• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1150-1156
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• 2009

In this paper, we propose the gradual encryption method of image using LFSR(Linear Feedback Shift Register) and 2D CAT(Two-Dimensional Cellular Automata Transform). First, an LFSR is used to create a PN(pseudo noise) sequence, which is identical to the size of the original image. Then the created sequence goes through an XOR operation with the original image resulting to the first encrypted image. Next, the gateway value is set to produce a 2D CAT basis function.The created basis function multiplied with the first encrypted image produces the 2D CAT encrypted image which is the final output. Lastly, the stability analysis verifies that the proposed method holds a high encryption quality status.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.164-167
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• 2009

In this paper, we propose the image encryption using LFSR(Linear Feedback Shift Register) and 2D CAT(Two-Dimensional Cellular Automata Transform). First, a LFSR is used to create a PN(pseudo noise) sequence, which is identical to the size of the original image. Then, the created sequence goes through a XOR operation with the original image to convert the original image. Next, the gateway value is set to produce a 2D CAT basis function. Using the created basis function, multiplication is done with the converted original image to process 2D CAT image encipherment. Lastly, the stability analysis verifies that the proposed method holds a high encryption quality status.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2646-2648
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• 2004

전력선 통신(Power-Line Communi-cation)에 있어서 전력선은 유선 매체임에도 불구하고 수많은 분기 및 부하접속, 그리고 상호간의 임피던스 부정합에 의해 무선 통신 채널 환경과 같은 다중 경로 페이딩 특성을 갖게 된다. 따라서 채널의 다중경로 해석이 상당히 중요하며, 실제 전력선 통신 채널 연구 분야에서 신호 송수신단 사이의 임펄스 응답 측정을 바탕으로 다중경로를 분석하는 방안이 적용되고 있다. PN 시퀀스를 이용한 광대역 임펄스 응답 측정 방식은 무선 채널 환경에 대해 개발되었으나, 현재는 무선 채널은 물론 전력선 채널과 같은 유선 채널에서도 적용되고 있다. 게다가 고압 배전선로와 같이 다중 경로를 포함하는 장거리 통신채널은 PN 시퀀스 방식이 여러 가지 면에서 효율적이다[1]. 본 논문에서는 PN 시퀀스 방식의 광대역 임펄스응답 측정 방법을 통해 고압 배전선로 채널의 다중경로 특성을 측정, 검토하고 이를 제시하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1510-1521
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• 1996

This paper presents acquisition algorithm and an improved detection technique for the DS/CDMA (direction sequence code division multiple access) RAKE receiver in multipath fading channel. The DS/CDMA systems use the RAKE receiver, an accurate code acquisition is required for the RAKE branches. The algorithmis able to findthe pseudonoise (PN) code delay estimates for the RAKE branches in a multipath fading channel. In this paper a numerical method and computer simulation simulation have been developed for the acquisition system. The detection probability and mean acquisition time are investigated asa performance measure of the system using the Monte Carlo method. And also in order to analyze the effect of the acquisition on the RAKE receiver this paper bring out the effect of integration time, doppler frequency, processing gain and the number of users on the acquired code phase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1725-1731
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• 2010

In this paper, we proposed preamble structure and code acquisition method to improve code acquisition performance for DS-SS/TDMA packet communication systems. Proposed algorithm changes the short PN code position depending on the sub slot number. Proposed algorithm also saves position differences between short PN codes and position offsets between short PN codes and data starting position of the TDMA packet. By using the position difference table, proposed algorithm can find out exact data starting position even though some sub slots were defected. As a result of simulation, we concluded that proposed algorithm has at least 5dB gain compared to conventional method when same short PN code is used. Moreover, proposed algorithm shows same code acquisition performance only with 1/4 shortened short PN code compared to conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.682-688
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• 2006

In this paper, a soft-decision method for initial PN code acquisition in pilot-channel aided Direct Sequence Code Division Multiple Access (DS-CDMA) systems is proposed in order to improve the acquisition performance. We apply this technique to the conventional hybrid search algorithm and analyze it in terms of mean code acquisition time. For the analysis, we present mathematical model of proposed algorithm and also perform the simulation under IMT-2000 channel models. Numerical results show that our proposed scheme outperforms the conventional one by 0.2 - 0.4 sec with respect to the mean code acquisition time because the soft decision technique can mitigate the possible decline in search performance caused by the use of a hard-decision technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1201-1208
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• 2010

In this paper, we propose an image encryption method using two linear MLCA(Maximum Length Cellular Automata). The encryption method first sets arbitrary 8 bit initial values. Next, we create high quality PN(pseudo noise) sequences by converting rows and columns with the set initial values. hen we generate a basis image using the set PN sequences. Lastly, the final image with high encryption level is produced by XOR operation of the basis image and the original image. In order to verify that the proposed method has the high encryption level, we performed histogram and stability analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.416-425
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• 2013

A hybrid PN code phase acquisition system based on a least-mean-square adaptive filter, interpreted as a channel estimator is proposed and analyzed for direct-sequence spread-spectrum systems under frequency selective Rayleigh fading channels. Closed form expressions are derived for the filter tap weights and detection/false alarm probabilities. Compared to previously proposed systems, the proposed system achieves smaller mean acquisition times, is more robust to the operating signal-to-noise ratio and allows for multiplication free tap weight updates.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.44-54
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• 1996

In DS/SS systems it is necessary to synchronize the locally generated despreading signal with the received spreading signal to demodulate the received signal. The synch process between the two signals is usually accomplished in two steps : first acquisition then tracking. In this paper, an acquisition system aided by the neural network is proposed for the rapid and exact acquisition in DS/SS. the neural netowrk is composed o fthree-layered perpecptrons and trained by the backpropagation algorithm. The performance of the proposed system is analyzed and compared with ones of conventional systems using the sequential estimation technique under an additive while gaussian noisy channel. In all of th econsidered simulations, the proposed system outperforms conventional systems.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.165-171
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• 1996

A noncoherent full-digital PN(pseudo noise) code acquisition/tracking loop has been presetned and implemented in FPGA for the CDMA band-limited direct-sequence spread-spectrum (DS-SS) signals. It employs a simple decimator to control of local PN code phase to lower the hardware cost, and a second order loop to enable the more accurate tracking. The proposed acquisition/tracking loop has been designed in RTL-level VHDL, synthesized into logic gates using the design analyzer of synopsys software, implemented in an ALTERA FPGA chip, and tested. The number of logic gates used in the implemented FPGA chip is around 7000. The functionality has been verified using a PC interface circuitry and a logic analyzer.