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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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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
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Volume 28, Issue 1 - 00 2003
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Turbo Perallel Space-Time Processing System with LDPC Code in MIMO Channel for High-Speed Wireless Communications
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 923~929
Turbo processing have been known as methods close to Shannon limit in the aspect of wireless multi-input multi-output (MIMO) communications similarly to wireless single antenna communication. The iterative processing can maximize the mutual effect of coding and interference cancellation, but LDPC coding has not been used for turbo processing because of the inherent decoding process delay. This paper suggests a LDPC coded MIMO system with turbo parallel space-time (Turbo-PAST) processing for high-speed wireless communications and proposes a average soft-output syndrome (ASS) check scheme at low signal to noise ratio (SNR) for the Turbo-PAST system to decide the reliability of decoded frame. Simulation results show that the suggested system outperforms conventional system and the proposed ASS scheme effectively reduces the amount of turbo processing iterations without performance degradation from the point of average number of iterations.
New Constructions of p-ary Bent Sequences
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 930~935
In this paper, using bent functions defined [n the finite field we generalized the construction method of the family of p-ary bent sequences with balanced and optimal correlation property introduced by Kumar and Moreno for an odd prime p, called a generalized p-ary bent sequence. It turns out that the family of balanced p-ary sequences with optimal correlation property introduced by Moriuchi and Imamura  is a special case of the generalized p-ary bent sequences.
Convergence of Min-Sum Decoding of LDPC codes under a Gaussian Approximation
Heo, Jun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 936~941
Density evolution was developed as a method for computing the capacity of low-density parity-check(LDPC) codes under the sum-product algorithm . Based on the assumption that the passed messages on the belief propagation model can be approximated well by Gaussian random variables, a modified and simplified version of density evolution technique was introduced in . Recently, the min-sum algorithm was applied to the density evolution of LDPC codes as an alternative decoding algorithm in . Next question is how the min-sum algorithm is combined with a Gaussian approximation. In this paper, the capacity of various rate LDPC codes is obtained using the min-sum algorithm combined with the Gaussian approximation, which gives a simplest way of LDPC code analysis. Unlike the sum-product algorithm, the symmetry condition  is not maintained in the min-sum algorithm. Therefore, the variance as well as the mean of Gaussian distribution are recursively computed in this analysis. It is also shown that the min-sum threshold under a gaussian approximation is well matched to the simulation results.
Performance Analysis on the Multiple Trellis Coded CPFSK for the Noncoherent Receiver without CSI
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 942~948
In this paper, we analyze the performance of multiple trellis coded modulation applied to continuous phase frequency shift keying (MTCM/CPFSK) for the noncoherent receiver without channel state information (CSI) on the interleaved Rician fading channel. In this system, the squared cross-correlation between the received signal and a candidate signal is used as the branch metric of the Viterbi decoder. To obtain the bit error performance of this system, we analyze the approximated pairwise error probability (PEP) and the exact PEP. We also derive the equivalent normalized squared distance (ENSD) and compare it with the ENSD of the noncoherent receiver with perfect CSI. Simulation results are also provided to verify the theoretical performance analysis.
Gradient On-Off Beamforming Algorithm Based On Eigen-Space Method For a Smart Antenna In IS-2000 1X Signal Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 949~957
This paper presents a gradient ON-OFF algorithm of which the performance is very robust even when the angle spread increases in the mobile communication environments. The proposed method getting the diversity gain by utilizing the primary and secondary eigenvector, which corresponds to the largest and the second largest eigenvalue of the autocovariance matrix of the received signal vector, outperforms the method which just utilizes one eigenvector. By applying the proposed method to IS-2000 1X signal environments, it is observed that the proposed method shows excellent performance compared to a typical beamforming method using just one eigenvector, which considerably degrades the receiving performance as the angle spread increases.
