How do Officers and commanders track their soldiers in battle?

Is it all done via radioing in positions, or is there a gps unit on soldiers (or at least on vehicles)? I've seen very cool technologies that track ammunition and fuel levels in tanks and other ground vehicles but my exaughstive searches haven't found anything on how soldiers are tracked on the battlefield. Also: if anyone knows about radio hierarchy in the military (who gets what signal and communications, etc) I'd really like to hear about it... thanks!