The technology that lets many people use the same radio channel at the same time is called smart antenna technology or adaptive array technology or interference mitigation. This technology uses computer processors to take the signals from multiple antennas at each location and sorts the various signals out so they don't interfere with each other.
Even though you can't get along without your smartphone, there are not many essential services on your smartphone. They're mostly convenience; you could live without it. Essential means you die without it. A gadget that warns you're about to have a heart attack - that's essential. We're about to go into that phase with smartphones.
I'm at the doctor's office. I'm in the waiting room. And there's this guy on his cell phone, talking really loud. Does he think he owns the place? Apparently. I think this is so offensive. But you have to remember: It doesn't take a cell phone to make people rude. People were rude before there were cell phones.