• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.431-439
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• 2010

In this paper, multiple-relay cooperative communication network with multiple antennas is considered. Applying the soft-decision-and-forward protocol to this system, pairwise error probability(PEP) is derived and then symbol error rate(SER) is also calculated. However, in general, signals are transmitted through the orthogonal channel in the multiple-relay cooperative communication network for the prevention of interference, which is inefficient in terms of the throughput. For the improvement of throughput, the relay selection is considered, where the relay having the maximum instantaneous end-to-end signal-to-noise ratio is chosen. Performance of the system is analyzed in terms of PEP and SER. As the number of the relay increases, relay selection method outperforms the conventional multiple-relay transmission system where all relays participate in the second time slot.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.35-41
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• 2012

Due to the technology scaling, more transistors can be placed on a cache memories of a processor. However, processors become more vulnerable to the soft error because of the highly integrated transistors, and consequently, the reliability of the cache memory must consider seriously at the design space level. In this paper, we propose the reliability improving technique which can be achieved with low energy and low area overheads. The simulation experiments of the proposed scheme shows over 95.4% of protection rate against the soft error with only 0.26% of performance degradations. Also, It requires only 2.96% of extra energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.3
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• pp.121-126
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• 2014

Demand of the data storage becomes more and more growing. This requests the next generation of storage devices to have the dominated storage capability associated with superfast read/write rate. Holographic data storage (HDS) is investigated for a long time and is considered to be a candidate for the future storage system. However, it has two-dimensional intersymbol interference that conventional one-dimensional detection solutions have not yet handled strictly because of the complexity level of system as well as the cost. We propose a new scheme that combines iterative soft output Viterbi algorithm with noise filter for improving the bit error rate performance of HDS.

• Journal of Communications and Networks
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• v.5 no.3
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• pp.187-196
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• 2003

We consider the use of error control coding in direct sequence-code-division multiple access (OS-COMA) systems that employ multiuser detection (MUO) and space diversity. The relative performance gain between Reed-Solomon (RS) code and convolutional code (CC) is well known in [1] for the single user, additive white Gaussian noise (AWGN) channel. In this case, RS codes outperform CC's at high signal-to-noise ratios. We find that this is not the case for the multiuser interference channel mentioned above. For useful error rates, we find that soft-decision CC's to be uniformly better than RS codes when used with DS-COMA modulation in multiuser space-time channels. In our development, we use the Gaussian approximation on the interference to determine performance error bounds for systems with low number of users. Then, we check their accuracy in error rate estimation via system's simulation. These performance bounds will in turn allow us to consider a large number of users where we can estimate the gain in user-capacity due to channel coding. Lastly, the use of turbo codes is considered where it is shown that they offer a coding gain of 2.5 dB relative to soft-decision CC.

• ETRI Journal
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• v.25 no.1
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• pp.1-8
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• 2003

This paper introduces an efficient iterative decoding method for high-dimensional block turbo codes. To improve the decoding performance, we modified the soft decision Viterbi decoding algorithm, which is a trellis-based method. The iteration number can be significantly reduced in the soft output decoding process by applying multiple usage of extrinsic reliability information from all available axes and appropriately normalizing them. Our simulation results reveal that the proposed decoding process needs only about 30% of the iterations required to obtain the same performance with the conventional method at a bit error rate range of $10^{-5}\;to\;10^{-6}$.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.663-666
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• 2004

In this paper, a modified-SOYA (soft output viterbi algorithm) of turbo codes is proposed for quantized channel receiver filter outputs. We derive optimum branch values for the Viterbi algorithm. Here we assume that received filter outputs are quantized and the channel is additive white Gaussian noise. The optimum non-uniform quantizer is used to quantize channel receiver filter outputs. To compare the BER (bit error rate) performance we perform simulations for the modified SOYA algorithm and the general SOYA

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.230-236
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• 2022

In this paper, we propose an efficient concatenated code for both random and ISI errors on diffusion-based molecular communication channels. The proposed concatenated code was constructed by combining the ISI-mitigating code designed for ISI mitigation and the ISI-Hamming code strong against random errors, and the BER(bit error rate) performance was analyzed through simulation. In the case of the above M=1,200 channel environment, it was found that the error rate performance of the concatenated code follows the error rate performance of the ISI-mitigating code, which is strong against ISI, and follows the error rate performance of the ISI-Hamming code, which is strong against random errors, in the channel environment below M=600. In M=600~1,200, the concatenated code shows the best error rate performance among those of three codes, which is analyzed because it can correct both random errors and errors caused by ISI. In the following cases of below M=800, it can be seen that the error rate of the concatenated code and the ISI-mitigating code shows an error rate difference of about 1.0×10^-1 on average.

• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.355-372
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• 2017

Objective: The aim of this study is to investigate the performance and usability of ten-finger text entry on Tablet PCs. Background: Generally a soft keyboard is used on Tablet PCs. However, the soft keyboard's performance is usually worse than physical keyboard's performance. In this study, we proposed a modified keyboard for tablet PCs to improve the performance of ten-finger text entry and evaluated the performance and subjective ratings of the keyboard. Method: The modified soft keyboard that is suggested in this study was compared with current Google and Samsung soft keyboards on Tablet PCs. Results: The three keyboards were not significantly different in terms of typing speed, error rate, and mental workload and showed bad performance. Also, the subjective ratings were not shown positively. Conclusion: Based on our results, ten-finger text entry using soft keyboards on Tablet PCs seems to be very difficult. However, we need to research the possibility continuously since ten-finger text entry can improve typing speed. Application: Our study can be a starting point of research that explores ten-finger text entry on Tablet PCs. The new soft keyboard design can be one of the soft keyboard alternatives. However, the key factors to improve the performance and usability of the soft keyboard will not be 'key size' or 'convenience to typing special characters or numbers', but other factors (e.g., 'tactile feedback').

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.6
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• pp.540-549
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• 2013

An adaptive non-uniform quantization scheme is proposed for soft-decision error correction in NAND flash memory. Even though the conventional maximizing mutual information (MMI) quantizer shows the optimal post-FEC (forward error correction) bit error rate (BER) performance, this quantization scheme demands heavy computational overheads due to the exhaustive search to find the optimal parameter values. The proposed quantization scheme has a simple structure that is constructed by only six parameters, and the optimal values of them are found by maximizing the mutual information between the input and the output symbols. It is demonstrated that the proposed quantization scheme improves the BER performance of soft-decision decoding with only small computational overheads.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.140-143
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• 2000

In this paper, forward error control coding in multicarrier direct sequence code division multiple access (DS/CDMA) systems is considered. In order to accommodate a number of coding rates easily and make the encoder and do-coder structure simple, we use the rate compatible punctured convolutional (RCPC) code. We obtain data throughputs at several coding rates and choose the coding rate which has the highest data throughput in the SINR sense. To achieve maximum data throughput, a rate adaptive system using channel state information (the SINR estimate) is proposed. The SINR estimate is obtain by the soft decision Viterbi decoding metric. We show that the proposed rate adaptive convolutionally coded multicarrier DS/CDMA system can enhance spectral efficiency and provide frequency diversity.