The problem isn't bandwidth or frequency per se, although the available is becoming less and less. Up there where the air is rarefied, are all manner of overmodulated/off cycle/power to the umph electrons, across all the frequencies you can think of. As one can imagine, some strong filtering is required to "sort out the good stuff". Sometimes it works great, sometimes it doesn't. When it doesn't, then it's up to the "pre programmed, lost link action(s)" in the onboard gubbins. Young snuffy in the control shack can push, pull, scream and yell, qualified pilot or mere operator as may be, they are purely spectators at this point.
Now we all know the wonders of computer code, and the millions of lines required. Somehow, somewhere, someone may have forgot to insert a correct "if this happens, then do that". Well this happens, and it don't do that, so proceed to the site of the crash.
Humble opinion, to correct this problem to safely, and I do stress safely operate in controlled airspace, you would end up with an unaffordable, unmanned aircraft. Keep an eye on Global hawk, it's at that point already.
There are only two things that I can see that unmanned has over manned:
Endurance/Persistence (shift the crews on the ground instead. Pottie breaks instead of a pee tube/diaper, sheer luxury!).
And if it does go down in enemy territory, no "Gary Powers moment".
I guess you could call it the PC form of aerial warfare.
Anyone remember Aquila?
Just my tuppence.