Table Of ContentP .D. T
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Routing and Scheduling Algorithms in Resource-Limited
Wireless Multi-Hop Networks
by Anastassios Michail
Advisor: Anthony Ephremides
CSHCN PhD 2001-1
(ISR PhD 2001-1)
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Routing and Scheduling Algorithms in Resource-Limited Wireless
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Multi-Hop Networks
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ABSTRACT
Title of Dissertation: Routing and Scheduling Algorithms in Resource-limited
Wireless Multi-hop Networks
Anastassios Michail, Doctor of Philosophy, 2001
Dissertation directed by: Professor Anthony Ephremides
Department of Electrical and Computer Engineering
The recent advances in the area of wireless networking present novel oppor-
tunities for network operators to expand their services to infrastructure-less wire-
less systems. Such networks, often referred to as ad-hoc or multi-hop or peer-
to-peer networks, require architectures which do not necessarily follow the cellular
paradigm. Theyconsistofentirelywirelessnodes, (cid:12)xedand/ormobile, thatrequire
multiple hops (and hence relaying by intermediate nodes) to transmit their mes-
sages to the desired destinations. The distinguishing features of such all-wireless
network architectures give rise to new trade-o(cid:11)s between traditional concerns in
wireless communications (such as spectral e(cid:14)ciency, and energy conservation) and
the notions of routing, scheduling and resource allocation. The purpose of this
work is to identify and study some of these novel issues, propose solutions in the
context of network control and evaluate the usual network performance measures
as functions of the new trade-o(cid:11)s.
To these ends, we address (cid:12)rst the problem of routing connection-oriented
tra(cid:14)c with energy e(cid:14)ciency in all-wireless multi-hop networks. We take advantage
of the flexibility of wireless nodes to transmit at di(cid:11)erent power levels and de(cid:12)ne a
framework for formulating the problem of session routing from the perspective of
energy expenditure. A set of heuristics are developed for determining end-to-end
unicast paths with su(cid:14)cient bandwidth and transceiver resources, in which nodes
use local information in order to select their transmission power and bandwidth
allocation. Wepropose a set of metrics thatassociate each link transmission with a
cost and consider both the cases of plentiful and limited bandwidth resources, the
latter jointly with a set of channel allocation algorithms. Performance is measured
bycallblockingprobabilityandaverageconsumedenergyandadetailedsimulation
model that incorporates all the components of our algorithms has been developed
and used for performance evaluation of a variety of networks.
In the sequel, we propose a "blueprint" for approaching the problem of link
bandwidth management in conjunction with routing, for ad-hoc wireless networks
carrying packet-switched tra(cid:14)c. We discuss the dependencies between routing,
access control and scheduling functions and propose an adaptive mechanism for
solving the capacity allocation (at both the node-level and the flow-level) and
the route assignment problems, that manages delays due to congestion at nodes
and packet loss due to error prone wireless links, to provide improved end-to-end
delay/throughput. The capacity allocations to the nodes and flows and the route
assignmentsareiteratedperiodicallyandtheadaptabilityoftheproposedapproach
allows the network to respond to random channel error bursts and congestion
arising from bursty and new flows.
Routing and Scheduling Algorithms in Resource-limited Wireless Multi-hop Networks
by
Anastassios Michail
Dissertation submitted to the Faculty of the Graduate School of the
University of Maryland, College Park in partial ful(cid:12)llment
of the requirements for the degree of
Doctor of Philosophy
2001
Advisory Committee:
Professor Anthony Ephremides, Chairman/Advisor
Dr. M. Scott Corson
Professor Evaggelos Geraniotis
Professor Steven Marcus
Professor A. Udaya Shankar
(cid:13)c Copyright by
Anastassios Michail
2001
ACKNOWLEDGEMENTS
I would like to express my gratitude to my advisor, Professor Anthony
Ephremides. His valuable support and exceptional guidance through-
out my graduate school years have helped me achieve much more than
I had expected when I came to Maryland. He made me believe in
myself and without his persistence and encouragement I would have
never felt con(cid:12)dent to pursue the Doctoral program. I gained a lot of
knowledge andvaluable experience while working withhim. His unique
personality turned every single moment of interaction into a learning
experience.
I am thankful to the members of the dissertation committee, Dr. Scott
Corson and Professors Evaggelos Geraniotis, Steve Marcus and Udaya
Shankarforkindlyreviewingmydissertationandconsenting toserveon
the defense committee. I also wish to specially thank Professors Steve
Marcus and Leandros Tassiulas fortheir valuable comments and advice
onmy research proposal. They provided me with constructive criticism
that helped improve my work. Unfortunately Professor Tassiulas was
on leave at the time of the defense and could not participate in the
committee.
ii
I had the opportunity to work closely on one of the research problems
with Dr. Deepak Ayyagari. Deepak has been a very good friend and
having known each other very well made it easier to collaborate. I wish
to thank him for several discussions we had and for his valuable help.
It is extremely hard to (cid:12)nd words that express my gratitude to my
parents Tolis and Dora and my sister Nadia for their invaluable help
over all these years. They gave me courage and strength whenever
I needed it and supported me in every possible way throughout the
course of my studies. I am also gratefulto Marianna who has been very
supportive and patient all this time and with her love and dedication
she gave me the extra courage and con(cid:12)dence I needed to accomplish
this work.
Throughout the six years I spent in Maryland I had the chance to meet
a lot of new friends. They made life easier and I wish them all luck
in their future plans. It would be a very long list if I had to mention
names but I ought to express my special thanks to all my roommates
for sharing a house with me most of these years and for bearing with
me during both the good and the bad times.
Least, but not last, I wish to thank my fellow graduate students, all
my o(cid:14)cemates and the members of the Systems Engineering and Inte-
gration Lab for creating a pleasant working environment.
This work wouldn’t have been possible without the (cid:12)nancial support of
the Institute for Systems Research. Funding was provided by the Ad-
vanced Telecommunications/Information Distribution Research Pro-
gram (ATIRP) Consortium sponsored by the U.S. Army Research Lab-
iii
oratory under Cooperative Agreement DAAL01-96-2-0002.
iv
