The Hong Kong University of Science and Technology
Department of Computer Science


PhD Thesis Defence


"ON BANDWIDTH ADAPTATION FOR MULTI-RATE VIDEO MULTICAST"

By

Mr. Jiangchuan Liu


Abstract

Video multicast over the heterogeneous Internet is a challenging
undertaking. A promising solution is the use of multi-rate delivery, by
which the receivers in a session can receive video data at different rates
commensurate with their respective bandwidths. In recent year, numerous
multi-rate schemes have been proposed in the literature; however, the
optimal bandwidth adaptation policies for these schemes, especially with
advanced video coding techniques, have yet to be established. This thesis
presents a systematic study on the above problem for principal multi-rate
video multicast schemes, including layered and proxy-based schemes.

We first study the optimal layering and bandwidth allocation for
cumulative layered video multicast. We answer two fundamental questions.
First, how bandwidth is allocated among video multicast sessions with
uneven populations? Second, for a video session under a given bandwidth
budget, how the layering structure for this session should be organized?
Our study explores the flexible and dynamic property of advanced video
encoders to meet the diverse requirements from the receivers. By using a
simple 2-step decomposition of inter-session and intra-session allocation,
we derive computationally efficient (polynomial time) algorithms for both
inter-session and intra-session optimization problems.

We then demonstrate that the above optimal bandwidth allocation can be
seamlessly integrated into an end-to-end adaptation protocol called HALM
(Hybrid Adaptation Layered Multicast). This protocol is fully compatible
with the current best-effort Internet where FIFO drop-tail routers are
widely used and the dominant traffic is the congestion-sensitive TCP
traffic.

Besides cumulative layering, we also study the optimal bandwidth
adaptation for noncumulative layered video multicast. We show that this
problem is considerably more complex than that in the cumulative layering
case. We then present efficient heuristic solutions that achieve nearly
optimal performance.

Finally, we propose a novel proxy framework that is specifically designed
for multicasting MPEG-4 video. We introduce the concept of Object
Transmission Proxy (OTP). An OTP filters incoming streams using a
bandwidth adaptation algorithm to meet dynamic network conditions.
Multiple OTPs can partition the multicast tree into confined regions to
handle the heterogeneity of the receivers. We also devise a set of novel
adaptation algorithms that leverage the MPEG-4 object scalability.
Simulation results demonstrate that, under the same link speed and network
topology, our framework has substantial performance improvement over
conventional frame-based bandwidth adaptation schemes. The improvement is
particularly noticeable when video objects have uneven utilities, i.e.,
with different levels of importance to the receivers.


Date:				Monday, 2 June 2003

Time:				2:00p.m.-4:00p.m.

Venue:				Room 2303
				Lifts 17-18

Chairman:			Dr. Jiannong Wang (PHYS)

Committee Members:			Dr. Bo Li (Supervisor)
				Dr. Gary Chan
				Prof. Lionel Ni
				Dr. Bing Zeng (ELEC)
				Prof. Peter Yum (Information Engg., CUHK)


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