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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 34, Issue 12C - Dec 2009
Volume 34, Issue 12B - Dec 2009
Volume 34, Issue 12A - Dec 2009
Volume 34, Issue 11C - Nov 2009
Volume 34, Issue 11B - Nov 2009
Volume 34, Issue 11A - Nov 2009
Volume 34, Issue 10C - Oct 2009
Volume 34, Issue 10B - Oct 2009
Volume 34, Issue 10A - Oct 2009
Volume 34, Issue 9C - Sep 2009
Volume 34, Issue 9B - Sep 2009
Volume 34, Issue 9A - Sep 2009
Volume 34, Issue 8C - Aug 2009
Volume 34, Issue 8B - Aug 2009
Volume 34, Issue 8A - Aug 2009
Volume 34, Issue 7C - Jul 2009
Volume 34, Issue 7B - Jul 2009
Volume 34, Issue 7A - Jul 2009
Volume 34, Issue 6C - Jun 2009
Volume 34, Issue 6B - Jun 2009
Volume 34, Issue 6A - Jun 2009
Volume 34, Issue 5C - May 2009
Volume 34, Issue 5B - May 2009
Volume 34, Issue 5A - May 2009
Volume 34, Issue 4C - Apr 2009
Volume 34, Issue 4B - Apr 2009
Volume 34, Issue 4A - Apr 2009
Volume 34, Issue 3C - Mar 2009
Volume 34, Issue 3B - Mar 2009
Volume 34, Issue 3A - Mar 2009
Volume 34, Issue 2C - Feb 2009
Volume 34, Issue 2B - Feb 2009
Volume 34, Issue 2A - Feb 2009
Volume 34, Issue 1C - Jan 2009
Volume 34, Issue 1B - Jan 2009
Volume 34, Issue 1A - Jan 2009
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Relay-assisted Multiple Access Channel Protocol for Cooperative Diversity
Kim, Dong-Hyun ; Kim, Gil ; Lee, Kwang-Bok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 1~8
Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.
A New Construction of Quaternary LCZ Sequence Set Using Binary LCZ Sequence Set
Jang, Ji-Woong ; Kim, Sang-Hyo ; Lim, Dae-Woon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 9~14
In this paper, using the binary (N,M,L,1) low correlation zone(LCZ) sequence set with specific property, we propose the construction method of a quaternary LCZ sequence set with parameters (2N,2M,L,2). The binary LCZ sequence using this method must have period
mod 4, balance property, and specific correlation property. The proposed method is modified from the construction method of binary LCZ sequence set by using binary LCZ sequence with specific condition proposed by Kim, Jang, No, and Chung.
Performance of the Recursive Systematic Convolutional Code with Turbo-Equalization Method for PMR Channel
Park, Dong-Hyuk ; Lee, Jae-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 15~20
For perpendicular magnetic recording (PMR) channels, noise-predictive maximum likelihood (NPML) detection method has been used. But, it is hard to expect improving the performance when the bit density is increased. Hence, we exploit the coding methods which has good performance. In this paper, we show the performance of the recursive systematic convolutional (RSC) codes with turbo-equalization method with different channel bit densities. The noise model is 80% jitter noise and 20% AWGN.
NAP and Optimal Normal Basis of Type II and Efficient Exponentiation in
Kwon, Soon-Hak ; Go, Byeong-Hwan ; Koo, Nam-Hun ; Kim, Chang-Hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 21~27
We present an efficient exponentiation algorithm for a finite field
determined by an optimal normal basis of type II using signed digit representation of the exponents. Our signed digit representation uses a non-adjacent form (NAF) for
. It is generally believed that a signed digit representation is hard to use when a normal basis is given because the inversion of a normal element requires quite a computational delay. However our result shows that a special normal basis, called an optimal normal basis (ONB) of type II, has a nice property which admits an effective exponentiation using signed digit representations of the exponents.
