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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 29, Issue 12C - Dec 2004
Volume 29, Issue 12B - Dec 2004
Volume 29, Issue 12A - Dec 2004
Volume 29, Issue 11C - Nov 2004
Volume 29, Issue 11B - Nov 2004
Volume 29, Issue 11A - Nov 2004
Volume 29, Issue 10C - Oct 2004
Volume 29, Issue 10B - Oct 2004
Volume 29, Issue 10A - Oct 2004
Volume 29, Issue 9C - Sep 2004
Volume 29, Issue 9B - Sep 2004
Volume 29, Issue 9A - Sep 2004
Volume 29, Issue 8C - Aug 2004
Volume 29, Issue 8B - Aug 2004
Volume 29, Issue 8A - Aug 2004
Volume 29, Issue 7C - Jul 2004
Volume 29, Issue 7B - Jul 2004
Volume 29, Issue 7A - Jul 2004
Volume 29, Issue 6C - Jun 2004
Volume 29, Issue 6B - Jun 2004
Volume 29, Issue 6A - Jun 2004
Volume 29, Issue 5C - May 2004
Volume 29, Issue 5B - May 2004
Volume 29, Issue 5A - May 2004
Volume 29, Issue 4C - Apr 2004
Volume 29, Issue 4B - Apr 2004
Volume 29, Issue 4A - Apr 2004
Volume 29, Issue 3C - Mar 2004
Volume 29, Issue 3B - Mar 2004
Volume 29, Issue 3A - Mar 2004
Volume 29, Issue 2C - Feb 2004
Volume 29, Issue 2B - Feb 2004
Volume 29, Issue 2A - Feb 2004
Volume 29, Issue 1C - Jan 2004
Volume 29, Issue 1B - Jan 2004
Volume 29, Issue 1A - Jan 2004
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Performance Analysis of Turbo Product Code Using Parallel Structure
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 181~186
Recently, there has been intensive focus on Turbo Product Codes(TPCs) which have low decoding complexity and achieve near-optimum performances at high code-rate. This paper present a parallel algorithm of turbo product codes enable simultaneous decoding of row and column. The row and column decoders operate in parallel and update each other after row and column has been decoded. simulation results show that the performance of proposed parallel turbo code is almost the same as that conventional scheme for several turbo product codes.
Performance Analysis of BPM UWB Multiple Access System Using PN Code Based Time Hopping Sequence in Indoor Wireless Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 187~198
In this paper, we analyze the performance of BPM (Bi-Phase Modulation) UWB (Ultra Wide Band) multiple access system using PN (Pseudo Noise) code based time hopping sequence in indoor wireless channels. In particular, we compare BPM UWB multiple access system with PPM (Pulse Position Modulation) UWB multiple access system in terms of signalling and demodulation schemes. Moreover, we analytically evaluate the performance of these UWB systems by deriving the bit error rate expressions under the assumption that pulse energy and data transmission rate are identical for both systems. Simulation results in additive white Gaussian noise and realistic indoor multipath wireless channels show that the performance of BPM scheme is approximately 1 dB better than that of PPM scheme. However, the performance discrepancy becomes negligible as the number of users increases.
UWB Channel Model Reflecting Phase Factor
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 199~205
This paper presents a method of UWB channel modeling, which includes the phase characteristics of the UWB channel. This is accomplished by decomposing a UWB pulse into several narrowband signal components. We show the ray-tracing algorithm can be used to acquire the amplitude and the phase of each signal component. Finally, it is shown that the received pulses simulated can have various shapes due to frequency-dependent reflectivity coefficient resulting from the intrinsic nature of ultra-wide bandwidth of a UWB pulse.
STF-OFDM Transmission Scheme with Frequency Diversity
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 206~212
In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. STBC(Space-Time Block Coding) has been proposed as a simple diversity scheme using two transmit antennas. Also ST-OFDM(Space-Time Block Coded OFDM) and SF-OFDM(Space-Frequency Block Coded OFDM) transmission scheme, that the STBC is applied to the OFDM, has been proposed. In this paper, we propose STF-OFDM transmission scheme that to coded in time, space and frequency domain. The STF-OFDM transmission scheme that we propose in this paper is the way to improve a performance of conventional ST-OFDM, by using frequency diversity.
