• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.304-310
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• 2006

This paper evaluates the performance of three types of data delivery mechanisms in clustered sensor networks, as a basic research to develop an energy efficient topology management scheme. In the first mechanism, one node per cluster(clusterhead) turns on its radio(or wakes up) to transmit and receive RTS/CTS/DATA/ACK messages, but in the second one, k nodes per cluster wake up and participate in the message exchange. In the last mechanism, clusterheads turn on the radio to exchange RTS/CTS messages, and if a clusterhead receives RTS containing its cluster m as a destination, it makes k nodes in the cluster hun on the radio to receive DATA and transmit ACK. Through simulation, we show the energy consumption of the three types of data delivery mechanisms as functions of the number of active nodes per cluster, offered load, and packet loss probability.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.903-909
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• 2010

ADAS is the air defense control system performing air surveillance and identification of ROK and near air. This system is self-developed by Air Force, currently operated successfully as the alternative system of MCRC. ADAS processes converting and combining transferred the real time radar data detected by radars. additionally, it displays significant radar data as producing in tracks. Then, it uses the message queue for IPC(Inter Process Communication). the various tactical data processed in the server is ultimately send to the network management process through the message queue for transmitting to the weapon director console. the weapon director receives this transmitted tactical data through the console to execute air defense operations. However, there is a problem that data packet is delayed or lost since the weapon Director does not receive as the amount of tactical data from the server overflowed with air tracks and missions increased. This paper improved the algorism to display and transmit the various tactical data processed from ADAS server to numbers of the weapon director console in the real time without any delay or lost. Improved the algorism, established at exercise, the development server in the real operation network and the weapon director console, is proved by comparing the number of sending tactical data packets in the server and receiving packets in the weapon director.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5179-5202
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• 2018

Transmission Control Protocol (TCP) is the most widely used protocol in the cloud data centers today. However, cloud data centers using TCP experience many issues as TCP was designed based on the assumption that it would primarily be used in Wide Area Networks (WANs). One of the major issues with TCP in the cloud data centers is the Incast issue. This issue arises because of the many-to-one communication pattern that commonly exists in the modern cloud data centers. In many-to-one communication pattern, multiple senders simultaneously send data to a single receiver. This causes packet loss at the switch buffer which results in TCP throughput collapse that leads to high Flow Completion Time (FCT). Recently, Software-Defined Networking (SDN) has been used by many researchers to mitigate the Incast issue. In this paper, a detailed survey of various SDN based solutions to the Incast issue is carried out. In this survey, various SDN based solutions are classified into four categories i.e. TCP Receive Window based solutions, Tuning TCP Parameters based solutions, Quick Recovery based solutions and Application Layer based solutions. All the solutions are critically evaluated in terms of their principles, advantages, and shortcomings. Another important feature of this survey is to compare various SDN based solutions with respect to different performance metrics e.g. maximum number of concurrent senders supported, calculation of delay at the controller etc. These performance metrics are important for deployment of any SDN based solution in modern cloud data centers. In addition, future research directions are also discussed in this survey that can be explored to design and develop better SDN based solutions to the Incast issue.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.93-99
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• 2011

Recently, the development of internet technology makes user's personal data used by being saved in USB. But there is a critical issue that personal data can be exposed with malicious purpose because that personal data doesn't need to be certificate to use. This paper proposes USB security framework to prevent a duplicate use of personal data for protecting the data which in USB. The proposed USB security framework performs certification process of user with additional 4bite of user's identification data and usage choice of USB security token before certification data when the framework uses USB security product in different network. It makes communication overhead and service delay increased. As a result of the experiment, packet certification delay time is more increased by average 7.6% in the proposed USB security framework than simple USB driver and USB Token, and procedure rate of certification server on the number of USB is also increased by average 9.8%.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.63-71
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• 2003

In this paper, we propose an DSR(Dynamic Source Routing) protocol to support QoS for reliable data transmission in the mobile ad-hoc network. The proposed algorithm uses DSR protocol to support QoS as its basic routing protocol, and uses the nodes which are between source and destination nodes as key QoS support. Because of moving nodes there is some problem that is restricted reliable data transmission. For solve this problem, source node set up the QoS link with destination node. The nodes that are located at QoS link and find out loss of transmission path save the transmitting data packets. Those search a new transmission path to destination node and transmit the saved data packet to destination node. As the result of evaluation, we found the proposed QoS network guaranteed reliable data transmission with almost 100% data reception rate for slowly moving mobile ad-hoc network and with more 96% data reception rate, which is improvement of 3.7737% reception rate compared with none QoS network, for continuously fast moving mobile ad-hoc network.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.37-45
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• 2013

