• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.251-257
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• 2014

The Viterbi algorithm(VA) is used to estimate the state transition of discrete-time finite state machine(FSM) that is in an uncorrelated noisy environment. This paper modified the Hamming Network to estimate the state transitions in the finite state machines, and proposed state-parallel and block-parallel Viterbi decoder. The modified Hamming Network(mHN) can perform the decoding of convolutional codes correctly as conventional Viterbi decoder. Furthermore, the complexities of the proposed Viterbi decoder are reduced approximately 10% less than conventional Viterbi decoder, and the processing times are improved approximately 40% more than conventional Viterbi decoder.

• Journal of the Korea Society of Computer and Information
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• v.11 no.3
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• pp.271-279
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• 2006

This study proposes a new diversity algorithm to improve the signal-to-noise ratio. In the wireless channel, if fading occurs due to the multipaths, the performance of the system is apparently reduced. One of the methods to reduce fadings like this is the diversity method, and this study aims to improve the performance of the system by proposing a new diversity algorithm. This study applied rake receiver It applied QPSK and OQPSK modulation methods and applied the convolutional codes, where the code rate is 1/3 and the constraint length is 9, and the turbo code where the constraint length is 4. Under these conditions, this study compared and analyzed the average error probability of Multicarrier CDMA system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.169-177
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• 2020

In South Korea, the results of R&D in science and technology are submitted to the National Science and Technology Information Service (NTIS) in reports that have Korea national science and technology standard classification codes (K-NSCC). However, considering there are more than 2000 sub-categories, it is non-trivial to choose correct classification codes without a clear understanding of the K-NSCC. In addition, there are few cases of automatic document classification research based on the K-NSCC, and there are no training data in the public domain. To the best of our knowledge, this study is the first attempt to build a highly performing K-NSCC classification system based on NTIS report meta-information from the last five years (2013-2017). To this end, about 210 mid-level categories were selected, and we conducted preprocessing considering the characteristics of research report metadata. More specifically, we propose a convolutional neural network (CNN) technique using only task names and keywords, which are the most influential fields. The proposed model is compared with several machine learning methods (e.g., the linear support vector classifier, CNN, gated recurrent unit, etc.) that show good performance in text classification, and that have a performance advantage of 1% to 7% based on a top-three F1 score.

• Journal of Internet Computing and Services
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• v.19 no.5
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• pp.33-41
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• 2018

Recently, Internet technology has developed, various programs are being created and therefore various codes are being made through many authors. On this aspect, some author deceive a program or code written by other particular author as they make it themselves and use other writers' code indiscriminately, or not indicating the exact code which has been used. Due to this makes it more and more difficult to protect the code. In this paper, we propose author identification framework using Authorship Analysis theory and Natural Language Processing(NLP) based on Convolutional Neural Network(CNN). We apply Authorship Analysis theory to extract features for author identification in the source code, and combine them with the features being used text mining to perform author identification using machine learning. In addition, applying CNN based natural language processing method to source code for code author classification. Therefore, we propose a framework for the identification of authors using the Authorship Analysis theory and the CNN. In order to identify the author, we need special features for identifying the authors only, and the NLP method based on the CNN is able to apply language with a special system such as source code and identify the author. identification accuracy based on Authorship Analysis theory is 95.1% and identification accuracy applied to CNN is 98%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.1-9
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• 1993

In this paper, a new digital mobile channel has been modeled. And concatenated code systems have been proposed to transmit information reliably in the newly modeled mobile fading channels. The BCH code has been used as the outer code and the convolutional code as the inner code. We have modeled the channels which have multipath fading phenomena and additive white Gaussian noise. As a result, the characteristics of the channels are identical to that of the mobile fading channel. To find the best code system, we have tested (7, 4), (63, 45), (63, 57) and (31.26) BCH codes as an outer code. Results show that the concatenated code with (7, 4) outer code gives the best performance. And if we use the soft decision, we can improve about 2 -6 dB in the SNR

• Journal of Navigation and Port Research
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• v.41 no.4
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• pp.173-180
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• 2017

