• KIISE Transactions on Computing Practices
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• v.23 no.10
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• pp.594-598
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• 2017

Tremendous quantities of numerical data are generated every day from various sources, including the stock market. Universal codes such as Elias gamma coding, Elias delta coding and Fibonacci coding are generally used to store arrays of integers. Studies have been conducted to support fast access to specific elements in an integer array, while occupying less space. We suggest an improved code system that utilizes the concepts of succinct data structures. This system is based on a data structure that allows compressing a delimiter bit array while supporting queries in constant time. The results of an experiment show that the encoded array uses lower space, while not sacrificing time efficiency.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.9 s.351
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• pp.31-37
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• 2006

Low-density parity-check (LDPC) codes are recently emerged due to its excellent performance. The standard for European high definition satellite digital video broadcast, DVB-S2 has adopted LDPC codes as a channel coding scheme. This paper proposes a DVB-S2 LDPC decoder architecture using a hybrid parity check matrix which is efficient in hardware implementation for both decoders and encoders. The hybrid H-matrices are constructed so that both the semi-random technique and the partly parallel structure can be applied to design encoders and decoders. Using the hybrid H-matrix scheme, the architecture of LDPC decoder for DVB-S2 can be very practical and efficient. In addition, we show a new Variable Node processor Unit (VNU) architecture to reuse the VNU for various code rates and optimized block memory placement to reuse. We design a DVB-S2 LDPC decoder of code rate 1/2 usng the proposed architecture. We estimate the performance of the DVB-S2 LDPC decoder and compare it with other decoders.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.209-212
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• 2000

In this paper, effect of imperfect power control on performance of a pseudonoise (PN) code tracking loop is analyzed and simulated for a direct-sequence/code-division multiple access (DS/CDMA) system. The multipath fading channel is modeled as a two-ray Rayleigh fading model. Power control error is modeled as a log-normally distributed random variable. The tracking performance of DLL (delay-locked-loop) is evaluated in terms of tracking jitter and mean-time-to-lose-lock (MTLL). From the simulation results, it is shown that the PN tracking performance is very sensitive to the power control error.

• Journal of Korea Spatial Information System Society
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• v.11 no.2
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• pp.13-18
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• 2009

This paper presents the implementation procedure of encoding and decoding algorithms for Tornado code that can provide fault tolerance for storage and transmission system. The degree distribution satisfying heavy tail distribution is produced. Based on this distribution, a good random irregular bipartite graph is attained after plenty of trails. Such graph construction is proved to be efficient, and the experiments also demonstrate that the implementation obtains good performance in terms of decoding overhead.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.55.2-55.2
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• 2017

We present a numerical code for the random scattering histories of Lyman alpha photons in the intergalactic medium. The numerical code calculates the radiative transfer under generic three dimensional density, ionization fraction, and peculiar velocity fields based on N-body + radiation transfer simulations of the epoch of reionization. The code is tested with models having analytical solutions, which have idealized geometry and simplified velocity fields. The emergent line profiles can give constraints to the ionization structure around Lyman alpha sources in the early universe.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.1-9
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• 2013

This paper propose a human action recognition method that uses bag-of-features (BoF) based on CS-LBP (center-symmetric local binary pattern) and a spatial pyramid in addition to the random forest classifier. To construct the BoF, an image divided into dense regular grids and extract from each patch. A code word which is a visual vocabulary, is formed by k-means clustering of a random subset of patches. For enhanced action discrimination, local BoF histogram from three subdivided levels of a spatial pyramid is estimated, and a weighted BoF histogram is generated by concatenating the local histograms. For action classification, a random forest, which is an ensemble of decision trees, is built to model the distribution of each action class. The random forest combined with the weighted BoF histogram is successfully applied to Standford Action 40 including various human action images, and its classification performance is better than that of other methods. Furthermore, the proposed method allows action recognition to be performed in near real-time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.659-664
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• 2006

We propose two error correcting algorithms for high-density optical storage systems. The first algorithm reduces the false-erasure declaration by reducing the sensitivity on random errors and increases the code rate using a simple erasure indication method. The second one exploits just the known indicator flag instead of error correcting code such as Reed-Solomon(RS) code. The proposed algorithms are superior to the error correcting algorithms of conventional systems such as DVD and BD.

• 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.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.137-140
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• 2000

In this paper. we analyzed the performance of a SFH (slow frequency hopping) system under partial-band jamming, multiple access interference and wide-band random noise. For the correction of burst errors due to channel hit, Reed-Solomon coding followed by block interleaving is employed. Errors-and-erasures decoding with side information is exploited to enhance the correctional capability. We derived a closed-form solution for the BER estimation. Errors resulting from random noise and erasures resulting from burst interference are separately analyzed and finally BER is computed due to these composite noise sources. Estimated BER performance is verified by computer simulation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.10-21
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• 1998

In this paper, we analyze the anynchrous cellular hybrid DS/FH spread spectrum system with diversity on nonselective Nakagami fading channel. Binary Psk scheme is considered and random spreading code sequences and random hopping patterns are used. We compare the performance of system using hard-limiting correlation receiver with diversity and linear corrleation receiver in Nakagami fading channel. We compute the average bit error probabilities with/without diversity according to spreading code sequence and the number of hop-ping frequencies under the same handwith espansion, and analyze near-far effect. The results show that hard-limiting correlation receiver with diversity gives a good performance over severe fading channel.