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


PhD Thesis Defence


"Scheduling Optical Packet Switches With Reconfiguration Delay"

By

Miss Xin Li


Abstract

Using optical technology for the design of high-performance packet
switches offers several advantages such as scalability, high bandwidth,
lower power consumption, and reduction in cost. However, reconfiguring the
optical fabric of these switches requires significant time using current
technology (micro-electro-mechanical system MEMS, tunable elements, bubble
switches, etc.). As a result, conventional slot-by-slot scheduling may
severely cripple the performance of these optical switches due to the
frequent fabric reconfiguration that may entail.

This thesis undertakes a comprehensive study on the scheduling of optical
packet switches with reconfiguration delay. We consider the scheduling of
both synchronous and asynchronous optical fabrics, working with unicast or
multicast traffic. The general solution is to reduce the scheduling rate
to compensate for the reconfiguration delay. The scheduling problems for
both synchronous and asynchronous optical fabrics are formally defined and
proven to be NP-hard. As a result, efficient heuristic scheduling
algorithms are proposed for both types of fabrics. Specifically, a burst
scheduling approach and a self-adjustable time slot assignment (TSA)
approach are suggested for synchronous fabric scheduling. On the other
hand, a non-preemptive dense scheduling approach is proposed when the
fabric is asynchronous. All of the proposed algorithms are shown to
achieve 100% throughput under different unicast traffic patterns. In
addition, a multi-rack switch architecture with passive optical fabric and
active local crossbars is proposed and evaluated for the multicast
traffic. It makes good use of the available switching capacity and is
practical to be implemented using current technology.


Date:			Tuesday, 28 June 2005

Time:			10:30a.m.-12:30p.m.

Venue:			Room 2465
			Lifts 25-26

Chairman:		Prof. Raymond S.C. Wong (BICH)

Committee Members:	Prof. Mounir Hamdi (Supervisor)
                    	Prof. Brahim Bensaou
                        Prof. Gary S.H. Chan
			Prof. Jogesh Muppala
                        Prof. Amine Bermak (ELEC)
                        Prof. Victor O.K. Li (Electrical & Electronic Engg.,
					      HKU)


**** ALL are Welcome ****