• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.821-824
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• 2022

최근 딥러닝(Deep Learning) 기술이 다양한 분야에서 활용되고 있으며, 사전 학습된 딥러닝 모델에 대한 압축과 전송 방안에 관한 연구 또한 활발히 진행되고 있다. 이와 관련하여, 국제 표준화 기구인 ISO/IEC 산하 MPEG(Moving Picture Expert Group)에서는 인공신경망 모델을 다양한 딥러닝 프레임워크(Deep Learning Framework)에서 상호운용 가능한 포맷으로 압축 표현할 수 있는 NNC(Compression of Neural Network for Multimedia Content Description nd Analysis) 표준화를 진행하고 있다. 압축된 딥러닝 모델의 데이터를 효과적으로 저장하여 전송 및 사용하기 위해서는 ISOBMFF(ISO based Media File Format) 캡슐화 과정이 필요하다. 본 논문에서는 MPEG의 NNC 표준에 따라 사전 학습된 딥러닝 모델을 압축한 후 이를 통해 생성된 비트스트림(bitstream)을 ISOBMFF로 캡슐화하기 위한 기술을 제안 및 실험한다. 또한, 실험에 대한 검증을 위하여 생성된 ISOBMFF 데이터를 비트스트림으로 복원한 뒤 복호화하여 입력 비트스트림과 차이가 없음을 확인한다.

• The KIPS Transactions:PartC
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• v.13C no.1 s.104
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• pp.55-62
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• 2006

It is growing to use the E-Commerce, recently However, if a cracking tool that detects e keyboard input is set up, users' input values and personal information could be taken away. This paper shows the design and implementation of security system that prevent the keyboard input information leaking. The ideas of thus paper are encrypting the keyboard input values with using the keyboard interrupt hooking, the browser embedding program's decrypting the values in case of need and decrypting all values in the web server. The own input control was developed for direct attacks to the browser, and that the values of password fields which are showed as *(asterisk character) won't be decrypted in the client PC is different from other commercial keyboard input security systems. Consequently, this paper shows the chance of realizing a lot safer customer information protective system than before.

• Information and Communications Magazine
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• v.24 no.5
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• pp.15-26
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• 2007

최근 WiBro/WiMAX에서 기지국의 용량증대와 셀의 크기를 확정하는 것을 목적으로 하는 RS(Relay Station)에 대한 표준화가 IEEE 802.16j에서 이루어지고 있다. RS는 기존의 아날로그 중계와 달리 수신신호를 복조 및 복호화한 후 특정 처리과정을 거친 후 다시 부호 및 부호화하여 전송하는 기능을 갖는다. 초고속 휴대인터넷서비스를 제공하고 있는 초고속 무선인터넷서비스 시장에 대한 수요의 증대로 WiBro/WiMax시장의 활성화와 IEEE 802.16j에 대한 표준화의 진척에 따라 WiBro용 RS(Relay Station)상용제품이 조만간 출시 될 것으로 보인다. 본고에서는 WiBrro용 MMR(Mobile Multi-hop relay)기술의 표준화 동향과 요소기술, MMR망의 성능분석에 대해서 기술한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.02a
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• pp.109-112
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• 2008

본 논문에서는 MPEG-4 HE-AAC의 SBR 부호기의 효율을 개선하기 위해 예측 SBR(Predictive-SBR)을 제안한다. SBR 부호기는 주부호기(core encoder)와 결합하여 적은 비트량으로 고주파 성분을 복원할 수 있게 한다. 본 논문에서는 SBR 데이터의 약 70%를 차지하는 포락선 정보를 부호화하는 방법을 개선하여 효율성을 높이고자 한다. 기존 SBR은 포락선 정보의 전송을 위해 다음과 같은 방법을 이용한다. 먼저 고주파 대역의 에너지를 스케일팩터 밴드 단위로 계산한다. 다음으로, 전송정보량의 감소를 위해 델타 코딩 방식을 이용하여 에너지 정보를 부호화한다. 본 논문에서는 SBR의 포락선 정보를 효과적으로 감축하기 위하여 고주파 대역의 에너지를 예측하는 방법을 이용한다. SBR 부호기의 입력 데이터가 SBR 복호기의 입력데이터와 동일하다는 가정 하에 선형 회귀(linear-regression) 기법을 이용하여 고주파 대역의 에너지를 추정한다. 그 후에 추정된 에너지와 원래의 고주파 대역 에너지의 오차를 델타 코딩을 이용하여 부호화한다. 정보를 전송할 때는 고주파 대역 에너지의 델타 코드와 예측 SBR에서 계산한 오차의 델타 코드 중 부호화에 필요한 비트량이 적은 방식을 선택하여 부호화하도록 한다. 그 결과 약 10% 정도의 정보량 감축 효과를 얻을 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.43-50
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• 2012

The use of an error-correcting code is essential in digital communication systems where the channel is noisy. Unless a receiver has accurate channel coding parameters, it becomes difficult to decode the digitized encoding bits correctly. In this paper, estimation algorithm for RM(Reed-Muller) codes using FHT (Fast Hadamard algorithm) is proposed. The proposed algorithm estimates the channel coding parameters of RM codes and then decodes the codes using the characteristic of FHT. And we also verify the algorithm by performing intensive computer simulation in additive white gaussian noise (AWGN) channel.