An Improved Design Method of FIR Quadrature Mirror-Image Filter Banks
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 213~221
A new method for design of two-channel finite-impulse response(FIR) quadrature mirror-image filter(QMF) banks with low reconstruction delay using weighting function is proposed. The weighting function used in this paper is calculated from the previous updated filter coefficients vector which is adjusted from iteration to iteration in the design of QMF banks. In this paper, passband and stopband edge frequency are used in design of QMF banks with low delay characteristic in time domain instead of specific frequency interval where the artifacts occur in conventional design method. The investigation of specific frequency interval where artifacts occur can not be required by using passband and stopband edge frequency. Some comparisons of performance are made with other existing design method to demonstrate the proposed method for QMF bank design. and it was observed that the proposed method using the weighted function and passband and stopband edge frequency improves the peak reconstruction error by 0.001 [dB], the peak-to-peak passband ripple by 0.003[dB], SNR with a white noise by 7[dB] and SNR with a step input by 32[dB], but with a reduction of the computational efficiency because of updating the weighting function over the conventional method in Ref .
An Analysis of its Convergence Characteristics and the Adaptive Algorithm for Reducing the Computational Quantities
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 222~228
This paper describes a new adaptive algorithm which can reduce the required computation quantities in the adaptive filter. The proposed adaptive algorithm uses only the signs of the normalized input signal rather than the input signals when coefficients of the filter are adapted. By doing so, there is no need for the multiplications and divisions which are mostly responsible for the computation quantities. To analyze the convergence characteristics of the proposed algorithm, the condition and speed of the convergence are derived mathematically. Also, we simulate an echo canceller adopting this algorithm and compare the performances of convergence for this algorithm with the ones for the other algorithm. As the results of simulations, it is proved that the echo canceller adopting this algorithm shows almost the same performances of convergence as the echo canceller adopting the SIA algorithm.
Estimation of Camera Parameters for 3D-Based Synthesis from Uncalibrated Image Sequence
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 229~237
In this paper. we propose a new autocalibration algorithm. 3D-based image synthesis is roughly divided into two methods. One is using autocalibration method, and the other is using real 3D data like pattern information. The former is more progressive method. because there is no constraint or information about the scenes. Therefore autocalibration method has very difficult progress dealing with complicate non-lineal equations. Nowadays, constraints of camera intrinsic parameters are used in many researches. Therefore we solve the linear equations instead of complicate non-lineal equations. For example, to fix principal point of camera is a representative method.
Channel Estimation for OFDM Systems under Non-Sampled Space and Fast Time-Varying Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 238~246
In this paper, an estimator that take advantages of time and frequency correlation within an OFDM symbol is investigated. OFDM systems using the proposed estimator can be very effective in detecting signals under non-sampled space and time-varying channels. Also, under same complexity, the proposed estimator outperforms the previously proposed estimator. Since even if there are no assumption about channel correlation, the linear interpolation method instead of optimal interpolation using correct channel correlation is proposed in case the receiver does not know the channel correlation function in time domain. Therefore the proposed channel estimator help improving the performance of OFDM systems under non-sampled spaced and fast time-varying channels.
A BER Analysis of a Space-Time Signal Processing Scheme that Combines Transmitter Diversity and Beamforming in Correlated Fading
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 247~254
We introduce a new space-time signal processing scheme that uses both transmitter diversity technique and transmitter beamforming technique for code-division multiple access (CDMA) systems. Over complex Gaussian Rayleigh channel, the introduced scheme achieves the diveristy gain through the transmitter diversity technique. and the SNR gain by th transmitter beamforming technique. Bit error rate (BER) analyses are given to each of the three cases in which the transmitter diversity scheme, the transmitter beamforming scheme and the introduced scheme are used, in the slowly varying Rayleigh frequency nonselective fading channel. The Monte-Carlo simulation results are shown to match to the analytic results. When the channels between distant antennas are independent, analytic results show that the introduced scheme achieves the lowest
at target BER 10
. When the channels between distant antennas are correlated, analytic and simulation results show that the introduced scheme is more robust to the change of channel correlation.n.
