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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 27, Issue 12C - Dec 2002
Volume 27, Issue 11C - Nov 2002
Volume 27, Issue 10C - Oct 2002
Volume 27, Issue 10A - Oct 2002
Volume 27, Issue 9C - Sep 2002
Volume 27, Issue 8C - Aug 2002
Volume 27, Issue 8B - Aug 2002
Volume 27, Issue 8A - Aug 2002
Volume 27, Issue 7C - Jul 2002
Volume 27, Issue 7B - Jul 2002
Volume 27, Issue 7A - Jul 2002
Volume 27, Issue 6C - Jun 2002
Volume 27, Issue 6B - Jun 2002
Volume 27, Issue 6A - Jun 2002
Volume 27, Issue 5C - May 2002
Volume 27, Issue 4C - Apr 2002
Volume 27, Issue 4B - Apr 2002
Volume 27, Issue 4A - Apr 2002
Volume 27, Issue 3C - Mar 2002
Volume 27, Issue 3B - Mar 2002
Volume 27, Issue 3A - Mar 2002
Volume 27, Issue 2B - Feb 2002
Volume 27, Issue 2A - Feb 2002
Volume 27, Issue 2C - Jan 2002
Volume 27, Issue 1C - Jan 2002
Volume 27, Issue 1B - Jan 2002
Volume 27, Issue 1A - Jan 2002
Volume 27, Issue 9 - 00 2002
Volume 27, Issue 8 - 00 2002
Volume 27, Issue 3 - 00 2002
Volume 27, Issue 12 - 00 2002
Volume 27, Issue 11 - 00 2002
Volume 27, Issue 10 - 00 2002
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Selective Power Control considering Transmission Rate Adaptation for a Multimedia CDMA system
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 559~568
In this paper, we studied on combining the control of transmission fates and power for the real system where a finite set of transmission rates are used. In , the combined control of transmission rates and power was first researched, and suggested the Selective Power Control (SPC) algorithm. However, it can't guarantee the minimum rate to each user and results in frequent changes of rate due to oscillation of the SIR (Signal to Interference Ratio) values. As a main purpose of this paper, we derive a formulation model and propose a distributed iteration algorithm to solve these problems. To evaluate the performance of the proposed algorithm, we carried out numerical analysis and computational experiments. The results indicate that the proposed algorithm achieves better throughput than conventional one by keeping the low average transmission power.
A Multicarrier CDMA System Using Divided Spreading Sequence for Time and Frequency Diversity
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 569~578
This paper proposes a new multicarrier code division multiple access (CDMA) system. The proposed multicarrier CDMA system provides the advantages that the transmission bandwidth is more efficiently utilized by using divided spreading sequence, time and frequency diversity is achieved in frequency selective nultipath (acting channel, and inter-carrier interference (ICI) can be minimized by using specific data and code pattern. In this system, transmitted data bits are serial-to-parallel converted to some parallel branches. On each branch each bit is direct-sequence spread-spectrum modulated by divided spreading sequences and transmitted using orthogonal carriers. The receiver providers a Rake for each carrier, and the outputs of Rakes are combined to get time and frequency diversity. This multicarrier CDMA system allows additional flexibility in the choice of system parameters. Upon varying system parameters, bit error rate (BER) performance is examined for the proposed multicarrier CDMA system. Simulation results show that the proposed multicarrier CDMA scheme can achieve better performance than the other types of conventional multicarrier CDMA systems.
Sensitivity of Feedback Channel Delay on Transmit Adaptive Array
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 579~585
The investigation into the effect of various feedback errors on system performance can help the robust feedback channel design and transmission of exact feedback channel information as well. In this paper, we address the algorithm that determines space combining weight vector maximizing received signal power at mobile on frequency flat fading channel and investigate the performance degradation by feedback channel delay in the FDD/CDMA systems employing transmit beamforming. We observe the effect of feedback channel delay corresponding to the number of transmit antennas and the temporal/spatial correlation of channel. The results show that performance is more sensitive to feedback delay with the larger number of antennas when fadings at transmit antennas are not spatially correlated.
Performance-based Channel Scheduler for AMC/TDM Wireless Network System
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 586~592
In this paper, new channel scheduling algorithms which reduce transmission delay caused by wireless network are proposed in AMC/TDM wireless data communication. The concept of the Proposed algorithms is based on the proportional fairness, M-LWDF, and performance-guaranteeing algorithm proposed by Xin Liu. The proposed algorithm can be applied to QoS guaranteeing services as well as best-effort services. Simulation results show that new algorithm reduced transmission delay upto 11.5% in case of proportional fairness algorithm and also decreased transmission delay unto 9% in case of M-LWBF algorithm.
Characteristics of the Required Signal Power for Multimedia Traffic in CDMA Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 593~600
The reverse link signal power required for multimedia traffic in multipath faded single-code (SC-) and multi-code CDMA (MC-CDMA) systems is investigated. The effect of orthogonality loss among multiple spreading code channels is herein characterized by the orthogonality factor. The required signal power in both the CDMA systems is then analyzed in terms of the relative required signal power ratio of data to voice traffic. The effect of varying system parameters including spreading bandwidth, the of orthogonality factor, and the number of spreading codes are examined. Analytical results show that MC-CDMA users transmitting only a single traffic type require significantly more power than SC-CDMA users with only a single traffic type. On the other hand, MC-CDMA users transmitting multimedia traffic require power levels approximately identical to SC-CDMA users with multimedia traffic. The results can be used in the design of radio resource management (e.g., power allocation) scheme for wireless multimedia services.
