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Prediction-based smart channel scanning with minimized service disruption for IEEE 802.11e WLAN
Kim, Igor,Young-Tak Kim IEEE 2011 IEEE TRANSACTIONS ON CONSUMER ELECTRONICS - Vol.57 No.2
<P>The recent proliferation of smart mobile devices with IEEE 802.11 interfaces for real-time multimedia services such as VoIP, IPTV and video conference, strongly requires guaranteed QoS provisioning with seamless secure mobility during handover among IEEE 802.11 access points. The most important element of handover delay is channel scanning. Most of the existing channel scanning schemes, however, take more than 100 ms and do not guarantee the jitter requirement of less than 50 ms, which is required to guarantee the QoS of real-time services. This paper proposes a smart channel scanning where the channel scanning is carefully scheduled based on predicting the channel scanning time and interleaved frame delivery with limited jitter. This paper also describes an analytical model for predicting smart channel scanning time. The correctness of the prediction of channel scanning delay is analyzed through a series of experiments in a real testbed environment with more than 20 mobile nodes with MadWiFi interface cards. Also, the performance of the proposed smart scanning is compared with that of other schemes via network simulations. It is verified that the proposed smart channel scanning can provide QoS-guaranteed handovers with limited jitter of less than 50 ms and no packet losses in various conditions. The proposed smart channel scanning outperforms the existing scanning scheme under various topology configurations in terms of packet loss, jitter, service disruption time and total scanning time.</P>
Kim, Igor,Park, Seungkeun IET 2017 IET COMMUNICATIONS Vol.11 No.9
<P>Reliable and QoS-aware multimedia delivery is one of the most important requirements to satisfy end user needs. IEEE 802.11 networks have become one of the most popular Internet access methods owing to their low-cost and fast connection speed. Multicasting is a transmission technique that can significantly increase network efficiency through the simultaneous delivery of the same multimedia content to multiple multicast group members. IEEE 802.11 describes several multicast protocols targeted to increase the robustness of audio and video delivery. Some researchers have investigated the performance of such multicast protocols in terms of their achievable throughput. However, for a better understanding of the suitability of the protocols for a QoS-aware multimedia transmission, an in-depth analysis of the achievable delay is needed. This study provides a detailed delay analysis and describes analytical models for estimating the average achievable delay of IEEE 802.11 multicast protocols co-existing with legacy stations. The proposed analytical models are compared against simulation results under various conditions and parameter configurations. The simulation results validate the accuracy of the proposed models.</P>
Kim, Igor,Kim, Young-Tak Institute of Embedded Engineering of Korea 2010 대한임베디드공학회논문지 Vol.5 No.4
In this paper, we propose an application layer-based vertical handover management protocol, called multihoming RTP (mhRTP), for real-time applications with seamless mobility across heterogeneous wireless access networks. The proposed multi-homing RTP provides a soft handover by utilizing multiple available wireless access network interfaces simultaneously. The newly available path is dynamically added to the ongoing session by the mhRTP session manager. Also the decision making of QoS-improving or QoS-guaranteed handover is possible based on the estimation of available bandwidth in each candidate network. The performances of the proposed mhRTP have been analyzed through a series of simulations on OPNET network simulator. From the performance analysis, we confirmed that the proposed mhRTP can provide QoS-guaranteed vertical handover with efficient session managements.
Igor Kim,김영탁 대한임베디드공학회 2010 대한임베디드공학회논문지 Vol.5 No.4
In this paper, we propose an application layer-based vertical handover management protocol, called multihoming RTP (mhRTP), for real-time applications with seamless mobility across heterogeneous wireless access networks. The proposed multi-homing RTP provides a soft handover by utilizing multiple available wireless access network interfaces simultaneously. The newly available path is dynamically added to the ongoing session by the mhRTP session manager. Also the decision making of QoS-improving or QoS-guaranteed handover is possible based on the estimation of available bandwidth in each candidate network. The performances of the proposed mhRTP have been analyzed through a series of simulations on OPNET network simulator. From the performance analysis, we confirmed that the proposed mhRTP can provide QoS-guaranteed vertical handover with efficient session managements.
Kim Yang Hwan,Ivanov Igor A.,Hwang Sung In,Kim Kyungseung,Nam Chang Hee,Kim Kyung Taec 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.9
An electron tunneled out in an intense laser feld can be driven back and rescattered by the parent ion, leading to rich physical phenomena. Recently, it has been shown that the streaking measurement of the rescattered electron is capable of the in situ characterization of the laser feld. Here, we demonstrate that the streaking of the rescattered electron is also useful for investigating the ultrafast electron rescattering dynamics, including the rescattering time. We show that the rescattering times in Ar and Xe can be resolved with an accuracy of a few attoseconds. This accurate measurement of the rescattering time of tunnel-ionized electrons will provide deeper insights into ultrafast electron dynamics, such as tunneling and rescattering in an intense laser feld
김이고르 ( Igor Kim ),김창현 ( Chang Hyun Kim ) 대한설비관리학회 2012 대한설비관리학회지 Vol.17 No.3
For the last two decades relations between Korea and Uzbekistan have been growing very fast, making Uzbekistan a good investment asset and beneficial market for Korean companies. Therefore well developed logistics industry of Uzbekistan would allow providing higher efficiency of Korean business activities in the country. This study dedicated to elaborate a number of major logistics problems and categorize them into groups. The main concept of the study became a classification scheme, which combines and categorizes major imperfections and problems of Uzbekistan`s logistics. The scheme has been elaborated to reveal origins, interconnections, and reasons of problems related to Uzbek logistics, describing and analyzing them. The research would be a push step of developing local logistics industry to stimulate further partnership of Korean-Uzbekistan collaboration and business projects.