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Dia 17/12/2002
das 13:00 às 14:00 – Sala H – 312 B
Exploiting Mobility in
Ad Hoc Network
Abstract - Node mobility in wireless networks
complicates various basic networking functions. For example, a wireless channel
between moving nodes tends to fluctuate because of multipath fading, requiring
sophisticated signal transmission and link scheduling techniques. Also, node
mobility makes it necessary to keep constant track of nodes' locations,
requiring dynamic location and routing algorithms. It is therefore not
surprising that mobility is normally viewed as a challenge that we need to
engineer around. In this talk, we are going to argue that there are actually
benefits to mobility. Nodes that move around can transport information from one
place to another for free, i.e., without incurring transmission overhead. Of
course, these movements are random and unpredictable in general. Nevertheless,
we show two instances where node mobility can be exploited in the context of
large-scale ad hoc wireless networks. In the first example, we focus on
applications with loose delay constraints and show that they can exploit node
mobility to increase network capacity through a new type of multiuser
diversity. Specifically, our main result shows that if nodes are mobile, the
average long-term throughput per node is dramatically higher than in a fixed
network scenario, and this improvement is obtained through the exploitation of
the time-variation of the users' channels due to mobility. This is an important
architectural insight, as it suggests that mobile ad-hoc networks (or hybrid
ad-hoc/cellular networks) may be a much more viable alternative for
delay-tolerant data applications than for telephony. In the second example, we
assume that delay constraints are tight, which makes it necessary for a packet
to be able to determine the current location of the destination through a
location service. Devising efficient, scalable, and robust location services
for ad hoc networks has received considerable attention in recent years. All of
these proposed services explicitly exchange node location information in some
form. However, we show that node mobility can be exploited to disseminate
destination location information without incurring any communication overhead.
These examples illustrate the principle that the free, but unpredictable
information transport capacity generated by node mobility can be exploited in
certain circumstances through appropriate techniques. We believe that there are
other cases yet to be discovered where mobility can help. In this conference we
will study the scalability issue in the design of a centralized policy server
controlling resources in the future IP-based telecom network generation. The
policy servers are in charge of controlling and managing QoS, security and
mobility in a centralized way in the future IP-based telecom networks. Our
study demonstrates that the policy servers can be designed in such a manner
that they scale with the increase in the network capacity.
Matthias Grossglauser is currently a member of the Internet and
Networking Research group at AT&T Labs-Research. He
received his Diploma of Electrical Engineering from the Swiss Federal Institute
of Technology (EPFL) in 1994, the M.Sc. from the Georgia Institute of
Technology in 1994, and his Ph.D. from the University of Paris 6 in 1998. He
did most of his thesis work at INRIA Sophia Antipolis, France. He received the
1998 Cor Baayen Award from the European Research Consortium for Informatics and
Mathematics (ERCIM), and the Best Paper Award at INFOCOM 2001. He is on the
editorial board of IEEE/ACM Transactions on Networking. His research interests
are in network traffic measurement and modeling, network management, and mobile
communications.