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


PhD Thesis Defence


"RWA and Wavelength Conversion in Wavelength-Routed All-Optical WDM
Networks"

By

Mr. Xiaowen Chu


Abstract

Wavelength Division Multiplexing (WDM) is a promising technology to
utilize the huge bandwidth of optical fiber. Wavelength-routed all-optical
network is a suitable architecture to serve as the backbone of wide-area
networks by providing lightpath services. Blocking has been the key
performance index in the design of a wavelength-routed network. Existing
research demonstrates that an effective routing and wavelength assignment
(RWA) algorithm and wavelength conversion are the two primary vehicles for
improving the blocking performance. However, these two issues have largely
been investigated separately in that the existing RWA algorithms have
seldom considered the presence of wavelength conversion, while the
wavelength converter placement algorithms have largely assumed that a
static routing and random wavelength assignment algorithm is employed.

In this dissertation, we first investigate the wavelength converter
placement problem for different RWA algorithms. Under the fixed-alternate
routing (FAR) algorithm, we propose a heuristic algorithm called Minimum
Blocking Probability First (MBPF) for wavelength converter placement.
Under the least-loaded routing (LLR) algorithm, we propose another
heuristic algorithm called Weighted Maximum Segment Length (WMSL). We
observe that the proposed algorithms not only outperform existing
wavelength converter placement algorithms by a large margin, but they also
can achieve almost the same performance comparing with full wavelength
conversion under the same RWA algorithm. The second work is to investigate
the dynamic routing algorithm in the presence of wavelength conversion. We
show that existing dynamic routing algorithms cannot utilize the fiber
link resources efficiently in the presence of wavelength conversion. We
then propose a weighted least-congestion routing (WLCR) algorithm that
considers both the distribution of free wavelengths and the lengths of
each route jointly. Finally, we propose the sparse-partial wavelength
conversion architecture, which can save the number of wavelength
converters significantly. In this architecture, two problems have been
examined. The first one is the wavelength assignment problem, and the
second one is the converter placement problem.


Date:			Saturday, 7 June 2003

Time:			2:30p.m.-4:30p.m.

Venue:			Room 2302
			Lifts 17-18

Chairman:			Dr. Yong Chang Zhu (MATH)

Committee Members:		Dr. Bo Li (Supervisor)
			Dr. Brahim Bensaou
			Dr. Mounir Hamdi
			Prof. Chin-Tau Lea (ELEC)
			Dr. Krishna M. Sivalingam (Comp. Sci. & Elec. Engg.,
					           Univ. of Maryland)


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