• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.268-277
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• 2001

In this paper, the system performance with the convolution code using a Viterbi decoding and the one tap LMS equalizer applied to the OFDM system, which is suitable for IEEE 802.1la wireless LAN in indoor wireless channel, is analyzed through computer simulation. Indoor wireless channel is modeled as Rician fading channel, and QPSK and 16QAM scheme are used for subchannel modulation. In Rician fading channel with the power ratio of the direct path signal to the scattered signals, K=5 dB, BER of $10^{-4}$ is satisfied if the SNRs of the QPSK/OFDM and the 16QAM/OFDM are 8.6 dB and 19.2 dB in hard decision and 5.3 dB and 9.8 dB in soft decision, respectively. Compared with convolution code scheme, it is observed that 16QAM/OFDM system with the one tap LMS equalizer has the performance improvement of 8.6 dB and 2 dB in hard decision and soft decision, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1895-1902
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• 2011

The soft-decision e-BCH decoding algorithm based on the Chase algorithm is adopted in DVB-RCS NG systems. For implementation, it is necessary to decide the number of optimal quantization bits when soft-decision e-BCH decoding algorithm is processed. Also, the performance must be satisfied. Therefore, in this paper, when the soft-decision e-BCH decoder is implemented, we select the number of optimal quantization bits using BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.905-912
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• 1999

In this paper we explain a trellis representation of block codes and derive their MAP decoding algorithm based on it. We also analyze the performance of block codes and concatenated codes with block codes as components by computer simulations, which were performed by changing the structures and constituent codes of concatenated codes. Computer simulations show that soft decision decoding of block codes get an extra coding gain than their hard decision decoding and that concatenated codes using block codes have good performance in the case of high code rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.734-742
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• 2008

In spatially multiplexed MIMO systems that enable high data rate transmission over wireless communication channels, the spatial demultiplexing at the receiver is a challenging task and various demultiplexing methods have been developed. Among the previous methods, maximum likelihood detection with QR decomposition and M-algorithm (QRM-MLD), sphere decoding (SD), QOC, and MOC schemes have been reported to achieve a (near) maximum likelihood (ML) hard decision performance. In general, however, the reliability of soft output of these schemes is not satisfactory. In this paper, we propose a method which enhances the reliability of soft output. By computer simulations, we demonstrate the improved performance by the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.10
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• pp.824-831
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• 2013

The delta driven GMSK is a modulation scheme to generate the gaussian pulse by the bipolar delta signal and to modulate the phase function with the differential gaussian pulse between $+T_b/2$ and $-T_b/2$. The demodulation of delta driven GMSK differs from conventional GMSK schemes. This paper proposed a demodulation with the differential phase detector at the end of each bit interval. A designed detector then finds the one of the possible region by hard decision, in which the phase difference lies. Finally the binary data can be recovered by state transition process. Through the BER simulation for AWGN channel, it was found that the proposed demodulation effected by the run length of binary data. The simulated BER degradation of about 2[dB] was analyzed, as compared to the theoretical coherent demodulation with $BT_b$=0.3.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.357-359
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• 2010

The Viterbi Decoding is one of the most researched areas of the convolutional decoding methods. In this paper, we use various parameters for the substantial Viterbi decoding and discuss some viterbi decoding methods. And, the viterbi algorithms of the methods, we discuss 'Hard Decision' and 'Soft Decision'. So, we compare differences of two methods about decoding methods, performance. Because of having various parameters and decision methods, we discuss the values of various parameter and decision methods in the Gaussian channel about the viterbi decoding methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4147-4152
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• 2011

Compared to the constant modulus algorithm (CMA), the modified CMA (MCMA) is easy not only to improve the steady-state performance but also to be expanded to higher-order constellations by using fewer moduli with evenly spaced. In this paper, it is shown that the MCMA is sufficient to achieve satisfactory steady-state performance by applying a variable step-size to the MCMA without switching to an hard decision-directed algorithm. Two new methods varying the step-size are proposed, and the performance improvement of the MCMA with the new methods of variable step-size is presented as compared to the CMA and the fixed step-size MCMA through computer simulations.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.23-27
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• 2014

In this paper, we propose a soft demapping method for 64-ary APSK in the DVB-S3 system. The proposed method in this paper uses the hard decision threshold (HDT) line for each constituent bit in a symbol, and calculates the soft bit information with the distance between the HDT line and the detected symbol. If the HDT lines are defined in a simple manner, the complexity to estimate soft information can be largely reduced compared with the maximum likelihood detection (MLD) which has an exponential complexity. By considering this, we first derive HDT lines for each constituent bit for a 64-APSK symbol, and propose a method to calculate soft bit information. We simulate the BER performance of the proposed scheme by using a turbo codes which requires soft-input-soft-output information, and compare it that of the MLD. The result show that the proposed scheme produces approximating performance to MLD with largely reduced complexity.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.3
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• pp.149-154
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• 2017

The MCT-Adaboost algorithm chooses an optimal set of features in each rounds. On each round, it chooses the best feature by calculate minimizing error rate using feature index and MCT kernel distribution. The involved process of weak classification executed by a hard decision. This decision occurs some problems when it chooses ambiguous kernel feature. In this paper, we propose the modified MCT-Adaboost classification using soft decision. The typical MCT-Adaboost assigns a same initial weights to each datum. This is because, they assume that all information of database is blind. We assign different initial weights with our propose new algorithm using some statistical properties of involved features. In experimental results, we confirm that our method shows better performance than the traditional one.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.41-51
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• 2001

In this paper, we presented that the performance of the TCM(Trellis Coded Modulation) using the Euclidean distance is better than that of the convolutional code using the hamming distance under the same bandwidth efficiency. And the TCM DECODER for next generation mobile communication replacing the using convolutional decoder is implemented. Also, for the implementation of the TCM DECODER, the convolutional decoder and the TCM decoder were made by C-language and simulated under AWGN channel with respect to the hard decision and the soft decision. So we proved that performance of the TCM is better than that of the convolutional code. From this result, TCM DECODER, of which constraint length is 3, 5 or 7 and which use the soft decision method, was implemented using the AHDL(Altera Hardware Description Language) and fortified using the Max+plus H version 8.2 of Altera corporation.