Memory-Efficient Time-Memory Trade-Off Cryptanalysis
Kim, Young-Sik ; Lim, Dae-Woon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 28~36
Time-memory trade-off (TMTO) cryptanalysis proposed by Hellman can be applied for the various crypto-systems such as block ciphers, stream ciphers, and hash functions. In this paper, we propose a novel method to reduce memory size for storing TMTO tables. The starting points in a TMTO table can be substituted by the indices of n-bit samples from a sequence in a family of pseudo-random sequences with good cross-correlation, which results in the reduction of memory size for the starting points. By using this method, it is possible to reduce the memory size by the factor of 1/10 at the cost of the slightly increasing of operation time in the online phase. Because the memory is considered as more expensive resource than the time, the TMTO cryptanalysis will be more feasible for many real crypto systems.
Error Concealment Method considering Distance and Direction of Motion Vectors in H.264
Son, Nam-Rye ; Lee, Guee-Sang ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 37~47
When H.264 encoded video streams are transmitted over wireless network, packet loss is unavoidable. Responding on this environment, we propose methods to recover missed motion vector in the decoder: At first, A candidate vector set for missing macroblock is estimated from high correlation coefficient of neighboring motion vectors and missing block vectors the algorithm clusters candidate vectors through distances amongst motion vectors of neighboring blocks. Then the optimal candidate vector is determined by the median value of the clustered motion vector set. In next stage, from the candidate vector set, the final candidate vector of missing block is determined it has minimum distortion value considering directions of neighboring pixels' boundary. Test results showed that the proposed algorithm decreases the candidate motion vectors
on average processing(decoding) time comparing the existing H.264 codec. The PSNR, in terms of visual quality is similar to existing methods.
Contents Adaptive MCTF Using JND
Heo, Jae-Seong ; Ryu, Chul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 48~55
In scalable video coding, MCTF plays an important role for time-scalability and SNR-scalability. But there is image quality decreasing as MCTF level is increased because time interval of each frame is extended so that is hard to find suitable motion vector. In this paper, we propose an algorithm to prevent image quality from decreasing with unsuitable motion vector during MCTF update process using JND. We adapt JND to find errors within blocks of image and set a threshold which is used to add high frequency components during update process. We can overcome time-gap between frames and achieve better image quality through the proposed algorithm.
Fast Rate Distortion Optimization Algorithm for Inter Predictive Coding of H.264/AVC
Sin, Se-Ill ; Oh, Jeong-Su ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 56~62
In H.264/AVC, rate distortion optimization algorithm is used to decide the best block mode from various block modes. It improves a bit rate but greatly increases an amount of computation. This paper proposes a fast rate distortion optimization algorithm that omits a rate distortion optimization adaptively by predicting its cost from the cost calculated for motion estimation. The simulation results show that the proposed algorithm, on average, keeps nearly the image quality and the bit rate made by the rate distortion optimization while reduces 69.86% and 69.63% of computation added by it in CIF and QCIF respectively.
A Distortion Estimation Method Using Integer Operations in H.264/AVC Encoder
Moon, Jeong-Mee ; Kim, Jae-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 63~71
In this paper, a new low-complexity distortion estimation method for H.264 rate-distortion optimized mode decision is proposed. The coding processes, such as DCT, quantization, inverse quantization, inverse DCT, and reconstruction are needed to compute the distortion in an H.264 encoder. To reduce these processes, we estimate distortion using integer operations with coefficients obtained in the quantization process. Inverse quantization, inverse DCT, and reconstruction processes are not needed by the proposed method. For quantization parameters 24 to 36, experimental results show that the time saving of rate-distortion optimized mode decision is on average 29 % and as high as 42 % with negligible degradation in coding performance.
Inverse Halftoning of Digital Color Image using Look-Up Table and Vector Adaptive Filter
Kim, Chan-Su ; Yi, Tai-Hong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 72~80
Look-up table based inverse halftoning from the digital color halftone image is proposed in this paper, which uses vector adaptive filter for the nonexisting patterns in the table. Halftone image is obtained from a continuous -tone image, which can be restored into continuous one from the digital binary image by way of inverse halftoning method. Look-up table based method usually processes fast and has even performances over the various halftoning. The numbers of pixels in the pattern of table and the method how to define the table elements for each R, G, B channels can effect largely for its performance. The proposed method uses 16 pixels in the table considering the diversity of the expressions from their patterns and with memory size as well. This also proposed how to combine R, G, B channels into one. Experimental results showed the better performance in the expression of colors, better color restoration and the short processing time compared with the conventional ones.
