• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1256-1265
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• 1996

Soft-decision detectors are used in many FEC and ARQ schemes to enhance the bit-error-probability and system throughput. Also, the hybrid-ARQ protocol is a very efficient schemeto achieve overall performance improvement. In this paper, we propose a new hybrid-ARQ protocol based on the first-order Reed-Muller codes employing soft-decision detectors. The Reed-Muller codes have the virtue of being able to use the fast Green machine decoder that is simple to implement. As the performance measures, the bit-error-probability and system throughput are evaluted for the proposed hybrid-ARQ procol, and compared with those of other hybrid-ARQ schemes. It is shown that the use of the proposed hybrid-ARQ protocol results in significant performance improvement without causing much loss in view of system complexity.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.215-220
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• 1999

In fabricated linear power amplifier(LPA), the third-order inter-modulation distortion(IMD) for main amplifier alone is 10.61dBc, and the IMD for LPA with predistorter and feedforward loop combined is 32.50dBc. Therefore, the IMD characteristic results an improvement of approximately 22dB. The main amplifier efficiency with single tone input is close to 30%, and the efficiency of the overall LPA with predistorter is 27.4% and predicted feedforward loop efficiency without predistorter is about 20%. Therefore, LPA with predistorter and feedforward loop combined is improved by 7.4%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1303-1312
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• 2008

Satellite WiBro system has high PAPR characteristics in addition to the nonlinear characteristics of the power amplifier. These characteristics reduce amplifying efficiency of the power amplifier and also cause high error rate and interference with adjacent channels. This paper proposed satellite WiBro based system to reduce input signal's IBO of TWTA remarkably by adapting simultaneously PAPR reduction techniques, active-constellation extension technique and pre-distortion technique.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.634-639
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• 2008

In mobile communication networks, the main power consumption is due to the actual transmissions power. Therefore, power efficiency network structures have gained considerable importance in mobile multi-hop systems and networks in recent years. In this paper, the performance of mobile multi-hop wireless system with M-QAM signal and forward error control (FEC) technique are analyzed The FEC technique uses extra processing power related to encoding and decoding, it is need complex functions to be built into the communication node. The probability of receiving a correct bit and codeword for relaying a data frame over h hop relay station to the final station is evaluated as a function of channel parameter and number of hops, and the distance between the different station.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.73-79
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• 2004

In this paper, we propose an efficient soft decision decoding algorithm for linear block codes. A conventional soft decision decoder have to invoke a hard decision decoder several times to estimate its soft decision values. However, in this method, we may not have candidate codewords, thus it is very difficult to produce soft decision values. We solve this problem by introducing an efficient algorithm to search candidate codewords. By using this, we can highly reduce the cases we cannot find candidate codewords. We estimate the performance of the proposed algorithm by using the computer simulations. The simulation is performed for binary (63, 36) BCH code in fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1812-1823
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• 1994

In this paper, we focus on the simulation of receiver algorithms for the Q-CDMA reverse link modem to analyze its structure and performance. Receiver algorithm is to be characterized by processing a large amount of data for reliable data transmission through poor mobile channel environment. According to Q-CDMA receiver scheme, we connect the code acqusition and code tracking models for despreading of input signals and the RAKE structure demodulator used to resolve the time diversity signal due to multipath propagation. And this connected system is under test. The bit error rates are found for an arbitrary user under the AWGN and multipath fading environments.

• Journal of Satellite, Information and Communications
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• v.11 no.2
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• pp.65-68
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• 2016

In this paper, visible light wireless communication system according to the climate is studied in the marine environment. The light visibility can be determined by the different weather conditions (clear air, rain, storm, fog) in Kim's atmospheric channel model. By simulating the OOK-NRZ modulation technique, the BER performances are compared in the different weather conditions. In the field test, the error bit is measured in the visible-light communication. The effectiveness of visible light communication in the marine environment is confirmed by comparing the analysis of simulations and field experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.836-843
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• 2008

In this paper we derive the theoretical performance of orthogonal STBC algorithms in spatially correlated Rayleigh fading environments and compare their performances for various correlation conditions. We first derive the theoretical BER of the orthogonal STBC algorithms for both M-ary PSK and M-ary QAM modulation schemes by using the eigenvalues of the channel correlation matrix and then investigate the effect of the spatial correlation on the performance for various transmission rates of $1{\sim}4bps/Hz$. Performance analysis illustrates that the Alamouti scheme provides the better performance than the Tarokh scheme for all the transmission rates in highly correlated fading environments with a correlation being larger than 0.9.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.55-60
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• 2018

This paper shows the initial results of a study applying deep learning technology in power line communication. In this paper, we propose a system that effectively removes noise by applying a deep learning technique to eliminate noise, which is a cause of reduced power line communication performance, by adding a deep learning model at the receive part. To train the deep learning model, it is necessary to store the data. Therefore, it is assumed that the existing data is stored, and the proposed system is simulated. we compare the theoretical result of the additive white Gaussian noise channel with the bit error rate and confirm that the proposed system model improves the communication performance by removing the noise.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.409-411
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• 2016

Salt and pepper noise is caused by various causes such as camera malfunction, storage media memory error, and transmission channel error. Representative filters to remove salt and pepper noise include SMF(standard median filter), CWMF(center weighted median filter), and AMF(adaptive median filter). However previous filters have inadequate noise removal characteristics in high density salt-and-pepper noise environment. Therefore the study suggested a composite filter which, through noise evaluation, preserves original pixels when the central pixel is non-noise, and uses spatial weighted value mask and median when there is noise.