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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 31, Issue 12C - Dec 2006
Volume 31, Issue 12B - Dec 2006
Volume 31, Issue 12A - Dec 2006
Volume 31, Issue 11C - Nov 2006
Volume 31, Issue 11B - Nov 2006
Volume 31, Issue 11A - Nov 2006
Volume 31, Issue 10C - Oct 2006
Volume 31, Issue 10B - Oct 2006
Volume 31, Issue 10A - Oct 2006
Volume 31, Issue 9C - Sep 2006
Volume 31, Issue 9B - Sep 2006
Volume 31, Issue 9A - Sep 2006
Volume 31, Issue 8C - Aug 2006
Volume 31, Issue 8B - Aug 2006
Volume 31, Issue 8A - Aug 2006
Volume 31, Issue 7C - Jul 2006
Volume 31, Issue 7B - Jul 2006
Volume 31, Issue 7A - Jul 2006
Volume 31, Issue 6C - Jun 2006
Volume 31, Issue 6B - Jun 2006
Volume 31, Issue 6A - Jun 2006
Volume 31, Issue 5C - May 2006
Volume 31, Issue 5B - May 2006
Volume 31, Issue 5A - May 2006
Volume 31, Issue 4C - Apr 2006
Volume 31, Issue 4B - Apr 2006
Volume 31, Issue 4A - Apr 2006
Volume 31, Issue 3C - Mar 2006
Volume 31, Issue 3B - Mar 2006
Volume 31, Issue 3A - Mar 2006
Volume 31, Issue 2C - Feb 2006
Volume 31, Issue 2B - Feb 2006
Volume 31, Issue 2A - Feb 2006
Volume 31, Issue 1C - Jan 2006
Volume 31, Issue 1B - Jan 2006
Volume 31, Issue 1A - Jan 2006
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Error Correction Algorithms for High-density Optical Storage Systems
Yang Gi-Joo ; Lee Jae-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 659~664
We propose two error correcting algorithms for high-density optical storage systems. The first algorithm reduces the false-erasure declaration by reducing the sensitivity on random errors and increases the code rate using a simple erasure indication method. The second one exploits just the known indicator flag instead of error correcting code such as Reed-Solomon(RS) code. The proposed algorithms are superior to the error correcting algorithms of conventional systems such as DVD and BD.
Perfonnance Analysis of the Combined AMC-MIMO Systems with MCS Level Selection Method
Hwang In-Tae ; Kang Min-Goo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 665~671
In this paper, we propose and observe a system that adopts Independent-MCS (Modulation and Coding Scheme) level for each layer in the combined AMC-V-BLAST (Adaptive Modulation and Coding-Vertical-Bell-lab Layered Space-Time) system. Also, comparing with the combined system using Common-MCS level, we observe throughput performance improvement. As a result of simulation, Independent-MCS level case adapts modulation and coding scheme for maximum throughput to each channel condition in separate layer, resulting in improved throughput compared to Common-MCS level case. Especially, the results show that the combined AMC-V-BLAST system with Independent-MCS level achieves a gain of 700kbps in
SNR (Signal-to-Noise Ratio) range.
A Spectral Correlation Based Detection Method for Spectrum Sensing in Cognitive Radio
Han Ning ; Song Jeong-Ig ; Sohn Sung-Hwan ; Kim Jae-Moung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 672~679
Cognitive radio, which is designed to dynamically adapt its transmission to the environments, is believed to be one of the fundamental techniques for future spectrum utilization. As the first step of cognitive radio, spectrum sensing is treated as the most important technique, through which cognition is well explained. In this paper, we propose a spectral correlation based detection method for spectrum sensing. An unlicensed secondary user system operating in TV broadcast bands is taken as an example. Based on the cyclostationarity of communication signals, spectral correlation function is used to minimize the effect of random noise and interference. Energy measurement and peak detection based criteria are proposed. Simulation results show that the proposed detection method outperforms the energy detection and is more suitable for spectrum sensing in cognitive radios.
