• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.8
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• pp.307-317
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• 2003

We analyze the performance of MC-CDMA and MC-DS/CDMA system on quasi-synchronized moble satellite return link. Quasi-synchronization is considered that chip offset between terminals is within a few chips. In 10-3 BER, performance of MC-DS/CDMA system with walsh code is 0.3dB better than that of MC-CDMA system when the number of user is 5 from -0.5 $T_{c}$ to 0.5 $T_{c}$ quasi-synchronization of MC-DS/CDMA system and from -5/64 $T_{c}$ $^{MC}$ to 5/64 $T_{c}$ $^{MC}$ quasi-synchronization of MC-CDMA system. MC-DS/CDMA system with walsh code is over 0.2dB better than that of MC-DS/CDMA system with extended m code and gold code. MC-CDMA system with walsh code is over 1.2dB better than that of MC-CDMA system with gold code when the number of user is 5 and lower than from -5/32 $T_{c}$ $^{MC}$ to 5/32 $T_{c}$ $^{MC}$ quasi-synchronization.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.649-652
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• 2004

In this paper, a concatenated RS and Turbo code is proposed for OFDM system over burst error channel. The concatenated code used in this study is a RS(255,2D2) code and a rate 1/2 turbo code. The turbo code uses 2 recursive systematic convolutional (RSC) code as the constituent codes and the parity bit are punctured to get the desired code rate. It is shown by simulation that the conventional OFDM system fails when there exists burst noise. The concatenated RS and turbo code obtains at least 5dB gain over the turbo code at the bit error probability of $10^{-3}$.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.268-271
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• 2011

본 논문에서는 지상파 3D HDTV 방송 서비스를 제공하기 위하여 기존의 유럽형 HDTV 방송 서비스인 DVB-T2 전송 시스템의 채널 부호군을 연구하고, 이 시스템의 외부 부호(Outer Code)로 쓰이는 BCH 부호의 경판정(Hard Decision)을 통한 복호를 연판정(Soft Decision)을 통한 복호로 수정함으로써 성능에 미치는 영향에 대해 살펴보았다. 또한 기존의 DVB-T2 전송시스템의 성능을 살펴보고, 이를 바탕으로 기존의 외부 부호(Outer Code)인 BCH 부호와 내부 부호(Inner Code)인 LDPC 부호의 조합을 연판정이 가능하고 복호하는 블록(Block)의 길이가 더 짧아진 BTC(Block Turbo Code)부호와 LDPC 부호와의 조합으로 바꿈으로써 기존의 DVB-T2 전송 시스템보다 블록 오류율이 낮아짐을 확인하였다.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1277-1288
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• 2018

In this work, the reactor kinetics capability is used to compute the design safety parameters in a PWR due to complete loss of coolant flow during protected and unprotected accidents. A thermal-hydraulic code coupled with a point reactor kinetic model are used for these calculations; where kinetics parameters have been developed from the neutronic SRAC code to provide inputs to RELAP5-3D code to calculate parameters related to safety and guarantee that they meet the regulatory requirements. In RELAP5-3D the reactivity feedback is computed by both separable and tabular models. The results show the importance of the reactivity feedback on calculating the power which is the key parameter that controls the clad and fuel temperatures to maintain them below their melting point and therefore prevent core melt. In addition, extending modeling capability from separable to tabular model has nonremarkable influence on calculated safety parameters.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.233-235
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• 2005

As a class of block codes, LDPC code with any desired code rate and code length is easily constructed. In OFDM system high data transmission is possible, In this paper, we examined the performance of four high-rate(0.75, 0.8, 0.889, 09412) LDPC coded OFDM in image transmission over Rayleigh fading channel. The high-rate of 0.9412 LDPC coded OFDM system obtained about 12dB gain over the OFDM at BER of $10^{-3}$ over Rayleigh fading channel. Also, the PSNR of code rate 0.9412 LDPC coded OFDM system at SNR=10dB is given by 18.8047dB where uncoded OFDM system gives 9.7303 dB.

