advantage of textural similarity. The usefulness of the proposed feature is analyzed qualitatively by comparing the feature with the local variance of a difference image, and is verified by measuring the improvements in the separability of vehicle from shadowy or shadowless road for a real test image. Experimental results from field tests show that the proposed vehicle detection and classification algorithm performs well even under abrupt intensity change due to the characteristics of sensor and occurrence of shadow.
A Convergence Analysis of Normalized Sign Algorithm for Adaptive Noise Canceler
The Journal of Korean Institute of Communications and Information Sciences, volume 24, issue 6B, 1999, Pages 1203~1210
Coefficients of the adaptive filter are misadjusted by primary signals which are uncorrelated with reference signals of the adaptive filter. In this paper, the normalized sign algorithm is analyzed and compared with the NLMS algorithm by the steady state performance and the transient characteristics when target signals are included in primary signals. The excess mean square error of the NLMS algorithm is proportional to the power of target signals. That of normalized sign algorithm is proportional to the square root of the target signal power. However, the convergence speed of the normalized sign algorithm is slower than that of NLMS algorithm. In this paper, it is shown that theoretical analysis of the steady state performance and the transient characteristics are well consisted with the results of computer simulation.