p231-hu - Caching Strategies in On-Demand Routing Protocols...

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Caching Strategies in On-Demand Routing Protocols for Wireless Ad Hoc Networks Yih-Chun Hu David B. Johnson Computer Science Department Carnegie Mellon University Pittsburgh, PA 15213-3891 USA http : //www. monarch, cs. cmu. edu/ { yihchun,dbj } @cs. cmu.edu Abstract An on-demand routing protocol for wireless ad hoc networks is one that searches for and attempts to discover a route to some destination node only when a sending node originates a data packet addressed to that node. In order to avoid the need for such a route discovery to be performed before each data packet is sent, such routing protocols must cache routes previously discovered. This paper presents an analysis of the effects of different design choices for this caching in on-demand routing protocols in wireless ad hoc networks, dividing the problem into choices of cache structure, cache capacity, and timeout. Our analysis is based on the Dynamic Source Routing protocol (DSR), which operates entirely on-demand. Using detailed simulations of wireless ad hoc networks of 50 mobile nodes, we studied a large number of different caching algorithms that utilize a range of design choices, and simulated each cache primarily over a set of 50 different movement scenarios drawn from 5 different types of mobility models. We also define a set of new mobility metrics that allow accurate characterization of the relative difficulty that a given movement scenario presents to an ad hoc network routing protocol, and we analyze each mobility metric's ability to predict the actual difficulty in terms of routing overhead experienced by the routing protocol across the scenarios in our study. 1. Introduction Caching is an important part of any on-demand routing protocol for wireless ad hoc networks. In an ad hoc network [10, 6], all nodes cooperate in order to dynamically establish and maintain routing in the network, forwarding packets for each other to allow communica- tion between nodes not directly within wireless transmission range. Rather than using the periodic or background exchange of routing in- formation common in most routing protocols, an on-demand routing protocol is one that searches for and attempts to discover a route to This work was supported in part by the Air Force Materiel Command (AFMC) under DARPA contract number F19628-96-C-0061. Yih-Chun Hu was also supported by an NSF Graduate Fellowship. The views and conclusions contained here are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either express or implied, of AFMC, DARPA, NSE Carnegie Mellon University, or the U.S. Government. Po'mission to make digital or hard copies of all oi part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.
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This note was uploaded on 08/25/2011 for the course EEL 5937 taught by Professor Staff during the Spring '08 term at University of Central Florida.

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p231-hu - Caching Strategies in On-Demand Routing Protocols...

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