• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.221-231
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• 1997

This paper presents an analysis of a hybrid direct-sequence/slow frequency hopped code division multiple access(DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple m-distribution fading environment. Multipath interfer- ence(MPI) and multiuser interference(MUI) is taken into accout and the spectral efficiency is calculated for uncoded as well as simple channel coding systems. The predetection multipath CCI canceller in conjunction with convolution coding is employed for improving the bit error rate(BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation. From the results, we know that the error performance more deteriorates as the depth of fading becomes deeper. The DS part of the modulation combats the multipath interference, whereas the FH part is a predetection against large multiuser interference. It is shown that, for the con- sidered types of a channel coding, the use of a predetection coding is still essential for obtained a satisfactory bit error performance. The results show that the capacity of the DS/SFG-CDMA MFSK communication system increases in proportion to the length of PN code sequence in the presence of AWGN and MUI. In m-distribution fading environment the capacity increases in proportion to the fading index. The capacity is increased and error performance is improved when the CCI Canceller and Convolution code technique are adopted, respectively. From the results, it is known that the error performance of $4\times10^{-2}$ by adopting Canceller technique. Also convolutional coding technique is the improvement of error performance attains about $10^{-5}$ in code rate 1/2.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.179-186
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• 2009

This paper describes the design and implementation for spread spectrum FTS encoder and decoder. The FTS command format is defined by 64 bit encrypted packet that contains all required information relayed between the ground and the vehicle. Encryption is accomplished using the Tripple-DES encryption algorithm in block encryption form. The proposed FTS encoder and decoder is using the Convolution Encoding and Viterbi Decoding for forward error correction. The Spread Spectrum Modulation is done using a PN code, which is 256 bit gold code. The simulation result shows that the designed FTS decoder is compatible with the designed FTS encoder.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.32-37
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• 2011

Underwater communication is affected by reverberation and noise characteristics of the underwater channel and time delay takes place by multipath. Hence, Signal is distorted and a lot of error is generated in the transmitting/receiving by multipath effects, so a channel coding for error correction is required. We propose a channel coding algorithm which is possible to correct error of received signal. We compare and analyze BER(bit error rate) performance depending on the depth of each transmitter-receiver using channel coding algorithm. QPSK was used as a modulation method, and 1/2 code rate convolution coding was used as a coding rate. A convolution coding method shows increase of BER performances.

• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.494-501
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• 2013

The convolution code(CC) of code rate 1/2 as a forward error correction (FEC) in Quadrature Phase Shift Keying (QPSK) is applied to decrease bit error rate (BER) by background noise and multipath in shallow water acoustic channel. Ratio of transmitting signal bandwidth to channel coherence bandwidth is defined as frequency selectivity index. BER and bit energy-to-noise ratio gain of transmitted signal according to frequency selectivity index are evaluated. In the results of indoor water tank experiment, BER is well matched theoretical results at frequency selectivity index less than about 1.0. And bit energy-to-noise ratio gain is also matched theoretical value of 5 dB. BER is effectively decreased at frequency selective multipath channel with frequency selectivity index higher than 1.0. But bit energy-to-noise ratio greater than a certain size in terms of CC weaving is effective in reducing bit errors. In the results, the defined frequency selectivity index in this study could be applied to evaluate a performance of CC in multipath channel. Also it could effectively reduced BER in a low speed underwater acoustic communication system without an equalizer.

• The Journal of Information Technology
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• v.3 no.1
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• pp.29-36
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• 2000

Viterbi decoder is a maximum likelihood decoding method for convolution coding used in satellite and mobile communications. In this paper, a Viterbi decoder with constraint length of K=7, 3 bit soft decision and traceback depth of ${\Gamma}=96$ for convolution code is implemented using VHDL. The hardware size of designed decoder is reduced by 4 bit pre-traceback in the survivor memory.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.43-51
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• 2006

A fluid transient analysis on the Koreasat 1 & 2 pipeline system is conducted through numerical parametric studies in which unsteady friction results are compared with quasi-steady friction results and show relatively accurate prediction of the response curve with the unsteady friction. The code developed and used in this analysis has finished verification through comparing with the original Zielke model, the full and recursive convolution model and quasi-steady model as a reference. The unsteady friction is calculated by the recursive convolution Zielke model in which a complete evolution history of velocity field is no longer required so that it makes the fluid transient analysis on the complicated system possible. The results show that the application of quasi-steady friction to model cannot predict the entire response curve properly except the first peak amplitude but the application of unsteady friction to model can predict reasonably the response curve, therefore it is to know the characteristics of the propulsion system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.1
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• pp.41-48
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• 2004

In this paper, we analyzed channel performance of PPM modulated UWB communication system in indoor radio fading environment that consider amplitude characteristic of channel. Fading channel considered various channel environments by fading index m utilizing Nakagami-m distribution model with data through an UBW radio signal experiment that announced in existing. Also, we improved performance of system that it is decreased in fading environment employing convolution encoding techniques.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.320-323
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• 2006

A fluid transient analysis on the Koreasat 1 & 2 pipeline system is conducted through numerical parametric studies in which unsteady friction results are compared with quasi-steady friction results and show relatively accurate prediction of the response curve with the unsteady friction. The code developed and used in this analysis has finished verification through comparing with the original Zielke model, the full and recursive convolution model and quasi-steady model as a reference. The unsteady friction is calculated by the recursive convolution Zielke model in which a complete evolution history of velocity field is no longer required so that it makes the fluid transient analysis on the complicated system possible. The results show that the application of quasi-steady friction to model cannot predict the entire response curve properly except the first peak amplitude but application of unsteady friction to model can predict reasonably he response curve, therefore it is to know the characteristics of the propulsion system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1195-1201
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• 2005

This paper deals with procedures and results for teal time implementation of G.729 speech coder and channel coder including convolution codec, viterbi decoder, and interleaver using a fixed point DSP chip for radio communication systems. We described the method for real-time implementation based on integer simulation results and explained the implemented results by quality performance and required complexity for real-time operation. The required complexity was 24MIPS and 9MIPS in computational load, and 12K words and 4K words in execution code length for speech and channel. The functional evaluation was performed into two steps. The one was bit exact comparison with a fixed point C code, the other was executed by actual speech samples and error test vectors. Unlik other results such as individual implementation, We implemented speech and channel coders on a DSP chip with 160MIPS computation capability and 64 K words memory on chip. This results outweigh the conventional methods in the point of system complexity and implementation cost for radio communication system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.25-29
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• 2021

The strip binary is a binary from which debug symbol information has been deleted, and therefore it is difficult to analyze the binary through techniques such as reverse engineering. Traditional binary analysis tools rely on debug symbolic information to analyze binaries, making it difficult to detect or analyze malicious code with features of these strip binaries. In order to solve this problem, the need for a technology capable of effectively extracting the information of the strip binary has emerged. In this paper, focusing on the fact that the byte code of the binary file is generated very differently depending on compiler version, optimazer level, etc. For effective compiler version extraction, the entire byte code is read and imaged as the target of the stripped binaries and this is applied to the convolution neural network. Finally, we achieve an accuracy of 93.5%, and we provide an opportunity to analyze stripped binary more effectively than before.