The Geolocation Based on Total Least Squares Algorithm Using Satellites
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 255~261
The problem of geolocation using multiple satellites is to determine the position of a transmitter located on the Earth by processing received signals. The specific problem addressed in this paper is that of estimating the position of a stationary transmitter located on or above the Earth's surface from measured time difference of arrivals (TDOA) by a geostationary orbiting (GSO) satellite and a low earth orbiting (LEO) satellite. The proposed geolocation method is based on the total least squares (TLS) algorithm. Under erroneous positions of the satellites together with noisy TDOA measurements, the TLS algorithm provides a better solution. By running Monte-Carlo simulations, the proposed method is compared with the ordinary least squares (LS) approach.
Error Detection and Concealment of Transmission Error Using Watermark
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 262~271
There are channel errors when video data are transmitted between encoder and decoder. These channel errors would make decoded image incorrect, so it is very important to detect and recover channel errors. This paper proposes a method of error detection and recovery by hiding specific information into video bitstream using fragile watermark and checking it later. The proposed method requires no additional bits into compressed bitstream since it embeds a user-specific data pattern in the least significant bits of LEVELs in VLC codewords. The decoder can extract the information to check whether the received bitstream has an error or not. We also propose to use this method to embed essential data such as motion vectors that can be used for error recovery. The proposed method can detect corrupted MBs that usually escape the conventional syntax-based error detection scheme. This proposed method is quite simple and of low complexity. So the method can be applied to multimedia communication system in low bitrate wireless channel.
A Regularized Mixed Norm Multi-Channel Image Restoration Algorithm
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 272~282
This paper introduces a regularized mixed norm multi-channel image restoration algorithm using both within-and between- channel deterministic information. For each channel a functional which combines the least mean squares (LMS), the least mean fourth (LMF), and a smoothing functional is proposed. We introduce a mixed norm parameter that controls the relative contribution between the LMS and the LMF, and a regularization parameter defining the degree of smoothness of the solution, where both parameters are updated at each iteration according to the noise characteristics of each channel. The novelty of the proposed algorithm is that no knowledge of the noise distribution for each channel is required and that the parameters mentioned above are adjusted based on the partially restored image.
A Design of Redirection System for Server Selection on the Content Distribution Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 283~290
With the development of Web technologies, the demand for multimedia contents and network bandwidth is increasing explosively. In this situation, Caching, P2P and CDN are using for fast transmission with low traffic. In this research, we designed and implemented a redirection system for best replica selection where contents are distributed to multiple replicated web servers. This redirection system selects a close and least loaded replica and redirect a client's request to the replica. As a result, this system improved user-perceived performance. It is expected that this redirection system will contribute to the faster and more stable transmission of massive multimedia contents.
Design and Implementation of Acoustic Echo Canceller
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 291~297
In this paper, a new structure for the AEC(Acoustic Echo Canceller) is proposed in which echo signal components that can be created in mobile communications is effectively eliminated. Block Data Flow Architecture is a parallel architecture that achieves high performance, high efficiency, high throughput, and almost linear speed up. The proposed architecture employs AEC and is implemented using the TMS320C6711 for real-time applications. The proposed AEC shows improved performance by eliminating echoes at 55ms delay path. Since the proposed AEC can also be implemented in Firmware, it is believed to effectively work on various types of echoes if it is applied on CDMA mobile devices. The TMS320C6711 shows much better performance comparing to previous DSPs. For experimental verifications, filtering operation using adaptive algorithm is performed on TMS320C6711 board and error signals resulted from computations are monitored on PC, and then the performance of the implemented AEC is verified through ERLE computation. According the results of simulation, good characteristic of 100dB are shown after 500 sampling data.
Design of Low-error Fixed-width Modified Booth Multiplier Using Booth Encoder Outputs
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 298~305
This paper presents an error compensation method for a fixed-width modified Booth multiplier that receives a W-bit input and produces a W-bit product. To efficiently compensate for the quantization error, Booth encoder outputs (not multiplier coefficients) are used for the generation of error compensation bias. The truncated bits are divided into two groups depending upon their effects on the quantization error. Then, different error compensation methods are applied to each group. By simulations, it is shown that quantization error can be reduced up to 50％ by the proposed error compensation method compared with the existing method with approximately the same hardware overhead in the bias generation circuit. It is also shown that the proposed method leads to up to 40％ reduction in area and power consumption of a multiplier compared with the ideal multiplier.