Differential- Average Transmitted Reference Ultra Wide Band Communication System
Kim, Se-Kwon ; Kim, Jae-Woon ; Shin, Yo-An ; Roh, Don-Suk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 81~89
We propose a D-ATR UWB (Differential-Average Transmitted Reference Ultra Wide Band) system based on impulse radio. The TR-UWB systems including traditional TR (Transmitted Reference) and ATR (Average TR), exhibit a problem of reduced data rate, since reference signals are additionally transmitted. To tackle this issue, the transmitter of the proposed D-ATR system employs a differential coding like the conventional D-TR system. In addition, the receiver of the proposed system has the structure that can improve signal-to-noise ratio of the reference template used in the correlation process, by recursively averaging the received reference signals like the conventional ATR system. The simulation results in the IEEE 802.15.4a UWB multipath channel models reveal that the proposed D-ATR system achieves much better bit error rate performance as compared to the conventional D- TR system.
The Optimal Subchannel and Bit Allocation for Multiuser OFDM System: A Dual-Decomposition Approach
Park, Tae-Hyung ; Im, Sung-Bin ; Seo, Man-Jung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 90~97
The advantages of the orthogonal frequency division multiplexing (OFDM) are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. To further utilize vast channel capacity of the multiuser OFDM, one has to find the efficient adaptive subchannel and bit allocation among users. In this paper, we propose an 0-1 integer programming model formulating the optimal subchannel and bit allocation problem of the multiuser OFDM. We employ a dual-decomposition method that provides a tight linear programming (LP) relaxation bound. Simulation results are provided to show the effectiveness of the 0-1 integer programming model. MATLAB simulation on a system employing M-ary quardarature amplitude modulation (MQAM) assuming a frequency-selective channel consisting of three independent Rayleigh multi-paths are carried with the optimal subchannel and bit allocation solution generated by 0-1 integer programming model.
Genetic Algorithm based Tone Injection PAPR Reduction
Park, Soon-Kyu ; Choi, Joo-Pyoung ; Lee, Won-Cheol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 98~104
Tone injection scheme has been known as one of PAPR(Peak to Average Power Ratio) reduction methods deployable to multi-carrier system like OFDM(Orthogonal Frequency Division Multiplexing). The basic idea in tone injection scheme is to enforce the constellation size larger so that each of original constellation points is mapped into the preassigned distinct points. Along the accomplishment of tone injection, it needs great amount of computations to search out not only an appropriate frequency but a phase. Although there is no loss of transmission rate is expected because of no need to send the overhead, the tone injection scheme has not been preferable due to its enormous computations. To alleviate the amount of complexity, this paper proposes the GA(Genetic Algorithm) based tone injection scheme such that its complexity is reduced comparing with that of the conventional method. The simulation results show that the proposed GA based tone injection scheme approaches the PAPR performance associated with the conventional exhaustive search method at the expense of low computations.
Digital Watermarking using Multi-resolution Characteristic of 2D Cellular Automata Transform
Piao, Yong-Ri ; Kim, Seok-Tae ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 105~112
In this paper, we propose a digital watermarking method using Multi-resolution Characteristic of 2D CAT (2D cellular automata transform). Firstly, we select the gateway values to generate a basis function and the basis function transforms images into cellular automata space. Then, we embed the random bit sequence as watermark in specific parts of cellular automata transform coefficients. The proposed method not only verifies higher fidelity than the existing method but also stronger stability on JPEG lossy compression, filtering, sharpening and noise through tests for robustness. Moreover, the proposed scheme allows only one 2D CAT basis function per gateway value. Since there are
possible gateway values.
