• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.129-138
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• 2007

AAA(Aluthentieation, Authorization, Accounting) protocol is an information securitv technology that offer secure and reliable user Authentication, Authorization, Accounting function systematically in various services. protocol and wireless network work as well as win network. Currently IETF(Internet Engineering Task Force) AAA Working Group deal with about AAA protocol and studying with activity, But, recently it exposing much problems side to user's anonymity and privacv violation. Therefore, in this paper, AAAH(Home Authentication Server) authenticaters Mobile device, after that, use ticket that is issued from AAAH even if move to outside network and can be serviced offering authentication in outside network without approaching by AAAH, Also, we study mechanism that can offer user's privacy and anonymousness to when use service. Our mechanism is using Time Synchronization OTP and focusing authentication and authorization. Therefore, our mechanism is secure from third party attack and offer secure and effective authentication scheme. Also only right user can offer services by using ticket. can reduce signal and reduce delay of message exchanged, can offer persistent service and beighten security and efficiency.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.112-118
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• 2005

Workflow is a collection of tasks organized to accomplish some business processes. It also defines the order of task invocation or conditions under which task must be invoked, task synchronization, and information flow. And activity based costing(ABC) provides accurate cost information for decision making. In ABC systems, costs must be separable into cost pools each of which corresponding to a single cost driver. These two systems are closely related to each other. But recent research deals with workflows and ABC systems separately. Thus, this research proposes an extended workflow model which is expressed cost information using activity based costing.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2489-2491
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• 2005

Currently, Programmable Logic Contorller(PLC) uses Real Time Operation System(RTOS) as basic OS. RTOS executes defined results as to defined time. General features of RTOS emphasize the priority in each task, high-speed process of external interrupt, task scheduling, synchronization in task, the limitation of memory capacity. For safety critical placement, PLC software needs Verification and Validation(V&V). For example, nuclear power plant. In this paper, PLC RTOS is verified by formal methods. Particularly, formal method V&V uses verification tool called 'STATEMATE', and shows the results.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.275-280
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• 2009

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner Femtocells can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage. TThe frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) forapplications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. The IEEE 1588 specification provides a low-cost means for clock synchronisation over a broadband Internet connection. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. However, the timing synchronization over packet switched networks is a difficult task because packet networks introduce large and highly variable packet delays. This paper proposes an enhanced filter algorithm to reduce ths packet delay variation effects and maintain ToP slave clock synchronization performance. The results are presented to demonstrate in the intra-networks and show the improved performance case when the efficient ToP filter algorithm is applied.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.203-206
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• 2005

This paper presents a design experience of supervisory control system for agile and intelligent manufacturing(AIM). For effectively program job instructions, a Petri net-type graphical language is proposed and it can be applied to a various task such as concurrency and synchronization. PGL is consisted of PGL editor, PGL analyzer and PGL translator; PGL editor generates a job instruction program using graphic symbol. PGL analyzer prevents a deadlock or resource allocation of unit cell. PGL translator transfers to adequate sequential job commands of each unit cell.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.57-67
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• 1996

This paper aims to support delay-sensitive multimedia applications by suggesting a mechanism in which maintains almost constant end-to-end delay thus providing the optimum playout synchronization. For this task the sum of network delay and buffering delay is entiredly managed and to eliminate little delay fluctuations and instantaneous delays at a buffer and a network, a low pass filter is used. Furthermore the correction function, which is used for maintaining the buffering level ot a reference value, is a non-linear step function, unlike the existing linear and continuous function. it has a different step sizes adapting to a traffic characteristics of a network congestion. the proposed mechanism has been confirmed of it sefficiency through SLAM-II netowrk.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5C
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• pp.550-555
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• 2007

We propose how to improve the performance of TOA estimation in UWB MB-OFDM systems. The scheme is based on the correlation between the OFDM preamble and the template signal. The validity of the proposed scheme is shown using the simulation results, where it is shown that the performance of the proposed scheme outperforms that of the existing schemes

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.677-680
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• 2003

In this paper, the analysis of practical end-to-end delay in worst case is performed for distributed control system considering the implementation of the system. The control system delay is composed of the delay caused by multi-task scheduling of operating system, the delay caused by network communication, and the delay caused by the asynchronous between them. Through simulation tests based on CAN(Controller Area Network), the proposed end-to-end delay in worst case is validated. Additionally, online clock synchronization algorithm is proposed here for the control system. Through another simulation test, the online algorithm is proved to have better performance than offline one in the view of network bandwidth utilization.

• ETRI Journal
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• v.29 no.3
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• pp.259-269
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• 2007

The ubiquitous flexible operating system (UbiFOS) is a real-time operating system designed for cost-conscious, low-power, small to medium-sized embedded systems such as cellular phones, MP3 players, and wearable computers. It offers efficient real-time operating system services like multi-task scheduling, memory management, inter-task communication and synchronization, and timers while keeping the kernel size to just a few to tens of kilobytes. For flexibility, UbiFOS uses various task scheduling policies such as cyclic time-slice (round-robin), priority-based preemption with round-robin, priority-based preemptive, and bitmap. When there are less than 64 tasks, bitmap scheduling is the best policy. The scheduling overhead is under 9 ${\mu}s$ on the ARM926EJ processor. UbiFOS also provides the flexibility for user to select from several inter-task communication techniques according to their applications. We ported UbiFOS on the ARM9-based DVD player (20 kB), the Calm16-based MP3 player (under 7 kB), and the ATmega128-based ubiquitous sensor node (under 6 kB). Also, we adopted the dynamic power management (DPM) scheme. Comparative experimental results show that UbiFOS could save energy up to 30% using DPM.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.5
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• pp.219-231
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• 2005

Many applications in cluster computing require QoS (Quality of Service) services. Since performance predictability is essential to provide QoS service, underlying systems must provide predictable performance guarantees. One way to ensure such guarantees from network subsystems is to generate global schedules from applications'network requests and to execute the local portion of the schedules at each network interface. To ensure accurate execution of the schedules, it is essential that a global time base must be maintained by local clocks at each network interface. The task of providing a single time base is called a synchronization problem and this paper addresses the problem for system area networks. To solve the synchronization problem, FM-QoS (1) proposed a simple synchronization mechanism called FBS(Feedback-Based Synchronization) which uses built-in How control signals. This paper extends the basic notion of FM-QoS to a theoretical framework and generalizes it: 1) to identify a set of built-in network flow control signals for synchrony and to formalize it as a synchronizing schedule, and 2) to analyze the synchronization precision of FBS in terms of flow control parameters. Based on generalization, two application classes are studied for a single switch network and a multiple switch network. For each class, a synchroniring schedule is proposed and its bounded skew is analyzed. Unlike FM-QoS, the synchronizing schedule is proven to minimize the bounded skew value for a single switch network. To understand the analysis results in practical networks, skew values are obtained with flow control parameters of Myrinet-1280/SAN. We observed that the maximum bounded skew of FBS is 9.2 Usec or less over all our experiments. Based on this result, we came to a conclusion that FBS was a feasible synchronization mechanism in system area networks.