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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 18, Issue 12 - Dec 1993
Volume 18, Issue 11 - Nov 1993
Volume 18, Issue 10 - Oct 1993
Volume 18, Issue 9 - Sep 1993
Volume 18, Issue 8 - Aug 1993
Volume 18, Issue 7 - Jul 1993
Volume 18, Issue 6 - Jun 1993
Volume 18, Issue 5 - May 1993
Volume 18, Issue 4 - Apr 1993
Volume 18, Issue 3 - Mar 1993
Volume 18, Issue 2 - Feb 1993
Volume 18, Issue 1 - Jan 1993
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An Improved Acquisition of the Noncoherent DS/SS-CSK
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1797~1805
An algorithm for the threshold decision from the maximum mismatching correlation value in a direct-sequence spread-spectrum system is presented. This algorithm is named the TDMMC(Threshold Decision from the Maximum Mismatching Correlation value). The purpose of the algorithm is to set the decision threshold in the system which will provide large probability of signal detection. Using this algorithm, the proper setting of the threshold for various SNRs is possible. An additional block called the Threshold Block is used to improve the system performance. The result from the computer simmulation has shown that appling the TDMMC to the noncoherent DS/SS-CSK system can achieve performance improvement.
Robust Tree Coding Combined with Harmonic Scaling of Speech at 4.8 Kbps
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1806~1814
Efficient speech coders using tree coding combined with harmonic scaling are designed at the rate of 4.8 kilobitts/sec (kbps). A time domain harmonic scaling algorithm (TDHS) is used to compress input speech by a factor of two. This process allows the tree coder have 1.5 bits/sample for 4.8 kbps in the case of a 6.4 kHz sampling rate. In the backward adaptive tree coder, there are three components of the code generator, including a hybrid adaptive quantizer, a short-term predictor and a pitch predictor. The robustness of the tree coder is achieved by carefully choosing the input of the short term predictor adaptation. Also, inclusion of a smoother in the pitch predictor improves the error performance of tree coder in the noisy channel. Subjectively, tree coding combined with TDHS provides good quality speech at 4.8 kbps.
Performance Analysis of Futurebus+ based Multiprocessor Systems with MESI Cache Coherence Protocol
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1815~1827
In this paper, we evaluate the performance of a Futurebus based multiprocessor system with MESI cache coherence protocol for four bus transaction types. Graphical symbols and compiler of SLAM II are used in modeling and simulation. A steady-state probability of each state for MESI protocol is computed by a Markov chain. The probability of each state is used as an input value for a correct simulation. Processor utilization, memory utilization, bus utilization, and the waiting time for bus arbitration are measured in terms of the number of processors, the hit ratio of cache memory, the probability of internal operation, and bus bandwidth.
Centralized Protocol Model for Videoconference Service over Wide-Area-Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1828~1840
In this paper, a centralized protocol model for videoconference service over a wide-area-network is presented. the model is comprised of three distinct components : clients, server and mixer. The server handles all can management functions, and the mixer performs realtime traffic mixing. The control and data are separated, flowing over separated connections in the model. A set of new protocols are defined : call management protocol, media transport protocol, and multimedia synchronization protocol. This paper also presents the functional design of the mixer.
Implementation of Packet Voice Protocol
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1841~1854
In this paper, the packet voice protocol for the transmission of voice signal onto ethernet is implemented in a personal computer (PC). The packet voice protocol used is a modified one from CCITT G.764 packetized voice protocol. The hardware system to facilitate the voice communication onto ethernet is divided into telephone interface, speech processing, PC interface and controllers. The software structure of the protocol is designed according to the OSI seven layer architecture and is divided into three routines : ethernet device driver, telephone interface, and processing routine of the packet voice protocol. Experiments through ethernet with telephone interface show that this packet voice communication achieves satisfactory quality when the network traffic is light.
A Stability Issue on Controlled ALOHA System with Capture Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1855~1869
For the traditional ALOHA system without capture, the Markov chain obtained using the number of backlogged users at each slot if shown to be non-ergodic. So the infinite population ALOHA with fixed retransmission probabilities is unstable for any choice of the arrival rates and retransmission probabilities. The capture ALOHA system of also shown to be unstable for any arrival rate unless it has perfect. In this paper, we study a stabilization policy for capture ALOHA system that controls the retransmission probabilities and prove the stability of its multidimensional Markovian model by empolying a continuous Lyapunov function, and thus identify the stability region. We also study a delay performance through computer simulation th show the stability for any input rate below the maximum achievable channel throughput.
