• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.81-89
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• 2011

Underwater wireless network can be useful in various fields such as underwater environment observation, catastrophe prevention, ocean resources exploration, ocean organism research, and vessel sinking exploration. We need to develop an efficient design for Medium Access Control (MAC) protocol to improve multiple data communication in underwater environment. Aloha protocol is one of the basic and simple protocols, but it has disadvantage such as collision occurs oftenly in communication. If there is collision occured in RF communication, problem can be solved by re-sending the data, but using low frequency in underwater, the re-transmission has difficulties due to slow bit-rate. So, Time Division Multiple Access (TDMA) based MAC protocol is going to be used to avoid collisions, but if there is no data to send in existing TDMA, time slot should not be used. Therefore, this paper proposes dynamic TDMA protocol mechanism with reducing the time slots by sending short "I Have No Data" (IHND) message, if there is no data to transmit. Also, this paper presents mathematic analysis model in relation to data throughput, channel efficiency and verifies performance superiority by comparing the existing TDMA protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.365-373
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• 2003

In this paper, we design a versatle RS decoder which can decode RS codes of any block length n as well as any message length k, based on a modified Euclid's algorithm (MEA). This unique feature is favorable for a shortened RS code of any block length it eliminates the need to insert zeros before decoding a shortened RS code. Furthermore, the value of error correcting capability t can be changed in real time at every codeword block. Thus, when a return channel is available, the error correcting capability can be adaptiverly altered according to channel state. The decoder permits 4-step pipelined processing : (1) syndrome calculation (2) MEA block (3) error magnitude calculation (4) decoder failure check. Each step is designed to form a structure suitable for decoding a RS code with varying block length. A new architecture is proposed for a MEA block in step (2) and an architecture of outputting in reversed order is employed for a polynomial evaluation in step (3). To maintain to throughput rate with less circuitry, the MEA block uses not only a multiplexing and recursive technique but also an overclocking technique. The adaptive RS decoder over GF($2^8$) with the maximal error correcting capability of 10 has been designed in VHDL, and successfully synthesized in a FPGA.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.245-256
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• 2009

Pastry overlay network is one of structured P2Ps using DHT(Distributed Hash Table). To reduce the number of messages among nodes, Rosary and LAR have been proposed by exploiting spatial locality and caching, respectively, in the Pastry. Rosary consists of Inter-Pastry and Intra-Pastry. A root node is assigned as a representative in each Intra-Pastry and it has the responsibility of Inter-Pastry and Intra-Pastry routing. Therefore, Rosary has several disadvantages; 1) low fault tolerance in case of root node failure 2) routing hop count increases because of the use of root nodes compared to the existing structured P2Ps, and 3) the communication load is concentrated in some specific areas. LAR has inefficient problems in that caching is not distributed among nodes in Intra-Pastry and caching is used by only nodes in the Intra-Pastry. In this paper, we propose an improved Pastry called Doughnut to overcome the above problems of Rosary and LAR. By dividing nodes with the local characteristics, the Doughnut consists of Inter-Pastry and Intra-Pastry, and all nodes have the responsibility of Inter-Pastry and Intra-Pastry routing. This results in that all nodes perform the role of the existing root node. This solves the problems of the reducing of fault-tolerance, the increasing of routing hop count, and the not-distributed communication load. Also Doughnut can use cache effectively because it guarantees the even cache distribution in local(Intra-Pastry) and the cache contents in local can be used in the other local. The proposed algorithm is implemented using simulator and the experimental results show the effectiveness of the proposed method compared to the existing method.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.108-115
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• 2012

Many studies relating the satellite navigation has been done by a relatively small research community in Korea. Most of domestic research has been focused on the application of the satellite navigation technology, but recently the topics of the next generation satellite navigation system are emphasized for its importance. Even opinions suggesting a future Korea's own satellite navigation system are not that uncommon. Due to the geographic, economic, and technological reasons, it is not widely discussed yet. However, a development technical roadmap regarding the Korea's own navigation satellite was established on the Korea Space Development Plan in general term. Currently four global navigation satellite systems are operating or being deployed. Several regional navigation satellite systems are in planning and development phase. Particularly in Asia, China has launched several satellites to complete their own global navigation satellite system, COMPASS until 2020. Japan launched one satellite and has planned to launch rest of set until 2013. It is proper time to develop Korea's own navigation satellite system to acquire the domestic space development technology and the security of navigational infrastructure. In this study, the validity or the feasibility of the Korea's own satellite navigation system is not discussed; rather the possibility and suitability of the additional information to the current operational navigation message is main target. For the first payload of the future Korea's satellite navigation satellite, a regional augmented system is more likely. This study also is focused on that aspect.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.521-530
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• 2018

This paper proposes "The Agriculture Decision-making System(ADS) based on Deep Learning for improving crop productivity" that collects weather information based on location supporting precision agriculture, predicts current crop condition by using the collected information and real time crop data, and notifies a farmer of the result. The system works as follows. The ICM(Information Collection Module) collects weather information based on location supporting precision agriculture. The DRCM(Deep learning based Risk Calculation Module) predicts whether the C, H, N and moisture content of soil are appropriate to grow specific crops according to current weather. The RNM(Risk Notification Module) notifies a farmer of the prediction result based on the DRCM. The proposed system improves the stability because it reduces the accuracy reduction rate as the amount of data increases and is apply the unsupervised learning to the analysis stage compared to the existing system. As a result, the simulation result shows that the ADS improved the success rate of data analysis by about 6%. And the ADS predicts the current crop growth condition accurately, prevents in advance the crop diseases in various environments, and provides the optimized condition for growing crops.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.223-226
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• 2017

