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

A high-throughput path metric for multi-hop wireless routing,10.1145/938985.939000,Douglas S. J. De Couto,Daniel Aguayo,John C. Bicket,Robert Morris

A high-throughput path metric for multi-hop wireless routing   (Citations: 1260)
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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.
Conference: Mobile Computing and Networking - MOBICOM , pp. 134-146, 2003
Cumulative Annual
    • ...Specifically, recent efforts that have considered the problem [9], [5], [10], [12], make a major implicit or explicit assumption that there are an infinite number of retransmission attempts per packet at the link layer...
    • ...At first glance, it may seem that it is better to use the path [S, X, Y, R] instead of [S, A, B, C, R]. In fact, previous strategies such as [9], will choose that path...
    • ...We evaluate its performance on an indoor wireless mesh network consisting of 25 nodes and compare it with that of ETX-based routing [9]...
    • ...This has been observed in prior work [9], [13] and we observe that losses due to failed MAC layer retransmissions are common in our indoor network...
    • ...ETX: In [9], the authors design a link metric called ETX (for expected transmission count), which is equal to the inverse of a link’s reliability...
    • ...Experiments on a 29-node 802.11 testbed showed that ETX-based routing results in better endto-end throughput as compared to minimum-hop routing [9]...
    • ...3This assumption is made to keep the computation tractable; a similar assumption is made in almost all related work (for example, in [9], [11])...
    • ...Routing Implementation: We implement ETOP-based routing as part of a modified version of the dynamic source routing protocol (DSR) [16] developed by De Couto et al [9] for the Linux kernel...
    • ...Furthermore, we consider the ETX metric for comparison and use the implementation of the routing strategy based on ETX [9]...
    • ...Note that as in [9], the route error messages (RERR messages) induced by DSR are disabled during the experiments; this functionality of DSR is not utilized with either ETX-R or ETOP-R...
    • ...[9] as a separate element in Click [19]; it runs on every node and uses small broadcast packets to estimate the delivery probability from this node to each of its neighbors...
    • ...However, our contribution is not a new way of computing the link delivery probabilities; instead we rely on a previously used method (the one used in the original work on ETX [9])...
    • ...Comparisons: We compare ETOP-based routing with ETXbased routing [9], since it represents a large class of previously proposed metrics...
    • ...To make the results between the metrics comparable, the following setup (similar to that in [9]) is used...

    Gentian Jakllariet al. Link Positions Matter: A Noncommutative Routing Metric for Wireless Me...

    • ...1) Transmission-Count Metric (ETX): As a first example of ALC, we can generalize the expected transmission count (ETX) [10] metric for unicast transmission...

    Henri Dubois-Ferriereet al. Valuable Detours: Least-Cost Anypath Routing

    • ...In MORE, the source calculates and assigns a transmission credit to each FN using the ETX metric [12] computed from loss rate measurements...

    Dimitrios Koutsonikolaset al. Efficient Network-Coding-Based Opportunistic Routing Through Cumulativ...

    • ...If v is in u’s transmission range, there is a directed edge (u, v) in G .A s in [6], ad istributed node pre-selection procedure is performed to add the nodes into the intermediate forwarder list for a user, such that each forwarder is closer (in ETX metric [10]) to the destination than its predecessors...
    • ...Since probing is a standard technique [10] widely being used in wireless networks, integrating this information into probes can reduce the overheads introduced by broadcasting this information...

    Xi Fanget al. Consort: Node-Constrained Opportunistic Routing in wireless mesh netwo...

    • ...This metric is generic and could be used by various routing protocols to estimate link and path “weights.” Similar to the Expected Transmission count (ETX) metric [9], our metric estimates the number of transmissions (including retransmissions) required to send a packet over a link...
    • ...Our interference-aware routing metric borrows essential design properties of the ETX routing metric [9]; we postpone a discussion on how could we support other routing metrics, originally relying on active probing, in the Section 9. ETX estimates the number of transmissions (including retransmissions) required to send a packet over a link...
    • ...Note that according to the 802.11 performance analysis models (see [9], [10], [11], [12]), the collision probability is constant for given transmission attempt rate � —in fact, it is a monotonically decreasing function of � in½0; 1� . On the other hand, larger packet sizes should make transmissions more prone to errors for given link quality (Bit Error Rate)...
    • ...The minimum hop count represents the alma mater of metrics used by default on most routing protocols, whereas the active-probe measurements of ETX [9], [29] are the base for a whole family of metrics, which are viewed as current “state-of-the-art” [30]...
    • ...the throughput of a single-hop path due to interfering transmissions of two consecutive hops [9], [32]...
    • ...Yet, as admitted also in the ETX paper [9], heavy load causes the MAC protocol to become extremely unfair, distorting the probe-based measurements...

    Georgios Parissidiset al. Interference-Aware Routing in Wireless Multihop Networks

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