Chapter 12

Controlling Wire-less
(and Hence the Physical Layer)

On the wall in my office is a multicolored poster. The poster is large
(maybe 30 by 42 inches), and it is titled, in beautifully retro typewriter
font, "United States Frequency Allocations -- The Radio Spectrum." To the
left are thirty-three colored boxes, listing the legends for the poster. Thirty
list "radio services." Three list "activity codes." Among the activity codes are
"government exclusive," "government/non-government shared," and "non-
governmental exclusive." (Appropriately enough, government exclusive is
red, while nongovernmental exclusive is green.)

If you could tilt this poster and give it a bit of a 3D look, it might remind
you of the famous _New_Yorker_ cartoon maps, where everything close is de-
tailed and significant, while everything far is wide open and unimportant.

So it is with spectrum as well. At the highest frequency (30-300 gigahertz),
the allocations are a patchwork of tiny colored boxes, sometimes four
deep; but as you move down the frequency range, the allocations get wider
and less precise. The largest swath is AM radio.

This map, however, doesn't mark out any physical space. It marks the al-
location of radio spectrum. The map says what kind of use will be permitted
at what range of radio spectrum in any particular part of the territorial
United States. It does not say by whom.

As I described in chapter 5, the "by whom" part is determined by a com-
plex set of federal regulations. The FCC makes a decision about who gets to
use what spectrum when, and under what conditions. These "licenses" are
not really licenses to spectrum. As Thomas Hazlett describes them, they are
simply permissions to use certain kinds of equipment at certain times for

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