a high-throughput path metric for multi-hop wireless routing

Abstract

This paper presents the expected transmission count metric (ETX), which finds high-throughput paths on multi-hop wireless networks. ETX minimizes the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet to the ultimate destination. 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.

Generic Routing Metric and Policies for WSNs

“…Its goal is to minimize the sum of the expected number of transmissions over each link (i, j) ∈ P ath: (i,j)∈P ath 1/p ij . Compared to the other two, this metric has been shown to behave best, especially in the presence of low mobility [1]. Other metrics based on latency, like the ones presented in [2], have shown poor behavior when used in sensor network scenarios.…”

An Ad-hoc Routing Protocol for High-speed Multimedia Traffic Based on Path Quality and Bandwidth Estimation in Wireless Ad Hoc Networks

“…In wireless ad hoc network, many wireless links have intermediate loss ratio due to the poor link quality [5] . A link that can not deliver packet sufficiently is not useful for multimedia data, even though the link might deliver enough routing update or routing query packets.…”

Quality-Aware Routing Metrics in Wireless Mesh Networks

“…The ETX metric is composable, since the expected value of total number of transmissions over a path is the sum of the individual expected number of transmissions of the links along the path. In the presence of bit rate adaptation, the only modification required for ETX is to use the Expected Transmission Time (rather than Count) as the metric [14], because a lower bit rate ends up using the channel for a longer period of time.…”