With the development of information technology, users are provided with information they want through mobile device in various situations. When users communicate with information, there is interaction through gesture activities such as tapping and experience in the process. Experience through interaction in mobile affect the user's psychology. This is important because it is related to the behavior of the user in the future. Various types of information presentation methods have been researched in mobile environment. However, there are more research focusing on functional interactivity. The purpose of this study is to investigate the effect of interaction and usage mode on satisfaction, usefulness, and intention to use for sound text presentation that is user-centered. As variables for my study, there are two factors which are interactivity and usage mode. The interactivity type is composed of two ways that are: High and Low depending on modality and message interactivity; and the usage mode is composed of Action mode and Goal mode depending on whether user has a task or not. The experimental design is $2{\times}2$. The same content is provided in (a) only Modality interactivity, and (b) Modality and Message interactivity are provided. Depending on usage mode, (a) Action mode is processed without a specific task, and (b) Goal mode is performed with a specific task to participants. The experimental study demonstrated that there is a difference in satisfaction, usefulness, and intention to use depending on the difference of interaction and usage mode when providing information in mobile environment. The results of this study are summarized as follows: interaction and usage mode have significant influence on mobile user's satisfaction, usefulness, intention to use.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.119-131
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• 2009

The world's widely used key exchange protocols are open cryptographic communication protocols, such as TLS/SSL, whereas in the financial field in Korea, key exchange protocols developed by industrial classification group have been used that are based on PKI(Public Key Infrastructure) which is suitable for the financial environments of Korea. However, the key exchange protocols are not only vulnerable to client impersonation attacks and known-key attacks, but also do not provide forward secrecy. Especially, an attacker with the private keys of the financial security server can easily get an old session-key that can decrypt the encrypted messages between the clients and the server. The exposure of the server's private keys by internal management problems, etc, results in a huge problem, such as exposure of a lot of private information and financial information of clients. In this paper, we analyze the weaknesses of the cryptographic communication protocols in use in Korea. We then propose two key exchange protocols which reduce the replacement cost of protocols and are also secure against client impersonation attacks and session-key and private key reveal attacks. The forward secrecy of the second protocol is reduced to the HDH(Hash Diffie-Hellman) problem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.1
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• pp.43-56
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• 2012

Wireless sensor networks consist of numerous small-sized nodes equipped with limited computing power and storage as well as energy-limited disposable batteries. In this networks, nodes are deployed in a large given area and communicate with each other in short distances via wireless links. For energy efficient networks, dynamic clustering protocol is an effective technique to achieve prolonged network lifetime, scalability, and load balancing which are known as important requirements. this technique has a characteristic that sensing data which gathered by many nodes are aggregated by cluster head node. In the case of cluster head node is exposed by attacker, there is no guarantee of safe and stable network. Therefore, for secure communications in such a sensor network, it is important to be able to encrypt the messages transmitted by sensor nodes. Especially, cluster based sensor networks that are designed for energy efficient, strongly recommended suitable key management and authentication methods to guarantee optimal stability. To achieve secured network, we propose a key management scheme which is appropriate for hierarchical sensor networks. Proposed scheme is based on polynomial key pool pre-distribution scheme, and sustain a stable network through key authentication process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.12
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• pp.1646-1653
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• 2020

In case that the train driving with diverse high-speeds is manipulates by real-time remote control in long-term evolution-railway (LTE-R) system with frequent handovers, the real-time safe transmission of train control messages is important element. The handover delay time stability method regardless of train speed in order to enhance the real-time remote train control stability in LTE-R system is proposed in the paper. Furthermore, the variable speeds and altitudes of train collected by real measurements are applied for upgrading simulation accuracy. The simulation results inform that not only there are stable and unstable ranges to A3 offset values, but the optimal offset value for average handover delay is in unstable range. However, the late handover with A3 offset values in stable range should be chosen to get the predictable handover delay regardless of train speed rather than the early handover with A3 offset values in unstable range, since the key value of high-speed Korea railway system is the stability.

• Journal of the Korea Convergence Society
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• v.13 no.4
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• pp.45-51
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• 2022

Fear of contact exists due to the prevention of the spread of infectious diseases such as COVID-19. When using the common entrance door of an apartment, access is possible only if the resident enters a password or obtains the resident's permission. There is the inconvenience of having to manually enter the number and password for the common entrance door to enter. Also, contactless entry is required due to COVID-19. Due to the development of ICT, users can be easily identified through the development of face recognition and voice recognition technology. The proposed method detects a visitor's face through a CCTV or camera attached to the common entrance door, recognizes the face, and identifies it as a registered resident. Then, based on the registered information of the resident, it is possible to operate without contact by interworking with the elevator on the server. In particular, if face recognition fails with a hat or mask, the visitor is identified by voice or additional authentication of the visitor is performed based on the voice message. It is possible to block the spread of contagiousness without leaving any contactless function and fingerprint information when entering and exiting the front door of an apartment house, and without the inconvenience of access.