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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
Selecting the target year
A new modular neural network training algorithm for step-like discontinuous function approximation
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2613~2625
Theoretically, a multi-layered feedforward network has been known to be able to approximate a continuous function to an arbitrary degree of accuracy. However, these networks fail to approximate discontinuous functions when they are trained by well-known training algorithms. This paper presents a training algorithm which doesn't work consists of one or more modules, which are trained in a sequential order within subspaces of the input space, and is trained very rapidely once all modules are trained and merged. The experimantal results of applying this method indicates the proposed training algorithm is superior to traditional ones such as baskpagation.
An efficient dynamic routing scheme for delay-bounded multicasting
Kang, Moon-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2626~2634
The purpose of multicasting is to reduce the network costs for transmitting the same traffic to multiple destinations. In this paper, an efficient delay-bounded multicasting routing algorithm is proposed, which satistifies the network conditions of cost minimization and can adjust the dynamic events, such as 'leave and/or join ones' from the multicast group. Also, our algorithm is designed for various network requirements such as the efficiet dynamic group support, high-quality data distribution, and adaptability to variable situation. After the delay tolerance and the maximum group size are determined according to network state and requirements for delay and cost, the dynamic delay-bounded multicast tree is constructed using partial multicast routing. We evaluate the performance of the proposed algorithm by running simulations on randomly generated test networks using a Sun Sparc 20 workstation. We were able to obtain good simulation resutls, which means solutions that lies between the minimum cost solution and the minimum delay one.
Adaptive routing algorithm for equitable load balancing with propagation delay
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2635~2643
In this paepr, a routing algorithm is proposed in order to reduce average end-to-end delay and congesting in the high speed network. The algorithm proposed here uses the existing one which adaptively modifies routes and the amount of traffic allocated to each link as user traffic partterns flutuate. This algorithm is ELB(Equitable Load Balancing). Also, the new algorithm considers the proportional to the distance between source and destination. It reduces congestion from the ELB and average end-to-end delay from the propagation dealy concepts respectively. Through the simulation, it shows that the algorithm proposed here reduces average end-to-end delay over low load to high load, and it also guarantees the congestion control.
Approximations to blocking probability in two-stage queueing model
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2644~2652
We ivestigate a two-stage queueing system which frequently arises in the study of overflow problems. A primary service facility consists of multiple primary queues where blocked calls are overflowed to a secondary queue. By approximating the input to the secondary queue with a two-state Markov Modulated Poisson Process (MMPP), we derive the blocking probability of the secondary queue. For the approximation, we employ the well-known Heffes' method and the SAM procedure.
Performance analysis of multistage interference cancellation schemes for a DS/CDMA system subject to delay constraint
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2653~2663
The successive and parallel interference cancellation schemes are two well-known types of multi-stage interference cancellation schemes using the conventional correlator receivers as a basic building block, which has been known to significantly improve the performance of DS/CDMA system in the multiple access communication. Performance comparison between these two schemes is made strictly based on the analytical and it has been shown that the successive interference cancellation (SIC) scheme is more resistant to fading than the parallel interference cancellation (PIC) scheme. We further investigate the performance of the successive IC scheme subject to the delay constraint, which may be imposed typically on most of service applications with a real-time transmission requirement, including speech and video applications. Our analysis demonstrates that the performance may be significantly improved by the groupwise successive interference cancellation (GSIC) scheme, which can be properly optimized to meet the given delay constraint.
A study on the call processing of DS-CDMA system using the simulcasting scheme
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2664~2673
The signal fading distortion has effect on the capacity of cellular mobile communication systems. The short term fading is solved by signal processing techniques depending on the radio communication methods, but another distortion compensation techniques are necessary to combat long term fading. in this paper, we have simulated the call processing in DS-CDMA system using distributed antennas to overcome the long term fading. From the simulation results, we have conformed that the blocking probability of a new call andthe forced probability of handoff-request-call have decreased by increasing the number of distributed antennas.
Design and implementation of dual band power amplifier for 800MHz CDMA and PCS handset
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2674~2685
In this paper, the design and imprlementation of dual-band power amplifier which is used as a critical part for mobile phone to be simultaneously working at a dual band, 800MHz CDAM and PCS frequency band is described. DC operating point of power FET is limited to Class-B to enable long talk time considering that the tyupical power range of CDMA phones in working is around 10 to Class-B to enable long talk time considering that the typical power range of CDMA phones in working is around 10 to 15dBm, i.e., liner range. The power amplifier which employs two GaAs FETs with good linerity at a low operating point has duplexer cuplexer circuit to separate two frequency bands at input and output stage. Electromagnetic analysis for via holes and coupling between narrow transmission lines is included to design a circuit. Moduld size of 0.96CC(
) and maximum module current of 130mA at output power range, 10 to 15dBm are attained. The power amplifer module has achieved ACPR performance with 2 to 3dB marging from IS-95 requirement at output powers, 23.5dBm for PCS and 28dBm for 800MHz CDMA respectively.
