QoS Maps for Mobile Wireless Networks: Coherence Time versus Node Mobility

SPEAKER: Prof. Volkan Rodoplu, Dpt. of Electrical and Computer Engineering, University of California Santa BarbaraABSTRACT: 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.
This is joint work with Min Kyoung Park (Ph.D. alumna, UCSB)BIO: 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 2000-2001, 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 ComputerEngineering at UCSB as an Assistant Professor. His research investigates the 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 networks. 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).Host: Bhaskar Krishnamachari, bkrishna@usc.edu

Location: Frank R. Seaver Science Center (SSC) - 319

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher