• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.189-195
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• 2008

The OFDMA Physical layer in the WiMAX standard of IEEE 802.16e adopts 114 LDPC codes with various code rates and block sizes as a channel coding scheme to meet varying channel environments and different requirements for transmission performance. In this paper, the performances of the LDPC codes are evaluated according to various code rates and block-lengths throueh simulation studies using min-sum decoding algorithm in AWGN chamois. As the block-length increases and the code rate decreases, the BER performance improves. In the cases with code rates of 2/3 and 3/4, where two different codes ate specified for each code rate, the codes with code rates of 2/3A and 3/4B outperform those of 2/3B and 3/4A, respectively. Through the statistical analyses of the number of decoding iterations the decoding complexity and the word error rates of LDPC codes are estimated. The results can be used to trade-off between the performance and the complexity in designs of LDPC decoders.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.29-32
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• 2000

In this paper, we present an extension of the multi-code CDMA (code division multiple access) systems based on bi-orthogonal modulation by employing a convolutional encoder and an interleaver before serial-to-parallel conversion in the modulator. Bandwidth expansion by the convolutional encoder can be compensated for by the bi-orthogonal modulation, and the interleaver in the system scrambles the convolutionally encoded data bits so that, after serial-to-parallel conversion, each code channel conveys those bits far apart in time. The result is that the proposed system with several order of magnitude less implementational complexity, achieves quite close performance of the conventional systems comprised of Walsh modulation and multiple convolutional encoders and interleavers in all the code channels.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.61-68
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• 2017

In this paper, the coarse acquisition code (C/A code), for civil navigation, of the ranging codes for Global Positioning System (GPS) is studied, simulated and analyzed by using Matlab. We can see with the simulation results that the correctness of the method and feasibility, which is at simulation platform to further study on the real environment of GPS signal, can be confirmed. With using this results, we think, the complexity of tracking the satellite signal environment can be captured, and the performance of satellite receiver will be improved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2C
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• pp.123-129
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• 2006

In this paper, we concentrate on reducing the complexity for efficient encoder. We design structural LDPC code using circulant matrix and permutation matrix and eIRA code. It is possible to design low complex encoder by using shift register and differential encoder and interleaver than general LDPC encoder that use matrix multiplication operation. The code designed by this structure shows similar performance as random code. And the proposed codes can considerably reduce a number of XOR gates.

• Korean Journal of Computational Design and Engineering
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• v.21 no.4
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• pp.433-442
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• 2016

This paper aims to define the relational logic of in-between code articles as well as within atomic sentences in Korean Building Code, as an intermediate research and development process for the automated building permit system of Korea. The approach depicted in this paper enables the software developers to figure out the logical relations in order to compose KBimCode and its databases. KBimCode is a computer-readable form of Korean Building Code sentences based on a logic rule-based mechanism. Two types of relational logic definition are described in this paper. First type is a logic definition of relation between code sentences. Due to the complexity of Korean Building code structure that consists of decree, regulation or ordinance, an intensive analysis of sentence relations has been performed. Code sentences have a relation based on delegation or reference each other. Another type is a relational logic definition in a code sentence based on translated atomic sentence(TAS) which is an explicit form of atomic sentence(AS). The analysis has been performed because the natural language has intrinsic ambiguity which hinders interpreting embedded meaning of Building Code. Thus, both analyses have been conducted for capturing accurate meaning of building permit-related requirements as a part of the logic rule-based mechanism.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.9-14
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• 2009

Recently, a rate-2, $2{\times}2$ space-time code with simple ML decoding has been designed. Though the simple ML decoding algorithm does reduce the ML decoding complexity, there is still need for improvement. In this paper, we propose an efficient decoding algorithm for the rate-2, $2{\times}2$ space-time code using interference cancellation techniques with performance virtually identical to that of ML decoding. Also, the decoding complexity of the proposed algorithm is significantly reduced compared to the conventional simple ML decoding, especially for large modulation orders.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.637-642
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• 2014

In this paper, we propose a efficient shift index searching algorithm for design of the block LDPC codes. It is combined with the message-passing based cycle search algorithm and ACE algorithm. We can determine the shift indices by ordering of priority factors which are effect on the LDPC code performance. Using this algorithm, we can construct the LDPC codes with low complexity compare to trellis-based search algorithm and save the memory for storing the parity check matrix.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4C
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• pp.307-312
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• 2012

In this paper, we perform a complexity analysis for implementation of the ISO/IEEE 11073 Personal Health Device (PHD) standards in order to check the required system resources when ISO/IEEE 11073 PHD standards are implemented on the embedded system. Base on the implemented programs complying the PHD standards for a weighing scale, a blood pressure monitor, and a glucose meter among the various personal health devices, we make a pseudo-code. And then from the two different points of view such as program memory space and data memory space, we make a complexity analysis model. Because system resources or capability are strongly restricted in the personal health devices, our research work is very useful to estimate the required system resources.

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.961-967
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• 2014

Raptor codes are a class of rateless codes originally designed for binary erasure channels. This paper presents a compact set of mathematical expressions for iterative soft decoding of raptor codes. In addition, an early termination scheme is employed, and it is embedded in a single algorithm with the formula. In the proposed algorithm, the performance is enhanced by adopting iterative decoding, both in each inner and outer code and in the concatenated code itself between the inner and outer codes. At the same time, the complexity is reduced by applying an efficient early termination scheme. Simulation results show that our proposed method can achieve better performance with reduced decoding complexity compared to the conventional schemes.

• Journal of Communications and Networks
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• v.8 no.1
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• pp.1-7
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• 2006

Quadrature amplitude modulation-spread spectrum (QAM-SS) and code division multiplexing (CDM) are multi-level modulation schemes with high performance but they cause a large peak-average power ratio (PAPR). Therefore, this paper proposes a novel modulation scheme for high-rate transmission which follows a sequence of CDM-mapping-CDM not only to correct the above-mentioned problem but also offer a high flexibility in obtaining arbitrary multilevel modulation with very low implementation complexity and high performance.