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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 28, Issue 12C - Dec 2003
Volume 28, Issue 12B - Dec 2003
Volume 28, Issue 12A - Dec 2003
Volume 28, Issue 11C - Nov 2003
Volume 28, Issue 11B - Nov 2003
Volume 28, Issue 11A - Nov 2003
Volume 28, Issue 10C - Oct 2003
Volume 28, Issue 10B - Oct 2003
Volume 28, Issue 10A - Oct 2003
Volume 28, Issue 9C - Sep 2003
Volume 28, Issue 9B - Sep 2003
Volume 28, Issue 9A - Sep 2003
Volume 28, Issue 8C - Aug 2003
Volume 28, Issue 8B - Aug 2003
Volume 28, Issue 8A - Aug 2003
Volume 28, Issue 7C - Jul 2003
Volume 28, Issue 7B - Jul 2003
Volume 28, Issue 7A - Jul 2003
Volume 28, Issue 6C - Jun 2003
Volume 28, Issue 6B - Jun 2003
Volume 28, Issue 6A - Jun 2003
Volume 28, Issue 5C - May 2003
Volume 28, Issue 5B - May 2003
Volume 28, Issue 5A - May 2003
Volume 28, Issue 4C - Apr 2003
Volume 28, Issue 4B - Apr 2003
Volume 28, Issue 4A - Apr 2003
Volume 28, Issue 3C - Mar 2003
Volume 28, Issue 3B - Mar 2003
Volume 28, Issue 3A - Mar 2003
Volume 28, Issue 2C - Feb 2003
Volume 28, Issue 2B - Feb 2003
Volume 28, Issue 2A - Feb 2003
Volume 28, Issue 1C - Jan 2003
Volume 28, Issue 1B - Jan 2003
Volume 28, Issue 1A - Jan 2003
Volume 28, Issue 9 - 00 2003
Volume 28, Issue 8 - 00 2003
Volume 28, Issue 7 - 00 2003
Volume 28, Issue 6 - 00 2003
Volume 28, Issue 5 - 00 2003
Volume 28, Issue 3 - 00 2003
Volume 28, Issue 2 - 00 2003
Volume 28, Issue 1 - 00 2003
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Closed-form Expression for the Symbol Error Probability of Orthogonal Space-Time Block Codes with Quadrature Amplitude Modulation
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 561~569
In this paper, for my linear orthogonal space-time block including the orthogonal space-time codes introduced by Alamouti［1］, Tarokh［14］, and Xia［11］, the exact expression for the pairwise error probability in the slow Rayleigh fading channel is derived in terms of the message symbol distance between two message vectors rather than the codeword symbol distance between two transmitted codeword matrices. Using the one-dimensional component symbol error probability, the exact closed form expressions for the symbol error probability of linear orthogonal space-time codes are derived for QPSK, 16-QAM, 64-QAM, and 256-QAM.
Performance of Turbo Codes in the Direct Detection Optical PPM Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 570~579
The performance of turbo codes is investigated in the direct detection optical PPM channel. We assume that an ideal photon counter is used as an optical detector and that the channel has background noise as well as quantum noise. Resulting channel model is M-ary PPM Poisson channel. We propose the structure of the transmitter and receiver for applying turbo codes to this channel. We also derive turbo decoding algorithm for the proposed coding system, by modifying the calculation of the branch metric inherent in the original turbo decoding algorithm developed for the AWGN channel. Analytical bounds are derived and computer simulation is performed to analyze the performance of the proposed coding scheme, and the results are compared with the performances of Reed-Solomon codes and convolutional codes.
Joint Optimization of Source Codebooks and Channel Modulation Signal for AWGN Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 580~593
A joint design scheme has been proposed to optimize the source encoder and the modulation signal constellation based on the minimization of the end-to-end distortion including both the quantization error and channel distortion. The proposed scheme first optimizes the VQ codebook for a fixed modulation signal set, and then the modulation signals for the fixed VQ codebook. These two steps are iteratively repeated until they reach a local optimum solution. It has been shown that the performance of the proposed system can be enhanced by employing a new efficient mapping scheme between codevectors and modulation signals. Simulation results show that a jointly optimized system based on the proposed algorithms outperforms the conventional system based on a conventional QAM modulation signal set and the VQ codebook designed for a noiseless channel.
A Study on the Synchronization Techniques for 5GHz High-speed WLANs
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 594~601
High-speed WLAN(Wireless Local Area Network) systems operating in 5GHz band use OFDM transmission technique. OFDM technique transmits data in parallel and has many advantage compared with the serial transmission system-for example, robustness to time variance of channel. OFDM technique use the orthogonal multicarriers. The ICI(InterChannel Interference) caused by the orthogonality destruction between subcarriers. hamper the BER performance. In this paper, we propose the synchronization techniques for high-speed WLAN system designed to support user data rates up to 54Mbps at 5GHz. The proposed synchronization techniques are the reduced complexity structure having the similar performance compared with the conventional synchronization techniques.
An Efficient DCT Calculation Method Based on SAD
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 602~608
In this paper, we propose an efficient DCT calculation method for fast video encoding. We show that the SAD obtained in the motion estimation and compensation process is decomposed into the positive and negative terms. Based on a theoretical analysis, it is shown that the DCT calculation is classified into 4 cases - DCT Skip, Reduced_DCT1 , Reduced_DCT2, and original DCT- according to the positive and negative terms. In the proposed algorithm, one of 4 cases is used for DCT in order to reduce the computational complexity. The simulation results show that the proposed algorithm achieves computational saving approximately 25.2% without image degradation and computational overhead.
