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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
The Journal of Korean Institute of Communications and Information Sciences
Journal Basic Information
Journal DOI :
The Korean Institute of Communications and Information Sciences
Editor in Chief :
Kyung-Hi Chang / Song Chong / Jong-Taek Oh / Jae-Jin Lee / Myung-Sik Yoo
Volume & Issues
Volume 23, Issue 9A - Sep 1998
Volume 23, Issue 8 - Aug 1998
Volume 23, Issue 7 - Jul 1998
Volume 23, Issue 6 - Jun 1998
Volume 23, Issue 5 - May 1998
Volume 23, Issue 4 - Apr 1998
Volume 23, Issue 9 - 00 1998
Selecting the target year
Performance analysis of cache strategy for signaling traffic management in wireless ATM network
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1639~1649
For mobile multimedia services, wireless ATM(Asynchronous transfer Mode) network is studied actively. In wireless ATM network, the existing signaling protocols generate heavy traffics for HLR due to the centralized structure that all signaling loads mush be handled in HLR(Home Location Register). Also, centralized structure causes critical connection setup delays. Thus, it is important that wireless ATM reduces the connection setup delays occurred due to high traffic loads of signaling based on distributed processing. In this thesis, we propose a cache strategy for call delivery as well as the cache updates of registration based on ATM multicasting and compares the cost of cache scheme with that of conventional scheme. Our study shows that cache scheme has better performance than the conventional methods in the case that the portable mobility is low and traffic density is large.
Adaptive echo canceller combined with speech coder for mobile communication systems
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1650~1658
This paper describes how to remove echoes effectively using speech parameter information provided form speech coder. More specially, the proposed adaptive echo canceller utilizes the excitation signal or linearly predicted error signal instead of output speech signal of vocoder as the input signal for adaptation algorithm. The normalized least mean ssquare(NLMS) algorithm is used for the adaptive echo canceller. The proposed algorithm showed a fast convergece charactersitcis in the sinulatio compared to the conventional method. Specially, the proposed echo canceller utilizing the excitation signal of speech coder showed about four times fast convergence speed over the echo canceller utilizing the output speech signal of the speech coder for the adaptation input.
An Improvement on Multicode CDMA Systems Using a Convolutional Code and a Bi-Orthogonal Code
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1659~1666
The multicode CDMA systems that are widely studied as an effective transmission methodology in the IMT-2000 systems, employ orthogonal codes to transform high rate data into parallel, low rate data for simultaneous transmission. In this paper, we propose a new multicode CDMA system which achieves the same data rate and processing gain of the conventional systems, while significantly improves bit error rate performance by exploiting a convolutional code with code rate r=1/2 and a bi-orthogonal code. The simulation results for synchronous systems using maximal ratio combining Rake receivers under additive white Gaussian noise and multi-path fading channels, show significant improviements by the proposed system.
A new structure and algorithm for adaptive MMSE receivers in fading environments
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1667~1676
It is known that adaptive minimum mean square error (MMSE) receivers exhibit better performance than coventional single-user code division multiple access (CDMA) receivers in fixed (or static) channels and have the simple structure compared to other multi-user CDMA receivers. In practice, the radio channels are fading channels where the amplitude and phase of the received signal are time-varying and the sufficient signal-to-noise ratio is not always guaranteed. Thus, the performance of adaptive MMSE receivers is severely degraded in fading environments. We propose a new structure and adaptation algorithm for an adaptive MMSE receivers. Based on computer simulation results, it is observed that the proposed receiver demonstrates substantial performance improvement over currently available adaptive MMSE receivers in fading environments.
Analysis on the interference reduction by smart antenna in CDMA reverse channel
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1677~1688
In this paper, we analyze the performance of a DS-CDMA system employing adaptive adaptive array antenna technology at base-station. For the analysis the receiving architecture of a multiple team adaptive base-station array antenna is proposed as a major system omponent, and signal to interference and noise ratio(SINR) on the proposed architecture is developed. We show that the perfomance enhancement of the CDMA system is represented as great reduction of interfreence by employing an array antenna capable of resolving the angular distribution of the mobile users as seen at the ase-station. The energy associated with each mobile or a group of mobiles is thus confined within the addressed volume, greatly reducing the amount of co-channel interference experienced from and by neighboring co-channel cells. In order to ascertain the benefits of such an antenna, a theoretical approach, which eis based on the conventional and proposed antenna systems in a typical mobile radio environment, is adopted. Finally computer simulation results show the insight into how the adaptive array antenna operates when used in conjunction with DS-CDMA and illustrate the potential benefits in the SINR point of view.
