3,623 research outputs found
vSkyConf: Cloud-assisted Multi-party Mobile Video Conferencing
As an important application in the busy world today, mobile video
conferencing facilitates virtual face-to-face communication with friends,
families and colleagues, via their mobile devices on the move. However, how to
provision high-quality, multi-party video conferencing experiences over mobile
devices is still an open challenge. The fundamental reason behind is the lack
of computation and communication capacities on the mobile devices, to scale to
large conferencing sessions. In this paper, we present vSkyConf, a
cloud-assisted mobile video conferencing system to fundamentally improve the
quality and scale of multi-party mobile video conferencing. By novelly
employing a surrogate virtual machine in the cloud for each mobile user, we
allow fully scalable communication among the conference participants via their
surrogates, rather than directly. The surrogates exchange conferencing streams
among each other, transcode the streams to the most appropriate bit rates, and
buffer the streams for the most efficient delivery to the mobile recipients. A
fully decentralized, optimal algorithm is designed to decide the best paths of
streams and the most suitable surrogates for video transcoding along the paths,
such that the limited bandwidth is fully utilized to deliver streams of the
highest possible quality to the mobile recipients. We also carefully tailor a
buffering mechanism on each surrogate to cooperate with optimal stream
distribution. We have implemented vSkyConf based on Amazon EC2 and verified the
excellent performance of our design, as compared to the widely adopted unicast
solutions.Comment: 10 page
Efficient computations on meshes with express links
At head of title: Computer science publication.Cover title.Includes bibliographical references (p. 10-12).published_or_final_versio
Joint Design of Source-Channel Codes with Linear Source Encoding Complexity and Good Channel Thresholds Based on Double-Protograph LDPC Codes
We propose the use of a lower or upper triangular sub-base matrix to replace
the identity matrix in the source-check-channel-variable linking protomatrix of
a double-protograph low-density parity-check joint-source-channel code (DP-LDPC
JSCC). The elements along the diagonal of the proposed lower or upper
triangular sub-base matrix are assigned as "1" and the other non-zero elements
can take any non-negative integral values. Compared with the traditional
DP-LDPC JSCC designs, the new designs show a theoretical channel threshold
improvement of up to 0.41 dB and a simulated source symbol error rate
improvement of up to 0.5 dB at an error rate of 1e-6.Comment: 7 pages, 5 figures, 3 tables, to appear in IEEE Communications
Letter
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