• The KIPS Transactions:PartB
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• v.15B no.6
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• pp.575-584
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• 2008

According to the network condition, the communication network overload could be occurred when media transmitting. Many researches are being carried out to lessen the network overload, such as the filtering, load distributing, frame dropping and many other methods. Among these methods, one of effective method is frame dropping that reduces specified video frames for bandwidth diminution. B frames are dropped and then I, P frames are dropped according to dependency among the frames in frame dropping. This paper proposes a scheme for protecting copyrights by encryption, when we apply frame dropping to reduce bandwidth of media following MPEG-4 file format. We designed two kinds of frame dropping: first one stores and then sends the dropped files and the other drops frames in real-time when transmitting. We designed three kinds of encryption methods in which DES algorithm is used to encrypt MPEG-4 data: macro block encryption in I-VOP, macro block and motion vector encryption in P-VOP, and macro block and motion vector encryption in I, P-VOP. Based on these three methods, we implemented a digital right management solution for MPEG-4 data streaming. We compared the results of dropping, encryption, decryption and quality of video sequences to select an optimal method, and there is no noticeable difference between the video sequences recovered after frame dropping and the ones recovered without frame dropping. The best performance in encryption and decryption of frames was obtained when we apply the macro block and motion vector encryption in I, P-VOP.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.359-369
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• 2021

In underwater communications, to compensate performance degradation induced from rapidly changing channel transfer characteristic, multi-band communication method which allocate the same data to different frequency bands is used. However, the multi-band configuration may have worse performance than the single-band one because performance degradation in a particular band affects the output from the entire bands. This problem can be solved through a receiving end that analyzes error rates of each band, sets threshold values and allocates lower weights to inferior bands. Therefore, this paper proposed a weighting algorithm based on estimated Bit Error Rate (BER) which analyzes reliability of received data based on the performance difference between demodulated and decoded data. Employing turbo codes with coding rate of 1/3, we evaluate the performance of the proposed weighted multi-band transmission model in real underwater environments based on optimal simulation parameters. Through the sea trial experiment, we confirmed error performance was improved by applying the proposed weighting algorithm.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.58-66
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• 2009

Recently the emerging demands of the light-video encoder promotes lots of research efforts on DVC (Distributed Video Coding). As an appropriate video compression method, DVC has been studied, and Wyner-Ziv (WZ) video compression is its one representative structure. The WZ encoder splits the image into two kinds of frames, one is key frame which is compressed by conventional intra coding, and the other is WZ frame which is encoded by WZ coding. The WZ decoder decodes the key frame first, and estimates the WZ frame using temporal correlation between key frames. Estimated WZ frame (Side Information) cannot be the same as the original WZ frame due to the absence of the WZ frame information at decoder. As a result, the difference between the estimated and original WZ frames are regarded as virtual channel noise. The WZ frame is reconstructed by removing noise in side information. Therefore precise noise estimation produces good performance gain in WZ video compression by improving error correcting capability by channel code. But noise cannot be estimated precisely at WZ decoder unless there is good WZ frame information, and generally it is estimated from the difference of corresponding key frames. Also the estimated noise is limited by comparing with frame level noise to reduce the uncertainty of the estimation method. However these methods cannot provide good noise estimation for every frame or each bit plane. In this paper, we propose a noise nodel selection method which chooses a better noise model for each bit plane after generating candidate noise models. Experimental result shows PSNR gain up to 0.8 dB.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.338-343
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• 2020

In this paper, it was shown that the decoding method of Hamming codes using soft values can be applied to molecular communication channels. A soft value criterion that can be used for decoding of Hamming codes for a molecular communication channel was proposed, and it has been shown through simulation that the decoding method using these values can improve reliability even in the molecular communication channel. A diffusion-based molecular communication channel was assumed, and information symbols were transmitted using BCSK modulation. After demodulating the number of molecules absorbed by the receiver at each symbol interval with an appropriate threshold, the number of molecules is no longer used. In this paper, the BER performance of the decoder was improved by utilizing information on the number of molecules that are no longer used as soft values in the decoding process. Simulation was performed to confirm the improvement in BER performance. When the number of molecules per bit is 600, the error rate of the Hamming code (15,11) was improved about 5.0×10^-3 to the error rate of the BCSK system without the Hamming code. It can be seen that the error rate of (15,11) Hamming code with the soft values was improved to the same extent. In the case of (7,4) Hamming code, the result is similar to that of (15,11) Hamming code. Therefore, it can be seen that the BER performance of the Hamming code can be greatly improved even in the molecular communication channel by using the difference between the number of molecules absorbed by the receiver and the threshold value as a soft value.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.113-119
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• 2010

In this paper, the considered cognitive radio system has a pair of PT-PR and a pair of ST-SR. In first time slot(1 Phase), PT broadcast signal $x_p$ to PR, ST and SR. Then, each receivers(PR, ST, SR) decode received signal $x_p$. In second time slot(2 Phase), ST combine decoded signal ${x_p}^{\prime}$ and signal $x_s$, and it broadcast combined signal to PR and SR. PR and SR decode combined signal. At this time, PR can achieve diversity gain, due to using MRC, it combine 'received and decoded signal ${x_p}^{\prime}$ at 1 phase' and 'detected signal $x_p$ at 2 phase'. SR use linear combining technique and it can obtain $x_s$.