An Improved Nonparametric Change Detection Algorithm Using Euler Number and Structure Tensor
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 958~966
Change detection algorithms based on frame difference are frequently used for finding moving objects in image sequences. These algorithms detect the change of frames using estimated statistical background model. But, if this estimated background model is different from the actual statistical distribution, false detections are generated. In this paper, we propose an improved change detection algorithm using euler number and structure tensor. The proposed mapping method which is based on the euler number can be used for reducing the false detections that generated by nonparametric change detection algorithm. In this paper, the change in the region of moving object also can be detected by the proposed method using structure tensor. Experimental result shows that the proposed method reduces the false detections effectively by 90% on "Weather", by 34% on "Mother & daughter" and by 43% on "Aisle" than an existing method does.
On Adaptive Narrowband Interference Cancellers for Direct-Sequence Spread-Spectrum Communication Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 967~983
In wireless spread-spectrum communication systems utilizing PN (pseudo noise) sequences, a variety of noise sources from the channel affect the data reception performance. Among them, in this paper we are concerned with the narrowband interference that may arise from the use of the spectral bands overlapped by the existing narrowband users or the intentional jammers as in military communication. The effect of this interference can be reduced to some extent at the receiver with the PN demodulation by processing gain. It is known, however, that when the interferers are strong, the reduction cannot be sufficient and thereby requiring the extra use of narrowband interference cancellers (NIC's) at the receivers. A class of adaptive NIC's are studied here based on different two cost functions. One is the chip mean-squared error (MSE) computed prior to the PN demodulation and used in the conventional cancellers. Since thses conventional cancellers should be operated at the chip rate, the computational requirements are enormous. The other is the symbol MSE computed after the PN demodulation in which case the weights of the NIC's can be updated at a lot lower symbol rate. To compare the performance of these NIC's, we derive a common measure of performance, i.e., the symbol MSE after the PN demodulation. The analytical results are verified by computer simulation. As a result, it is shown that the cancellation capability of the symbol-rate NIC's are similar or better than the conventional one while the computational complexity can be reduced a lot.
A NEW ADAPTIVE BEAM-FORMING ALGORITHM BASED ON GENERALIZED ON-OFF METHOD FOR SMART ANTENNA SYSTEM
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 984~994
This paper proposes a novel blind adaptive algorithm for computing the weight vector of an antenna array system. The new technique utilizes a Generalized On-Off algorithm to obtain the weight vector maximizing the SINR(Signal to Interference plus Noise Ratio) of the received signal. It is observed that the proposed algorithm generates a suboptimal weight vector with a linear computational load(O(6N+8)). From the various simulations, it is confirmed that, when the signal environment becomes adverse, e.g., low Processing Gain, and/or wide angular spread. the proposed algorithm outperforms the conventional one in terms of the communication capacity by about 3 times. Applying the proposed algorithm to satellite tracking systems as well as IS2000 1X mobile communication system, we have found that both communication capacity and communication quality are significantly improved.
Optimum Rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 995~1006
It is well know that in the wireless communication systems the transmitted signals can suffer from multipath fading due to the wave propagation characteristics and the obstacles over the paths, resulting in serious reduction in the power of the received signals. However, it is possible to take advantage of the inherent diversity imposed in the multipath reception if the underlying channel can be properly estimated. One of the diversity reception methods in this case is Rake processing. In this paper we study the Rake receivers for the direct-sequence spread-spectrum communication systems utilizing PN (pseudo noise) sequences to achieve spread spectrum. A conventional Rake receiver can use the finite-duration impulse (FIR) filter followed by the PN sequence demodulator, where the FIR filter coefficients are the reverse-ordered complex conjugate values of the fading channel impulse response estimates. Here, we propose a new Rake processing method by replacing the aforementioned PN code sequence with a new set of optimum demodulator coefficients. More specifically, the concept of the new optimum Rake processing is first introduced and then the optimum demodulator coefficients are theoretically derived. The performance obtained using the new optimum Rake processing is also calculated. The analytical results are verified by computer simulation. As a result, it is shown that the new optimum Rake processing method improves the MSE performance more than 10 dB over the conventional one using the fixed PN sequence demodulator. It is also shown that the new optimum Rake processing method improves the MSE performance about 10 dB over the Adaptive Correlator that performs the combining of the multipath components and PN demodulation concurrently. And finally, the MSE performance of the optimum Rake demodulator is very close to the MSE performance of OPSK demodulator under the AWGN channel.
