PhD Thesis at UCL Computer Science Department

by Soo-Hyun Choi (


The Internet is getting richer, and so the services. The more the services,
the more the users demand. The more they demand, the more we1 guarantee.

This thesis investigates the congestion control mechanisms for
interactive multimedia streaming applications. We start by raising a
question as to why the congestion control schemes are not widely
deployed in real-world applications, and study what options are
available at present. We then discuss and show some of the good
reasonings that might have made the control mechanism, specifically
speaking the rate-based congestion control mechanism, not so attractive.

In an effort to address the problems, we identify the existing problems
from which the rate-based congestion control protocol cannot easily
escape. We therefore propose a simple but novel window-based congestion
control protocol that can retain smooth throughput property while being
fair when competing with TCP, yet still being responsive to the network

Through the extensive ns-2 simulations and the real-world experiments,
we evaluate TFWC, our proposed mechanisms, and TFRC, the proposed IETF
standard, in terms of network-oriented metrics(fairness, smoothness,
stability, and responsive), and end-user oriented metrics (PSNR and MOS)
to throughly study the protocol’s behaviors. We then discuss and
conclude the options of the evaluated protocols for the real application.

1 We as congestion control mechanisms in the Internet.

Soo-Hyun Choi,
Apr 13, 2011, 7:03 AM