[burfog]

Given that there is more space at higher frequencies, how would you express it? For example: It could be 1% of a band. It could be 0.1% of the center frequency, or perhaps 0.1% of the frequency at the lower edge. Maybe it needs to be expressed in some kind of log(Hz) unit, such as milli-Bel-Hz.

I don't think this accommodates spread spectrum very well. One might want to do something like CDMA, spread across the entire band but down in the noise level from the perspective of a traditional transmission.