A high Throughput Path Metric for Multi-Hop Wireless Routing

A high Throughput Path Metric for Multi-Hop Wireless...

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A High-Throughput Path Metric for Multi-Hop Wireless Routing Douglas S. J. De Couto Daniel Aguayo John Bicket Robert Morris M.I.T. Computer Science and Artificial Intelligence Laboratory { decouto, aguayo, jbicket, rtm } @csail.mit.edu http://www.pdos.lcs.mit.edu/grid Abstract This paper presents the expected transmission count metric (ETX), which finds high-throughput paths on multi-hop wireless networks. ETX mini- mizes the expected total number of packet transmissions (including retrans- missions) required to successfully deliver a packet to the ultimate destina- tion. The ETX metric incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and interference among the successive links of a path. In contrast, the minimum hop-count metric chooses arbitrarily among the different paths of the same minimum length, regardless of the often large differences in throughput among those paths, and ignoring the possibility that a longer path might offer higher throughput. This paper describes the design and implementation of ETX as a metric for the DSDV and DSR routing protocols, as well as modifications to DSDV and DSR which allow them to use ETX. Measurements taken from a 29- node 802.11b test-bed demonstrate the poor performance of minimum hop- count, illustrate the causes of that poor performance, and confirm that ETX improves performance. For long paths the throughput improvement is often a factor of two or more, suggesting that ETX will become more useful as networks grow larger and paths become longer. Categories and Subject Descriptors C.2.1 [ Computer-Communication Networks ]: Network Archi- tecture and Design— Wireless communication ; C.2.2 [ Computer- Communication Networks ]: Network Protocols— Routing proto- cols General Terms Design, Experimentation, Measurement, Performance Keywords Multi-hop wireless networks, Ad hoc networks, Rooftop networks, Wireless routing, Route metrics, 802.11b, DSR, DSDV, ETX This research was supported by grants from NTT Corporation un- der the NTT-MIT collaboration, and by MIT’s Project Oxygen. Permission to make digital or hard copies of all or 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. MobiCom ’03, September 14–19, 2003, San Diego, California, USA. Copyright 2003 ACM 1-58113-753-2/03/0009 . ..$5.00. 1. Introduction Much of the recent work in ad hoc routing protocols for wireless networks [25, 15, 26] has focused on coping with mobile nodes, rapidly changing topologies, and scalability. Less attention has been paid to finding high-quality paths in the face of lossy wireless links. This paper presents measurements of link loss characteris-
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This note was uploaded on 11/03/2009 for the course COMPUTERS CS537 taught by Professor Salman during the Spring '09 term at Texas A&M University–Commerce.

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A high Throughput Path Metric for Multi-Hop Wireless...

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