Does SMS messaging keep going when cellular voice is down? [telecom]

There's a big "it depends".

If the entire cell network (towers, backhaul, etc.) is "down" for fifty miles around you, you ain't getting through.

If it's up but the voice channels are all in use, then yes, the SMS should get through.

If the towers near you are down but the one 9 miles away is working, then it's quite possible you _won't_ be able to get a voice line through it. But since SMS is "stored", so to speak, it can stay "on your handset" for fifteen minutes (number for illustration) until you walk on the other side of the road and get a short-in-time workable link to the tower.

(And vice versa for someone sending you something).

Well, it depends why the voice service is down.

If it's down because too many people are trying to make calls in the same area and clogging up the links between towers, then lower bandwidth SMS messages are apt to go through even when you cannot get a call through.

If it's down because there's no power to the tower, or a storm blew it over, or for some other reason the handset cannot get a connection to the tower, then indeed SMS messages won't go through any more than phone calls.

--scott