Analysis of Transient Signal Using Autocorrelation-like Matrix
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1689~1698
In this paper, we present a new method for estimating the parameters of transient-type signal in additive white Gaussian noise. This method makes use of the truncated singular value decomposition of an extended-order auto-correlation-like matrix based on the linear-prediction model. The method is tested on data consisting of two exponentially dampled sinusoidal signals with the same damping factor and different damping factor. Simulation results are illustrated to demonstrate the better performance of the method applied to the auto-correlation-like matrix than that applied to the data matrix.
Detection technique for code acquisition in DS-SS systems employing PN matched filters
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1699~1706
This paper presents a threshold decision technique for direct sequence code acquistion employing Pseudo-Noise(PN) matched filter. The probabilities of detection and false alarm are derived as a measure of the system performance in both nonfading and nonselective Rician fading channels. For received PN codes with different SNR, the proposed acquisition scheme is able to detect a desired threshold in the search mode so that this value is utilized as a threshold for the verification mode. Thus, there is no need to determine a threshold by applying the Neyman-Person ciriteron. It is shown that this scheme achieves lower probability of false alarm than the acquisition scheme based on the Neyman-Person criterion, giving comparable performance in terms of the probability of detection.
Polyphase jammer suppression on DS-CDMA forward link using multi-rate techniques
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1707~1717
Polyphase filtering techniques is used to suppress the narrowband jammer signal such as USDC TDMA overlaying the band occupied by DS-CDMA system. In the proposed jammer suppression, the received signal is separated into 64 subchannels in two stages by polyphase filtering and the location of the narrowband jammer signal is determined by measuring each subchannel power and the contaminated subchannels are simply blocked. The
0/ improvement of the CDMA system from jammer suppession was outstanding. The
degradation in comparison with a performance of no jammer is around 0.8dB in the worst case. The results are also compared with those of linear prediction jammer suppression. The implementation of the ployphase jammer suppression requires great amount of data processing and computation compared to linear predication filter. Thus it is more appropriate to implement with a ASIC rather than WITH several DSPs for user terminals of forward link.
VLSI Implementation of CORDIC-Based Digital Quadrature Demodulator
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1718~1731
Digital quadrature demodulator is needed for the coherent demodulation in the digital communication systems such as Binary Phase-Shift-Keying, Quadrature Phase-Shift-Keying, and Quadrature Anmplitude Modulation. Conventaionally, the DDFS (Direct Digital Frequency Synthsizer) is used for generating the carrier signal and seperate multi-pliers are used for mixing. And the DDFS is implemented using the ROM (Read Only Memory), which can be a bottle-neck neck when the fast-speed and small-area implementation is required. A new architecture is developed, which employs the circular rotation mode of the CORDIC algorithm for signal mixing as well as carrier generation. To optimize the hardware design parameters, the finiteword-length effects of the proposed implementation arachitecture are analyzed in comparison with a conventional ROM-based architecture. The hardware costs are also estimated, which showed that the proposed architecture occupies only a third of the area of the conventional ROM-based architecture for the same performance. A full-custom VLSI is developed using the proposed architecture.
Dynamic prioritized channel assignment for multiple traffic classes in a overlay-cell structure
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1732~1743
In this paper, we have proposed a channel assignment shceme for the multiple traffic class environment where the traffic volume varies with time. Our basic idea is to assign radio channels considering the characteristics of each traffic class and mobile speed and change the number of allocated channels for each traffic class according to vaiation of traffic volume. To evalute the perfomance of our proposed algorithms, we conducted analyical and simulation studies. We derived new call blocking probability and hand-off failure probability of the proposed scheme analytically. The simulatioh results show that our proposed algorithms can grantee GOS of each traffic class and provide a fairness between the new call and the hand-off call.
Performance Analysis of Interworking Protocol for Efficient Mobile Data Service
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1744~1754
In this paper, the data service protocol which could support data service more efficiently between mobile host and fixed host in wire network is investigated. Wireless link has high bit error rate compared with wire link. Therefore, TCP performance for the data service is degraded in wire and wireless interworking environment. Thus, to reduce performance degradation. Interworking module withsimple protocol processing function is proposed. This, interworking module analyzes the hearder information of TCP fram. If received TCP freame is a duplicated frame, TCP frame is discared. Also, if interworking moudule receives retransmission request frame is a duplicated frame, TCP freme is discarded. Also, if interworking module receives retansmission request frame, interworking module performs retransmission procedure. According to simulation results, the proposed IWF shows better performance than traditional IWF in view of delay and throughput in the wire and wireless interworking environments.