• Nuclear Engineering and Technology
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• v.19 no.1
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• pp.34-41
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• 1987

This work concerns with a comparison of the 1-dimensional (or 1-D) load follow analysis method with reference to the detailed 3-dimensional (or 3-D) computations. For this purpose a 1-D two-group finite difference code, HLOFO, and a 3-D coarse-mesh code based on the modified Borresen's method, CMSNAC, are developed. The CMSNAC code is used to obtain the 3-D power peaks and reactivity parameters in response to power swing from 100 to 50 and back to 100% in the 12-3-6-3 load cycle for the BOL of the KORI Unit 1 PWR core. The 3-D result is then compared with the 1-D HLOFO computations, the cross section and buckling inputs of which are obtained by combining the flux-volume weighting scheme with the approximate flux from the auxiliary 3-D computations. It is shown that the 1-D computation has a limited accuracy, yet it is confirmed that it can describe the core axial average behavior which is fairly consistent with the detailed 3-D computation.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.43-54
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• 2016

In the present paper, development of the three-dimensional (3D) computational code based on Galerkin finite element method (GFEM) for solving the multigroup forward/adjoint diffusion equation in both rectangular and hexagonal geometries is reported. Linear approximation of shape functions in the GFEM with unstructured tetrahedron elements is used in the calculation. Both criticality and fixed source calculations may be performed using the developed GFEM-3D computational code. An acceptable level of accuracy at a low computational cost is the main advantage of applying the unstructured tetrahedron elements. The unstructured tetrahedron elements generated with Gambit software are used in the GFEM-3D computational code through a developed interface. The forward/adjoint multiplication factor, forward/adjoint flux distribution, and power distribution in the reactor core are calculated using the power iteration method. Criticality calculations are benchmarked against the valid solution of the neutron diffusion equation for International Atomic Energy Agency (IAEA)-3D and Water-Water Energetic Reactor (VVER)-1000 reactor cores. In addition, validation of the calculations against the $P_1$ approximation of the transport theory is investigated in relation to the liquid metal fast breeder reactor benchmark problem. The neutron fixed source calculations are benchmarked through a comparison with the results obtained from similar computational codes. Finally, an analysis of the sensitivity of calculations to the number of elements is performed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1960-1965
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• 1999

In this paper, we propose a new method of erased concatenated code with RS-convolutional code. In the method, we make use of erasure for undecoded information when we have some errors in RS decoding. For decoding with erasure, the method is processed inner decoding and outer decoding again. After the erasure decoding, if the decoding result is better than the previous one, then we use this result. If not, use the previous one. In this paper, we use concatenated RS(63,31)-convolutional(4.1/2) code. Simulation result is compared with calculation result for performance analysis. According to the result, the proposed method has better performance than the others without erasure such that 2dB when 0.5$\leq\rho\leq$1 and 4dB when $\rho\leq$0.3.

• Journal of Broadcast Engineering
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• v.15 no.5
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• pp.681-696
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• 2010

In this paper, we examined the possibility of the transmission capacity increase by an extension and a modification of ATSC 8-VSB transmission system[1] for broadcasting a 3D HDTV services through 6 MHz terrestrial channel. First we examined the performance and the limit of conventional ATSC 8-VSB transmission system. After that LDPC & BCH code are employed instead of conventional RS & TCM code and the transmission parameter is founded for the capacity increase with resonable TOV by varying the code-rates and increasing the modulation constellation. We do not consider the perfect backward compatibility for maximum transmission capacity increase like DVB-S2 system.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1996.11a
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• pp.286-294
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• 1996

In a remarkable paper 〔3〕, Hammons et al. showed that, when properly defined, the binary nonlinear Preparata code can be considered as the Gray map of a linear code eve. Z$_4$, the so-called Preparata code eve. Z$_4$. Recently, Yang and Helleseth 〔12〕 considered the generalized Hamming weights d$\_$r/(m) for Preparata codes of length 2$\^$m/ over Z$_4$ and exactly determined d$\_$r/, for r = 0.5,1.0,1.5,2,2.5 and 3.0. In particular, they completely determined d$\_$r/(m) for any r in the case of m $\leq$ 6. In this paper we show that the Preparata code of length 16 over Z$_4$ does not satisfy the chain condition.