Performance analysis of a MC-CDMA cellular system with antenna arrays in a fading channel
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2686~2695
The MC-CDMA(multi-carrier code division multiple access) technique is known to be appropriate for high data-rate wireless communications such as mobile multimedia communication due to its robustness to multipath fading and its capability of handing high data rates with a simple one-tap equalizer. In this paepr, the performance of a MC-CDMA cellular system employing antenna arrays at the based station in a fading channel is presented. It is whown that the interference from other users within the cell can be significantly reduced for both reverse link (mobile to base station) and forward link (base station to mobile) using a MC-CDMA with antenna arrays, thus incresig the system's user-capacity. Computer simulations that demonstrate user-capacity improvement of the proposed approach are discussed.
The average SER of MPSK signals with selection diversity in nakagami fading channels
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2696~2705
An exact experssion for the average symbol error rate(SER) of L-order selection diversity for MPSK signals in a frequency-nonselective slowy m-distributed Nakagami fading and additive white Gaussian noise(AWGN) is determs of finite sums is obtained. To derive the SER of MPSK signals with selection combining, the new expression of pdf is introduced and many other mathmatical methods are used. When fading index m is 1, the derived exppression lead to those of MPSK with selection combining in Rayleight fading channels. The results show that the error probability decreases as the order of diversity increases.
A fast M-band discrete wavelet transform algorithm using factorization of lossless matrix when the length of bases equals to 2M
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2706~2713
The fast implementation algorithm of M-band discrete wavelet transform is propsed using the factorization of lossless matrix when the length of discrete orthogonal wavelet bases equals to 2M. In computational complexity when direct filtering method is employed, the number of multiplicationand addition is (2M
) and (2M
-M), respectively. But by proposed algorithm, it can be reduced to (M
+M) and (M
+2M-1), respectively. and it is possible to reduce the compuatational complexity further when unitary matrix employed to design the discrete or thogonal wavelet basis has the fast algorithm.
A binary adaptive arithmetic coding algorithm based on adaptive symbol changes for lossless medical image compression
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2714~2726
In this paper, adaptive symbol changes-based medical image compression method is presented. First, the differenctial image domain is obtained using the differentiation rules or obaptive predictors applied to original mdeical image. Also, the algorithm determines the context associated with the differential image from the domain. Then prediction symbols which are thought tobe the most probable differential image values are maintained at a high value through the adaptive symbol changes procedure based on estimates of the symbols with polarity coincidence between the differential image values to be coded under to context and differential image values in the model template. At the coding step, the differential image values are encoded as "predicted" or "non-predicted" by the binary adaptive arithmetic encoder, where a binary decision tree is employed. The simlation results indicate that the prediction hit ratios of differential image values using the proposed algorithm improve the coding gain by 25% and 23% than arithmetic coder with ISO JPEG lossless predictor and arithmetic coder with differentiation rules or adaptive predictors, respectively. It can be used in compression part of medical PACS because the proposed method allows the encoder be directly applied to the full bit-planes medical image without a decomposition of the full bit-plane into a series of binary bit-planes as well as lower complexity of encoder through using an additions when sub-dividing recursively unit intervals.
A study on the fading compensation scheme for wireless ATM systems
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2727~2735
This paper describes a new fading compensation scheme for Wireless ATM(WATM) sytem using pilot symbols. We have carried out a simulation for bit error rate(BER) and cell loss probability(CLP) to analyze the performance of a new scheme. As the resutls, BER performance we improved by means of HEC only above 3 dB of
in AWGN, but not at all in fading environment. However, by using a new fading compenstion scheme with HEC, BER performance degraded below to 1 dB of
in AWGN, but BER and CLP performances in WATM system were improved remarkably, and meeted at CLP performance criterion for K=10 dB rician fading. Also, code rate will be high and harware size of codec will be small by using this new scheme with HEC OR FEC.
An analysis of microwave active circuit using the extended FDTD method
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2736~2743
In this paper, the extended finite difference time domain(FDTD) algorithm is applied to carry out full-wave analysis of a microwave amplifier circuit. The active device included in the amplifier is modeled by equivalent current sources. Equivalent current sources are characterizing interaction between electronmagnetic waves and active devices and can be directly incorporated into the FDTD algorithm. To confirm this analysis, an amplifier is implemented. The FDTD simulation shows good agreement with measured results.