Multipath Searcher for W-CDMA System
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 601~609
In multi-path wireless channels with time-variant delay profile, a mobile station measures the received signal strength and report it to network which performs network control function such as handover. In order to improve the maximum ratio combining (MRC) gain, it also should search the strongest signal paths and measure their time offsets fast and exactly. This paper proposes some methods of fast and exactly measuring the multi-path signal strength and time offset. Since the W-CDMA system adopts antenna diversity technique for the next generation high speed packet access (HSDPA) service, we derive the optimum design parameter values for the proposed methods through computer simulations under the HSDPA conditions o( low speed of mobile, of no power control, and of multi-path wireless environment with transmit and receive antenna diversity. Finally, we prove the validity of the proposed methods by showing the improvement of the bit error rate (BER) performance.
Vector Quantization for Optimum Quadrature Amplitude Modulated Signals in Rayleigh Fading Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 610~615
This paper considers a communication system consisting of a vector quantizer with selected code vectors with mapped into points in the modulated signal space. The modulated signal is transmitted over a Rayleigh flat fading channel. We optimize the modulated signal constellation to minimize the overall distortion of the system with the fixed vector quantization codebook. The optimization is obtained by partitioning the modulated signal space. Simulation results show that the signal constellation based on the proposed optimization scheme outperforms the conventional methods.
TT&C security algorithm of satellite based on CBC-MAC
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 616~624
In satellite communication, which use the satellite, the protection of TT&C channel which controls the position, performance, and operation is required. In this thesis, we analyzed the weakness of authentication algorithm which is used for protection of TT&C generation and operation. Also, we proposed the authentication algorithm which complements key recovery attack structurely without increasing additional computational amount and verified its performance. The proposed authentication algorithm can satisfy Rivest's recommendation by increasing the computational complexity from
operations. In addition, it can be applied to the existing satellite system because the length of TT&C data and message authentication codes used for the input of authentication algorithm are unchanged.
Decision Feedback Demodulation-based Adaptive Equalizers for DDPSK Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 625~637
This study extends the modified linear feedback equalizer (MLFE), normally used for differentially coherent DPSK systems, to the equalization of double differentially coherent PSK (DDPSK) signals. By feeding back into the feedback part after modifying the equalizer output using decision feedback-based demodulation, the proposed equalizer can operate like an equalizer with a decision feedback structure. Simulation results showthat performances of the decision feedback demodulation-based feedback equalizer (DFD-FE) approach those of the DFE/coherent.
New blind adaptive algorithm using RLS algorithm
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 629~637
RLS a1gorithm is a kind of the adaptive a1gorithms in smart antennas and adapts the weight vector using the difference between the output signal of array antennas and the known training sequence. In this paper, we propose a new algorithm based on the RLS algorithm. It calculates the error signal with reference signal derived from blind scheme. Simulation results show that the proposed algorithm yields more user capacity by 67∼74% than other blind adaptive algorithms(LS-DRMTA, LS-DRMTCMA) at the same BER and the beamformer forms null beams toward interference signals and the main beam toward desired signal.
Three-Dimensional Image Display System using Stereogram and Holographic Optical Memory Techniques
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 638~644
In this paper, we implemented a three dimensional image display system using stereogram and holographic optical memory techniques which can store many images and reconstruct them automatically. In this system, to store and reconstruct stereo images, incident angle of reference beam must be controlled in real time, so we used BPH(binary phase hologram) and LCD(liquid crystal display) for controlling reference beam. The reference beams are acquired by Fourier transform of BPHs which designed with SA(simulated annealing)algorithm, and the BPHs are represented on the LCD with the 0.05 seconds time interval using application software for reconstructing the stereo images. And input images are represented on the LCD without polarizer/analyzer for maintaining uniform beam intensities regardless of the brightness of input images. The input images and BPHs are edited using application software(Photoshop) with having the same recording scheduled time interval in storing. The reconstructed stereo images are acquired by capturing the output images with CCD camera at the behind of the analyzer which transforms phase information into brightness information of images. In output plane, we used a LCD shutter that is synchronized to a monitor that display alternate left and right eye images for depth perception. We demonstrated optical experiment which store and reconstruct four stereo images in BaTiO
repeatedly using the proposed holographic optical memory techniques.
Efficient Optical Wavelength Allocation Algorithms for WDM Ring Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 27, issue 6B, 2002, Pages 645~651
This thesis describes two wavelength allocation algorithms applied to OMS (Optical Multiplex Section) or OCh (Optical Channel) SPRING (Shared Protection Ring) and compares their characteristics by simulations. Two wavelength allocation algorithms are optimal algorithm and nonblocking algorithm applicable on SPRING WDM networks. In particular, when a node is added in previous ring network, how to work for each algorithm is considered. The optimal algorithm is better than nonblocking for most of comparisons. Nonblocking algorithm has an important advantage, though. Nonblocking algorithm has no wavelength connection or allocation to reconfigure some previous connections.