• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.4
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• pp.86-94
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• 2012

VANETs can provide traffic warring service to help drivers drive safely based on the information of the traffic condition. The driver can drive safely through the warning service information provided by the VANET and know the traffic condition exactly more than through only the sight of driver. In this paper we suggest a new mechanism of updating the table to broadcast the message more rapidly based on the table driven method as the way of sending the emergency message in the VANETs. When updating the table, nodes sends only based on the message transmission success rate. In the result of simulation we could find that the suggested mechanism would reduce the delay time of the emergency message broadcast compared to the existing mechanism.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.203-206
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• 2004

Recently home network has been developed in the field of Information Technology. And there are many protocols for smart home, such as Lonworks, Echonet, KNX, LnCP etc. However, the performance evaluation has not been nearly known between the protocols. Hence, this paper evaluates the performance of KNX by Konnex Association and LnCP(Living network Control Protocol) by LG Electronics. We developed simulation model using flowchart of KNX and LnCP and simulation scenario through analysis of message to be generated in the home network. Furthermore, we evaluate simulation performance, such as mean transmission delay, maximum transmission delay, and collision rate of both protocols.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.119-124
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• 2001

A new WDM-based protocol for scheduling a variable-length message is proposed in this paper. Two control slots, Pre-reservation slot and Reservation Slot, are used to coordinate transmission and diminish the collisions of packet to minimize the access delay. When there is an idle reservation slot, a control packet is transmitted on that slot and message is transferred. And the node continues to transmit its control packet through the corresponding slot every cycle, until the message is completely transmitted. If an idle reservation slot is not available, the node schedules the transmission time of message in earliest available time using Pre-reservation slots. The proposed scheduling protocol has several advantages; any new node can join the network anytime without network re-initialization. Moreover, with the pre-reservation slots, we can avoid the packet collisions and destination conflicts, and we can improve the access delay time for message transmissions.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.625-628
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• 2011

Dynamic sensor network(DSN) technology which is based on swarming flight type air node offers analyzed and acquired information on target data gathered by air nodes in rotation flight or 3 dimension array flight. Efficient operation of dynamic sensor network based on air node is possible when problems of processing time, data transmission reliability, power consumption and intermittent connectivity are solved. Delay tolerant network (DTN) can be a desirable alternative to solve those problems. DTN using store-and-forward message switching technology is a solution to intermittent network connectivity, long and variable delay time, asymmetric data rates, and high error rates. However, all processes are performed at the bundle layer, so high power consumption, long processing time, and repeated reliability technique occur. DSN based on swarming flight type air node need to adopt store-and-forward message switching technique of DTN, the cancelation scheme of repeated reliability technique, fast processing time with simplified layer composition.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.5
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• pp.218-225
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• 2001

This paper analyses the performance of network system using the CAN(Controller Area Network) protocol. Given messages are assumed to be scheduled by the DMS(Deadline Monotonic Scheduling) algorithm. The mathematical models for time-delay that can be occurred between CAN nodes are defined. The effectiveness of modeling is shown by comparing the difference of time-delay between simulations and practical experiments. We analyse the results according to the variation of factors, such as the number of nodes, the transmission speed, the message size and the number of aperiodic messages through simulation and confirm the real-time performance of lower priority messages. We also investigate the real-time performance of periodic messages when aperiodic message generates.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2747-2749
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• 2000

The KEPRI has been developing the medium/small scale Distribution Automation System(DAS) that adopts wireless transmission media for exchanging information between master and remote terminals. It was concluded that Short Message Service(SMS) of Personal Communication Service(PCS) was the best wireless transmission media for the medium/small scale DAS in the last year. However. we had problem that PCS had long transmission delay. Therefore. SMS phones will be substituted with Radio Link Protocol(RLP) modems having transmission delay less than 5 seconds. This paper describes wireless networks for DAS, practical experience.

• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.571-582
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• 2007

Vehicular ad-hoc networks is temporarily established through inter-vehicle communication without any additional infrastructure aids. It requires a immediate message propagation because it mainly deals with critical traffic information such as traffic accidents. The distance-based broadcast scheme is one of the representative broadcast schemes for vehicular ad-hoc network. In this scheme, a node to disseminate messages is selected based on a distance from a source node. However, a message propagation delay will be increased if the relay nodes are not placed at the border of transmission range of the source node. In particular, when the node density is low, the message propagation delay is getting longer. In this paper, we propose a time-window reservation based relay node selection scheme. A node receiving the alert message from the source node has its time-window and randomly selects its waiting time within the given time-window range. A proportional time period of the given time-window is reserved in order to reduce the message propagation delay. The experimental results show that the proposed scheme has shorter message propagation delay than the distance-based broadcast scheme irrespective of node density in VANET. In particular, when the node density is low, the proposed scheme shows about 26% shorter delay and about 46% better performance in terms of compound metric, which is a function of propagation latency and network traffic.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.12
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• pp.1604-1610
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• 2018

The speech recognition service is used as an ancillary means of communication by converting and visualizing the speaker's voice into text to the hearing impaired persons. However, in open environments such as classrooms and conference rooms it is difficult to provide speech recognition service to many hearing impaired persons. For this, a method is needed to efficiently provide it according to the surrounding environment. In this paper, we propose a system that recognizes the speaker's voice and transmits the converted text to many hearing impaired persons as messages. The proposed system uses the MQTT protocol to deliver messages to many users at the same time. The end-to-end delay was measured to confirm the service delay of the proposed system according to the QoS level setting of the MQTT protocol. As a result of the measurement, the delay between the most reliable Qos level 2 and 0 is 111ms, confirming that it does not have a great influence on conversation recognition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.482-491
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• 2007

This paper proposes a k-disjoint-path routing algorithm that provides energy efficient and reliable message transmission in wireless sensor networks. The proposed algorithm sends messages through a single path without the occurrence of critical events. However, it sends through k disjoint paths(k>1) under the occurrence of critical events. The proposed algorithm detects the occurrence of critical events by monitoring changing data patterns, and calculates k from a well-defined fault model and the target-delivery ratio. Our simulations reveal that the proposed algorithm is more resilient to node failure than other routing algorithms, and it also decreases energy consumption and reduces the average delay much more than multi-path and path-repair algorithms.

• Journal of IKEEE
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• v.21 no.2
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• pp.115-122
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• 2017

In vehicular safety service, every vehicle broadcasts Basic Safety Message (BSM) periodically to inform neighbor vehicles of host vehicle information. However, this can cause network congestion in a region that is crowded with vehicles resulting in a reduction in the message delivery ratio and an increase in the end-to-end delay. Therefore, it could destabilize the vehicular safety service system. In this paper, in order to improve the congestion control and to consider the hidden node problem, we propose a congestion control scheme using entire network congestion level estimation combined with transmission power control, data rate control and time slot based transmission control algorithm. The performance of this scheme is evaluated using a Qualnet network simulator. The simulation result shows that our scheme mitigates network congestion in heavy traffic cases and enhances network capacity in light traffic cases, so that packet error rate is perfectly within 10% and entire network load level is maintained within 60~70%. Thus, it can be concluded that the proposed congestion control scheme has quite good performance.