MPhil Thesis Defence


"Joint Allocation of FEC and Bandwidth Across Layers for Video Multicast
over Wired and Wireless Networks"

By

Mr. Angus Tak-Wan Lee


Abstract

Layered multicast is an efficient technique to deliver video to its end
users. In this paper, we consider such a layered multicast video system to
serve both wireless and wireline users when there is error over the wired
network and wireless hop. The server encodes the videos stored or captured
live into a certain (fixed) number of layers (i.e., a base layer and
several enhancement layers) and multicasts the layers via different
multicast groups to their end-users distributed over a network. The base
layer guarantees a certain minimum video quality and hence has to bea
received with rather low loss. Depending on the end-to-end bandwidth
between a client and the server, the client may progressively get a
further number of enhancement layers by joining the corresponding
multicast groups so as to improve the
video quality.

Due to the heterogeneous nature of channel conditions in terms of
bandwidth and error rate among the clients, the source has to continuously
adapt the error recovery mechanisms and bandwidth of each layer in order
to optimize the overall video quality.  In a system with heterogeneous
receivers, such joint rate and error control across the layers are the
main challenges.  This is the topic of concern in this work. Since packets
are likely to be dropped in the wired networks while bit errors are more
likely over the wireless hop, a combination of both packet-level and
byte-level FEC is required to recover these errors. Given the estimated
error and bandwidth characteristics reported by end users, the server
needs to optimally allocate the packet-level and byte-level FEC to achieve
maximum video quality.

We study two schemes pertaining to whether or not the wireless gateway is
able to transcode the video packet from the wired network before
forwarding it to the wireless users. We first study the video multicast
system over wired and wireless networks with joint bandwidth and FEC
allocation for each layer in order to maximize overall video quality. We
then developed an analytic model of the system, and a dynamic program
approach on optimal allocation of enhancement layers. Also, we investigate
the advantage of using transcoding gateway with packet-level and
byte-level FEC in the wireless hop.


Date:			Friday, 17 August 2001

Time:			3:00p.m.-5:00p.m.

Venue:			Room 2302
			Lifts 17-18

Committee Members:		Dr. Gary Chan (Supervisor)
			Prof. Samuel Chanson (Chairman)
			Dr. Brahim Bensaou


**** ALL are Welcome ****