Estimation of Rain-Attenuation for Millimeter-Wave Propagation in Domestic Environments
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1755~1763
The rain attenuatio of a radio channel above 10 GHz can have impact on the availability of the radio channel. The severity of the rain impairments increases with frequency and varies with regional location. This paper presents an estimation method for rain attenuation for millimeter-wave propagation in domestic environments. the dropsize distribution is assumed to be exponential, and the measurement data in the various countries which are simlar to the domestic environments are compared with the theoretical one by varying the dropsize distribution. A rain-rate conversion model which can convert .tau.-minutes rain-rate data to 1-minute rain-rate data for domestic environments is also discussed. Using the converted domestic rain-rate data, probabilty distributions of rain attenuation are computed.
A General Rigorous Analysis of Arbitrary-shaped Multiaperture-coupled Directional Coupler Between Two Dissimilar Rectangular Waveguides Crossing with an Arbitrary Angle
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1764~1769
The FE-BI (finite element- boundary integral) method is used for the characterization of an arbitrary-shaped multiaperture-coupled directional coupler between two retangular waveguides crossing with an arbitrary angle. The method is shown to be much more effective than the ordinary FEM for the structures under consideration. the computation time is compared with that of the ordinary FEM. The results of other papers for Moreno coupler are compared with the theoretical prediction and a good agreement is obtained.
Design and fabrication of rectangular waveguide-to-microstrip transition at Ka-band
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1770~1776
This paper presents a waveguide-to-mircostrip transition at Ka-band using antipodal finlines. Critical design parameters were identified with the help of theoretical analysis. Experimental optimization was performed together with 3-D FEM analysis in an effort to find optimum dimensions of the transition. In addition to the conventional antipodal finline transition, a new dielectric impedance transformer was introduced to further reduce the insertion loss. Optimized waveguide-to-microstrip transition showed an insertion loss of 0.3~0.4dB/transition at Ka-band. This transition provides superior reproducibility and better performance than conventional coaxcable-to-microstrip transition.
Packet Error Rate Characteristics of an Optical Packet Switching Node with an Optical Packet Address Processor Using an EDFA Preamplifier
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1777~1784
The packet error rates of an optical packet switching node with an optical address processor using an EDFA in order to detect M-ary correlation pulses at a fiber-optical delay line matched filter output have been evaluated. Effects of A PIN diode NEP, the gain and noise figure of the EDFA, and the bandwidth of an optical filter on the packet error rate of the switching node have been compared. There is negligible error rate change depending upon the variation of the PIN diode NEP and the EDFA gain. If the bandwidth of the optical filter is below 10 times of the data rate, there is no appreciable effect on the error rate. If the noise figure of the EDFA increases, however, the power penalty increases as much as the noise figure increment at all the bit rates and for address code sets considered in this work.
Relationships between optimal number of wavelenghs and tuning time in WDM/TDM passive star network
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1785~1796
This paper is concerned with the relationships between optimal number of wavelengths and tuning time in time division multiplexing(TDM) scheduling on wavelength division multiplexing(WDM) optical passive star networks. We assume that the traffic is nonuniform and each node has a tunable transmitter and a fixed receiver. Each node transmits spckets to all other nodes. Most of the earlier protocols on TDM based scheduling for WDM star networks [7, 8, etc.] use whold given wavelength chnnels. But in this paper, we investigate the optimal number of wavelengths that yidels minimum frame length when tuning time exists. It appears within the availble number of wavelengths that yields minimum frame length when tuning time exists. It appears within the available number of wavelengths. We analyze the relationships between optimal number of wavelengths and tuning time by experiments. We analyze the reationships between optimal number of wavelengths and tuning time by experiments. We also discuss on the possibility of reduction of frame length by increasing the number of nodes trans-mitters and receivers.
The study on the capacity of synchronous CDMA return link for a Ka band satellite communication system
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1797~1806
Future satellite communication systems will be developed at Ka-band (20/30 GHz) owing to the relatively wide frequency allocation and current freedom from terrestrial interference for multimedia services. A serious disadvantage of the Ka-band, however, is the very high atmospheric attenuation in rainy weather. Synchronous CDMA drastically redces the effect of self-noise with several interesting features of CDMA for mobile communications such as fixible freuqncy rese, the capability of performin soft-handover and a lower sensitivity to interference. This paper evaluates the performance of a synchronous CDMA reture link for a Ka-band geostationary satellite communication system. For a fixed satellite channel whose characteristics depend on weather conditions, the signal envelope and phase for this channel is modelled as Gaussian. The bit error and outage probability, and the detection loss due to imperfect chip timing synchronization is analytically evaluated and the system capacity degaradation due to the weather condition is estimated. The two cases consist of the general case in which all users are affected by rain condition, and the worst case in which the reference user is only affected by rain attenuation. the results for two cases of rain condition clearly show that synchronous CDMA eases the power control requirements and has less sensitivity to imperfect power control.
