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.