In recent years, the demands of multimedia data in wireless sensor networks have been significantly increased for the high-quality environment monitoring applications that utilize sensor nodes. However, since the amount of multimedia data is very large, the network lifetime is significantly reduced due to excessive energy consumption on particular nodes. To overcome this problem, in this paper, we propose a high efficiency data compression scheme in wireless multimedia sensor networks. The proposed scheme reduces the packet size by a multiple compression technique that consists of primary compression that deletes the lower priority bits considering characteristics of multimedia data and secondary compression based on Chinese Remainder Theorem. To show the superiority of our scheme, we compare it with the existing compression scheme. Our experimental results show that our proposed scheme reduces the amount of transmitted data by about 55% and increases network lifetime by about 16% over the existing scheme on average.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.29-34
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• 2008

Demand for car navigation systems has been an explosive increase because of prevalence of owner-drivers, spare time spread, and so on. In addition, car navigation systems are achieving a rapid growth to be the important part of telematics industry with services such as real-time traffic information and DMB(Digital Multimedia Broadcasting). The network data, one of the composition components in car navigation systems, is most important component because that is abstract of real world road network and base data in pathfinding. However most of the car navigation systems have been stand-alone system. Thus user's network data becomes outdated according to the time passing and does not reflect the change of road information in real world. To overcome this problem, users have to update network data in car navigation systems periodically. This method is quite cumbersome process. For this reason, this study proposed a new update method to serve the difference network data on user's device and the real world in real time, and simulated to verify.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.867-874
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• 2010

Since high packet losses occur in multi-hop transmission of wireless sensor networks, reliable data transmission is required. Especially, in case of event-driven data, a loss recovery mechanism should be provided for lost packets. Because retransmission for lost packets is requested to a node that caches the packets, the caching node should maintains all of data for transmission in its buffer. However, nodes of wireless sensor networks have limited resources. Thus, both a loss recovery mechanism and a buffer management technique are provided for reliable data transmission in wireless sensor networks. In this paper, we propose a buffer management technique at a caching position determined by a loss recovery mechanism. The caching position of data is determined according to desirable reliability for the data. In addition, we validate the performance of the proposed method through computer simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.26-33
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• 2012

Please WBAN(Wireless Body Area Networks) is wireless communication of within 3 m radius from inside and outside of the body. WBAN is many uses IEEE 802.15.4 MAC protocol for WBAN MAC protocol requirements. IEEE 802.15.4 MAC protocol applies GTS(Guaranteed Time Slot) allocation scheme for guarantee packet delivery of application which requests QoS(Quality of Service). However, GTS allocation scheme of IEEE 802.15.4 MAC protocol uses FIFS(First In First Service) queueing. So it reduces data transmission reliability and has many problems. Therefore, IEEE 802.15.4 applies not WBAN MAC protocol for emergency data transmission. In this paper, we proposes a priority based MAC protocol for emergency data transmission in wireless body area networks. the proposal MAC protocol sets priority the data. So GTS reqeuest throughput of emergency data increasing and GTS allocation delay of emergency data decreasing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.147-158
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• 2008

Recently, Intelligent Transportation System (ITS) has been actively developed and built since the Transportation System Efficiency Promotion Act was enacted. However, since mutual connection among transportation information systems was not considered, the integration of transportation information services did not occur. Accordingly, the Ministry of Land Transport and Maritime Affairs established and announced the technical standard on ITS. In this study, the conformance testing of the transportation information and communication system interface standard on data exchange between the Transportation Information Center and terminals was researched The test items were categorized as data request tests and data providing tests by analyzing the communication procedures specified in the standard. A detail testing scenario was created for each item. The test assessment was established based on the conformance of data exchange procedures and the accuracy of data packet messages. Under the established technical standard, the number of times that tests should be performed was thought set to 30 and the success rate was set to 95%. The purpose of this study is to help the ITS of Korea perform the integrated management of transportation information by researching methods for conformance testing on the technical standard on ITS.