• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.509-520
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• 2007

In this paper, we propose a real-time sensor node platform that guarantees the real-time scheduling of periodic and aperiodic tasks through a multitask-based software decomposition technique. Since existing sensor networking operation systems available in literature are not capable of supporting the real-time scheduling of periodic and aperiodic tasks, the preemption of aperiodic task with high priority can block periodic tasks, and so periodic tasks are likely to miss their deadlines. This paper presents a comprehensive evaluation of how to structure periodic or aperiodic task decomposition in real-time sensor-networking platforms as regard to guaranteeing the deadlines of all the periodic tasks and aiming to providing aperiodic tasks with average good response time. A case study based on real system experiments is conducted to illustrate the application and efficiency of the multitask-based dynamic component execution environment in the sensor node equipped with a low-power 8-bit microcontroller, an IEEE802.15.4 compliant 2.4GHz RF transceiver, and several sensors. It shows that our periodic and aperiodic task decomposition technique yields efficient performance in terms of three significant, objective goals: deadline miss ratio of periodic tasks, average response time of aperiodic tasks, and processor utilization of periodic and aperiodic tasks.

• Journal of Korea Multimedia Society
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• v.9 no.10
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• pp.1322-1331
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• 2006

Concurrency control is one of the important factors to maintain consistent conditions of a game because most participants of the game should be shared information to play the game through a distributed network system. replay delay times should establish in every event and the received event should be saved and performed simultaneously for Concurrency Control. However, it is not easy to practice the event with same speed in environment having various moving speed. Therefore, expansion have to be provided. In other words, one of the most important factors of a game's efficiency is the process of bandwidth and delay. the process of concurrency control method based on scalable prediction for Multi-platform games would minimize the loss rate of a event and then would improve the interaction capacity of a game. It also might get reliability between clients. This paper analyzes some problems in terms of a layout of a game that integrates a cable and a wireless system. In addition, this paper provides methods to expand bandwidth and delay that might be an obstacle of a On-line game and to ensure reliability between a server and a client.

• Journal of KIISE:Information Networking
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• v.33 no.4
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• pp.310-323
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• 2006

In this paper, we describe a secure cluster-routing protocol based on a multi-layer scheme in ad hoc networks. We propose efficient protocols, Authentication based on Multi-layer Clustering for Ad hoc Networks (AMCAN), for detailed security threats against ad hoc routing protocols using the selection of the cluster head (CH) and control cluster head (CCH) using a modification of cluster-based routing ARCH and DMAC. This protocol provides scalability of Shadow Key using threshold authentication scheme in ad hoc networks. The proposed protocol comprises an end-to-end authentication protocol that relies on mutual trust between nodes in other clusters. This scheme takes advantage of Shadow Key using threshold authentication key configuration in large ad hoc networks. In experiments, we show security threats against multilayer routing scheme, thereby successfully including, establishment of secure channels, the detection of reply attacks, mutual end-to-end authentication, prevention of node identity fabrication, and the secure distribution of provisional session keys using threshold key configuration.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.3
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• pp.19-25
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• 2012

Underwater sensor networks (UWSNs) employ acoustic channels for communications. One of the main characteristics of the underwater acoustic channel is long propagation delay. Previously proposed MAC (medium access control) protocols for wireless sensor networks cannot be directly used in UWSNs due to the long propagation delay. The long propagation delay and uneven nodes deployments cause spatial fairness in UWSNs. Therefore, a new MAC protocol for UWSNs needs to be developed to provide efficient communications. In this paper, we propose an efficient MAC protocol in order to alleviate the fairness problem. In the proposed scheme, when a node receives a RTS packet, it does not immediately send back but delays a CTS packet. The node collects several RTS packets from source nodes during the delay time. It chooses one of the RTS packets based on the queue status information. And then, it sends a CTS packet to the source node which sent the chosen RTS packet. The performance of the proposed scheme is investigated via simulation. Simulation results show that our scheme is effective and alleviates the fairness problem.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06a
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• pp.166-170
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• 2010

센서네트워크는 유비쿼터스 환경을 실현할 수 있는 기술로서, 최근 무인 경비 시스템이나 에너지 관리, 환경 모니터링, 홈 자동화, 헬스케어 응용 등과 같은 다양한 응용 분야에 활용되고 있다. 하지만 자신의 정보가 무선통신상에 쉽게 노출됨으로써 도청과 전송 메시지에 대한 위변조, 서비스 거부 공격을 받을 위험이 있다. 더욱이 센서네트워크의 자원 제약성(적은 메모리, 컴퓨팅 성능의 제약)과 키분배 관리의 어려움으로 인해 기존의 공개키, 대칭키 기반의 면안프로토콜을 대체할 수 있는 프로토콜이 필요하다. 그러므로 키분배 관리에 장 접을 가지는 Bilinear map 기반 프로토콜은 적합한 대안이다. 하지만 프로토콜에 사용되는 Pairing연산은 높은 컴퓨팅 성능이 요구된다. 따라서 제한된 성능을 가진 센서상의 구현을 위해서는 Computation Cost를 줄이고 연산 수행 속도를 가속화 할 필요성이 있다. 본 논문에서는 프로토콜 구현에 필요한 Pairing의 핵심 연산인 Multiplication을 대표적인 센서노드 프로세서인 MSP430상에서 최적화 구현함으로써 성능을 개선한다.