A Simple Bit Allocation Scheme Based on Grouped Sub-Channels for V-BLAST OFDM Systems
Park Dae-Jin ; Yang Suck-Chel ; Kim Jong-Won ; Yoo Myung-Sik ; Lee Won-Cheol ; Shin Yo-An ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 680~690
In this paper, we present a bit allocation scheme based on grouped sub-channels for MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) systems using V-BLAST (Vertical-Bell laboratories LAyered Space-Time) detector. A fully adaptive modulation and coding scheme may provide optimal performance in the MIMO-OFDM systems, however it requires excessive feedback information. Instead, SBA (Simplified Bit Allocation) scheme for reduction of feedback overhead, which applies the same modulation and coding to all the good sub-channels, may be considered. The proposed scheme in this paper named SBA-GS (Simplified Bit Allocation based on Grouped Sub-channels) groups sub-channels and assigns the same modulation and coding to the set of selected sub-channel groups. Simulation results show that the proposed scheme achieves comparable bit error rate performance of the conventional SBA scheme, while significantly reducing the feedback overhead in multipath channels with small delay spreads.
Packet Loss Concealment Algorithm Based on Speech Characteristics
Yoon Sung-Wan ; Kang Hong-Goo ; Youn Dae-Hee ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 691~699
Despite of the in-depth effort to cantrol the variability in IP networks, quality of service (QoS) is still not guaranteed in the IP networks. Thus, it is necessary to deal with the audible artifacts caused by packet lasses. To overcame the packet loss problem, most speech coding standard have their own embedded packet loss concealment (PLC) algorithms which adapt extrapolation methods utilizing the dependency on adjacent frames. Since many low bit rate CELP coders use predictive schemes for increasing coding efficiency, however, error propagation occurs even if single packet is lost. In this paper, we propose an efficient PLC algorithm with consideration about the speech characteristics of lost frames. To design an efficient PLC algorithm, we perform several experiments on investigating the error propagation effect of lost frames of a predictive coder. And then, we summarize the impact of packet loss to the speech characteristics and analyze the importance of the encoded parameters depending on each speech classes. From the result of the experiments, we propose a new PLC algorithm that mainly focuses on reducing the error propagation time. Experimental results show that the performance is much higher than conventional extrapolation methods over various frame erasure rate (FER) conditions. Especially the difference is remarkable in high FER condition.
Watermarking-based Error Concealment in Video Communications
Oh Tae-Suk ; Kim Yong-Cheol ; Adsumilli Chowdary ; Mitra Sanjit ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 700~705
In this paper, an informed watermarking algorithm is proposed that aids in concealing packet loss errors in video communications. This watermark-based error concealment (WEC) method embeds a low resolution version of the video frame inside itself as watermark data. At the receiver, the extracted watermark is used as a reference for error concealment. The proposed DCT-based algorithm employs informed watermarking techniques in order to minimize the distortion of host frames. At the encoder, a predictive feedback loop is employed which helps to adjust the strength of the data embedding. Furthermore, the distortion of the DCT coefficients introduced in the embedding can be removed to a considerable extent, by employing bit-sign adaptivity. Simulation results on standard video sequences show that the proposed informed WEC scheme has an advantage of 3
4 dB in PSNR over non-informed WEC and that even a non-informed WEC is still superior to conventional error concealment techniques.
An Implementation Method of Frequency Offset Synchronization Using Compact CORDIC for OFDM Systems
Lee Kyu-In ; Yu Sung-Wook ; Kim Jong-Han ; Lee Jae-Kon ; Cho Yong-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 706~712
In this letter, we propose a compact CORDIC processor for implementation of carrier frequency synchronization block in an OFDM (Orthogonal Frequency Division Multiplexing) system. The compact CORDIC processor is proposed by using inherenct properties of an OFDM system for estimation and compensation of carrier frequency offset, and is composed of a compact CORDIC preprocessor and a compact CORDIC processor. The compact CORDIC preprocessor plays a role of normalizing input signal efficiently, and the compact CORDIC processor is proposed to perform the vectoring mode and rotational mode jointly in CORDIC operation for carrier frequency synchronization. It is shown by FPGA implementation that the proposed compact CORDIC processor can achieve better performance with a significantly reduced hardware complexity than the conventional CORDIC approach.
