Abstract
The prevalence of the IEEE 802.11b technology has made Wi-Fi based Audio/Video (AV) conferencing applications a viable service. However, due to the “best-effort” transport service and other unpredictable factors such as user mobility, location and background traffic, the transport channel behavior often fluctuates drastically. It thus becomes rather difficult to configure an appropriate de-jitter buffer to maintain the temporal fidelity of the AV presentation. We propose in this paper an adaptive delay and synchronization control scheme for AV conferencing applications over campus-wide WLANs. Making use of a distributed timing mechanism, the scheme monitors the synchronization errors and estimates the delay jitters among adjacent Media Data Units (MDUs) in real-time. It piece-wisely controls the equalization delay to compensate for the delay jitters experienced by MDUs in a closed-loop manner. We investigate the performance of the proposed scheme through trace-driven simulations. We collected network traces from a production campus-wide IEEE 802.11b WLAN by emulating real conferencing sessions. Simulation results show that the scheme is capable of dynamically balancing between synchronization requirements and latency requirements in all scenarios. Small synchronization phase distortions, low MDU loss percentages and low average end-to-end delay can be achieved simultaneously. In particular, compared with solutions using a static setting, the proposed scheme is able to achieve a reduction of around 100ms in end-to-end delay with the same amount of MDU losses under some media-unfriendly situations.
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Haining Liu Haining Liu is currently a graduate student researcher in the Donald Bren School of Information and Computer Sciences at the University of California, Irvine. He received the B.E degree and M.S.E. degree in Electrical Engineering from Tianjin University (China) in 1994 and 1997, respectively. After that, he was with the Beijing Posts and Telecommunications Design Institute of Ministry of Information Industry (China) as a telecommunications design engineer from 1997 to 1999. He received another M.S.E. degree in Systems Engineering from the University of Pennsylvania in 2000. His research interests include multimedia networking, wireless networks and real-time systems.
Prof. Magda El Zarki Magda El Zarki received the B.E.E. from Cairo University, Cairo, Egypt in 1979 and the Ph.D. degree in Electrical Engineering from Columbia University, New York City, NY in 1981 in December 1987.
Currently she holds the position of Professor in the Donald Bren School of Information and Computer Sciences at the University of California, Irvine, where she is involved in the telecommunication networks program. Prior to that she was an Associate Professor in the Department of Electrical Engineering at the University of Pennsylvania in Philadelphia where she also held the position of Director of the Telecommunications Program. From 1992 - 1996 she held the position of Professor of Telecommunications at the Technical University of Delft, Delft, The Netherlands.
Ms. El Zarki is the co-author of a new text: Mastering Networks: An Internet Lab Manual. She is also on the editorial board of several journals in the telecommunications area, and is actively involved in many international conferences.
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Liu, H., Zarki, M.E. An adaptive delay and synchronization control scheme for Wi-Fi based audio/video conferencing. Wireless Netw 12, 511–522 (2006). https://doi.org/10.1007/s11276-006-6549-7
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DOI: https://doi.org/10.1007/s11276-006-6549-7