Edited by author 03-24-2006 11:47 AM
First the end of conventional modulation should come.
Really, more and more applications use spread spectrum, or CDMA(tm). This is _the_ modulation without interference. It's popularity comes out:
1. Existing interference avoidance.
2. Security.
3. Encryption available.
Broadcasting which doesn't requires subscription becomes obsolete, and so comes to digital technologies by need to encrypt content.
Field applications go digital by need to avoid interference ;-) and security.

So, conventional narrow-band modulation becomes narrower-used.
And IMHO in 5 or 10 years it will have no usage.

And then, when all transmission will be spread spectrum, spectrum will be open.

For Open Spectrum there must be no modulation but CDMA.
And Open Spectrum could be here only when all other modulations die.

(CDMA is trademark of Qualcomm)