Implementation and Verification of Linear Phase filter with Variable Cutoff Frequency for PCM/FM transmission
Lee Sang-Rae ; Ra Sung-Woong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 713~724
The purpose of this study is to design, implement and verify the pre-modulation filter with the variable -3dB cutoff frequency and linear phase response for bandlimiting the allocation of radio frequency bandwidth for PCM/FM transmission. For the design of this required filter, the digital FIR filter, DAC system and tuneable 2nd order LPF have been constructed and simulated according to the attenuation characteristic requirement of the amplitude frequency response by each stage. From these results, we have implemented the filter and verified the analog conversion hardware part which is composed of DAC system and tuneable 2nd order LPF for the interpolation of the discrete sequences. Especially this paper proposes and carries out the verification processes using the tone generator and the calibration procedures for more precise frequency response of the filter.
Code Acquisition with Receive Diversity and Constant False Alarm Rate Schemes: 2. Nonhomogeneous Fading Circumstance
Kwon Hyoung-Moon ; Kang Hyun-Gu ; Park Ju-Ho ; Ahn Tae-Hoon ; Lee Sung-Ro ; Song Iick-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 725~734
As a sequel to Part 1, the performance characteristics of the cell averaging (CA), greatest of (GO), and smallest of (SO) constant false alarm rate (CFAR) processors in nonhomogeneous environment are obtained and compared when receiving antenna diversity is employed in the pseudonoise (PN) code acquisition of direct-sequence code division multiple access (DS/CDMA) systems. Unlike in homogeneous environment, the GO CFAR processor is observed to exhibit the best performance in nonhomogeneous environment, with the CA CFAR processor performing the second best.
Optimization of Fixed-point Design on the Digital Front End in IEEE 802.16e OFDMA-TDD System
Kang Seung-Won ; Sun Tae-Hyoung ; Chang Kyung-Hi ; Lim In-Gi ; Eo Ik-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 735~742
In this paper, we explain the operation scheme and fixed-point design method of DFE (Digital Front End), which performs DC offset compensation, automatic frequency control, and automatic gain control over the input signal to the UE (User Equipment) receiver of IEEE 802.16e OFDMA-TDD system. Then, we analyze the performance of DFE under ITU-R M. 1225 Veh-A 60km/h channel environment. To optimize the fixed-point design of DFE, we reduce the number of bit resulted from calculation without performance degradation, leading to the decreased complexity of the operation in H/W, and design the Loop filter with considering trade-off between the Acquisition time and the Stability.
Detection Robustness Enhancement and Utility Scheme of Alternating Automotive Dual Beam Laser Radar
Lee Seung-Gi ; Yoo Seung-Sun ; You Kang-Soo ; Kim Sam-Tek ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 743~754
In the proposed method, two regular laser working at two different wavelengths perform moving object detection alternatively in time. The laser intensity and the beaming period of each laser is equally maintain as to the single laser radar, hence, externally, dual beam lasers radar works exactly same as the single beam laser radar except that the proposed dual lasers radar needs additional post-processing of received signals in the receiver. To verify the robustness of the proposed method, a set of computer simulation has been performed. The communication channel is assumed to be additive white Gaussian noise, and the perfect synchronization is assumed. All other simulation parameters such as signal power and signalling period are equally maintain in both systems while the signal processing time such as spreading and filtering are expected to be trivial in call cases.
Mutual Authentication Protocol Of The Low-cost RFID Using Random Partial ID
Li Yong-Zhen ; Mun Hyung-Jin ; Jeong Yoon-Su ; Lee Sang-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 7C, 2006, Pages 755~761
Previous RFID technique, it is recognizable without the physical contact between the reader and the tag, causes the serious privacy infringement such as excessive information exposure and user's location information tracking due to the wireless characteristics. Especially the information security problem of read only tag is solved by physical method. In this paper, we propose a low-cost mutual authentication protocol which is adopted to read-only tag and secure to several attacks using XOR and Partial ID. The proposed protocol is secure against reply attacking, eavesdropping, spoofing attacking and location tracking.