Multi-layer restoration strategy to restore the multi-link and node failures in DCS mesh networks
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2744~2754
Recently, the Multi-Layer Restoration(MLR) algorithm was proposed by British Telecom(BT) to restore the network failures in Digital Cross-connect System(DCS) mesh survival network[1, 2]. This algorithm has multi restoration stage which is composed of the pre-planned and dynamic restoration. This algorithm is effective its ability in link or node failures. This reason is that it does not restore in the pre-planned rstoration stage but in dynamic restoration stage. In this paper, we propose the MLR with pre-planned Multi-Chooser(PMC) and successive restoration ratio algorithm. This proposed algorithm has a excellent performance for restortion time and ratio, spare channel availability and fast restoration from multiple link failure or node failure. This paper proposed the modeling and restoration algorithm, and analyzed the performance of the algorithm by simulation using OPNET(OPtimized Network Engineering Tools).
A multiple expert system for intelligent computer network management
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2755~2762
Open Network Management Systems (NMS) are not sufficient to use in a large and complex computer network environment because many-year experiences and skills are requeired for using NMS. And also, customizing NMS means a difficult programming with API(Application programming Interface) supplied by NMs. The more intelligent NMS you want, the more difficult programming you must do. In this paper, we proposed an intelligent network management system suign a structure of multiple and distributed expert systems, so as to represent expertises and knowledges of network managers into rule format, maintain the knowledgesstructurally and perform the network managmenet intelligently. expert system for amanaging computer network should understand the management protocol, analyze messages from agents, take a proper action, and report the situations by pre-defined network operation principle and strategy. A multiple expert sytem is composed of monitor expert module, fault expert module and manager expert module which are controlled by enconded knowledges.
A method for the satellite orbital prositions determination in the fixed satellite communication
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2763~2771
To determine the satellite orbital positions considering interference caused by inter-satellite systems is one of the most improtant issues in terms of optimal usage of satellite network resources. In this paper, considering ITU filing situation, we present the satellite orbital positions determination method to minimize iter-satellite system interference effect in the fixed satellite communication using an optimization method. Through the computer simulatio, it was shown that the proposed method is suitable to determine the satellite orbital positions.
Denosing of images using locally adaptive wiener filter in wavelet domain
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2772~2782
In this paepr, a Wiener filtering method in wavelet domain is proposed for restoring an image corrupted by additive white noise. The proposed method utilizes the characteristics of wavelet transform signals and the local statistics of each subband. When estimating the local statistics in each subband, the size of filter window is varied according to each scale. At this point, the local statistics in each wavelet subband is estimated only by using pixedls which have similar statistical property. Experimental results show that the proposed method has better performance over the conventional Lee filter with a window of fixed size.
Image warping using an adaptive partial matching method
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2783~2797
This paper proposes a new motion estimation algorithm that employs matching in a variable search area. Instead of uisg a fixed search range for coarse motion estimation, we examine a varying search range, which is determined adaptively by the peak signal to noise ratio (PSNR) of the frame difference. The hexagonal matching method is one of the refined methods in image warping. It produces improved image quality, but it requires a large amount of computataions. The proposed adaptive partial matching method reduces computational complexity below about 50% of the hexagonal matching method, while maintaining the image quality comparable. The performance of two motion compensation methods, which combine the affine or bilinear transformation with the proposed motion estimation algorithm, is evaluated based on the following criteria:computtational complexity, number of coding bits, and reconstructed image quality. The quality of reconstructed images by the proposed method is substantially improved relative to the conventional BMA method, and is comparable to the full hexagonal matching method;in addition, computational complexity and the number of coding bits are reduced significantly.
The end-to-end ATM performance QoS requirements in CBR guaranteed real-time services
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2798~2805
The paper studies the Quality of Service(QoS) concept in Broadband Integrated Services Digital Network (B-ISDN). Guaranteeing the QoS requirements indistributed multimedia systems and networks is fundamentally an end-to-end issus, that is, from application to application. An important issue in the QoS translation between the application-level QoS and network-level QoS is that the translation depends not only on the translation between system resources and network resources, but also on the translation between thelayered protocol and the access procedures. In this paepr, we propose a methodology for translating the AAL(ATM Adaptation Layer) QoS parameters into the ATM layer QoS parameters in end-systems. The QoS parameters in the ATM layer and AAL are defined, and we concentrate on the translation from the AAL to the ATM layer, because the AAL must be designed to be service dependent and specific. As an example, we concentrate on the constant bit rate(CBR) guaranteed real-time service using AAL1 protocol.