Traffic Control using Multi Rule-Base in an ATM Network
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1870~1883
In this paper, in order to build up the User Network Interface based on ATM, a study on traffic control techniques which should be performed by main function groups-B 75,5 NT2, LEX-is discussed. The structure of B-NT2 which is the most important function group In the User Network Interface is defined in quite a simple manner in addition, the functional blocks of LEX are defined in a similar manner as those of B NT2. It is possible to distribute total traffic control functions by using the similarities between B-NT2 and LEX and by allocating virtual path identifiers fixedly according to the characteristics of the traffics. For the traffic control techniques of ATM, relations among Connection Admtsslon Control, Usage Parameter Control and Bandwidth Allocation Control are defined and Multi Rule Base structure to realize optimal control functions according to the characteristics of the source traffics is proposed. And the Real-time Variable Window algorithmsimply designed to be suitable for the Multi Rule Base architecture is also proposed. The performances of the proposed algorithm are analyzed through the computer simulation by generating on-off source traffic in a virtual system that has the form of the proposed hardware. The analyzed results show that the distributed control is possible and that the implementation of the proposed architecture and algorithm is possible.
A Study on Buffer Processing using Push Out Scheme with Variable Threshold
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1884~1892
In push out scheme, high priority cell which arrives when the buffer is full pushs low priority cell. The PBS scheme provides priority by variable threshold in buffer.In this paper, for Controlling congestion in ATM network we propose buffer processing method in which the PBS scheme has variable threshold. And we analysis The performance of this scheme. As a result of simulation, the proposed push out scheme with variable threshold reduces the loss of low priority cell compared with existing push out scheme. This proposed method not only reduces the loss of high priority cell like existing push out scheme but also reduces the loss of low priority cell by variable threshold.
Field Strength Standards in 30~ 1000MHz Frequency Range
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1893~1901
This paper presents the field strength standard established using a standard antenna method in the frequency range of 30~1000MHz at KRISS(Korea Research Institute of Standards and Science). Designs on antenna elements and a balun, and the characteristics of an antenna voltmeter are described. The uncertainties in generation the standard fields are analzed and estimated to be 5~14%.
A Parallel Emulation Scheme for Data-Flow Architecture on Loosely Coupled Multiprocessor Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1902~1918
Parallel architecture based on the von Neumann computation model has a limitation as a massively parallel architecture due to its inherent drawback of architectural features. The data-flow model of computation has a high programmability in software perspective and high scalability in hardware perspective. However, the practical programming and experimentaion of date-flow architectures are hardly available due to the absence of practical data-flow, we present a programming environment for performing the data-flow computation on conventional parallel machines in general, loosely compled multiprocessor system in particular. We build an emulator for tagged token data-flow architecture on the iPSC/2 hypercube, a loosely coupled multiprocessor system. The emulator is a shallow layer of software executing on an iPSC/2 system, and thus makes the iPSC/2 system work as a data-flow architecture from the programmer`s viewpoint. We implement various numerical and non-numerical algorithm in a data-flow assembler language, and then compare the performance of the program with those of the versions of conventional C language, Consequently, We verify the effectiveness of this programming environment based on the emulator in experimenting the data-flow computation on a conventional parallel machine.
Balanced DQDB Applying the System with Cyclic Service for a Fair MAC Procotol
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1919~1927
A new MAC protocol has been proposed and analysed to relieve the unfairness problems exhibited by the basic version of the DQDB standard. DQDB MAC protocol has the unfairness problems in throughputs. message delay and so or. And when the slots are reused or the file transmissions takes long, the unfairness problems in the system become worse. The new access protocol proposed here, which of called the Balanced DQDB, guarantees a fair bandwidth distribution by using one bit of the dual bus network protocol and keeps up all characteristics of DQDB. the DQDB analysis model introduced by Wen Jing, et al, was considered to analyse a sequential balance distribution of solts. And the probabilities of the empty in operation mode were represented to determine the probabilities for busy bits to generate on each node of the bus using the Markov chain. Through the simulations. the performances of the proposed Balanced DQDB and that of the standard DQDB of the BWB mechanism were compared at the state that the values of the RQ or CD counter on each node varied dynamically. As the results, it is shown that the Balanced DQDB has the decrement of throughputs in upstream, but the numbers of the used empty slots at each node of the Balanced DQDB had more than that of the others because the Balanced DQDB has over 0.9 throughputs in the 70~80% nodes of total node and it has constant throughputs at each node. And there results were analogous to that of the analytical model.
Development of Integer DCT for VLSI Implementation
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1928~1934
This paper presents a fast algorithm of integer discrete cosine transform(IDCT) allowing VLSI implementation by integer arithmetic. The proposed fast algorithm has been developed using Chen`s matrix decomposition in DCT, and requires less number of arithmetic operations compared to the IDCT. In the presented algorithm, the number of addition number is the same as the one of Chen`s algorithm if DCT, and the number of multiplication if the same as that in DCT at N=8 but drastically decreasing when N is above 8. In addition, the drawbacks of DCT such as performance degradation at the finite length arithmetic could be overcome by the IDCT.
Comparison of the Numerical Methods for the Optimum Antireflection Coatings of Laser Diode Facets
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1935~1944
We calculate the optimum refractive index and thickness for a single layer antireflection coating as a function of active layer thickness of a laser diode using three different simplified numerical methods. The difference of the results using three methods comes from that of the effective refractive index of a laser used in three methods. We compare three simplified methods to an exact method to check the validity of the simplified methods. We conclude that the simplified method, choosing the effective index of a laser diode as a function of incidence angle of each plane wave composing of a guided mode agree well to an exact method for both TE and TM modes and the cases of strongly and weakly guiding.
