• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.246-247
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• 2014

케이블 방송망에서 최대 10Gbps 테이터 전송을 위해 최근 북미에서 표준화된 DOCSIS 3.1(Data over Cable Service Interface Specifications Version 3.1)에서는 고차 혼합 변조(Mixed Modulation) 방식을 제시하였다. DOCSIS 3.1 은 하향 데이터 전송을 위해 최대 192MHz 의 대역에서 4K 또는 8K 다중 직교 반송파를 사용한다. 특히 채널 오류 정정을 위한 채널 부호화 방법으로 유럽의 차세대 케이블 방송 표준인 DVB-C2(Digital Video Broadcasting - Cable Version 2)에 정의된 BCH(Bose, Chaudhuri, and Hocquenghem)와 LDPC(Low Density Parity Check) 연접부호를 사용한다. 단, DOCSIS 3.1 에서는 DVB-C2 와 달리 부호율 8/9 의 Short Mode 부호만을 사용하며 최대 16384-QAM 까지 사용한다. 하나의 부호율을 사용하기 때문에 QAM 차수에 따른 요구 SNR 의 차가 크게 된다. 주어진 채널 상황에서 최적의 전송용량을 얻기 위해 QAM 차수에 따른 요구 SNR 의 차를 줄일 수 있는 방법으로 혼합 변조가 도입되었으며, 본 논문에서는 혼합 변조에 따른 수신 성능을 제시한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.6 no.4
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• pp.97-106
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• 1996

In this paper, we define an equivalence relation on the group of all permutations over the finite field GF($2^n$) and show each equivalence class has common cryptographic properties. And, we classify all exponent permutations over GF($2^7$) and GF($2^8$). Then, three applications of our results are described. We suggest a method for designing $n\;{\times}\;2n$ S(ubstitution)-boxes by the concatenation of two exponent permutations over GF($2^n$) and study the differential and linear resistance of them. And we can easily indicate that the conjecture of Beth in Eurocrypt '93 is wrong, and discuss the security of S-box in LOKI encryption algorithm.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.335-338
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• 2002

For high data rate transmission over wireless fading channels, space-time trellis ceding techniques can be employed to increase the Information capacity of the communication system dramatically. In this paper, we consider the concatenated space time LDPC (Low Density Parity Check) codes. Extra ceding gains In addition to the diversity advantage is shown to be achieved for certain space-time trellis codes transmitted over quasi-static lading channels.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.105-105
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• 2004

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8C
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• pp.762-768
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• 2005

This paper proposes new space-time block codes achieving full rate and full diversity for QAM and quasi-static Rayleigh fading channels when using any number of transmit antennas larger than 3 transmit antennas. These codes are constructed by serially concatenating the constellation rotating $precoders^{[4,5]}$ with the Alamouti scheme$3^{[3]}$ Bike the conventional A-ST-CR code$^{[6,7]}$. Computer simulations show that the proposed codes achieve approximately 1.3dB, 1.4dB and 1.5dB larger coding gains than the ST-CR $codes^{[4,5]}$ for QPSK with 3, 4 and 5 transmit antennas, respectively, and about 3dB for 16QAM with 3 transmit antennas.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.13-23
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• 2009

In this paper, the network performance of a turbo coded optical code division multiple access (CDMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated. We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) is considered. In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical CDMA network can be substantially improved by increasing e interleaver length and e number of iterations in e decoding process. The results of this paper can be applied to implement the indoor optical wireless LANs.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.738-745
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• 2009

Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes receive signal to make error floor. In this paper, we propose the underwater communication system using various channel coding schemes such as RS coding, convolutional code, turbo code and concatenated code for overcoming the multipath effect in underwater channel. As shown in simulation results, characteristic of multipath error is similar to that of random error. So interleaver has not effect on error correcting. For correcting of error floor by multipath, it is necessary to use strong channel codes like turbo code. Turbo code is one of the iterative codes. And the performance of concatenated codes including RS code has better performance than using singular channel codes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.895-901
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• 2016

The next generation wireless and satellite communications require high transmission efficiency and high reliability to provide various services with subscribers. To satisfied these requirements, incorporated MIMO (Multiple Input Multiple Output) system with FTN (Faster Than Nyquist) techniques based on layered space time coded method are considered in the paper. To improve performance, STTC (Space Time Trellis Code) was employed as an inner code. As the same as SISO (Single Input Single Output) system, the outer codes are turbo codes. In receiver side, BCJR algorithm is used for STTC decoding in order to eliminate interferences induced by FTN transmission. They can yield significantly increased the data rates and improved link reliability without additional bandwidth. Therefore, we proposed a new decoding model for MIMO FTN model and confirmed that performance was improved compared to conventional SISO model according to amount of interference for FTN.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2295-2303
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• 2009

Underwater acoustic(UWA) communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of UWA channel causes signal distortion and error floor. In this paper, we proposed the compensation method of multipath effect using the impulse response of the UWA channel and then analysis the performance of channel coding such as LDPC code, concatenate code. Also we analysed the time-delay errors and estimated amplitude errors of estimated channel information and its affection on the performance. As shown in simulation results, the performance of proposed compensation method is better than the performance of conventional method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.63-70
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• 2016

To increase throughput efficiency and improve performance, FTN(Faster Than Nyquist) method and LDPC(Low Density Parity Code) codes are employed in DVB-S3 system. In this paper, we proposed efficient turbo equalization model to minimize inter symbol interference induced by FTN transmission. This paper introduces two conventional scheme employing SIC(Successive Interference Cancellation) and BCJR equalizer. Then, we proposed new scheme to resolve problems in this two conventional scheme. To make performance improved in turbo equalization model, the outputs of LDPC and BCJR equalizer are iteratively exchange probabilistic information. In fed LDPC outputs as extrinsic informa tion of BCJR equalizer. we split LDPC output to separate bit probabilities. We compare performance of proposed scheme to that of conventional methods through using simulation in AWGN(Additive White Gaussian Noise) channel. We confirmed that performance was improved compared to conventional methods as increasing throughput parameters of FTN.