International Journal of Virtual Technology and Multimedia (5 papers in press)
Analysis of Handover Interruption in Vertical Handover Procedures based on 3GPP standard
by Sungjin Shin, Donghyuk Han, Hyoungjun Cho, Jong-Moon Chung
Abstract: Applications which required real-time communications like mobile clouds, augmented reality, and Voice over IP (VoIP) have significantly increased, and therefore the need to support seamless connectivity across overlaid heterogeneous networks are becoming more and more important. Handover interruptions (HI) may occur when mobile users move from the long-term evolution (LTE) to wireless local area network (WLAN) (or from WLAN to LTE) during active real-time applications. This paper analyzes vertical handover (VHO) schemes and VHO procedures based on 3GPP for confirming interruption time.
Keywords: VHO, handover interruption, WLAN, LTE
Special Issue on: ICONI 2014 Internet Communication and its Applications
Selective Algorithms for Eliminating Redundant Piggybacked Control Information for Consistent Message Recovery of SBML with Transient Message Loss
by Jinho Ahn
Abstract: Our previous work has introduced a lightweight SBML protocol to address the following two problems of the original SBML recovery algorithm; it may no longer be progressing in some transient communication error cases and all the message send operations generated after having received some unstable messages should be delayed until they are known to be stable. However, it may make the full log information of each application message recorded on its senders buffer as well as on buffers of senders of its successors. This paper presents two selective stable message log purging algorithms to purge effectively message log from volatile memories of their successors' senders. The first only piggybacks a variable on original control messages for logging each application message to impose minimum overhead on network link. The second uses a vector sized piggybacking information to speed up eliminating useless log information and make enough spare space of log buffer remained as late as possible. They incur both no extra message and forced checkpoint.
Keywords: consistent recovery; distributed system; log purging; message logging; transient message loss.
Cooperative Transmission Scheme with Single Antenna for Low-Rate Wireless Personal Area Networks
by Jung-In Baik, Seung-Jun Yu, Sung-Jin Kang, Hyoung-Kyu Song
Abstract: Cooperative communications are the useful wireless communication system that gets diversity gain by sharing other antennas. This communication system can be also possible to maintain battery life for long time. Nevertheless, IEEE 802.15.4 which employs cooperative transmission scheme does not have been researched. Thus, IEEE 802.15.4 based cooperative communication system is proposed according to various scenarios. The proposed system can efficiently transmit data and reduce energy consumption. Moreover, the proposed system has an effect on the extension of transmission range by high reliability.
Keywords: ZigBee; cooperative relaying; diversity; sensor network.
An Improved Quasi-OSTBC Scheme for MIMO-OFDM Systems
by Eui-Hak Lee, Hyun-Woo Jang, Jung-In Baik, Sung-Jin Kang, Hyoung-Kyu Song
Abstract: Quasi-orthogonal Space-Time Block Code (Quasi-OSTBC) usingrnthe adaptive constant feedback is proposed to improve BER performance. Thernconventional quasi-OSTBC scheme feeds backs to the fixed antenna usingrnthe estimated channel components. However, it is not efficient in the wirelessrncommunications that has the diverse channel environments. To make the efficientrnsystem, the noise in the receiver has to be minimized and the interference has to berncanceled as the conventional scheme. In this paper, the proposed quasi-OSTBCrnscheme feeds back to an antenna adaptively according to the estimated channelrncomponents. As a result, the BER performance of the system is improved.
Keywords: STBC; Quasi-OSTBC; Alamouti; Cooerative Communications;rnMIMO.
Design a smart construction work management system for improving the safety and productivity using wearable devices
by Young-Hwan Choi, Mi-Sun Woo, Seung-Hyun Lee, Min Hong
Abstract: The main purpose of this research is to design a smart construction work management system for improving the productivity of construction operations and the workers safety by using wearable smart devices. The proposed smart management system includes the development of smart safety helmets, watches, shoes, and applications to convenientlyaccumulate various construction fielddata in real-time. It can be applied to manage the construction workers productivity and toimprove their safety by providing a warning notification for abnormal situations. Also, it stores the data regarding construction workers safety, physical states, and their construction work progress on to the server effectivelyby using a smartphone.
Keywords: wearable devices; construction operation; productivity management; quality management; safety management