magnetic waves can pass through almost anything, even rock. that same rock blocks rf after only a few feet. an rf signal falls off as 1/"r", whereas the strength of a magnetic wave falls off far faster at the rate of 1/"r"³. this means that the magnetic signal will not travel nearly as far as the rf signal. at first glance this difference in fall-off rate may appear as a negative for the range of a tag using magnetic signaling, but, as explained below, it turns out to be quite a plus in a local visibility network. secondly, an unexpected advantage is that the noise rubee sees is also magnetic, so it too falls off 1/"r"³. noise and interference sources must be much more local to have significant strength, and tend to be easy to locate and minimize in an ieee 1902.1 network.