• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.516-520
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• 1996

This paper focues on development of a timer selection algorithm for IEEE802.4 token bus networks to serve large-scale integrated manufacturing systems. Such factory automation networks have to satisfy delay constraints imposed on time-critical messages while maintaining as much network capacity as possible for non-time-critical messages. Therefore, the object of this paper is to develop timer selection algorithm to minimize a certain penalty function. This paper presents an algorithm based on Genetic Algorithm. The efficacy of the algorithm has been demonstrated by a series of simulation experiments.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.54-64
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• 1998

In this paper, a cell scheduling algorithm is proposed to satisfy the service requirements of CBR, VBR traffics. Particularly, inthe proposed algorithm an ABR traffic which is not included in the conventional cell schedulaing algorithm is treated as one kind of traffic types. The algorithm of RT-VBR and NRT-VBR traffic such that the service requrements of RT-VBR and NRT-VBR traffic are satisfied. The proposed algorithm dynamically schedules cells in a real time by considerin the current traffic conditions. The simulation of the proposed algorithms such as WRR or DWRR in terms of the mean delay time and the maximum queue length.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.9-17
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• 1994

This paper proposes Double queue threshold QLT(Queue Length Threshold) algorithm and Hysteresis effect QLT algorithm. as being DPS(Dynamic Priority Scheduling) techniques. in order to advance the processing of multiple class traffics. Also, the performance of the proposed algorithms is analyzed through computer simulations,and the priority scheduling is analyzed using a retrial queue with two types of calls. Our simulation results show that the performance of the proposed Double queue length threshold QLT algorithm is superior to that of the conventinal QLT algorithm for 2 or more classes delay sensitive traffics. Also we find that Hysteresis effecT QLT algorithm is better mechanism than that of the existing QLT for real time and non-real time traffics.

• Convergence Security Journal
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• v.8 no.2
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• pp.95-102
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• 2008

In this paper, we proposed topology aggregation method that efficiently aggregating topology information in simple node topology. And, it improved QoS of networks by improving call success rate and call access time. Proposed method can improving performance of network by decreasing aggregation information and aggregating multi-links information between boundary nodes using the line segment scheme within bandwidth and delay parameter. To evaluate performance of the proposed scheme, we compare/analyze the current method with the proposed scheme in respect to call success rate, access time.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.144-149
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• 2003

Encryption/decryption delay is minimized, because there are constraints in transporting a multimedia data through the Internet. Therefore, encryption algorithm is needed which is changed with considering network traffic and load. And during many users participate in the same multimedia service, an user who already left the service can receive and the method which decrypt the RTP payload is needed because of knowing the encryption key. Therefore in this paper, Security Control Protocol for RTP is designed and implemented for changing the encryption algorithm and the key.

• Convergence Security Journal
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• v.2 no.1
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• pp.49-57
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• 2002

Real-Time Protocol (RTP) is used for multimedia information transmission and RTP payload must be encrypted for providing multimedia information security. Encryption/decryption delay is minimized, because there are constraints in transporting a multimedia data through the Internet. Therefore, encryption algorithm is changed with considering network traffic and load. During many users participate in the same multimedia service, an user who already left the service can receive and decrypt the RTP payload because of knowing the encryption key. In this paper, Security Control Protocol for RTP is designed and implemented for changing the encryption algorithm and the key.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.107-112
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• 2009

Spectral efficiency of current two-phase cooperative communications protocols is low since in the second time the relay forwards the same signal received from the source to the destination, the source keeps silent in this time. In this paper, we propose a novel cooperative communications protocol where the signal needed to transmit to the destination is sent in both phases, the source and the relay also transmit different signal to the destination thus no loss of spectral efficiency. This protocol performs signal selection based on log-likelihood ratio (LLR) at relay and maximum likelihood (ML) detection at destination. While existing protocols pay for a worse performance than direct transmission in the low SNR regime which is of special interest in ad hoc networks, ours is better over the whole range of SNR. In addition, the proposal takes advantages of bandwidth efficiency, long delay and interference among many terminals in ad hoc network. Simulation results show that the proposed protocol can significantly save total energy for wireless ad hoc networks.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.393-406
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• 2023

Smart structures are those structure that could adopt some behavior to prevent instability in their responses. The recognition of stability deterioration has been performed through rigid mathematical formulations in control theory and unpredicted results could not be addressed in control systems since they are able to only work under their predefined condition. On the other hand, incorporating all affecting parameters could result in high computational cost and delay time in the response of the systems. Artificial intelligence (AI) method has shown to be a promising methodology not only in the computer science by at everyday life and in engineering problems. In the present study, we exploit the capabilities of artificial intelligence method to obtain frequency response of a smart structure. In this regard, a comprehensive development of equations is presented using Hamilton' principle and first order shear deformation theory. The equations were solved by numerical methods and the results are used to train an artificial neural network (ANN). It is demonstrated that ANN modeling could provide accurate results in comparison to the numerical solutions and it take less time than numerical solution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11B
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• pp.987-996
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• 2006

In NEMO scenarios, mobile node's variety of movements and mobile router's point of attachment changes can result in handover. This handover process needs additional time to finish due to the multiple levels of indirection involved in NEMO. And the performance issues of mobile node's handover such as handover delay and packet loss in above cases haven't been studied thoroughly. So, in this paper, we define fast handover failure cases in hierarchical mobile IPv6 network based NEMO. We briefly described NEMO architecture and handover procedures of FMIPv6 and HMIPv6. And then, we classified mobile node or mobile router's movement pattern into several scenarios. Analysis for the fast handover classified NEMO scenarios, in terms of handover latency and packet delivery cost have been performed.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.317-324
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• 2003

In this paper, we propose the ATM based Passive Optical Network (PON) using the optical CDMA scheme with optical switches and PN codes in time domain. We also propose the bipolar optical receiving correlator for PN codes. As optical CDMA is performed by driving directly an optical switch on-off switching with PN codes, the number of distinct code sequences can be increased and the flexibility in assigning PN codes can be improved. Finally we theoretically analyze the signal-to-interference -plus-noise ratio and the bit error probability of regenerated signal and compare the performance of proposed scheme compared with ATM based PON using conventional optical CDMA with optical delay lines.