Adaptive Error Constrained Backpropagation Algorithm
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 1007~1012
In order to accelerate the convergence speed of the conventional BP algorithm, constrained optimization techniques are applied to the BP algorithm. First, the noise-constrained least mean square algorithm and the zero noise-constrained LMS algorithm are applied (designated the NCBP and ZNCBP algorithms, respectively). These methods involve an important assumption: the filter or the receiver in the NCBP algorithm must know the noise variance. By means of extension and generalization of these algorithms, the authors derive an adaptive error-constrained BP algorithm, in which the error variance is estimated. This is achieved by modifying the error function of the conventional BP algorithm using Lagrangian multipliers. The convergence speeds of the proposed algorithms are 20 to 30 times faster than those of the conventional BP algorithm, and are faster than or almost the same as that achieved with a conventional linear adaptive filter using an LMS algorithm.
Implementation of Real-time Object Tracking Algorithm based on Non-parametric Difference Picture and Kalman Filter
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 1013~1022
This paper implemented the real-time object tracking algorithm that extracts and tracks the moving object adaptively to input frame sequence by using non-parametric image processing method and Kalman filter-based dynamic AR(2) process method. By applying non-parametric image processing to input frames, the moving object was extracted from the background adaptively to diverse environmental conditions. And the movement of object was able to be adaptively estimated and tracked by modeling the various movement of object as dynamic AR(2) process and estimating based on the Kalman filter the parameters of AR(2) process dynamically changing along time. The experiments of the implemented object tracking system showed that the proposed method tracked the moving object as more approximately as the estimation error became about l/2.5∼1/50 of one of the traditional tracking method based on linear Kalman filter.
A Study on Video Object Segmentation using Nonlinear Multiscale Filtering
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 1023~1032
Object-based coding, such as MPEG-4, enables various content-based functionalities for multimedia applications. In order to support such functionalities, as well as to improve coding efficiency, each frame of video sequences should be segmented into video objects. In this paper. we propose an effective video object segmentation method using nonlinear multiscale filtering and spatio-temporal information. Proposed method performs a spatial segmentation using a nonlinear multiscale filtering based on the stabilized inverse diffusion equation(SIDE). And, the segmented regions are merged using region adjacency graph(RAG). In this paper, we use a statistical significance test and a time-variant memory as temporal segmentation methods. By combining of extracted spatial and temporal segmentations, we can segment the video objects effectively. Proposed method is more robust to noise than the existing watershed algorithm. Experimental result shows that the proposed method improves a boundary accuracy ratio by 43% on "Akiyo" and by 29% on "Claire" than A. Neri's Method does.
Proposal of Network Security Management architecture using Programmable Network Technology
The Journal of Korean Institute of Communications and Information Sciences, volume 28, issue 10C, 2003, Pages 1033~1044
In this paper, we propose security management architecture that manages efficiently security systems that are produced by different companies and programmable middleware that can reduce the load of management traffic. The proposed architecture applies programmable networks technology to policy based network management (PBNM). The proposed architecture manages and cooperates various security systems using security policy. Also, the programmable middleware provides convenience of management and reduces the overhead of a policy server by translating security policy into execution command. In addition, using programmable middleware, an administrator can manage various security systems that are produced by different companies. We showed that the programmable middleware could reduce the load of management traffic by comparing processing time for enforcing and transferring of policies/messages between the proposed architecture and PBNM architecture.