Underwater communications are degraded as a result of inter symbol interference in multipath channels. Therefore, a channel coding scheme is essential for underwater communications. Packets consist of a PN sequence and a data field, and the uncoded PN sequence is used to estimate the frequency and phase offset using a Doppler and phase estimation algorithm. The estimated frequency and phase offset are fed to a coded data field to compensate for the Doppler and phase offset. The PN sequence is generally utilized to acquire the synchronization information, and the bit error rate of an uncoded PN sequence predicts the performance of the coded data field. To ensure few errors, we resort to powerful BCJR decoding algorithms of convolutional codes with rates of 1/2, 2/3, and 3/4. We use this powerful channel coding algorithm to present an efficient receiver structure based on the relation between the bit error of the uncoded PN sequence and coded data field in computer simulations and lake experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1635-1641
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• 2017

In this paper, a trellis-coded 3-dimensional (3-D) orthogonal frequency division multiplexing (OFDM) system is presented and its performance is analyzed. Here, a set-partitioning technique for trellis coding with respect to a 3-D signal constellation is also presented. We show theoretically that the proposed system, which exploits a trellis coding scheme with recursive systematic convolutional codes (RSC) of code rate R = 1/3 and 2/3, can improve symbol error rate (SER) up to 7.8 dB as compared with the uncoded OFDM system in an additive white Gaussian noise (AWGN) channel. Computer simulation confirms that the theoretical analysis of the proposed system is very accurate. It is, therefore, considered that the proposed trellis-coded 3-D OFDM system is well suited for the high quality digital transmission system without increase in the available bandwidth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2094-2100
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• 2014

The performance of underwater acoustic communication system is sensitive to the inter-symbol interference due to delay spread develop of multipath signal propagation. Thus, it is necessary technique of equalizer and channel code to eliminate inter-symbol interference. In this paper, underwater acoustic communication system were analyzed by experiment using these techniques on the Kyeong-chun lake, Munkyeong City. Based on the results of experiment, we confirmed that the performance of the proposed iterative BCJR equalization method is improved by increasing the number of iterations.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.44-51
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• 2002

This paper describes the performance evaluation and analysis of an Orthogonal Frequency-Division Multiplexing (OFDM) system having the least Inter Symbol Interference (ISI) in a multi-path fading channel environment. Wireless Local Area Network (W-LAN) in accordance with IEEE 802.11a and IEEE 802.11b provides high-speed transmission to universities, businesses and other various places. In addition, service providers can offer a public W-LAN service on restricted areas such as a subway. The proliferation of W-LAN has led to greater W-LAN service demands, but problems are also on the rise in offering a good W-LAN service. In particular, urban areas with high radio wave interference and many buildings are vulnerable to deteriorated QoS including disconnected data and errors. For example, when high-speed data is transmitted in such areas, the relatively high frequency generates ISI between Access Points (AP) and Mobile Terminals (such as a notebook computer), leading to a frequency selective fading channel environment. Consequently, it is difficult to expect a goodW-LAN service. The simulation proves that the OFDM system enables W-LAN to implement QoS in high-speed data transmission in a multi-path fading channel environment. The enhanced OFDM performance with 52 sub-carriers is verified via data modulation methods such as BPSK, QPSK and 16QAM based on IEEE 802.11a and punched convolutional codes with code rate of 1/2 and 3/4 and constraint length of 7. Especially, the simulation finds that the OFDM system has better performance and there is no data disconnection even in a mobile environment by applying a single tap equalizer and a decision feedback equalizer to a mobile channel environment with heavy fading influence. Given the above result, the OFDM system is an ideal solution to guarantee QoS of the W-LAN service in a high-speed mobile environment.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.37-43
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• 2002

This paper describes the performance evaluation and analysis of Wireless Local Area Network (W-LAN) in the 5 GHz ISM-band in compliance with IEEE 802.11a. At present, most W-LAN products are based on 2.4 GHz band, but low speed (11Mbps) has the limitation to serve systems demanding high-speed data transmission. To solve this problem, it is necessary to design next generation W-LAN system with 54Mbps in the 5GHz. It is sure that implementation of next generation W-LAN will bring competitive advantages. In particular, it will support telecommunications for high-speed mobile environments as well as for fixed places such as a school zone, a lecture room, a hospital and other premises. A few simulation methods are applied to more accurate and reliable performance analysis of next generation W-LAN. To verify if continuous data service is supported for a high-speed mobile notebook, multi-path fading channels between wireless Access Point (AP) and wireless Network Interface Card (NIC) are modeled. In addition, low interference is analyzed via convolutional codes and Orthogonal Frequency-Division Multiplexing (OFDM). Also, to obtain reliable Bit Error Rate (BER), a single tap Least Mean Square (LMS) equalizer is applied. Given the above simulation, next generation W-LAN is an ideal solution for continuous data transmission in high-speed mobile environments.