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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 26, Issue 12C - Dec 2001
Volume 26, Issue 12B - Dec 2001
Volume 26, Issue 12A - Dec 2001
Volume 26, Issue 11C - Nov 2001
Volume 26, Issue 11B - Nov 2001
Volume 26, Issue 11A - Nov 2001
Volume 26, Issue 10B - Oct 2001
Volume 26, Issue 10A - Oct 2001
Volume 26, Issue 9B - Sep 2001
Volume 26, Issue 9A - Sep 2001
Volume 26, Issue 8B - Aug 2001
Volume 26, Issue 8A - Aug 2001
Volume 26, Issue 7B - Jul 2001
Volume 26, Issue 7A - Jul 2001
Volume 26, Issue 6B - Jun 2001
Volume 26, Issue 6A - Jun 2001
Volume 26, Issue 5B - May 2001
Volume 26, Issue 5A - May 2001
Volume 26, Issue 4B - Apr 2001
Volume 26, Issue 3B - Mar 2001
Selecting the target year
Characteristics of Impulse Radios for Mu1tipath Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1501~1509
Recently, the use of wireless communication systems has been rapidly increasing, which results in a difficult problem in efficient control of limited frequency resources. As a way of solving this problem, the ultra wideband time hopping impulse radio system attracts much attention. The impulse radio system communicates pulse position modulated data using Gaussian monocycle pulses of very short duration less than 1 nsec. Thus the transmitted signal has very low power spectral density and ultra wide bandwidth from near D.C. to a few GHz. It is blown that it hardly interferes with the existing communication systems because of its very low power spectral density. The purpose of this paper is to characterize multipath propagation of the impulse radio signal and to evaluate the performance of the correlator-based receiver for the multipath environments. In this paper, we consider the deterministic two-path model and the statistical indoor multipath model of Saleh and Valenzuela. For the two-path model the output of the correlator with the ideal reference waveform varies according to the relative difference between the indirect path delay and the time interval of PPM, and to the indirect path gains. In addition, the characteristics of bit error rates is measured for the two models through computer simulation. The simulation results indicate that the performance of the impulse radio system depends both on the relative difference between the indirect path delay and the time interval of PPM, and on the indirect path gains. Furthermore, it is observed that the reference signal designed for the AWGN channel can not be applied to the multipath channels.
A Subspace-based Blind Interference Cancellation for the DS/CDMA System
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1510~1521
In this paper a subspace-based blind interference cancellation is proposed and its performance is analyzed. Then the blind adaptive implementation is devolped using the improved natural power method which is the signal subspace tracking algorithm. The theoretical analysis shows that when the exact covariance matrix is kown the performance of the proposed detector is the same as that of the decorrelating detector. And when the covariance matrix is estimated the asymptotic results are examined. The results of computer simulation demonstrate that the proposed detector outperforms the previous blind adaptive RLS MOE detector.
Performance Evaluation for Fast Closed-Loop Power Control of cdma2000 Forward Link in frequency-Selective Rayleigh Fading Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1522~1533
In this paper, we handle the estimation method of the received
for forward closed-loop power control in cdma2000 systems. The estimation of MS-received
utilizes the symbols related to the forward power control subchannel transmission. The estimation of the received bit energy and noise variance is analyzed for the frequency-selective Rayleigh fading channel. In order to improve SIR (signal-to-interference), the estimation of the received bit energy is made by the coherent combining of the rake-fingers and received I/Q symbols. And, in this paper, we evaluate the performance of forward closed-loop power control according to the mobile speed and the power adjustment step size in terms of the bit error rate (BER) and power control error. Simulation results present the optimal power adjustment step sizes according to the mobile speeds.
Effects of soft handoff region ratio on the reverse link capacity of a DS-CDMA cellular system
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1534~1539
In this paper, effects of soft handoff region on the reverse link capacity of a DS-CDMA cellular system are investigated. The reverse link capacity of a CDMA cellular system is calculated at a given soft handoff region ratio (SHRR) and path loss model. The results show that the reverse link capacity increases by 1 ∼ 4 channels according to the soft handoff region ratio and the path loss model. However, in the case of the path loss model having a large attenuation exponent (
= 5) and a small shadowing standard deviation (
= 6 dB), the reverse link capacity is no more increased by increasing SHRR.