A Noble Equalizer Structure with the Variable Length of Training Sequence for Increasing the Throughput in DS-UWB
Chung, Se-Myoung ; Kim, Eun-Jung ; Jin, Ren ; Lim, Myoung-Seob ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 113~119
The training sequence with the appropriate length for equalization and initial synchronization is necessary before sending the pure data in the burst transmission type DS-UWB system. The length of the training sequence is one of the factors which make throughput decreased. The noble structure with the variable length of the training sequence whose length can be adaptively tailored according to the channel conditions (CM1,CM2,CM3,CM4) in the DS-USB systems is proposed. This structure can increase the throughput without sacrificing the performance than the method with fixed length of training sequence considering the worst case channel conditions. Simulation results under IEEE 802.15.3a channel model show that the proposed scheme can achieve higher throughput than a conventional one with the slight loss of BER performance. And this structure can reduce the computation complexity and power consumption with selecting the short length of the training sequence.
Frequency Synchronization Algorithm for Improving Performance of OFDMA System in 3GPP LTE Downlink
Lee, Dae-Hong ; Im, Se-Bin ; Roh, Hee-Jin ; Choi, Hyung-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 120~130
In this paper, we propose a receiver structure for frequency synchronization in OFDMA (Orthogonal Frequency Division Multiple Access) system which is considered as 3GPP LTE(Long Term Evolution) downlink. In general, OFDMA frequency synchronization consists of two parts: coarse synchronization and fine synchronization. We consider P-SCH (Primary-Synchronization Channel) and CP (Cyclic Prefix) of OFDMA symbol for coarse synchronization and fine synchronization, respectively. The P-SCH signal has two remarkable disadvantages that it does not have sufficiently many sub-carriers and its differential correlation characteristic is not good due to ZC (Zadoff Chu) sequence-specific property. Hence, conventional frequency synchronization algorithms cannot obtain satisfactory performance gain. In this paper, we propose a modified differential correlation algorithm to improve performance of the coarse frequency synchronization. Also, we introduce an effective PLL (Phase Locked Loop) structure to guarantee stable performance of the fine frequency synchronization. Simulation results verify that the proposed algorithm has superior performance to the conventional algorithms and the 2nd-order PLL is effective to track the fine frequency offset even in high mobility.
A Novel Side-Peak Cancellation Method for BOC Signal Synchronization
Kim, Sang-Hun ; Yoon, Tae-Ung ; Lee, Young-Yoon ; Han, Tae-Hee ; Yoon, Seok-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 131~137
Binary offset carrier (BOC) signal synchronization is one of the most important steps to recover the transmitted information in global navigation satellite systems (GNSS) including Galileo and global positioning system (GPS). Generally, BOC signal synchronization is based on the correlation between the received and locally generated BOC signals. Thus, the multiple side-peaks in BOC autocorrelation are one of the main error sources in synchronizing BOC signals. Recently, a novel correlation function with reduced side-peaks was proposed for BOC signal synchronization by Julien ; however, Julien's correlation function not only still has the side-peaks, but also is only applicable to sine phased BOC(n, n), where n is the ratio of the pseudo random noise (PRN) code rate to 1.023 MHz. In this paper, we propose a new correlation function for BOC signal synchronization, which does not have any side-peaks and is applicable to general types of BOC signals, sine/cosine phased BOC(kn, n), where k is the ratio of a PRN chip duration to the period of a square wave sub-carrier used in BOC modulation. In addition, an efficient correlator structure is presented for generating the proposed correlation function.
Improved Channel Estimation for Selective RAKE Receiver in LR-UWB System
Kwon, Soon-Koo ; Jung, Yun-Ho ; Kim, Jae-Seok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 1C, 2009, Pages 138~144
This paper proposes an efficient scheme to estimate the channel parameters such as channel gain and delay for the IEEE802.15.4a LR-UWB systems. Sliding window (SW) method is generally used for the channel estimation of LR-UWB systems, which extracts the channel parameters by performing the cross-correlation with the repeatedly transmitted signal. However, the SW method experiences the severe performance degradation because the cross-correlation is performed just once for the received signal. In this paper, we propose a novel channel estimation scheme, which can achieve a great performance gain by performing the cross-correlation repeatedly with the repeated receive signal. In order to verify the performance gain of the proposed scheme, we performed the intensive simulation with the Saleh-Valenzuela channel model. Simulation results show that the proposed scheme has a performance improvement of 4dB compared to the conventional SW channel estimation scheme.