• Journal of Advanced Navigation Technology
• /
• v.11 no.4
• /
• pp.447-453
• /
• 2007

In this letter, we derive the Gallager random coding bound for discrete memoryless channels purely by simple manipulations of algebraic inequalities rather than invoking conceptually difficult random coding arguments. Gallager random coding bound is a very useful tool in information and coding theory due to its applicability to situations in which it is difficult to determine the decision regions and due to the fact that it can be used to derive the channel coding theorem. The readers will find it relatively easy to apply to many practical problems of interest the step-by-step algebraic derivations of the Gallager random coding bound with appropriate modifications.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.4C
• /
• pp.185-190
• /
• 2005

In IS-95 and IMT-2000 systems using variable code rates and constraint lengths, this paper limits code rate 1/2 and constraint length 3 and realizes forward real-time decoder using Sliding-Window with decoding length 6 and PVSL(Prototype Vector Selecting Logic), LVQ(Learning Vector Quantization) in Neural Network. In comparison condition to theoretically constrained AWGN channel environment at $S/(N_{0}/2)=1$ I verified the superiority of forward real-time decoder through hard-decision and soft-decision comparison between Viterbi decoder and forward real-time decoder such as BER and Secure Communication and H/W Structure.

• Journal of the Korean Data and Information Science Society
• /
• v.25 no.2
• /
• pp.385-392
• /
• 2014

Random walk hypothesis is a hypothesis that explains theoretically the difficulty in forecasting in financial market. Various tests for the hypothesis have been developed so far but it is known that those tests suffer from low power and size distortion. In this article, a sign test based on slopes are suggested to overcome these difficulties. A simulation study is conducted to compare this test to the often used Dickey and Fuller (1979) test.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.12A
• /
• pp.1960-1965
• /
• 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 the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.2
• /
• pp.52-59
• /
• 2008

Recommendation ITU-R S.1062 specifies the performance of digital satellite systems. The performance objectives were given in terms of bit error probability divided by the average number of errors per burst versus percentage of time. This performance objective is highly dependent on the forward error correction(FEC) coding schemes used in the system. This implies that we need an effective way of estimating the error performance of a system by the given FEC scheme. In this paper, we derive theoretical formula to estimate performance measure of digital satellite systems defined in Recommendation ITU-R S.1062. We demonstrate various estimation results, and verify them by comparing to the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.2C
• /
• pp.25-30
• /
• 2005

Turbo code is popularly used for the reliable communication in the presence of burst errors. Even if it shows good error performance near to the Shannon limits, it requires a large amount of memories and exhibits long latency. This paper proposes an architecture for the low power implementation of the Turbo decoder adopting the Max-Log-Map algorithm. In the proposed design, two SISO decoders are designed to operate in parallel, and a novel interleaver is designed to prevent the collision of memory accesses by two SISO decoders. Experimental results show that power consumption has been reduced by about 40% in the proposed decoder compared to previous Turbo decoders. The area overhead due to the additional interleaver controller is negligible.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.1
• /
• pp.81-88
• /
• 2004

Turbo code has been adopted in the 3GPP standard, since its performance is very close to the Shannon limit. However, the turbo decoder requires a lot of computations and the amount of the memory increases as the block size of turbo codes becomes larger. In order to reduce the complexity of the turbo decoder, the Log-MAP, the Max-Log-MAP and the sliding window algorithm have been proposed. In this paper, the performance of turbo codes adopted in the 3GPP standard is analyzed by using the floating point and the fixed point implementation. The efficient decoding method is also proposed. It is shown that the BER performance of the proposed method is close to that of the Log-MAP algorithm.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.4 no.3
• /
• pp.197-203
• /
• 2009

Finite field arithmetic is very important in the area of cryptographic applications and coding theory, and it is efficient to use normal bases in hardware implementation. Using the fact that $GF(2^{mk})$ having a type-I optimal normal basis becomes the extension field of $GF(2^m)$, we, in this paper, propose a new serial multiplier which reduce the critical XOR path delay of the best known Reyhani-Masoleh and Hasan's serial multiplier by 25% and the number of XOR gates of Kwon et al.'s multiplier by 2 based on the Reyhani-Masoleh and Hasan's serial multiplier for type-I optimal normal basis.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.4
• /
• pp.821-826
• /
• 2012

p-ary sequences of period $N=2^k-1$ are widely used in many areas of engineering and sciences. Some well-known applications include coding theory, code-division multiple-access (CDMA) communications, and stream cipher systems. The analysis of cross-correlations of these sequences is a very important problem in p-ary sequences research. In this paper, we analyze cross-correlations of p-ary sequences which is associated with the equation $(x+1)^d=x^d+1$ over finite fields.

• Korean Journal of Crystallography
• /
• v.12 no.1
• /
• pp.37-54
• /
• 2001

1960년대까지는 단결정 구조를 해석할 때 주로 Patterson 방법으로 중원자(heavy atom)를 찾고 이 중원자에 의한 위상에 기초하여 구조를 해석해 왔다. 회절점의 위상을 수학적으로 결정하는 직접법(direct method)은 1948년 Harker와 Kasper에 의해서 최초의 논문이 발표된 이후, 50∼60년 대에 이론적 기초가 구축되었으며, 70년대부터 컴퓨터 프로그램화되어 실용되기 시작하였다. 본 해설문에서는 직접법에 사용되는 정규화된 구조 인자(normalized structure factor)와 unitary 구조 인자의 정의를 소개한 후, 직접법의 기본식인 Sayre 방정식으로부터 유도되는 반전적 혹은 대칭중심적(centric)인 경우에서 성립하는 부호 관계(sign relationship) 및 ∑₂-관계(∑₂-relation)와 비반전적(acentric)경우에서 성립하는 탄젠트 공식(tangent formula)의 유도 과정을 설명하였고, 부호 관계와 탄젠트 공식이 필요로 하는 처음 몇 개의 회절점의 위상을 정하는 과정도 보였다.