[CPCC] TALK: Mobile Sensor Networks March 9 11 AM (fwd)

Ender Ayanoglu ayanoglu at uci.edu
Wed Feb 28 11:40:26 PST 2007


             Energy Maps for Mobile Wireless Sensor Networks:
                   Coherence Time versus Node Mobility

                          Friday March 9, 2007
                                 11 AM
                      Calit2 Building, Room 3414

                          Prof. Volkan Rodoplu
              Dept. of Electrical and Computer Engineering
                 University of California Santa Barbara


The wireless networks of the next 10 years will consist of a plethora of
microprocessor-sensor units embedded in clothes, shoes, cars, buses, as
well as the more traditional portable handhelds, and laptops. Today,
information flows in wireless networks via a limited number of wireless
gateways. In the future, information is expected to flow through thousands
to millions of wireless devices themselves. Most of these devices will be
mobile and energy-limited, and will have to make decisions on the fly on
how to communicate information through thousands to millions of other
devices in between to reach destination nodes, as well as gateways into
the wired domain. It will no longer be possible to track individual paths
and individual nodes; hence, it is essential that an aggregate view of the
essential qualities of the mobile network be built and be made available.
Quality-of-Service (QoS) decisions regarding energy consumption, delay, and
throughput will still play a prominent role in making intelligent
decisions to conserve the limited energy supply of devices, and meet delay
and throughput requirements in these future networks that consist of
thousands to millions of mobile, microprocessor-sensor devices.

With this vision, in this talk, we develop new methodologies for mobile,
large-scale wireless sensor networks. We propose a novel framework to
share, retain and refine end-to-end QoS metrics in the joint memory
of the nodes, over time scales over which this information can be spread
to the network and utilized for energy planning decisions. In analogy
with the point-to-point link concepts, we introduce the "coherence time"
of end-to-end QoS metrics for mobile wireless networks. We show that as
long as the coherence time of QoS metrics is much larger than the
"spreading period", mobile wireless networks can track end-to-end QoS
metrics. This is a surprising conclusion given our current understanding
of mobile networks, which correlates tractability with the amount of
individual node mobility rather than the coherence time of QoS metrics.

As an example of this methodology, we construct energy maps, which are
maps of the end-to-end energy metrics in space. We show how to (1)
compute the spatial derivatives of energy potentials in mobile networks,
(2) construct energy maps on-demand via path integration methods, and
(3) distribute, share, fuse, and refine energy maps over time by
information exchange during encounters. In order to put the energy maps
to use, we present an algorithm for energy optimization, based on the
energy maps, that finds the optimal bit allocation strategy to minimize
the energy consumption, subject to a delay constraint. We show that
significant energy savings are obtained by leveraging network mobility
and the energy maps, when compared with a competing algorithm that
allocates the traffic at a constant rate without utilizing the energy
map. These techniques show how future, large-scale, mobile wireless
sensor networks can be handled via new techniques, and how to generalize
physical layer concepts such as coherence time, to network-layer
concepts related to QoS issues.

Joint work with Min Kyoung Park (Ph.D. alumna, UCSB).

                          Speaker's Biography

Volkan Rodoplu received his B.S. degree in Electrical Engineering (summa
cum laude) from Princeton University in 1996 and his M.S. degree in
Electrical Engineering from Stanford University in 1998. He worked for
Texas Instruments (Dallas, TX) in the summer of 1998, on multiuser
detection and interference cancellation algorithms, and for Tensilica,
Inc. (Santa Clara, CA) in 2000 and 2001, on turbo decoding algorithms and
architectures for reconfigurable processors. He received his Ph.D. in
Electrical Engineering from Stanford University in 2003 and subsequently
joined the Department of Electrical and Computer Engineering at UCSB as an
Assistant Professor.

His research investigates the theoretical limits of minimum energy
networks as well as the delivery of minimum energy networking solutions.
His research areas span underwater networks, terrestrial wireless mobile
sensor networks, and applications of cooperative game theory to wireless

He is the recipient of the NSF CAREER Award (2007), UC Regents' Junior
Faculty Fellowship (2006), Department of Electrical Engineering
Outstanding Service Award at Stanford (2000), B.George B. Wood Legacy
Prize, and G. David Forney Prize (1996), and the John W. Tukey Award (1995).

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