Effect of Orthogonal Spreading on the Performance of Multipath Faded Multi-Code CDMA Systems
Kang, Chang Soon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1540~1545
This paper is concerned with the reverse link performance of multi-code CDMA systems in multipath fading environments. The degree of orthogonality loss among multiple spreading code channels is characterized as the orthogonality factor. It depends on various system parameters including multipath power profiles of propagation channels and the number of Paths resolved at a Rake receiver. The effect of the parameters on the system performance is then investigated in terms of bit error rate and required signal quality. The results show that multipath delay power profiles dominantly affect mutual interference among multi-code channels and multipath combining gain by bandwidth expansion is not so great due to the increase of the mutual interference. Moreover, the orthogonality factor is derived as the value of between (1/m) and 1.
Analysis of W-CDMA systems with different bandwidths over JTC channel model
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1546~1555
Conventionally, in a CDMA system analysis, we assume only a single path within one chip duration. But, in this paper, we assume various number of multipaths within one chip duration according to spreading bandwidth in fixed channel model. Thus we take into account of the effects of autocorrelation and relative phases among multipath components within one chip duration according to different bandwidth, and analyze fading effects. And we derive the pdf of output signal. Then, we derive the average error probability versus the number of users from derived pdf. We use a Maximal Ratio Combining (MRC) RAKE receiver under the JTC channel model which is one of the popular realistic wideband channel models. And we employ hybrid FDMA/CDMA systems to compare the performance of W-CBMA system for the same occupied total bandwidth. Then, we compare and analyze them for different bandwidth based on the number of users as a parameter. From the simulation results for different bandwidth, better performance can be obtained for wider bandwidth system where more resolvable multipath components are available.
Analysis of BER in Slow Frequency-Hopping System with False Alarm and Miss in Side Information
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1556~1564
Reed-Solomon code, block interleaving and SI (side information) are frequently used in SFH (slow frequency hopping) system. Erasing those symbols in the hit frequency slot greatly increases the error connection capacity. Packet error rate has been the major performance measure for SFH system. The analysis of BER has been limited to the case of perfect Sl, in which neither miss nor false alarm exists. BER with imperfect Sl has been obtained only by Monte Carlo simulation. In this paper, we present a unified solution to estimate BER with imperfect Sl. It is shown that previous formulae for packet error rate or BER with perfect Sl are special cases in the proposed solution. The computed BER with false alarm and miss of frequency hit is verified by comparing with the simulation result.
Design of Carrier Recovery Loop for Receiving Demodulator in Digital Satellite Broadcasting
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1565~1573
In order to resolve problems according to the phase error in QPSK demodulator in the digital satellite broadcasting, the demodulator requires carrier recovery loop which searches for the frequency and phase of the carrier. In this paper the drawback of NCO of the conventional carrier recovery loop is to wastes a amount of power for the structure of Look-up table , we designed the structure of combinational logic without the Look-up table. In the comparison with dynamic power of the proposed NCO, the power of NCO with the Look-up table is 175[
W], NCO with the proposed structure is 24.65[
W]. As the result, it is recognized that loss power is reduced about one eighth. In the simulation of carrier recovery loop designed QPSK demodulator, it is known that the carrier phase is compensated.
A Study on Technique for Synchronization Error Calibration of Standard frequency & Time Signal Dissemination System via KoreaSAT
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1573~1582
In this paper we analyze the main resources of error in GEO-satellite STFS(Standard Time & frequency Signal) dissemination system. For the case of small countries like Korea, we compare GEO-satellite STFS dissemination technique with the terrestrial network or with the GPS using LEO-satellites, and analyze its advantages over the forementioned systems. We also introduce the GEO-satellite STFS dissemination systems which are being developed or in service. Particularly, we put much efforts to develop the synchronization error calibration technique required to provide a highly accurate STFS service via KoreaSAT. We then propose the differential mode technique as the most effective and efficient calibration technique for mitigating errors in GEO-satellite STFS dissemination systems, and analyze its performance via computer simulation. We also analyze the relation between time accuracy and frequency accuracy. Our experimental results show that the time accuracy is better than 100 ns and the frequency accuracy is better than 10-13 over 7 days all around Korea peninsula. Finally, we propose methods to improve the performance of STFS dissemination system, and demonstrate that the proposed methods result in more accurate synchronization of GEO-satellite STFS.