An Online Calibration Algorithm for Cellular CDMA Antenna Arrays
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 306~314
Some receiver(and most transmit) beamforming algorithms with an array antenna at a cellular CDMA base stations require accurate internal and external calibrations. The external calibration, which usually needs to be done only once, determines the array manifolds, i.e. the complex response of each antenna as a function of DOA(Directions of Arrival). The internal calibrations are necessary because characteristics of RF/IF circuity of each receiver chain vary differently in response to temperature or humidity changes. We propose an iterative subspace-based calibration algorithm for an asynchronous CDMA-based antenna away in the presence of unknown gain and phase error is presented. We verify the subspace-based calibration algorithms by performing the experiment using measured data. Also, we propose an efficient algorithm using the simulated annealing technique. This algorithm overcomes the problem of the initial guessing in the subspace-based approach.
Generation of high quality stream for static picture quality test in DTV system
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 315~323
In this paper we present a method to generate the bit stream of static video test patterns for testing the picture quality in DTV system. The proposed user-defined quantization table is suitable for the static video test pattern and for minimizing the deterioration of picture quality by quantization, the underflow or overflow of video buffer generated on the process of coding the static video test pattern is compensated by a adaptive zero stuffing algorithm so that optimal picture quality is implemented. Experimental result showed that the test pattern stream encoded by MPEG-2 software with the proposed algorithm had a stable bit rate and good video quality during the decoding process, which is about 3 dB higher than that of the conventional case.
Multiple-ROI Image Coding Method for JPEG2000 Part1
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 324~332
In image communications related to web browsing, image database, and telemedicine, image data processing on the region of interest (ROI) for providing the primary information is needed in the view of saying search time and bandwidth. In this paper, an enhanced algorithm for processing image data that involves multiple ROIs is presented in order to increase PSNR vs. compression ratio performance above the previous JPEG2000 Part1 Maxshift method. Since the wavelet transform enables us to a progressive transmission mechanism, Multiple-ROI coding is possible to compress, transmit, and reconstruct the image data with a better quality than those of non-ROI method while the required transmission bandwidth is kept relatively low.
Object Wrapping Model and Application for Integration of Security Interface
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 333~341
Along with the innovative enhancement of Internet technology and the emergency of distributed systems extended from client-server computing, it becomes indispensible and necessary to integrate and interconnect old legacy systems. Since building a distributed system requires consistency of integration, the proper reuse of incumbent systems is critical to successful integration of current systems to distributed ones. CORBA(Common Object Request Broker Architecture) and object wrapping technique can provide middleware solutions that extend the applications of a legacy system with little modification to the application level while keeping client consistency of standard interface. By using these techniques for system integration it is easier and faster to extend services on application development to distributed environments. We propose a model on object wrapping system that can manage, integrate, and separate the functions delivered from CORBA. We apply the object wrapping model specifically to integration of security system interfaces and also perform a test to verify the usability and the efficiency of our model.
A Binding Mechanisms Using One-Time Attribute Certificates
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 342~347
An ID certificate is digitally signed by a certificate authority for authentication and an attribute certificate is digitally signed by an attribute certificate authority for authorization. In many applications in web, there should be a mechanism to bind attributes to proper identities. The dependencies between them should be maintained. So we analyzed some known binding methods, selective revocation methods and cryptographic binding methods. And we proposed a binding mechanism using one-time attribute certificates in order to solve their problems.
PayWord System using ID-based tripartite Key Agreement Protocol
The Journal of Korean Institute of Communications and Information Sciences, volume 29, issue 2C, 2004, Pages 348~353
Development of an efficient and secure payment system is prerequisite for the construction of electronic payment mechanism in mobile environment. Since current PayWord protocol system generates vendor's certificate for each transaction, it requires lot of operation for transaction. In this paper, we use a session key generated by ID-based tripartite Key agreement protocol which use an Elliptic Curve Cryptosystem over finite field
for transactions. Therefore, our protocol reduces algorithm operations. In particular, proposed protocol using ID-based public key cryptosystem has the advantages over the existing systems in speed and it is more secure in Man-in-the-middle attacks and Forward secrecy.