• Journal of the Korea Society of Computer and Information
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• v.20 no.11
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• pp.1-8
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• 2015

Flash memory has advantages in that it is fast access speed, low-power, and low-price. Therefore, they are widely used in electronics industry sectors. However, the flash memory has weak points, which are the limited number of erase operations and non-in-place update problem. To overcome the limited number of erase operations, many wear leveling techniques are studied. They use many tables storing information such as erase count of blocks, hot and cold block indicators, reference count of pages, and so on. These tables occupy some space of main memory for the wear leveling techniques. Accordingly, they are not appropriate for low-power devices limited main memory. In order to resolve it, a wear leveling technique using bit array and Bit Set Threshold (BST) for flash memory. The proposing technique reduces the used space of main memory using a bit array table, which saves the history of block erase operations. To enhance accuracy of cold block information, we use BST, which is calculated by using the number of invalid pages of the blocks in a one-to-many mode, where one bit is related to many blocks. The performance results illustrate that the proposed wear leveling technique improve life time of flash memory to about 6%, compared with previous wear leveling techniques using a bit array table in our experiment.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.51-57
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• 2014

In this paper, we introduce the adaptive threshold detection scheme based on an evolutionary arithmetic algorithm for the M-ary holographic data storage(HDS) system. The genetic algorithm is a particular class of evolutionary arithmetic based on the process of biological evolution, which is a very promising technique for optimization problem and estimation applications. In this study, to improve the detection performance that is degraded by the HDS channel environment and the pixel misalignment, the threshold value was assumed to be a population set of the evolutionary algorithm. The proposed method can find an appropriate population set of bit threshold, which minimizes bit error rate(BER) as increased generation. For performance evaluation, we consider severe misalignment effect in the 4-ary holographic data storage system. Furthermore, we measure the BER performance and compare the proposed methods with the conventional threshold detection scheme, which verifies the superiority of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.767-783
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• 2013

This paper aims at designing a selective demodulation scheme based on Log-likelihood Ratio threshold (SDLT) instead of the conventional adaptive demodulation (ADM) scheme, by using rateless codes. The major difference is that the Log-likelihood ratio (LLR) threshold is identified as a key factor to control the demodulation rate, while the ADM uses decision region set (DRS) to adjust the bit rate. In the 16-QAM SDLT scheme, we deduce the decision regions over an additive white Gaussian channel, corresponding to the variation of LLR threshold and channel states. We also derived the equations to calculate demodulation rate and bit error rate (BER), which could be proven by simulation results. We present an adaptation strategy for SDLT, and compare it with ADM and adaptive modulation (AM). The simulation results show that our scheme not only significantly outperforms the ADM in terms of BER, but also achieves a performance as good as the AM scheme. Moreover, the proposed scheme can support much more rate patterns over a wide range of channel states.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1169-1174
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• 2001

A new approach for determining global threshold value of binary image is proposed in this paper. In the proposed algorithm, bit-plane information which involve the shapes of original image is used for dividing image into two parts; object and background. Optimal threshold value are selected based on difference values of average between two regions, which is considered in global binary thresholding. Proposed method is no need to set a initial value, and consequently, it is relatively simple as well as robust. Experimental results showed a good performance in preserving edge not only continuous tone images but also document image.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.840-855
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• 2011

In the context of additive noise steganography model, we propose a method to detect least significant bit (LSB) matching steganography in grayscale images. Images are decomposed into detail sub-bands with local linear transform (LLT) masks which are sensitive to embedding. Novel normalized characteristic function features weighted by a bank of band-pass filters are extracted from the detail sub-bands. A suboptimal feature set is searched by using a threshold selection algorithm. Extensive experiments are performed on four diverse uncompressed image databases. In comparison with other well-known feature sets, the proposed feature set performs the best under most circumstances.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1025-1030
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• 2005

With the increasing use of multimedia technologies, image compression requires higher performance as well as new functionality. Specially, in the specific area of still image encoding, a new standard, JPEG2000 was developed. This paper proposed Set Partitioning Sorting Algorithm that uses a method to optimized selection of threshold from feature of wavelet transform coefficients and to removes sign bit in LL area on JPEG2000. Experimental results show the proposed algorithm achieves more improved bit rate.

• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.98-101
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• 2000

On CELP type Vocoders G.723.1 6.3kbps/5.3kbps Dual Rate Speech Codec, which is developed for Internet Phone and videoconferencing, uses VAD(Voice Activity Detection)/CNG (Comfort Noise Generator) in order to reduce the bit rate in a silence period. In order to reduce the bit rate effectively in this paper, we first set the boundary condition of the energy threshold to prevent the consumption of unnecessary processing time, and use three decision rules to detect an active frame by energy, pitch gain and LSP distance. To evaluate the performance of the proposed algorithm we use silence-inserted speech data with 0, 5, 10, 20dB of SNR. As a result when SNR is over 5dB, the bit rate is reduced up to about 40% without speech degradation and the processing time is additionally decreased.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.3
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• pp.107-111
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• 2005

With the increasing use of multimedia technologies, image compression requires higher performance as well as new functionality in the informationized society. Specially, in the specific area of still image encoding in embedded system, a new standard, JPEG2000 that improve various problem of JPEG was developed. This paper proposed a method that reduce quantity of data delivered in EBCOT(Embedded Block Coding with Optimized Truncation) process using SPIHT(Set Partitioning in Hierarchical Trees) Algorithm to optimize selection of threshold from feature of wavelet transform coefficients and to remove sign bit in LL area for the increment of compression efficiency on JPEG2000. The experimental results showed the proposed algorithm achieves more improved bit rate in embedded system.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.101-112
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• 1999

In this paper variable bit rate VBR Moving Picture Experts Group (MPEG) coded full-motion video traffic is modeled by a nonlinear time-series process. The threshold autoregressive (TAR) process is of particular interest. The TAR model is comprised of a set of autoregressive (AR) processes that are switched between amplitude sub-regions. To model the dynamics of the switching between the sub-regions a selection of amplitude dependent thresholds and a delay value is required. To this end, an efficient and accurate TAR model construction algorithm is developed to model VBR MPEG-coded video traffic. The TAR model is shown to accurately represent statistical characteristics of the actual full-motion video trace. Furthermore. in simulations for the bit-loss rate actual and TAR traces show good agreement.

• Speech Sciences
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• v.9 no.4
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• pp.253-263
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• 2002

In this paper, we propose new algorithm of speaker recognition which identifies the speaker using the information obtained by the intensive speech feature analysis such as pitch, intensity, duration, and formant, which are crucial parameters of individual voice, for candidates of high percentage of wrong recognition in the existing speaker recognition algorithm. For testing the power of discrimination of individual parameter, DTW (Dynamic Time Warping) is used. We newly set the range of threshold which affects the power of discrimination in speech verification such that the candidates in the new range of threshold are finally discriminated in the next stage of sound parameter analysis. In the speaker verification test by using voice DB which consists of secret words of 25 males and 25 females of 8 kHz 16 bit, the algorithm we propose shows about 1% of performance improvement to the existing algorithm.