One wonders why someone isn't pushing for a digital TDMA scheme for
amateurs. You could build a very nice full duplex repeater on a single
frequency that way. Sure it's totally incompatible with current FM
repeaters, but then, D-star isn't totally compatible either. D-star and
it's ilk are sort of half measures in that sense.

No filtering, much less intermod issues in multi station at onee site
systems... all kinds of good comes of it.

Digital schemes on HF to replace SSB I can see having real trouble (the
biggest is the lack of a "party line" capability, the other is the long
propagation delay on HF paths), but on VHF and up FM, you already have a
"one person talks at a time" by virtue of the standard FM demodulator.