cETX: Incorporating spatiotemporal correlation for better wireless networking

In this work, we experimentally observe the existence of spatiotemporal correlation among adjacent wireless links within short time intervals. Such an observation calls attention to potential errors in existing popular metrics built upon the assumption of link independence. Specifically we propose cETX (correlated ETX), a generalized metric, to compensate for estimation errors suffered by the widely-adopted ETX in the presence of correlated interference. To the best of our knowledge, this is the first work to introduce a unified metric embracing both temporal and spatiotemporal correlations. The highlight of the cETX metric is its broad applicability and effectiveness. Evaluations on ZigBee (802.15.4) and Wi-Fi (802.11b/g/n) testbeds deployed in a lab, corridor, and on a bridge reveal that: Simply replacing ETX with cETX (i) cuts down the error by 70.2% and 62.1%, respectively, and (ii) saves averages of 22% and 37% communication cost in three unicast [4, 13, 17] and nine broadcast protocols [7, 18, 23, 24, 27, 30, 40] at the price of only 0.7% additional overhead.