• Journal of Communications and Networks
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• v.18 no.5
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• pp.677-687
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• 2016

Multi-way relay networks (MWRNs) allow multiple users to exchange information with each other through a single relay terminal. MWRNs are often incorporated with capacity achieving lattice codes to enable the benefits of high-rate signal constellations to be extracted. In this paper, we analytically characterize the symbol error rate (SER) performance of a functional decode and forward (FDF) MWRN in the presence of channel estimation errors. Considering M-ary quadrature amplitude modulation (QAM) with square constellations as an important special case of lattice codes, we obtain asymptotic expressions for the average SER for a user in FDF MWRN. The accuracy of the analysis at high signal-to-noise ratio is validated by comparison with the simulation results. The analysis shows that when a user decodes other users with better channel conditions than itself, the decoding user experiences better error performance. The analytical results allow system designers to accurately assess the non-trivial impact of channel estimation errors and the users' channel conditions on the SER performance of a FDF MWRN with M-QAM modulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1141-1148
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• 1999

In this paper, an RRA_CDMA protocol is proposed for the integrated voice and data services in the cellular packet CDMA systems. The proposed protocol employs the RRA scheme. In the cellular CDMA systems, the backward logical channels are composed of time slots with multiple spreading codes per slot based on WB-TD-CDMA concept. When a voice terminal begins a talkspurt, it reserves one of the available spreading codes in the next slot and uses the reserved channel exclusively untill it ends the talkspurt. On th other hand, whenever a data terminal generates a packet, it selects an avaliable spreading code and transmits its packet. Throughout the results, it is shown that the system capacity increases in proportion to the number of spreading codes.

• Journal of Advanced Navigation Technology
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• v.16 no.5
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• pp.831-838
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• 2012

In the transmission system, the transmission efficiency can be increased by applying the proper character coding method. This paper is to show the character coding rule in computer and information equipment etc to improve the transmission efficiency in datacommunications. The character coding rule showing in this paper was suggested by considering the two view points. First one is FLAG bits in HDLC and PPP protocol on datalink layer in OSI 7 layer. Second one is one of the scrambling method, HDB-3, on physical layer in OSI 7 layer. The former is to prevent the sequence of over 5bits of "1" in the character codes. The latter is to prevent the sequence of over 4bits of "0" in the character codes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.760-770
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• 2002

Transmit diversity is an efficient diversity technique to improve performance and spectrum efficiency in wireless communication . Coding scheme designed for the transmit diversity is called space-time coding. In this paper, we propose a training structure to apply the transmit diversity to improve the performance of IEEE802.11a OFDM systems. Based on this training structure, we propose a channel estimation scheme using curve fitting. Also we compare and evaluate the performance of space-time codes. The performance of both diversity using space-time codes and channel estimation scheme is investigated by computer simulation in quasi-static 2-ray rayleigh fading environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.683-690
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• 2008

By using inherent stopping criteria of LDPC codes, the average number of iterations can be substantially reduced at high signal to noise ratio (SNR). However, we encounter a problem when hybrid automatic repeat request (H-ARQ) systems are applied. Frequent failures of decoding at low SNR region imply that the decoder leaches the maximum number of iterations frequently and thus the decoding complexity increases. In this paper, we propose a combination of stopping criteria using the syndrome weight of tentative codeword. By numerical analysis, it is shown that the decoding complexity of given H-ARQ system is reduced by 70-80% with the proposed algorithms.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.533-538
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• 2000

In R.C. flat slab system, a brittle punching failure is a very fatal problem. But there is no generally well-defined answer to the problem and there are wide differences in current practical design codes. therefore, in this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. Therefore, In this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. The conclusions in this study are summarized as follows; 1) The factors affecting to punching shear are concrete strength ($f_\alpha$), ratio of column side length to slab depth (c/d), ratio of distance from column center to radial contraflexure (l/d), yield strength of steel ($f_y$), flexural reinforcement ratio ($\rho$) and size effects. 2) It is shown that th use of $\surd{f_{ck}}$in applying($f_\alpha$ to punching shear strength estimation may be more sensitive in high concrete strength. 3) The effects of l/d, ($f_y$, size are no clear in the punching failure mechanism, so in the future, it should be investigated with the effects of various composed load.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.1
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• pp.13-20
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• 2006

In this paper, we constructed a spam-mail filtering system based on the lexical and conceptual information. There are two kinds of information that can distinguish the spam mail from the legitimate mil. The definite information is the mail sender's information, URL, a certain spam keyword list, and the less definite information is the word lists and concept codes extracted from the mail body. We first classified the spam mail by using the definite information, and then used the less definite information. We used the lexical information and concept codes contained in the email body for SVM learning. According to our results the spam precision was increased if more lexical information was used as features, and the spam recall was increased when the concept codes were included in features as well.

• Convergence Security Journal
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• v.14 no.5
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• pp.37-47
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• 2014

A Trojan malicious code is one of largest malicious codes and has been known as a virus that causes damage to a system as itself. However, it has been changed as a type that picks user information out stealthily through a backdoor method, and worms or viruses, which represent a characteristic of the Trojan malicious code, have recently been increased. Although several modeling methods for analyzing the diffusion characteristics of worms have proposed, it allows a macroscopic analysis only and shows limitations in estimating specific viruses and malicious codes. Thus, in this study an ESP model that can estimate future occurrences of Trojan malicious codes using the previous Trojan data is proposed. It is verified that the estimated value obtained using the proposed model is similar to the existing actual frequency in causes of the comparison between the obtained value and the result obtained by the Markov chain.

• The Research Journal of the Costume Culture
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• v.18 no.5
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• pp.942-959
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• 2010

The Realization of Ubiquitous is achieved by magic mirror and it is required more concrete study to realize it's functionality. Especially its function of professional fashion co-ordinator for managing the appearance could be of further use. The Objective of this Study is to establish RFID chip data base to put into a computer for making use of the functionality of the magic mirror aiming at suggesting the available information on the total fashion co-ordination. I sought firstly the code with binary system determining the criteria of accessories to be input in a RFID chip. Secondly, as the image with cloth is an important element for the total fashion co-ordination, desired co-ordination among the emphasis, harmony, character, season and accent can be made selectable classifying into a limit element and a common element to extract the codes. Thirdly, necessary conditions were given to the generated codes using Visual C++ program of Microsoft and the extracted codes as per groups were compared and analyzed.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.40-44
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• 2010

A layered coding scheme is one of the adaptive receiving techniques for unidirectional services such as multimedia broadcasting and multicasting services (MBMS), where we cannot utilize feedback information. The layered coding scheme can be used with hierarchical modulations by combining suitable code rates and modulation orders of each. In addition, it has been reported that hybrid and/or integrated satellite systems can effectively achieve transmit diversity gains by appropriate utilization of space time coding combined with turbo codes. This paper proposes a layered turbo coding schemes for hybrid and/or integrated satellite systems. We first introduce the system architecture and operational principle of the proposed scheme, and discuss the applicability.