A study onthe modeling of broadband access network for national information infrastructure and numerical analysis of its economics
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2806~2818
It is generallyaccepted that broadband access technologies will play an important role in the National Information Infrastructure. However, the provision of direct fibers to residential and small business customers has always been considered a challenge. To accelerage the provision of Broadband Access Facilities, alternatibe paths could be identified and actaivated in parallel. In this paepr, we present an overview of the alternative access technologies focusing on xDSL, FTTx, HFC, HFR, and suggest the modeling of the access netetwork systems which is using of the technologies. Also to investigate the economics of each access systems, we derve the numerical equations which is summed up the al parameter including the labor cost of the model system. The proposed equation has a variable which is the cell size (or subsciber clusters) and calculate the real cost values which is normalized by the copper cable unit cost. From the numerical resutls, we conclude that the economic access method to provide these broadband capabilities is depended on the subscriber penetration, the patterns of subscriber distribution density and existing communication infrastructures. It can be expected that our analytical model and equations provides an elegant solution to choose the optimal broadband access technologies to residential and small business customers.
Review of analysis for dielectric rectangual waveguides
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2819~2827
A dielectric waveguide structure using rectangular dielectic strip is analyzed directly in terms of the wave equation for quasi TE and quasi TE and quasiTM modes. This problem can be solved, with no approximation in the wave equation for the electric field
and magnetic field
inside and outside the dielectric rectangular waveguide matching the boundary conditions between interfaces. This leads to an eigenvalue problem where spurious modes do not appear. Dispersion characeristic examples are presented for square and rectangular waveguides. The formulation is general and can be used for compuarison with ogher methods such as FDM or FEM in various structures.
Architecture of time-division -division hybrid photonic ATM switch with large capacity
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2828~2833
In this paepr, we have proposed an enhanced TDM with WDM hybrid photonic switching architecture, which has much simpler configuration and requires less hard ware. the basic module consists of arrayed waveguide grating (AWG) for wavelength division, compressor and fiber delay lines for time division. When compared with other systems, we proved that the proposed switch is suitable for large capacity photonic switching system due to less complexity and lower cost in implementation than the previous ones.
A deisgn of VHDL compiler front-end for the VHDL-to-C mapping
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2834~2851
In this paper, a design and implementation of VHDL compiler front-end, aims at supporting the full-set of VHDL '87 & '93 LRM and carring out the preprocessing of VHDL-to-C, is described. The VHDL compiler front-end includes 1)the symbol tree of analyzed data to represent the hierarchy, the scope and visibility, the overloading and homograph, the concurrent multiple stacks in VHDL, 2)the data structure and supportig routies to deal with the objects, the type and subtype, the attribute and operation in VHDL, 3)the analysis of the concurrent/sequential statements, the behavior/structural descriptions, of semantic token and the propagation of symbol & type to improve the registration and retrieval procedure of analyzed data. In the experiments with Validation Suite, the VHDL compiler front-end could support the full-set specification of VHDL LRM '87 & '93; and in the experiments to asses the performance of symantic token for the VHDL hierachy/visibility/concurrency/semantic checking, the improvement of about 20-30% could be achieved.
Batching delivery for VCR-like functions in video-on-demand service system
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2852~2859
Video-On-Demand system provides electronic video rental services from remote video servers on a broadband communication networks. Most of proposed VOD systems are typically designed for one-to-one conncetion between a user and video server. Therefore, video server stream services to customers individually by allocating a dedicated transmission channel and a set of video server resources for each customer. However, it is inefficiency and wxpensive way when server support multiple users who access the same video stream with a dedicated video channel. Therefore, to achieve cost-effectiveness, batching have studied method that uses multicast communication to simultaneously service all users requesting the same video with a single video with a single video stream. However, the application of the multicast communication by batching detract from the VCR-like function and on-demand nature of the system. In this paepr, we propose a scheme that can support an interactive VCR for all user requesting the same video stream with batching. To reduce a server I/O and network bandwidth requirement, dynamic buffer is allocated to access node which has variable playout poit. Consequently, it makes possible interactive VCR operation as if customer uses true VOD system. Also, this scheme can just deliver a multicast stream without delay after an initial request or VCR action occurred. The policy can guarantee acceptable services to number of users at minimum cost.trans
The design of authentication mechanism using kerberos and X.509 protocol in distributed environment
The Journal of Korean Institute of Communications and Information Sciences, volume 22, issue 12, 1997, Pages 2860~2866
Kerberos is the most used example of authentication technology in distributed environment. In this paper, based on this method, a new authentication mechanism associated with X.509 protocol that authenticates services between regions is presented. Since any suggestions to regional services are not described in Kerberos, the authentication between regiona is performed via the connected chain obtained from x.509. These two protocols have distinguished key management systems -X.509 is designed using an asymmetric method, while Kerberos using a symmetric method. In order to provide regional services, X.509 is employed on connection part and Kerberos on actual authetication part.