Interference Probability Calculation of Frequency Sharing Between Non-Geostationary-Satellite Orbit Mobile Earth Station and Land Mobile Station
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1807~1816
The interference probability between non-geostationary-statellite orbit mobile station is calculated when the two systems are sharing the frquency band below 1 GHz. The probability density function of a mobile earth station(MES) is calculated based on the established propagation model and then, a probability of exceeding the threshold level is derived. By changing the average transimission per unit time of total MSS(Moblie satellite service) area and the ratio of transmitters for specific area, we obtain the average transmission per unit time for the area under consideration. From this, the exceedance probability for the given pfd threshold level is evaluated. The exceedance probability is increased as the average transmissio per unit time and ratio become larger. Also the effect of filter isolation between channels is accounted for.
Data compresson for high speed data transmission
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1817~1823
V.42bis, a type of LZW(Lempel-Ziv-Welch) code, is well-known as theinter national standard is asynchronous data compression. In this paper, we analyze several undesirable phenomena arising from the application of v.42bis to high speed data transmission, and we propose a modified technique to overcome them. the proposed technique determines the proper size of the dictionary, one of important factors affecting the compression ratio, and improves the method of dictionary generation for a higher compression ratio. Furthermore, we analyze the problem of excessive mode changes and solve it to a certain degree by adjusting the threshold for mode change. By doing this, we can achieve smiller variation of the compression ratio in time. This improvement chtributes to easier and better design and control of the buffer in high speed data transmission.
Noise Reduction Characteristics of A Modulated Orthogonal Sequence Under Weak-Signal Communication Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1824~1830
In this paper, we investigate a noise reduction scheme, based on the inherent characteristic of an orthogonal sequence. The modulated orthogonal code generates sequences of length
from N information symbols. Using the amplitudes of the received symbols, we first estimate the location of the smallest amplitude noise. Then the noise is reduced by the suggested system. The performance of the scheme is confirmed by computer simulation results.
An error control scheme based on selective retransmission for transmission control real-time communication
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1831~1839
A priority control algorithm using hop count for streamming mode CLS
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1840~1850
In this paper, we propose a priority control algorithm using hop count, called HC-PC(Priority Control Algorithm using Hop-Count) for steaming mode CLS, in wide area ATM networks. In our HC-PC algorithm, hop count of packet is increased by one as traverse CLS hop and is used as loss priority when a CLS buffer is congested. That guards packets with higher priority form congestion. The average packet loss probabilities are evaluated via mathematical analysis for HC-PC algorithm case and no priority control case. The simulationresults indicate that our algorithm may offer better performance in terms of loss fairness for pathe length and yield high utilization of newtork resource.
Extending the Password-based Authentication Protocol K1P
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1851~1859
We summarize the password-based authetication protocol K1P which was introduced in our easlier papers [1,2] and then propose three more extended protocols. These protocols preserve a design concept of K1P, i.e., security and efficiency, and canbe used for various purposes. They are a One-time key K1P, a Client public key K1P, and an Exponential key exchange K1P.
Blocky artifacts reduction by step-function modeling in DCT coded images
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1860~1868
A simple postprocessing algorithm is proposed to reduce the blocky artifacts of Block Discrete Cosine Transform (BDCT) coded images. Since the block noise is mostly antisymmetric relative to the block boundaries, we model the blocky noise as one-dimensional antisymmertric functions made by superposing DCT basis functions. observing the frequency characteristics of the noies model, we approximate its high frequency components as those of step functions. Then the proposed postprocessing algorithm eliminates the carefully selected high frequency components of step functions in the one-dimensional sN-point DCT domain, when the encoding block size is
. It is shown that the proposed algorithm can also be performed in the spatial domain without computational burden of transforms. The experimental results show that the proposed algorithm well reduces the blocky artifacts in both subjective and objectie viewpoints.
A convergence analysis of a differential method for 2-D motion parameter estimation
The Journal of Korean Institute of Communications and Information Sciences, volume 23, issue 7, 1998, Pages 1869~1882
In this paper, we investigae convergence behaviors of a differential method for 2-D motion parameter estimation. While the differential method is widely studied for motion compensated prediction in video coding, little attention hs been paid to its convergence properties. Based on the nonseparable exponential covariance image model, we derive the estimates of update terms for the 2- and 6-parameter motion models. And, the effect of noise, spatial correlation, choice of spatial gradient measures, andthe size of a region, are quantitatively anlyzed in relation to the convergence speed. Some empirical results are presented to verify the analysis.