Document Type

Technical Report

Publication Date


Technical Report Number



Most research on ad-hoc wireless networks makes simplifying assumptions about radio propagation. The ``Flat Earth'' model of the world is surprisingly popular: all radios have circular range, have perfect coverage in that range, and travel on a two-dimensional plane. CMU's ns-2 radio models are better but still fail to represent many aspects of realistic radio networks, including hills, obstacles, link asymmetries, and unpredictable fading. We briefly argue that key ``axioms'' of these types of propagation models lead to simulation results that do not adequately reflect real behavior of ad-hoc networks, and hence to network protocols that may not work well (or at all) in reality. We then present a set of 802.11 measurements that clearly demonstrate that these ``axioms'' are contrary to fact. The broad chasm between simulation and reality calls into question many of results from prior papers, and we summarize with a series of recommendations for researchers considering analytic or simulation models of wireless networks.


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