This paper provides an in-depth understanding of the per-frame energy consumption behavior in 802.11 wireless LAN devices. Extensive measurements are performed for seven devices of different types (wireless routers, smartphones, tablets, and embedded devices) and for both UDP and TCP traffic. Experimental results unveil that a substantial fraction of energy consumption, hereafter descriptively named cross-factor, may be ascribed to each individual frame while it crosses the protocol stack (OS, driver, NIC) and is independent of the frame size. Our findings, summarized in a convenient energy consumption model, contrast traditional models that (implicitly) amortize such energy cost component in a fixed baseline cost or in a toll proportional to the frame size and raise the alert that, in some cases, conclusions drawn using traditional energy models may be fallacious.
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