• Journal of KIISE:Computer Systems and Theory
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• v.30 no.10
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• pp.533-543
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• 2003

With the increase of interests in cluster, there have been a number of research efforts to address the high availability issues on cluster. However, there are no kernel-level group communication systems to support the development of kernel-level application programs and it is not easy to use traditional user-level group communication systems for the kernel-level applications. This paper presents the design and implementation issues of KCGCS(Kernel-level Cluster Group Communication System), which is a kernel-level group communication module for linux cluster. Unlike traditional user-level group communication systems, the KCGCS uses light-weight heartbeat messages and a ring-based heartbeat mechanism, which allows users to implement scalable failure detection mechanisms. Moreover, the KCGCS improves the reliability by using distributed coordinators to maintain membership information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6B
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• pp.683-688
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• 2011

Current is change to concept that management traffic of ship os magnified gradually to near shore waters from harbor. Therefore, introducing the technology of AIS in the ground station, lighthouse, bouy, sea facilities etc.. that is support equipment for safety sailing of ship and safety security of harbor and ship administration. The operation and maintenance of AIS for aids to navigation are required to efficient method. With this actuality, sea advanced nation of EU, USA, Japan that has been apply for developing AtoN AIS equipment that is connected equipment of technology standard in IALA. Because of it is expected to depend equipment in income, that is required to domestic technology of the AtoN AIS. This paper is targeted to development that is suitable automation AtoN AIS equipment in environmental peculiarity for constructor AtoN operating administration center. It has been realization send protocol for information interchange.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.10
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• pp.343-348
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• 2015

Due to the need for multilingual e-mail address, EAI Working Group of the IETF has created a wide range of standards associated with e-mail address internationalization(EAI) since 2006. One of the authors and colleagues designed and implemented the mail server, SMTPUTF8, that supports EAI RFC protocols. SMTPUTF8 mail server is composed of new SMTP and POP3 servers supporting EAI RFC protocols. However, SMTPUTF8 did not include a new IMAP server supporting EAI RFC protocol. Recently many people are using smart phones to read and send e-mail messages in a mobile environment. IMAP server is more useful than POP3 server in a mobile environment. Therefore, in this paper, the authors have designed and implemented IMAP server and client app that complies with the IMAP standard (RFC) published by EAI WG of IETF to support multilingual e-mail address. This IMAP server is added to the SMTPUTF8 mail server so that users can access e-mail messages via IMAP client app in a mobile environment.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.4
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• pp.247-258
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• 2009

Distributed file systems running on a cluster of inexpensive commodity hardware are being recognized as an effective solution to support the explosive growth of storage demand in large-scale Internet service companies. This paper presents the design and implementation of BeanFS, a distributed file system for large-scale e-mail services. BeanFS is adapted to e-mail services as follows. First, the volume-based replication scheme alleviates the metadata management overhead of the central metadata server in dealing with a very large number of small files. Second, BeanFS employs a light-weighted consistency maintenance protocol tailored to simple access patterns of e-mail message. Third, transient and permanent failures are treated separately and recovering from transient failures is done quickly and has less overhead.

• Journal of KIISE:Databases
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• v.36 no.4
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• pp.292-305
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• 2009

Wireless sensor networks have a lot of application areas such as industrial process control, machine and resource management, environment and habitat monitoring. One of the main objects of using wireless sensor networks in these areas is the event detection. To detect events at a user's request, we need a join processing between sensor data and the predicates of the events. If there are too many predicates of events compared with a node's capacity, it is impossible to store them in a node and to do an in-network join with the generated sensor data This paper proposes a predicate-merge based in-network join approach to efficiently detect multiple events, considering the limited capacity of a sensor node and many predicates of events. It reduces the number of the original predicates of events by substituting some pairs of original predicates with some merged predicates. We create an estimation model of a message transmission cost and apply it to the selection algorithm of targets for merged predicates. The experiments validate the cost estimation model and show the superior performance of the proposed approach compared with the existing approaches.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1071-1075
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• 2010

Because a sensor node in wireless sensor networks(WSNs) has limited resources, such as battery capacity and memory, data aggregation techniques have been studied to manage the limited resources efficiently. Because sensor network uses wireless communication, a data can be disclosed by attacker. Thus, the study on data protection schemes for data aggregation is essential in WSNs. But the existing data aggregation methods require both a large number of computation and communication, in case of network construction and data aggregation processing. To solve the problem, we propose a data protection scheme based on Hilbert-curve for data aggregation. Our scheme can minimizes communications among neighboring sensor nodes by using tree-based routing. Moreover, it can protect the data from attacker by doing encryption through a Hilbert-curve technique based on a private seed, Finally, we show that our scheme outperforms the existing methods in terms of message transmission and average sensor node lifetime.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1086-1090
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• 2010

In recent, as many applications of sensor networks increase, various techniques have been studied to efficiently operate network systems. The query optimization scheme that is one of such techniques has been studied to reduce the data transmission cost. The data transmission is of great importance to the energy consumption of sensor networks. In this paper, we propose an energy-efficient multiple queries processing scheme by sharing sensor readings for multiple queries, when they are occurred in sensor networks. The proposed scheme reduces unnecessary data transmissions among the sensor nodes by intuitively identifying their locations using the grid structure. It also efficiently shares the data by recognizing the redundant regions of sensor nodes. In order to show the superiority of the proposed scheme, we compare it with the existing scheme in various experiments. As the result, the proposed scheme reduces about 65% energy consumption over the existing scheme.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.137-142
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• 2005

Since wireless communication cost is relatively expensive, the mobile games using cellular phones or PDAs are mostly played after being downloaded unlike more updated types of phone-to-phone or online games. In particular, the upbringing games, in which garners foster virtual companion animals or vegetables as their avata, have been spotlighted. It is essential to supply variety of items for upbringing avatas. However, due to diverse tastes for avatas and limited storage of mobile terminals, game manias must download their desired items from homepages. In addition, game developers must inform users through SMS messages whenever a new item is created. To do so, they must link WEB server and WAP server to Call Back URL or ARS. This paper proposed a linkage method suitable for JAVA-based mobile phone operating system. The proposed method will consequently increase life cycle of a game and reinforce profitability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.499-508
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• 2004

The Smart Home or intelligent home network control system has the need for home devices to cooperate for the purpose of providing the automated services to residents. The cooperation of home devices can be defined as the service for residents that it controls simultaneously two or more home devices with the same purpose about user's control request of specific home device. A object of home device cooperation are the function object of home device, it is well defined in each device model in AHAM(Association of Home Appliance Manufactures) nth(Connected Home Appliances). AMAM CHA is to promote new appliance services and features enabled through networking by describing generic appliance models, objects, and high-level messages, but does not consider the description and process of cooperation between objects of each device model. This paper defines the cooperation relationship that could be discovered in among home devices, and proposes the cooperation model that AHAM objects could process the cooperation relationship.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.99-103
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• 2006

In this paper, we focus on the problem of designing an energy efficient MAC protocol for wireless sensor networks and analyze S(Sensor)-MAC and T(Time-out)-MAC. S-MAC is based on the concept of the 'listen/sleep mode cycle'. This applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data moves through the network. However unlike the S-MAC, where the duration of the cycle is fixed, T-MAC introduces an adaptive duty cycle in a novel way: by dynamical ending the active part of it. This reduces the amount of energy wasted on idle listening, in which nodes wait for potentially incoming messages while still maintaining a reasonable throughput. In this paper we discuss the design of these two Protocols. We analyze them from the aspect of latency, throughput, and power savings when using the OMNeT++ simulator in various environments.