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

The expected transmission count (ETX) metric is a new route metric for finding high-throughput paths in multi-hop wireless networks. The ETX of a path is the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet along that path. For practical networks, paths with the minimum ETX have the highest throughput. 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. Busy networks that use the ETX route metric will also maximize total network throughput. We describe 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 make them work well with ETX. Measurements taken from a 29-node 802.11b test-bed show that using ETX improves performance significantly over the widelyused minimum hop-count metric. For long paths the throughput increase is often a factor of two or more, suggesting that ETX will become more useful as networks

We revisit the problem of computing the path with the minimum cost in terms of the expected number of link layer retransmissions in wireless mesh networks. Unlike previous efforts (such as the popular ETX) we account for the fact that link layer protocols (such as the IEEE 802.11 MAC) incorporate a non-zero but finite number of retransmission attempts per packet. A key observation that motivates this work is that the performance of a path depends not only on the number of links on the path and their qualities, but also on the relative positions of the links on the path. In particular, the closer a lossy link to the destination, the higher is its impact on the performance of that path. We design a new path metric that captures all of the above factors and we call this metric ETOP. In this paper, we provide a synopsis of the analytical computation of ETOP. We also implement a routing strategy based on ETOP on a 25-node experimental testbed and provide sample results to showcase the performance with ETOP.