Phone trivia:

GSM's still around. Here in the US, there was GSM and mostly-Verizon CDMA. The major difference was in how crowded channels were handled; whether the intelligence to handle that was in the handset (CDMA) or the tower (GSM). There was a lot of "which one will win?" like there was between VHS and BetaMax, but unlike those, CDMA and GSM have pretty much merged into LTE - and channel congestion is mostly a non issue due to the move to spread spectrum - other connections are similar enough to noise that they can be filtered out.