Notice and Invitation

Oral Defense of Doctoral Dissertation

he College of Engineering and Computing, George Mason University

Massieh Kordi Boroujeny

Bachelor of Science, Shahid Bahonar University of Kerman, 2009

Master of Science, Isfahan University of Technology, 2012

Resource Allocation and Performance Guarantees in Communication Networks

Thursday, August 18, 2022, 1:00 PM  2:00 PM

Zoom Meeting Link:

All are invited to attend.


Dr. Brian L. Mark, Chair
Dr. Yariv Ephraim,
Dr. Monson H. Hayes,

Dr. John F. Shortle


One of the main challenges in modern communication networks, like the Internet, is providing performance guarantees, such as bounds on end-to-end delay, while avoiding underutilization of the network resources. In the early 1990s an approach to address this problem was proposed in which the input traffic was bounded either stochastically or deterministically by a so-called traffic envelope. Network calculus was developed to derive end-to-end delay bounds from the traffic burstiness bounds. Since deterministic network calculus can lead to loose bounds, our research focuses on stochastic network calculus.

In this dissertation, we address three open problems in applying stochastic network calculus to practical networks: 1) estimating an appropriate stochastic traffic envelope for an arbitrary traffic source; 2) enforcing conformance of a given traffic flow to a stochastic traffic envelope; 3) admission control based on an enforceable traffic envelope, while achieving statistical multiplexing gain. We develop a method to characterize an arbitrary traffic source by a traffic envelope that takes the form of a phase-type distribution. The versatility and generality of the phase-type distribution make it useful for obtaining tight bounds to characterize the traffic. We particularize a class of stochastic burtiness bounds using the proposed phase-type bounds. We also develop a stochastic traffic regulator that forces a traffic flow to conform to a given traffic envelope from a class of traffic envelopes, including our proposed phase-type envelopes. We propose a new traffic envelope, referred to as the W-envelope, based on the moment generating function of the workload process obtained from offering the traffic to a constant service rate queue. We show how the W-envelope satisfies can be used in a QoS (quality of service) framework for provisioning stochastic end-to-end delay guarantees in conjunction with the proposed traffic characterization method and stochastic traffic regulator. Finally, we develop a new available bandwidth estimation (ABE) method that can provide accurate estimates of the available bandwidth on an end-to-end network path even in presence of packets dropped due to congestion. Our ABE method could be used to discover the amount of available bandwidth on an end-to-end, which could then be used to provide stochastic delay guarantees for time-sensitive traffic via our proposed QoS framework.

A copy of this doctoral dissertation is on reserve at the Johnson Center Library.