• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.4
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• pp.219-226
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• 2019

One of the most widely studied protocols for tactical ad-hoc networks is Optimized Link State Routing Protocol (OLSR). As for OLSR research, most research work focus on reducing control traffic overhead and choosing relay point. In addition, because OLSR is mostly dependent on link detection and propagation, dynamic Hello timer become research challenges. However, different timer interval causes imbalance of link validity time by affecting link lifetime. To solve this problem, we propose a weighted topology graph model for constructing a robust network topology based on the link validity time. In order to calculate the link validity time, we use control message timer, which is set for each node. The simulation results show that the proposed mechanism is able to achieve high end-to-end reliability and low end-to-end delay in small networks.

• Journal of IKEEE
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• v.22 no.4
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• pp.1210-1213
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• 2018

In this paper, we propose a method to reduce the amount of current through the Timing Control of the duty cycle and the Report Attribute Control at the MAC Layer in consideration of the Sleep Mode under the IoT wireless environment. The use of a duty cycle is an effective way to reduce energy consumption on wireless sensor networks where the node is placed in sleep mode periodically. In particular, we studied how to control power efficiency through duty rate in Short Transition Time and ACK Time processing while satisfying radio channel limitation criterion. When comparing before and after the improvement considering the delay time constraint, we validated the correlation of the electrical current reduction.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.666-671
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• 2007

EPON is proposed to be used in an infrastructure of the next generation wireless network. EPON can reduce fiber deployment cost and easily decrease the occurrence of layer-3 handover by introducing group cell concept. An EPON-based layer-2 handover algorithm is suggested for fast handover. The time-delay of the control signals are examined using simulation.

• ETRI Journal
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• v.25 no.1
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• pp.34-40
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• 2003

This paper considers a TMN-based management system for the management of public ATM switching networks using a four-level hierarchical structure consisting of one network management system, several element management systems, and several agent-ATM switch pairs. Using Jackson's queuing model, we analyze the effects of one TMN command on the performance of the component ATM switch in processing local calls. The TMN command considered is the permanent virtual call connection. We analyze four performance measures of ATM switches- utilization, mean queue length and mean waiting time for the processor directly interfacing with the subscriber lines and trunks, and the call setup delay of the ATM switch- and compare the results with those from Jackson's queuing model.

• ETRI Journal
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• v.30 no.2
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• pp.255-260
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• 2008

We compare the performance of a wavelength remodulated wavelength-division-multiplexed passive optical network implemented using Manchester-coded or inverse-return-to-zero (IRZ)-coded signal downstream and non-return-to-zero remodulated signal upstream. We investigate the effects of varying differences between downstream and upstream bit rates on the two coding schemes. When the bit rate ratio of upstream to downstream is less than or equal to 50%, the performance of Manchester coding is better than that of IRZ coding. However, when the bit rate ratio of upstream to downstream is higher than 50%, Manchester code requires appropriate time delay between upstream and downstream signals, whereas IRZ code needs reduced extinction ratio in the downstream signal.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.4
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• pp.493-498
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• 2011

In this paper, Transmission performance over MANET(Mobile Ad-hoc Networks) under DDoS Intrusions is evaluated. Intrusion counterplan requirement, which have to be used for MANET under DDoS intrusions, is suggested through this evaluation. VoIP simulator based on NS-2 network simulator is used for performance measurement. MOS, network delay, packet loss rate and call connection rate is measured with this simulation. Finally, requirement of intrusion continuing time shorter then 10 seconds is suggested for VoIP service over MANETs under DDoS intrusions.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.511-513
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• 2000

종단간 전송 지연은 시각 동기, 네트워크 성능 측정 등에서 매우 중요한 요소이다. 그러나 IP에 기반하고 있는 Internet은 여러 통신망 상의 지연 요소를 정확히 전달할 수 있는 구조가 없기 때문에 종단간 전송에 있어 전송 지연을 정확하게 알 수 없다. 특히 UDP 네트워크의 경우 전송할 때와 수신할 때 경로가 같지 않기 때문에 일반적으로 일주 지연 시간을 이용하지만 각 편도 전송 지연 시간 차이는 시스템의 다른 요소에 대해서 오류 요소로 작용할 수 있다. 본 논문에서는 일주 지연 시간을 전송시 지연 시간과 수신시 지연 시간으로 따로 측정 분석하였다. 측정 결과 편도 전송 지연 시간 차이 값은 수십 밀리초 범위를 가지며 이는 NTP 등에서 시각을 동기화 할 때 통상적인 정확도, 수 밀리초를 훨씬 넘어선다. 이것은 편도 지연 시간 차이값이 시각 동기, 네트워크 성능 평가 등에서 중요한 오류값으로 작용한다는 것을 의미한다. 분석 결과를 실험 데이터에 적용할 경우 실제 편도 지연 시간에 근사한 값을 구할 수 있고 좀더 정확한 시각 동기, 네트워크 성능 평가가 가능하게 된다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.199-204
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• 2006

To develop a safety-critical network in nuclear power plants that puts more stringent requirements than the competitive commercial ones do, we establish four design criteria - deterministic communication, explicit separation/isolation structure, reliability, verification & validation. According to those design criteria, the fundamental design elements are chosen as follows - a star topology, point-to-point physical link, connection-oriented link control and fixed allocation access control. After analyzing the design elements, we also build a communication architecture with TDM (Time Division Multiplexing) bus switching scheme. Finally, We develop a DDCNet (Deterministic Data Communication Network) based on the established architecture. The DDCNet is composed of 64 nodes and guarantees the transmission bandwidth of 10Mbps and the delay of 10 msec for each node. It turns out that the DDCNet satisfies the aforementioned design criteria and can be adequately utilized for our purpose.

• ETRI Journal
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• v.17 no.1
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• pp.23-36
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• 1995

We present a performance evaluation model of cell reassembly mechanism in an ATM switching system. An ATM switching system may be designed so that communications between processors of its control part can be performed via its switching network rather than a separate inter-processor communications network. In such a system, there should be interface to convert inter-processor communication traffic from message format to cell format and vice versa, that is, mechanisms to perform the segmentation and reassembly sublayer. In this paper, we employ a continuous-time Markov chain for the performance evaluation model of cell reassembly mechanism with individual buffering, judicially defining the states of the mechanism. Performance measures such as message loss probability and average reassembly delay are obtained in closed forms. Some numerical illustrations are given for the performance analysis and dimensioning of the cell reassembly mechanism.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.43-48
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• 2005

A robot system encompassing a remote control and monitoring through a virtual robot design is addressed and a tracking problem for a 2D (2 dimension) moving target by a robot vision is chosen as a case study. The virtual robot is developed, and it synchronizes with the real robot by compensating delay time. Two systems are displayed on a remote panel by communicating command and image data. The virtual robot utilizes an OpenGL library in Visual $C^{++}$ environment. Additionally, the remote monitoring and control between the real robot and the virtual robot are accomplished by employing an appropriate data compression in a network communication.