Random access method for radio interface specification of IMT-2000 satellite component
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1583~1594
In this paper, the transmission structure and procedure of a random access channel for the IMT-2000 satellite radio specification are presented. The proposed random access method has much commonality with that of the 3GPP FD specification which is a terrestrial radio interface of IMT-2000. The proposed method was designed by considering characteristics of satellite link as we71 as the commonality with the terrestrial component. A preamble consists of sub-preamble repetition and a message is transmitted along with the preamble successively. The propose method has fast indication of preamble acquisition by physical layer. The proposed method has been included in the SAT-CDMA which is a radio transmission technology Proposed by TTA, KOREA and approved as a satellite radio interface at ITU-R. Additionally, in this Paper the signaling delay for the proposed random access channel will be analyzed and it will be compared to that of the random access methods using a conventional ALOHA procedure and the 3GPP procedure in aspect of the signaling delay. When the SAT-CDMA satellite constellation at the height of about 1600 km is considered, the delay of the proposed method was estimated to 100 ms less than that of the conventional ALOHA. This delay difference increases with 7he number of retransmissions. The delay is reduced by 30 ms, compared with the 3GPP method.
Design And Implementation Of ASK Modulator MMIC Operating At 5.8 GHz
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1595~1599
In this paper, we have desired and implemented of ASK modulator MMIC operating at 5.8 GHz for OBE used in AGPS(Automatic Gate Passing System). The proposed ASK modulator MMIC was implemented to apply a single supply voltage of 3 V to the drain in order to decrease ACP(Adjacent Channel Power). As a result, it is exhibits a broad linear modulation range from 0.7 V to 3 V and an On/off characteristic over 40 dB. The layouts of ASK modulator MMICs was designed and fabricated by using ETRI 0.57m MESFET library The chip size was 1.0mm
Resonant Frequency in Rectangular Microstrip Patch Antenna on Anisotropic Substrates with Airgap and Permittivity Superstrate
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1600~1606
Resonant frequency in rectangular microstrip patch antenna on anisotropic substrates with airgap and superstrate are analyzed. Dyadic Green function is derived for selected anisotropic material by constitutive relation. From these results, integral equations of electric fields are formulated using Fourier transform in space region. The electric field integral equations are discretized into the matrix form by applying Galerkin\`s moment method. Sinusoidal functions are selected as basis functions because they resemble in the actual standing wave on the patch. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the resonant frequency in the variation of air gap, patch length and anisotropy ratio are presented and analysed.
High Speed RZ-Format Transmission Using Very Short Pulses and the Chromatic Dispersion of the Transmission Fiber
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1607~1611
The dependence of the performance of 40-Gb/s optical transmission using short pulses on the fiber chromatic dispersion is numerically studied. When very short pulses are used, the wide spectrum of the optical signal and the chromatic dispersion of the fiber interact in such a way that results in the reduction of nonlinear impairments of the transmission performance. The degree of this reduction is determined by the combined effects of chromatic dispersion of the fiber and the strength of the optical signal and the transmission distance. When 3ps-long pulses were used for the transmission, the eye-closure penalty was highest with the dispersion D=4ps/nm/km.
Design of ISM-band Folded Dipole Active Integrated Antenna
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1612~1619
This paper examines the design, implementation characteristics of a folded dipole active integrated antenna. Our goal was to minimize the physical size of RF circuit and its insertion loss, and to make the high frequency tuning easier by directly integrating the ISM(Industrial Scientific & Medical) band power amplifier and antenna. Non-linear model has been used for highly accurate simulation of the power amplifier. The maximum power level was found by using the Load pull method before an impedance matching was achieved. It is found that the total power-added efficiency(PAE) including the driving amplifier was 31.5% and that the transmit power was 13.7 dBm. We also found that the proposed scheme with the smaller antenna as compared with the existing dipole antenna has 23.7 dB total gain including the antenna gain. The suppression of the second harmonic signal to the fundamental signal with respect to the fundamental signal was found to be more than 30 dBc.
A Broadband Microstrip Array Antenna for PCS/IMT-2000 Base-Station
The Journal of Korean Institute of Communications and Information Sciences, volume 26, issue 11B, 2001, Pages 1620~1627
In this paper, a broadband microstrip antenna for PCS and IMT-2000 service is designed. To obtain the broadband characteristics of an antenna, we utilized the multi-layered structure composed of two foam material layers, parasitic element and aperture coupled feeding network. The broadband characteristic is obtained by changing the size of parasitic element and the height of foam materials. In addition to that, the usage of metal layer at the distance of λ/4 from feed-line, back radiation is reduced. The bandwidth of a single element for VSWR less than 1.3 is about 550MHz. The bandwidth of a designed 1
4 array antenna for VSWR less than 1.3 is about 460MHz. The gain of a designed array antenna is about 11.15∼12.15dBi and the front-to-back ratio is about 30dB.