i'm totally curious. i don't get how any of these schemes are supposed to work except in small bursts or at short distance. 1. the amount of power that can be

i'm totally curious. i don't get how any of these schemes are supposed to work except in small bursts or at short distance. 1. the amount of power that can be used for transmission must be equal or smaller than that collected. 2. so if the device transmits, the transmission is weaker than the noise. 3. so perhaps power is stored and transmission is done in (short?) bursts? 4. or does it work only at some very short distance thats a (small?) fraction of the range of the powered wifi AP?