• Journal of the Korea Society of Computer and Information
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• v.15 no.10
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• pp.11-17
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• 2010

Mobile device, one of typical devices in ubiquitous environment, is received attention owing to portability. In these days, technical researches on a kind of the device are focusing on applications of smart phone. For example, the techniques using geographical position and applied instances such as augmented reality techniques are gradually increasing. That makes data processing important. Mobile application services for users also require various application techniques based on moving objects. In addition, they require the techniques that processed data are needed to be shown in visualization. However, this is reality that it lacks of showing visualization works to improve the understanding of thing what it is. To reduce or solve the problems, in this paper we show the results to implement the R tree based 3 dimension index architecture in visualization. Further, we implemented and present creating objects, showing in 3D for the objects, catching spatial position on a node map through mini map function and improving the understanding of R tree by visualizing.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.2
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• pp.163-168
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• 2008

Navigation system based on indoor location estimation is one of the core technologies in mobile robot systems. Wireless sensor network has great potential in the indoor location estimation due to its characteristics such as low power consumption, low cost, and simplicity. In this paper we present an algorithm to estimate the indoor location of mobile robot based on wireless sensor network and fuzzy modeling. ZigBee-based sensor network usually uses RSSI(Received Signal Strength Indication) values to measure the distance between two sensor nodes, which are affected by signal distortion, reflection, channel fading, and path loss. Therefore we need a proper correction method to obtain accurate distance information with RSSI. We develop the fuzzy distance models based on RSSI values and an efficient algorithm to estimate the robot location which applies to the navigation algorithm incorporating the time-varying data of environmental conditions which are received from the wireless sensor network.

• Journal of KIISE:Databases
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• v.31 no.6
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• pp.624-640
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• 2004

Recently, with the rapid development of location-based techniques, index structures to efficiently manage moving objects have been required. In this paper, we propose a new spatio-temporal index structure that supports a future position retrieval and minimizes a update cost. The proposed index structure combines an assistant index structure that directly accesses current positions of moving objects with KDB-tree that is a space partitioning access method. The internal node in our proposed index structure keeps time parameters in order to support the future position retrieval and to minimize a update cost. Moreover, we propose new update and split methods to maximize the space utilization and the search performance. We perform various experiments to show that our proposed index structure outperforms the existing index structure.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.27-30
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• 2012

In the Cluster-Based Routing Protocol (CBRP) a cluster header in each cluster should be elected. The cluster headers consume energy much more than other nodes because they manage and operate all of mobile nodes in their cluster. The traditional CBRP elects a cluster header without considering the remaining electric energy of each node. So, there exists problems that the cluster header has short average lifetime, and another cluster header should be elected again frequently. In this paper, we propose the improved protocol which prolongs the lifetime of the cluster header, decreases of header re-elected problem, decreases of header re-elected problem and enhances the stability of the path. In order to achieve this, when a cluster header is elected in a cluster, the remaining electric energies of all the nodes are compared with one another, and the node with the highest energy is elected as the cluster header. Also, the node with the second highest energy is elected as the second header. If the elected cluster header is unable to perform the role of the cluster header because the remaining energy level goes low, it sends a beacon message to neighbor member nodes and the second header will serve as the cluster header.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.197-206
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• 2011

The Korean government concentrates on supplying public transit facilities for the mobility handicapped. In other hands, increasing needs of transfer information when the mobility handicapped use transit facilities are substantial but not satisfactory as a whole. This study focuses on evaluating the applicability of developed K-path algorithm to provide user-customized route information that could make an active using of public transit while considering the mobility handicapped preferences. Developed algorithm reflects on requirements considering transfer attributes of the mobility handicapped. Trip attributes of the handicapped are addressed distinguished from handicapped types such as transfer walking time, transfer ratio, facility preferences and etc. This study examines the verification and application of the proposed algorithm that searches the least time K-paths by testing on actual subway networks in Seoul metropolitan areas. It is shown that the K-path algorithm is good enough to provide paths that meet the needs of the mobility handicapped and to be adoptable for the future expansion.