Go look at the Swedish ATC system - inexpensive, non complex, and reliable. But it is too late for the US...we have a 'standard' now.
Swedish translation of ATC system
Doesn't have all the mumble-jumbo that the current PTC system here has (Radio link to base, GPS signals, LCD monitors, etc...). The US one relies on too many radio communications links that are not needed in the ATC system.
The NEC uses the same Bombardier beacons as what SJ in Sweden uses.
Then again, ERMTS is another option...but it is expensive.
-K