Efficient DFDC Filter Design Using Interpolated Fourth-Order Polynomials
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 609~614
In this paper, a new filter structure to improve frequency response characteristics in CIC(Cascaded Integrator-Comb) decimation filters is proposed. Conventional filters improve passband characteristics, but they make worse aliasing band characteristics. In this paper, we propose a new filter which is called IFOP(Interpolated Fourth-Order Polynomials). By using this proposed filter, passband droop and aliasing band attenuation are simultaneously improved. Since proposed filter needs only one multiplication, computation is not much. And overall linear phase characteristics are maintained since the proposed filter is also linear phase. Finally, implementation cost of the proposed filter is compared with those of conventional filters.
Effective Quality-of-Service Renegotiating Schemes for Streaming Video
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 615~623
This paper presents effective quality-of-service renegotiating schemes for streaming video. The conventional network supporting quality-of-service generally allows a negotiation at call setup. However, it is not efficient for the video application since the compressed video traffic is statistically non-stationary. Thus, we consider the network supporting quality-of-service renegotiations during the data transmission, and study effective quality-of-service renegotiating schemes for streaming video. Simple token bucket model, whose parameters are token filling rate and token bucket size, is adopted for the video traffic model. The renegotiating time instants and the parameters are determined by analyzing the statistical information of compressed video traffic. In this paper, two renegotiating approaches, i.e. fixed renegotiating interval case and variable renegotiating interval case, are examined. Finally, the experimental results are provided to show the performance of the proposed schemes.
Key VOP by Shape in MPEG-4 Compressed Domain
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 624~633
We propose a novel method of selecting key VOPs from MPEG-4 compressed domain without fully decoding the compressed data. Approximated shapes of VOPs are obtained from the shape coding mode and then VOPs are clustered by shape similarity to generate key VOPs. The proposed method reduces the computation time of shape approximation, compared with Erol's method. Nevertheless, the resulting VOPs have a good summarizing capability of a video sequence. NMHD (normalized mean Hausdorff distance) values are 2-means clustered to generate key VOPs. In the video search, the MHD of a query VOP from key VOPs are computed and the VOP with the lowest distance is returned. Tests on standard MPEG-4 test sequences show that the computational complexity is very low. Recursive clustering proved to be very effective for generating suitable key VOPs.
Rectangular Region-based Selective Enhancement (RSE) for MPEG-4 FGS Video
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 634~647
In MPEG-4 FGS (fine granular scalability) video, SE (selective enhancement) function is adopted to enhance the subject quality of the region of interest (ROI). However, it has the problem of excessive bit-rate increase in the enhancement layer. We present a new rectangular region-based SE (RSE) algorithm to significantly reduce the overhead bits resulting from the standard SE. The proposed RSE is based on two new algorithms. The first is to apply the SE function to a rectangular region. By doing so, we can reduce the required bits for describing the selectively enhanced region. The second is to use constrained bit-plane scanning (CBS) to encode bit-planes of the enhancement layer. By using CBS, we can efficiently encode the ALL-ZERO symbols that are generated by applying the SE. It Is shown by simulation that the proposed RSE can provide a good visual quality for the selected rectangular region with significantly reduced overhead bits.
Selectively Partial Encryption of Images in Wavelet Domain
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 648~658
As the usage of image/video contents increase, a security problem for the payed image data or the ones requiring confidentiality is raised. This paper proposed an image encryption methodology to hide the image information. The target data of it is the result from quantization in wavelet domain. This method encrypts only part of the image data rather than the whole data of the original image, in which three types of data selection methodologies were involved. First, by using the fact that the wavelet transform decomposes the original image into frequency sub-bands, only some of the frequency sub-bands were included in encryption to make the resulting image unrecognizable. In the data to represent each pixel, only MSBs were taken for encryption. Finally, pixels to be encrypted in a specific sub-band were selected randomly by using LFSR(Linear Feedback Shift Register). Part of the key for encryption was used for the seed value of LFSR and in selecting the parallel output bits of the LFSR for random selection so that the strength of encryption algorithm increased. The experiments have been performed with the proposed methods implemented in software for about 500 images, from which the result showed that only about 1/1000 amount of data to the original image can obtain the encryption effect not to recognize the original image. Consequently, we are sure that the proposed are efficient image encryption methods to acquire the high encryption effect with small amount of encryption. Also, in this paper, several encryption scheme according to the selection of the sub-bands and the number of bits from LFSR outputs for pixel selection have been proposed, and it has been shown that there exits a relation of trade-off between the execution time and the effect of the encryption. It means that the proposed methods can be selectively used according to the application areas. Also, because the proposed methods are performed in the application layer, they are expected to be a good solution for the end-to-end security problem, which is appearing as one of the important problems in the networks with both wired and wireless sections.
Configuration of an IPSec VPN Testbed and Development of an Encryption Verification Tool
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 6C, 2003, Pages 659~667
IPsec refers to a standardized set of security protocols and algorithms which can provide the integrity, the authentication and the confidentiality services for IP packets in the Internet. Between two security gateways, IPsec provides the access control, the connectionless Integrity, data origin authentication, the anti-replay, and the confidentiality services, not only to the IP layer but also to the upper layers. In this paper, we describe a VPN (Virtual Private Network) testbed configuration using the FreeS/WAN and analyze the ISAKMP messages exchanged between the linux security gateway during the IKE SA setup. Also, we describe our development of an IPSEC encryption verification tool which can be used conveniently by VPN administrators.