A Key Distrubution Protocol with User Authentication for Mobile PCS
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1945~1955
Two types of key distribution protocols with user authentication are proposed for PCS(Personal Communication Service) and digital mobile communication systems. In this paper, we investigate the service procedure and security requirement for PCS. also discuss the security problems of KDPs previously proposed for digital mobile communication, and show that Park`s type II among the schemes is easily broken by an impersonation attack. Our proposed I, II are based on the modified cryptosystem of Rabin and ElGamal, and reduce the amount of computation for user authentication. Such a reduction is good solution coped with the limited capability of user terminal on PCS. As a result of making a comparison between our schemes and the previously presented schemes, we can know ours are more secure and efficient for PCS.
An Efficient Decoding Technique for Huffman Code Using Tilted Huffman Trees
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1956~1969
The tilted Huffman trees are used in JPEG and MPEG image compression standards for Huffman coding. In this paper we propose a new decoding technique for Huffman code, symbols are decoded by repeatedly obtaining the predefined number of consecutive bits and accessing symbol tables based on the obtaining bits. We show that the size of the symbol table can be small if the Huffman tree is tilted. Specifically, we show an upper bound on the size in this paper. Since the proposed method processes multiple bits at each clock, it can be used for real time processing. We show such evaluation results.
An Efficient Array Algorithm for VLSI Implementation of Vector-radix 2-D Fast Discrete Cosine Transform
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1970~1982
This paper describes an efficient array algorithm for parallel computation of vector-radix two-dimensional (2-D) fast discrete cosine transform (VR-FCT), and its VLSI implementation. By mapping the 2-D VR-FCT onto a 2-D array of processing elements (PEs), the butterfly structure of the VR-FCT can be efficiently importanted with high concurrency and local communication geometry. The proposed array algorithm features architectural modularity, regularity and locality, so that it is very suitable for VLSI realization. Also, no transposition memory is required, which is invitable in the conventional row-column decomposition approach. It has the time complexity of O(N+Nnzp-log2N) for (N*N) 2-D DCT, where Nnzd is the number of non-zero digits in canonic-signed digit(CSD) code, By adopting the CSD arithmetic in circuit desine, the number of addition is reduced by about 30%, as compared to the 2`s complement arithmetic. The computational accuracy analysis for finite wordlength processing is presented. From simulation result, it is estimated that (8*8) 2-D DCT (with Nnzp=4) can be computed in about 0.88 sec at 50 MHz clock frequency, resulting in the throughput rate of about 72 Mega pixels per second.
A Selective Current-supplying Parallel A/D Converter
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1983~1993
A power-reduction technique for full-flash A/D converters is proposed. As the resolution of a full-flash A/D converter increases linearly, the number of comparators increases exponentially. The power dissipation is generally larger than other A/D converter architectures because there are many comparators, and they are operating continuously. In this proposed architecture, only a selected number of conmarators are made to operate instead of activating all the comparators of the full-flash A/D convertor. To determine whichcomparators should be activated, voltage levelfider circuits are used. A new clock driver is developed to suppress the dynamic glitch noise which is fed back into the input stage of the comparator. By using this clock driver, the glitch noise in the current source is reduced to one fourth of that when the typical clock signal is applied. The proposed architecture has been implemented with 1.2 m 5GHz BiCMOS technology. The maximum conversion speed is 350Msamples/s. and dissipates only 900mW.
A Study on the Narrow-band Interference Rejection in DS Spread-spectrum Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 1994~2000
A new lattice structure using decision feedback and augmented prediction for estimating and suppressing the narrowband interference is presented. The performance of the proposed interference canceller is compared to the conventional interference cancellation filter. The reference signal of the interference canceller is formed by using the chip decisions, which is correlated with the narrowband interference components of the received signal. The decision feedback technique reduce the distortion of the desired signal which is introduced by the interference canceller through the use of feedback chip decisions. And by linear prediction of the error signal, the residual interference component of can be eliminated, Using this unconteminated error signal to update the adaptive filter coefficients, the performance of the rejection can be improved. In the simulation, it is assumed that the processing gains are 7 and 15, signal to interference ratio is -10[dB], and 5% interference band. The results show that the BER performance of the proposed filter structure is improved by 1~3dB.
Performance Evaluation of the ISDN Subscriber Interface Module in the TDX-1B Switching System
The Journal of Korean Institute of Communications and Information Sciences, volume 18, issue 12, 1993, Pages 2001~2012
The addition of ISDN function in an exiting electronic switching system results in structural changes in the user-network interfaces module. The changes may affect the performance of the system. Thus it is one of significant design consigerations not to cause the performance degradation of the system. In order to estimate the prospective performance of the interface module for the ISDN function to be implementation on TDX-IB switching system, the effect of the ISDN user-network interface on the system performance is analyzed to the satisifcation of the goal using an analytical method. And the performance of the proposal system is also analyzed by the measurement using ISDN call simulations, followed by the comparision with the existing system.